NATIONAL TECHNICAL UNIVERSITY OF ATHENS
Nuclear Engineering Section







RECENT PUBLICATIONS





  1. Atomkernenergie-Kerntechnik, 49(1/2):37-42, 1986

    THE EFFECT OF PRECURSORY COOLING ON THE REWETTING RATE

    S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  2. Atomkernenergie-Kerntechnik, 49(1/2):105-106, 1986

    ON THE EMANATION OF RADON INTO THE PORES OF A SOLID MATERIAL

    S.E.Simopoulos and D.J.Leonidou
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  3. Journal of Environmental Radioactivity, 5:379-389, 1987

    NATURAL RADIOACTIVITY RELEASES FROM LIGNITE POWER PLANTS IN GREECE

    S.E.Simopoulos and M.G. Angelopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece



  4. Proceedings of the 1st Balkan Scientific Conference on Environmental Protection in the Balkans, Vol. 2, pp. 334-344, September 20-23, 1988, Varna, Bulgaria

    ELECTRICITY GENERATION AND ITS ASSOCIATED RADIOLOGICAL IMPACT TO THE ENVIRONMENT

    S.E.Simopoulos and M.G. Angelopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece



  5. Appl. Radiat. Isot. Vol. 40, No. 7, pp. 607-613, 1989
    Int. J. Radiat. Appl. Instrum. Part A

    SOIL SAMPLING AND Cs-137 ANALYSIS OF THE CHERNOBYL FALLOUT IN GREECE

    S.E.Simopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece



  6. Health Physics, Vol. 61, No. 6 (December), pp. 885-888, 1991

    EFFECT OF DIETARY INTAKE ON THE Cs-137 RETENTION MODEL

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    S.E.Simopoulos and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  7. ASME International Conference Analysis of Thermal and Energy Systems, pp. 983-995, June 3-6, 1991, Athens

    INVESTIGATION OF THE LIQUID FLOWRATE EFFECT ON THE REWETTING RATE

    A.P. Konstantaropoulou and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  8. Workshop on the LONG TERM FOLLOW UP OF THE CHERNOBYL DISASTER
    World Health Organization
    International Union Against Cancer
    Hellenic Cancer Society
    pp. 157-171, December 6-8, 1991, Athens

    DEPOSITION MEASUREMENTS IN EUROPE AFTER THE CHERNOBYL ACCIDENT AND COMPARISON WITH THE GREEK "NTUA DATA SET"

    S.E.Simopoulos and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  9. Proceedings of the 1st Mediterranean Congress on Radiation Protection, pp. 240-244, April 5-7, 1994, Athens

    MEASUREMENTS OF NATURAL RADIOACTIVITY IN GREEK BUILDING MATERIALS

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    N.P.Petropoulos, M.J.Anagnostakis, S.E.Simopoulos, and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  10. Proceedings of the 1st Mediterranean Congress on Radiation Protection, pp. 252-267, April 5-7, 1994, Athens

    MINI RADON HOUSE : A PROTOTYPE CONTAINER FOR THE MEASUREMENT OF RADON EXHALATION FROM BUILDING MATERIALS AND STRUCTURAL MODULES

    A. Louizi and C. Proukakis Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece
    N.P.Petropoulos, E.P.Hinis, S.E.Simopoulos and D.J.Leonidou
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  11. Proceedings of "INDOOR AIR, An Integrated Approach, International Workshop" , pp. 131 - 134, November 27 - December 1, 1994, Gold Coast, Australia

    NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATES OF GREEK BUILDING MATERIALS


    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    N.P.Petropoulos and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  12. NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S3-S8,1996

    NATURAL RADIOACTIVITY MAPPING OF GREEK SURFACE SOILS

    M.J.Anagnostakis, E.P.Hinis, S.E.Simopoulos, and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  13. NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S369-S373, 1996

    Cs-137 CHERNOBYL FALLOUT IN GREECE AND ITS ASSOCIATED RADIOLOGICAL IMPACT

    N.P.Petropoulos, E.P.Hinis, and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  14. NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S375-S377,1996

    NATURAL RADIOACTIVITY CONTENT OF GREEK CIGARETTES

    S.Katsanevakis, N.P.Petropoulos, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    A.Louizi and C.Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece



  15. NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S93-S99, 1996

    AN EXPERIMENTAL-NUMERICAL METHOD FOR THE EFFICIENCY CALIBRATION OF LOW ENERGY GERMANIUM DETECTORS

    M.J.Anagnostakis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  16. Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    GEOGRAPHICAL MAPPING AND ASSOCIATED FRACTAL ANALYSIS
    OF THE LONG-LIVED CHERNOBYL FALLOUT ISOTOPES IN GREECE


    N.P.Petropoulos, M.J.Anagnostakis, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  17. Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    RADIOLOGICAL IMPACT OF THE LONG-LIVED CHERNOBYL FALLOUT ISOTOPES IN GREECE

    M.J.Anagnostakis, N.P.Petropoulos, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  18. Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    EXPERIMENTAL INVESTIGATION OF THE REWETTING PROCESS AT LOW STEAM PRESSURES

    E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  19. Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    COMPUTER CODES IN NUCLEAR ENGINEERING

    S.E.Simopoulos
    Prof. of Nuclear Engineering, National Technical University of Athens, 15780 Athens, Greece



  20. Radon in the Living Environment,
    Athens, 19-23 April 1999

    INTEGRATED NATURAL RADIATION EXPOSURE STUDIES IN STABLE YUGOSLAV RURAL COMMUNITIES

    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca"
    P.O. Box 522, 11001 Belgrade, Yugoslavia.

    J.P. McLaughlin, C. Walsh
    Physics Department, University College Dublin, Belfield, Dublin 4, Ireland.

    A. Birovljev
    Environmental Protection Department, Norwegian Radiation Protection Authority,
    P.O. Box 55, N­1345, Osteras, Norway.

    S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Department,
    National Technical University of Athens, 15 780 Athens, Greece.

    B. Jakupi
    Physics Department, Faculty of Natural Sciences and Mathematics,
    Vidovdanska bb, 38 00 Pristina, Yugoslavia.

    V. Gordanic
    Geoinsitute, Rovinjska 12, 11000 Belgrade, Yugoslavia.

    M. Demajo
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca"
    P.O. Box 522, 11001 Belgrade, Yugoslavia.

    F. Trotti
    Venetian Reference Laboratory for Environmental Radioactivity,
    CRR­ARPAV, Verona CRR­Policlinico B. Roma, Via Velle Menegone 32­34 Verona, Italy.

    R. Falk
    SSI, Stockholm, Sweden.

    H. Vanmarcke, J. Paridaens
    SCK­CEN, Boeretang 200, B­2400 Mol, Belgium.

    K. Fujimoto
    Human Radiation Environment Division, National Institute of Radiological Sciences,
    4­9­1 Anagawa, Inage­ku, Chiba, 263­8555, Japan.




  21. Radon in the Living Environment,
    Athens, 19-23 April 1999

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS LIGNITE FIELD BASIN

    P.K.Rouni, N.P.Petropoulos, M.J.Anagnostakis, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 157 80 Athens, Greece



  22. Radon in the Living Environment,
    Athens, 19-23 April 1999

    THE EFFECT OF HUMIDITY ON THE RADON COUNTING EFFICIENCY OF INTEGRATED INSTRUMENTS

    N.P.Petropoulos, E.P.Hinis, S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780, Greece



  23. Radon in the Living Environment,
    Athens, 19-23 April 1999

    BUILDING MATERIALS PHOTON ATTENUATION, NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATE

    N.P.Petropoulos, M.J. Anagnostakis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780, Greece



  24. Radon in the Living Environment,
    Athens, 19-23 April 1999

    BUILDING MATERIALS RADON EXHALATION RATE: ERRICCA INTERCOMPARISON EXERCISE RESULTS

    N.P. Petropoulos, M.J. Anagnostakis, and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780 Athens, Greece




  25. BEST Summer School for EU Students. NTUA, Athens, May, 14-20, 2000.

    RADON AND ITS DAUGHTERS AS AN EARTHQUAKE PRECURSORY TOOL.

    P. Rouni, N.Petropoulos, M. Anagnostakis, E. Hinis and S. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece




  26. Scuola Superiore di Radoprotezione "CARLO POLVANI"
    Roma, Italia, October 13, 2000.

    EXHALATION MEASUREMENT METHODOLOGIES: THE ERRICCA BUILDING MATERIALS RADON EXHALATION RATE INTERNATIONAL INTERCOMPARISON.

    N. Petropoulos, M. Anagnostakis, E. Hinis and S. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece




  27. Scuola Superiore di Radoprotezione "CARLO POLVANI"
    Roma, Italia, October 13, 2000.

    THE NTUA RADON CHAMBERS AND THE RADIOACTIVITY OF GREEK BUILDING MATERIALS.

    N. Petropoulos, M. Anagnostakis, E. Hinis and S. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  28. The Science of the Total Environment, Vol. 272, pp. 261-272, 2001

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS LIGNITE FIELD BASIN

    P.K. Rouni, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  29. Third International Symposium on Naturally Occuring Radioactive Materials
    Brussels 17-21 September 2001

    TECHNOLOGICALLY ENHANCED NATURAL RADIOACTIVITY OF FLY-ASH PRODUCED IN LIGNITE-FIRED POWER PLANTS AND THE ASSOCIATED RADIOLOGICAL IMPACT

    D.J. Karangelos, P.K.Rouni, N.P.Petropoulos, M.J. Anagnostakis, E.P.Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  30. 1ο Πανελλήνιο Συνέδριο "Ραδιενέργεια Περιβάλλοντος"
    Αθήνα 23-24.11.2001

    ΠΡΟΣΔΙΟΡΙΣΜΟΣ ΑΠΕΜΠΛΟΥΤΙΣΜΕΝΟΥ ΟΥΡΑΝΙΟΥ ΣΕ ΠΕΡΙΒΑΛΛΟΝΤΙΚΑ ΔΕΙΓΜΑΤΑ ΜΕ ΤΗΝ ΤΕΧΝΙΚΗ ΤΗΣ γ-ΦΑΣΜΑΤΟΣΚΟΠΙΑΣ

    Δ.Ι. Καράγγελος, Π.Κ. Ρούνη, N.Π. Πετρόπουλος, Μ.Ι. Αναγνωστάκης, Ε.Π. Χίνης και Σ.Ε. Σιμόπουλος

    Τομέας Πυρηνικής Τεχνολογίας, Τμήμα Μηχανολόγων Μηχανικών, Εθνικό Μετσόβιο Πολυτεχνείο



  31. Archive of Oncology 2001;9(4):231-6

    DETERMINATION OF DEPLETED URANIUM IN ENVIRONMENTAL SAMPLES BY GAMMA-SPECTROSCOPIC TECHNIQUES

    M.J. Anagnostakis, E.P. Hinis, D.J. Karangelos, N.P. Petropoulos, P.K. Rouni, S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "VINCA", Belgrade, Yugoslavia



  32. Kerntechnik 68 (2001) 1-2

    EXPERIMENTAL INVESTIGATION OF THE REWETTING PROCESS AT PRESSURES OF 1-7 BAR

    E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  33. ERRICCA 2 Kick-Off Meeting
    London, 25-26 February 2002

    LABORATORY FACILITIES ASSOCIATED WITH RADON MEASUREMENTS AT THE NUCLEAR ENG. LABORATORY OF NTUA

    D.J.Karangelos, P.K.Rouni, N.P.Petropoulos, M.J.Anagnostakis, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  34. ERRICCA 2 Kick-Off Meeting
    London, 25-26 February 2002

    NTUA'S VIEWS REGARDING ERRICCA-2

    M.J.Anagnostakis
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  35. ERRICCA 2 Kick-Off Meeting
    London, 25-26 February 2002

    CURRENT RADON RESEARCH AS COMPILED FROM THE ABSTRACTS SUBMITTED TO NRE-VII

    N.P. Petropoulos and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  36. ERRICCA 2 Kick-Off Meeting
    London, 25-26 February 2002

    EUROPEAN RADON WEBSITE

    E.P. Hinis
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  37. ERRICCA 2 Kick-Off Meeting
    London, 25-26 February 2002

    RADON-IN-WATER SECONDARY STANDARD PREPARATION

    D.J. Karangelos, N.P. Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  38. CCMS Workshop: "Risk Assesment of Chernobyl Accident Consequences"
    Kiev, 9-12 April 2002

    GEOGRAPHICAL MAPPING AND ASSOCIATED FRACTAL ANALYSIS OF THE LONG-LIVED CHERNOBYL FALLOUT RADIONUCLIDES IN GREECE

    N.P.Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece


  39. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS POWER PLANTS FLY-ASH DEPOSITS

    D.J. Karangelos, P.K. Rouni, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  40. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    DISTURBANCE OF RADIOACTIVE EQUILIBRIUM IN THE ASHES PRODUCED IN LIGNITE FIRED POWER PLANTS

    D.J. Karangelos, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  41. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    URANIUM-238 AND ITS DAUGHTER PRODUCTS IN GREEK SURFACE SOILS

    M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  42. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    SURVEY OF DEPLETED URANIUM CONTAMINATION IN SOIL AND VEGETATION USING γ-SPECTROSCOPY

    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca", PO Box 522, 11001 Belgrade, Yugoslavia

    D.J. Karangelos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780 Athens, Greece



  43. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    DATA LEADING TO THE INVESTIGATION OF A RELATION BETWEEN SEISMIC ACTIVITY AND RADON DAUGHTERS CONCENTRATION OUTDOORS

    D.J. Karangelos, N. P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  44. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    REDUCING THE NATURAL RADIOACTIVITY BACKGROUND IN Ge DETECTOR SHIELDS

    A.Nikoglou, D.J. Karangelos, P.K.Rouni, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  45. NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    ASSOCIATION OF THE CHERNOBYL FALLOUT ISOTOPES PATTERNS WITH THOSE OF RAINFALL IN GREECE

    M. Michelaraki
    Department of Climatology, Hellenic National Meteorological Service166 03 Athens, Greece

    P.F. Vrantzas, N.P.Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens157 80 Athens, Greece



  46. NRE VII, International Symposium,
    May 20-24, 2002, Rhodes, Greece

    RADON-IN-WATER SECONDARY STANDARD PREPARATION

    D.J. Karangelos, N. P. Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  47. Industry Technology Environment International Conference
    Moscow, 18-20 September 2002

    TECHNOLOGICALLY ENHANCED NATURAL RADIOACTIVITY OF FLY-ASH PRODUCED IN COAL BURNING POWER PLANTS AND THE ASSOCIATED RADIOLOGICAL IMPACT

    D.J. Karangelos, P.K.Rouni, N.P.Petropoulos, M.J. Anagnostakis, E.P.Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  48. First Workshop on Natural Radionuclides in Hydrology and Hydrogeology
    Luxembourg, 4-7 September 2002

    RADON-IN-WATER SECONDARY STANDARD PREPARATION IN A WIDE ACTIVITY CONCENTRATION RANGE

    D.J. Karangelos, N.P. Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  49. ERRICCA 2 Meeting
    Athens, October 2002

    EUROPEAN RADON WEBSITE

    E.P. Hinis
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  50. ERRICCA 2 Meeting
    Athens, October 2002

    STANDARDIZATION OF RADON MEASUREMENT PROCEDURES FOR BUILDING MATERIALS

    M.J. Anagnostakis
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  51. ERRICCA 2 Meeting
    Athens, October 2002

    CONTINUOUS STANDARDISATION THROUGH ACCREDITATION.
    APPLICATION IN THE CASE OF A RADIOACTIVITY MEASUREMENTS LABORATORY.


    G.N. Papadakos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  52. ERRICCA 2 Meeting
    Athens, October 2002

    THE 7TH NATURAL RADIATION ENVIRONMENT SYMPOSIUM : REPORT ON TOPICS RELATED TO RADON

    D.J. Karangelos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece




  53. Mid Term Meeting for ZEOGYP BOARD Project (EC Contact No. G1RD-CT-2001-03003)
    Limelette, Belgium, 21-22 October, 2002.

    Natural Radioactivity Content and Radon Exhalation Rate measurements of zeolites

    D.J. Karangelos, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece



  54. Journal of Environmental Radioactivity 61:257-269, 2002

    PHOTON ATTENUATION, NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATE OF BUILDING MATERIALS

    N.P. Petropoulos, M.J. Anagnostakis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece








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    Atomkernenergie-Kerntechnik 49(1/2):37-42, 1986

    THE EFFECT OF PRECURSORY COOLING ON THE REWETTING RATE

    S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    A numerical model to predict the rate of advance of the wet front along an overheated wall was developed and tested with available experimental data. The model shows that the predicted unsteady rate of advance of the wet front, which is in agreement with experimental results is due to precursory cooling.

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    Journal of Environmental Radioactivity 5:379-389, 1987

    NATURAL RADIOACTIVITY RELEASES FROM LIGNITE POWER PLANTS IN GREECE

    S.E.Simopoulos and M.G. Angelopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece

    Abstract


    In Greece, power stations burning lignite from two large deposits, in the regions of Megalopolis and Ptolemais, play an important role in meeting the energy needs of the country. The investigation reported
    here deals with the determination of Ra-226, Ra-228 and K-40 concentrations in the lignite feeding two power units in Megalopolis and in the product ash. Systematic sampling allowed evaluation of mean representative concentrations and estimation of the resulted atmosphere discharges of radioactivity. Furthermore, statistical analysis has shown that, at the 95% confidence level essentially all Ra-226 from the lignite feeding each unit is accounted for in the ash. The results of both the present and previous investigations on two units burning lignite from the Ptolemais deposit show that electricity generation from Greek lignites is associated with radioactivity discharge data from the literature.

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    Proceedings of the 1st Balkan Scientific Conference on Environmental Protection in the Balkans, Vol. 2, pp. 334-344, September 20-23, 1988, Varna, Bulgaria

    ELECTRICITY GENERATION AND ITS ASSOCIATED RADIOLOGICAL IMPACT TO THE ENVIRONMENT

    S.E.Simopoulos and M.G. Angelopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Nuclear power stations during normal or abnormal operation, as well as fossil fuel power stations release radioactivity to the environment. In the former case and mainly during an abnormal operation, these releases may affect even regions at great distances from the site of the station. In the latter case the radiological impact to this environment is of limited extent and is due to the trace quantities of the naturally occuring U-238 and Th-232, their associated daughter products and K-40, which are contained in fossil fuels. These radionuclides are released to the environment either directly, through the stack, or indirectly, from fly and bottom ash storage and from the use of fly ash in building materials.

    The purpose of this presentation is to report the concentrations of Ra-226, Ra-228 and K-40 determined in the lignite feeding four power units of the Greek grid and its product ashes. Furthermore, the atmospheric discharges of the above isotopes from these units as well as their radiological significance is evaluated. Finally, some remarks relevant to the evaluation of mean representative concentration and to the estimation of the resulting atmospheric discharges of radioactivity, are also included.

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    Appl. Radiat. Isot. Vol. 40, No. 7, pp. 607-613, 1989,
    Int. J. Radiat. Appl. Instrum. Part A

    SOIL SAMPLING AND Cs-137 ANALYSIS OF THE CHERNOBYL FALLOUT IN GREECE

    S.E.Simopoulos
    Nuclear Engineering Section, National Technical University of Athens, 15780 Athens, Greece

    Abstract


    A total of 1242 samples of soil, collected over Greece, during the period May-November 1986 were counted and analysed for Cs-137 from Chernobyl fallout. The counting was performed using a NaI detector on line to a microcomputer; morover, 252 of the samples were also analysed using Ge detectors, for inter-comparison and also for the assessment of other long-lived isotopes in the fallout. The results show that Cs-137 fallout from Chernobyl presents a remarkable
    geographical variability. The evaluated ground activity due to Cs-137 deposition ranges between 0.01 and 137 kBq/m².

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    Health Physics, Vol. 61, No. 6 (December), pp. 885-888, 1991

    EFFECT OF DIETARY INTAKE ON THE Cs-137 RETENTION MODEL

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    S.E.Simopoulos and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Whole-body counting measurements were conducted to monitor the Cs-137 biological half life of 14 individuals in Athens during the period June 1988 to June 1989. The results and the solution of a Cs-137 retention model showed that the individuals examined were receiving 0 - 3.7 Bq/d of Cs-137 through the food chain during the period investigated.

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    ASME International Conference, Analysis of Thermal and Energy Systems, pp. 983-995, June 3-6, 1991, Athens

    INVESTIGATION OF THE LIQUID FLOWRATE EFFECT ON THE REWETTING RATE

    A.P. Konstantaropoulou and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Following a Loss-of-Coolant Accident (LOCA) in a water cooled nuclear reactor, process of fundamental importance is the rewetting of the overheated fuel elements by an Emergency Core Cooling System (ECCS). It is well accepted that the rate of advance of the wet front depends upon several parameters, the most important being the initial temperature of the overheated fuel elements cladding, the system pressure, the heat transfer coefficient at the wet front, and the properties of the cladding. The effect of secondary parameters, such as the quenching liquid subcooling and flowrate, and the precursory cooling ahead of the wet front due to the droplet-vapor mixture, are still under investigation. The present work is a detailed statistical analysis of available experimental data. It uses the method of confidence interval ellipses, to investigate the liquid flowrate effect on the rewetting rate. The results of this analysis show that the rewetting rate increases with the liquid flowrate only when the wet front advances in an open air environment at atmospheric pressure, while it remains unaffected in a vapor environment at relatively high pressures.

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    Workshop on the LONG TERM FOLLOW UP OF THE CHERNOBYL DISASTER,
    World Health Organization,
    International Union Against Cancer,
    Hellenic Cancer Society,
    pp. 157-171, December 6-8, 1991, Athens

    DEPOSITION MEASUREMENTS IN EUROPE AFTER THE CHERNOBYL ACCIDENT AND COMPARISON WITH THE GREEK "NTUA DATA SET"

    S.E.Simopoulos and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Fission product deposition data, from the Chernobyl reactor accident, have been compiled by the Commission of the European Communities and put together as part of the Radioactivity Environmental Monitoring (REM) programme. Most of these data originate from surface soil sampling and analysis for longer-lived activity with emphasis to that due to Cs-137. According to this compilation, of 3233 data, 1460 of which come from the Greek NTUA soil sampling programme, the Cs-137 cumulative deposition ranges between 261 to less than 1 kBq/m², while the ratio Cs-134/Cs-137 is always close to 0.5. The data provided by the Greek NTUA soil sampling programme, which is considered by the CEC as "intensive and systematic", show that the mean value of the Cs-137
    deposition in Greece (7.3 kBq/m² - 1242 samples) was not as high as mean values of subregions of other EC countries, such as Southern Germany (14 kBq/m² - 98 samples) and Northern Italy (15 kBq/m² - 29 samples). The maximum observed cumulative deposition of Cs-137 is 149 kBq/m² detected near the city of Karditsa in Central Greece. The high resolution gamma spectrographic analysis of the above data set, provides also information about other longer-lived fission products in the fallout, the most important of which is Ru-103 with maximun observed cumulative deposition 337 kBq/m² detected near the city of Naoussa, in Northern Greece.

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    Proceedings of the 1st Mediterranean Congress on Radiation Protection, pp. 240-244, April 5-7, 1994, Athens

    MEASUREMENTS OF NATURAL RADIOACTIVITY IN GREEK BUILDING MATERIALS

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    N.P.Petropoulos, M.J.Anagnostakis, S.E.Simopoulos, and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Building materials and paints may release radon or cause direct radiation exposure because of their content of radium, thorium and potassium. Concrete, brick and granite-stone walls may produce significant external dose rates nGy/hr and -furthermore- give rise to radon exhalation rates of up to 50 Bq/m². A wide research project to investigate the radioactive behaviour of Greek building materials and structural modules has been set-up and is still in progress. In the framework of this project ample specimens of commonly used building materials have been collected randomly over the country. The specimens were dried under ambient temperature and then pulverised to less than 90 µm; finally, the water content of all specimens was determined before being hermetically sealed in 0.282 L cylindrical plastic boxes, covered with a film of epoxy resin to limit - as far as possible - escape of radon. Each box was analysed after secular equilibrium of Ra-226 and Th-232 with their decay products was obtained, using high resolution Ge-detectors setups; activity concentrations were averaged from photopeaks at several energies. The results obtained show that the natural radioactivity content of the various Greek building materials examined is very low. Only a few specimens of cement and clay bricks present a rather high Ra-226 concentration up to 144 and 48 Bq/kg respectively. However, these values are within the range of similar materials used in other European countries.

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    Proceedings of the 1st Mediterranean Congress on Radiation Protection, pp. 252-267, April 5-7, 1994, Athens

    MINI RADON HOUSE : A PROTOTYPE CONTAINER FOR THE MEASUREMENT OF RADON EXHALATION FROM BUILDING MATERIALS AND STRUCTURAL MODULES

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    N.P.Petropoulos, E.P.Hinis, S.E.Simopoulos and D.J.Leonidou
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Radon in indoor air is partly due to its exhalation from building materials. It is therefore important to develop techniques for measuring the exhalation rates from such materials and also from their structural modules, such as test walls and concrete slabs. These techniques could be also employed for estimating the remediating effect of coatings used as radon barriers on walls, floors and ceilings. For this purpose an air-tight, N2 filled, 1m³ steel container has been constructed, in which raw building materials and prototype structural modules of volume not exceeding 100 L are enclosed for evaluating their exhalation rate. The environment is conditioned by a heating unit, a humidifier and an air blower, in order to control temperature and humidity over the range 12-45 °C and 15-99% respectively; an aerosol generating system is used to produce particles. The container is equipped with several monitoring transducers on line to data acquisition computers. Radon progeny radiation is continuously monitored in-situ via a 2x2'' Am-doped NaI detector stabilised for spectrum shifts. Several port holes located on the upper and side walls, allow for grab sampling of the radon progeny on high efficiency filters by pumping approximately 15% of the enclosed N2 through the container using accurate flowrate control. The filters are then analysed using high-resolution gamma and alpha spectrographic techniques. The container is calibrated with a Ra-226 source of a nominal activity of 102.8 kBq, shielded in a small metal drum with a lid which can be remotely opened or closed. Concentration of the homogeneously distributed radon can be regulated up to 100 kBq/m³ by appropriately closing or opening the drum. The efficiency of the container has been experimentally determined ranging within 5-30% depending on the environmental conditions inside it.

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    Proceedings of "INDOOR AIR, An Integrated Approach, International Workshop" , pp. 131 - 134, November 27 - December 1, 1994, Gold Coast, Australia

    NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATES OF GREEK BUILDING MATERIALS

    A. Louizi and C. Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    N.P.Petropoulos and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Greek building materials were analysed for natural radioactivity (Ra-226, Th-232 and K-40) which, according to the results obtained, is low with the exception of a few specimens of cement and clay bricks with Ra-226 concentrations up to 147 and 48 Bq/kg respectively. The radon exhalation rate of the same materials has been evaluated using an air-tight 1m³ steel container. The container environment is conditioned by a heating unit and a humidifier, in order to control temperature and humidity over the range 12-45 °C and 15-99% respectively. A ±50 mbar differential pressure transducer is used for recording pressure changes inside the container, which is also equipped with an aerosol generating system. Radon progeny radiation is continuously monitored in-situ via a 2x2'' Am-doped NaI detector stabilised for spectrum shifts. Furthermore, grab sampling on high efficiency filters analysed using high-resolution gamma and alpha spectrometry is also conducted. The exhalation rate of the above Greek building materials already analysed range between 3-20 µBq/(kgs). Moreover, brick walls and concrete slabs constructed using these materials present exhalation rates between 2-3 mBq/(m²s).

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    NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S3-S8,1996

    NATURAL RADIOACTIVITY MAPPING OF GREEK SURFACE SOILS

    M.J.Anagnostakis, E.P.Hinis, S.E.Simopoulos, and M.G.Angelopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    A total of 1440 samples of soil, collected across Greece from the 1 cm surface layer, were analysed for natural radioactivity (Ra-226, Th-232 & K-40). The samples were air-dried and then hermetically sealed in 0.282 L plastic boxes covered with a film of epoxy resin to ensure that no gases escape from them. Secular equilibrium of Ra-226 and Th-232 with their decay products was obtained before the samples were analysed using high resolution Ge gamma-ray detectors. A Unix-based in-house built complex Data Base/Geographical Information System (DBGIS) was used to analyze the data and present them in
    map form. The analysis of a second 1 cm thick sample, collected at several sites at a depth of 10 cm, led to the statistically justified conclusion that the natural radioactivity content of the surface and of 10 cm deep soil layers do not significantly differ. According to these results the natural radioactivity content of Greek surface soils is rather low (mean ± standard deviation in Bq/kg):

    Ra-226(U-238): 25 ± 19      Ra-228(Th-232): 21 ± 16      K-40: 355 ± 220


    and entails a gamma-ray dose rate outdoors equal to 40 nGy/h. A statistical analysis showed that only 90 samples, collected at 67 locations, have Ra-226 content exceeding their mean value by more than 1.65 std. dev. The Ra-226/Th-232 and Ra-226/K-40 concentration ratios were equal to (mean value ± % std. dev.) 1.10 ± 44% and 0.06 ± 56%, respectively.

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    NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S369-S373, 1996

    Cs-137 CHERNOBYL FALLOUT IN GREECE AND ITS ASSOCIATED RADIOLOGICAL IMPACT

    N.P.Petropoulos, E.P.Hinis, and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Right after the Chernobyl reactor accident a systematic soil sampling and analysis programme has been undertaken by the Nuclear Engineering Section of the National Technical University of Athens in order to detect and quantitatively analyse the long-lived isotopes in the Chernobyl fallout in Greece. In the frame of this programme, 1242 soil samples of 1cm thick surface soil were collected over Greece during the period May - November 1986. The samples were counted and analysed using Ge-detector setups for fission products from the Chernobyl fallout, which led to the
    mapping of Cs-137 deposition in the form of a five-class histogram, extending between 0 - 150 kBq/m², with boundaries defined by isolines of 5, 15, 35, 65 & 150 kBq/m². To investigate the radiological impact of the Cs-137 fallout on the Greek population, the NEA/OECD computer code PABLM was run using as input the above isoline data. According to the results obtained, the total body collective effective dose commitment of the Greek population is estimated to 340 manSv over the first year after the accident and 8800 manSv over a period of 40 years. Concerning the 6000 inhabitants within the 65 kBq/m² isoline the results are 2 manSv over the first year after the accident and 55 manSv over a period of 40 years. The above radiological impact was further compared to that due to fly ash releases from the Ptolemais Lignite Power Plants, in northern Greece.

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    NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S375-S377,1996

    NATURAL RADIOACTIVITY CONTENT OF GREEK CIGARETTES

    S.Katsanevakis, N.P.Petropoulos, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    A.Louizi and C.Proukakis
    Department of Medical Physics, School of Medicine, Athens University, 11527 Athens, Greece

    Abstract


    Tobacco from Greek cigarettes was analysed for natural radioactivity; according to the results already obtained the concentrations of both Ra-226 and Th-232 are less than 13 Bq/kg, while that of K-40 is relatively high, up to 1250 Bq/kg.

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    NRE VI, International Symposium, June 5-9, 1995, Montreal, ENVIRONMENT INTERNATIONAL, Vol. 22, Suppl. 1, pp. S93-S99, 1996

    AN EXPERIMENTAL-NUMERICAL METHOD FOR THE EFFICIENCY CALIBRATION OF LOW ENERGY GERMANIUM DETECTORS

    M.J.Anagnostakis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Several radionuclides emit significant gamma rays at energies below 80 keV, which in many cases are essential for their detection in radioenvironmental assays. The gamma spectroscopic analysis at this energy region is conducted using planar Low Energy Germanium detectors, with high and almost constant efficiency in the energy region between 20 and 80 keV. When analysing solid and liquid samples, using these detectors, the count rate is highly affected by the intense self-absorption of the low energy photons. Thus, the difference of the absorption properties between the calibration source and the sample requires the introduction of an efficiency correction factor. A method which is applicable for cylindrical geometries was adapted for the determination of the above correction factor using a newly developed experimental-numerical technique and a FORTRAN program. This program, using as input the source-to-detector geometry and the values of the linear attenuation coefficient (µ) of both the calibration source and the material to be analysed, calculates the efficiency correction factor. The value of the linear attenuation coefficient (µ) needed for this calculation is being experimentally estimated for each material to be analysed. The technique has been cross-checked using standard materials. According to the results obtained, in the case of surface soil samples, lignite and fly ash values ranges from 0.2 to 0.9 cm¯¹ and leads to efficiency correction factors - for the geometry used and a 4M HCl mixed radionuclide calibration source - in the range of 0.5 to 1.2 for the photons emitted by Pb-210 at 46.52 keV and Am-241 at 59.54 keV. The correction factor in the case of 185.99 keV photons is slightly lower than 1.0, even for the most absorbing of the materials analysed.

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    Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    GEOGRAPHICAL MAPPING AND ASSOCIATED FRACTAL ANALYSIS
    OF THE LONG-LIVED CHERNOBYL FALLOUT ISOTOPES IN GREECE


    N.P.Petropoulos, M.J.Anagnostakis, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Right after the Chernobyl accident, a soil sampling programme has been undertaken by the Nuclear Engineering Section of the National Technical University of Athens in order to detect and quantitatively analyse the long-lived isotopes in the Chernobyl fallout. 1242 soil samples of 1cm thick surface soil were collected over Greece during the period May - November 1986. The samples were counted and analysed using Ge detector setups. The Cs-137 fallout data have already been graphically presented; this analysis led to the mapping of Cs-137 deposition in the form of a four-class histogram, extending between 0-150 kBqm¯¹. In an attempt to improve this analysis and also to extend it to other isotopes in the fallout an in-house built Unix-based Data Base/Geographical Information System (DBGIS) was developed. Multifractal analyses of the deposition patterns have also been performed by the use of relevant methods. In the present work, the deposition of
    Cs-137, Cs-134, Ce-144, Ce-141, Sb-125, Ag-110m, Ru-106, Ru-103, Zr-95 and Mn-54 in the form of contour histograms is presented and the results of the associated fractal analysis is communicated. The maximum detected values of the above mentioned isotopes are 149.5±0.1, 76.1±0.1, 32.9±0.2, 46±2, 4.56±0.02, 7.98±0.02, 79.1±0.4, 337±2, 20.1±0.2 and 3.02±0.02 kBqm¯¹ respectively. Furthermore, a statistical technique to compare contour mappings is introduced and applied to explain the differences in the mappings of the above isotopes.

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    Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    RADIOLOGICAL IMPACT OF THE LONG-LIVED CHERNOBYL FALLOUT ISOTOPES IN GREECE

    M.J.Anagnostakis, N.P.Petropoulos, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    1242 soil samples of 1cm thick surface soil were collected over Greece during the period May - November 1986. The samples were counted and analysed which led to detailed mappings of the depositions of Cs-137, Cs-134, Sb-125, Ag-110m, Zr-95, Ce-141, Ce-144, Ru-103, Ru-106 and Mn-54. The deposition mappings of the fission products Cs-137, Cs-134, Sb-125, Ce-144 and Ru-106 allowed the localization of the three most contaminated areas of the country, near the city of Karditsa (lat. 39.556°, long. 21.918°), about the city of Trikala (lat. 39.553°, long. 21.808°) and that about the city of Naoussa (lat. 46.634°, long. 22.091°). The Cs-137 deposition in those areas ranges between 65 - 150 kBqm¯². The geographical mean of Cs-137 deposition all over Greece was estimated to 8±9 kBqm¯². Furthermore, these deposition mappings can be used for the investigation of the accident's radiological impact on the Greek population. For this reason a computer code was developed to calculate the dose due to external irradiation ought to field deposition and the dose due to the ingestion of contaminated food. The present work communicates the radiological impact on the Greek population due to the accumulated effect of long-lived fallout isotopes. The dosimetric calculations are reported for a variety of radionuclides and exposure pathways. According to the results obtained, the committed effective dose due to ingestion, over a period of 50 years, of the average exposed 20 year old adult in Greece, who had been consuming contaminated food during the first year after the accident is estimated to about 548 µSv. The committed effective dose of the average exposed 20 year old adult due to external irradiation is estimated to 67 µSv for the first year after the accident and to 917 µSv for a period of 50 years. The committed effective dose due to ingestion, over a period of 50 years, of the maximum exposed 20 year old adult in the most contaminated areas of central and northern Greece, who had been consuming highly contaminated food during the first year after the accident is estimated to about 5.4 mSv. The committed effective dose of the maximum exposed 20 year old adult, due to external irradiation, is estimated to 0.7 mSv for the first year after the accident, and to 10.3 mSv over a period of 50 years.

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    Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    EXPERIMENTAL INVESTIGATION OF THE REWETTING PROCESS AT LOW STEAM PRESSURES

    E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    The rewetting of the overheated water cooled nuclear reactor fuel rods after a Loss-of-Coolant-Accident, which is defined as the re-establishment of a water film on the hot rod surfaces, is an important process for the safety of nuclear reactors. Several water experiments have been carried out to investigate the rewetting phenomena and to predict the liquid film behaviour either at atmospheric conditions or in a steam environment. Yet, there seems to be a scarcity of experimental data for the very important low pressure range from 2 to 7 bars with parameters the liquid film flowrate and the subcooling. An experimental facility to simulate two-phase low-pressure water flow phenomena has been designed, constructed and employed to investigate the rewetting process of hot surfaces in a water-steam environment at pressures in the above range, as well as at atmospheric conditions; the facility is on-line interfaced to computers which control its operation and undertake all the data acquisition tasks. The present paper describes the experimental work aimed at studying the wet front propagation along a stainless steel fuel rod in a top-flooding saturated water-steam environment in the pressure range 1 - 7 bars, under various initial wall temperatures up to 550 °C and at a liquid flowrate of 1Lmin¯¹. Following the experimental results a correlation has been derived to predict the rewetting rate as a function of pressure and initial wall temperature. This correlation agrees well with formerly proposed correlations at higher pressures by several other investigators, thus permitting to extend their validity down to the pressure of 1 bar. Furthermore, a numerical method is introduced to experimentally evaluate the wet front position along the rod.

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    Proceedings of the 1st Conference of the Yugoslav Nuclear Society (YUNSC '96), October 7-9, 1996, Belgrade (in press)

    COMPUTER CODES IN NUCLEAR ENGINEERING


    S.E.Simopoulos
    Prof. of Nuclear Engineering, National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Nuclear data refer to all the physical constants characterising nuclear fuel behaviour and that of the other materials under the effect of radiation so as to assess their contribution to the nuclear reaction. Likewise, computer programs and codes are the mathematical tools used for solving these problems through computer simulation of the operation of an installation or piece of equipment, which offers great potential for plant design, technical and economic optimisation and safety studies. More systematic analyses can be conducted and there is often no further need to undertake expensive trials using large-scale equipment.

    However, these concerns are leading to increasingly complex computer programs which require more and more powerful computers. On the other hand, in order to explore these possibilities computer codes must be adjusted, tested and, above all, homogeneous approaches must be found to ensure mutual compatibility of the codes and to maintain exchange opportunities among scientists. This is the purpose of the co-operation undertaken in large benchmark centres. The concept of a scientific data centre was at its origin very similar to that of a specialised library: it should collect and compile computer codes and numerical data, carry out limited verification and supply the information selectively in response to user requests. Furthermore, data centres play an important role in coordinating national efforts and in helping to avoid unnecessary duplication of work.

    Computer codes are distributed internationally by a network of three data centres: Energy, Science and Technology Software Centre (Oak Ridge, USA); Radiation Shielding Information Centre (Oak Ridge, USA); NEA Data Bank (serves OECD countries except US and Canada, also serves non-OECD countries on behalf of IAEA). Countries providing copies of nuclear energy software prefer to retain control of its distribution: the above three centres provide users with the assurance of a well-defined version of each code and originators with the assurance that their wishes will be respected.

    The OECD Nuclear Energy Agency Data Bank (NEADB) provides, in collaboration with the code centres in the United States, a service to its Member Countries, offering computer programs covering the full chain of computation needed for performance prediction and assessment of nuclear facilities. It also has service arrangements with IAEA. The Data Bank serves about 430 accredited institutions in the participating countries. The current collection of tested codes amounts to about 1500 packages, which is refreshed by the addition of about 100 new codes -or new version- each year; they fall into several categories of particular interest to nuclear engineers and physicists. Over the last few years, between 1500 and 1700 code requests have been answered each year, by sending both the source code and ample documentation. A recent development is the availability of versions of many of the most frequently requested codes for mainframe computers, adapted for personal computers. There exist several electronic ways to access the NEA Data Bank Services: by e-mail, by anonymous ftp, by telnet and by WWW.

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    Radon in the Living Environment,
    Athens, 19­23 April 1999

    INTEGRATED NATURAL RADIATION EXPOSURE STUDIES IN STABLE YUGOSLAV RURAL COMMUNITIES


    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca"
    P.O. Box 522, 11001 Belgrade, Yugoslavia.

    J.P. McLaughlin, C. Walsh
    Physics Department, University College Dublin, Belfield, Dublin 4, Ireland.

    A. Birovljev
    Environmental Protection Department, Norwegian Radiation Protection Authority,
    P.O. Box 55, N­1345, Osteras, Norway.

    S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Department,
    National Technical University of Athens, 15 780 Athens, Greece.

    B. Jakupi
    Physics Department, Faculty of Natural Sciences and Mathematics,
    Vidovdanska bb, 38 00 Pristina, Yugoslavia.

    V. Gordanic
    Geoinsitute, Rovinjska 12, 11000 Belgrade, Yugoslavia.

    M. Demajo
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca"
    P.O. Box 522, 11001 Belgrade, Yugoslavia.

    F. Trotti
    Venetian Reference Laboratory for Environmental Radioactivity,
    CRR­ARPAV, Verona CRR­Policlinico B. Roma, Via Velle Menegone 32­34 Verona, Italy.

    R. Falk
    SSI, Stockholm, Sweden.

    H. Vanmarcke, J. Paridaens
    SCK­CEN, Boeretang 200, B­2400 Mol, Belgium.

    K. Fujimoto
    Human Radiation Environment Division, National Institute of Radiological Sciences,
    4­9­1 Anagawa, Inage­ku, Chiba, 263­8555, Japan.


    Abstract


    The results of field investigations of natural radiation exposures of the general populations in two stable rural communities in Yugoslavia are presented. The principal emphasis was on exposures to contemporary indoor radon but measurements of external penetrating radiation absorbed dose rates in air were carried out in the majority of cases. In addition in a limited number of dwellings, measurements of thoron gas concentrations were made. By means of making a series of sequential three month radon measurements, both seasonal variations and annual average radon levels in the dwellings were determined. Using passive alpha track detectors, individual radon and thoron indoor concentrations as high as 9591 Bq/m3 and 709 Bq/m3 respectively were detected while absorbed dose rates in air in the dwellings as high as 430 nGy/hr were recorded.

    On the basis of these different types of measurements, assessments could be made of the integrated natural radiation exposures being received by the populations. In addition to contemporary radon measurements, retrospective radon exposure assessments in most of the dwellings were made on the basis of measurements of 210Po concentrations in both surface (glass) traps and in volume (porous materials) traps.

    A description is given of the sampling strategies and protocols used in this field work. It is shown that at least one stable rural community receiving high natural radiation exposures, has been clearly identified and plans for future health investigations of the population there are outlined.

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    Radon in the Living Environment,
    Athens, 19­23 April 1999

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS LIGNITE FIELD BASIN


    P.K.Rouni, N.P.Petropoulos, M.J.Anagnostakis, E.P.Hinis and S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 157 80 Athens, Greece

    Abstract


    The Megalopolis lignite field basin in southern Greece, with Megalopolis-A and B lignite-fired power plants in operation (total 900 MW), has been repeatedly investigated during the past 25 years by the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA). The present work aims at an integrated radioenvironmental approach leading to the dose assessment to the public and to the plants staff. This approach includes systematic sampling of lignite and barren at the local lignite mines feeding the power plants and sampling of lignite, fly-ash and bottom ash at the power plants for the determination of the activity of the natural radionuclides 226Ra, 232Th, 40K, 234Th and 210Pb. Furthermore, the following measurements and samplings were conducted in 25 selected sites within 10km around the power plants: soil sampling for the determination of the above radionuclides, radon concentration and exhalation rate measurements, soil gas radon concentration measurements, dose measurements and calculations, determination of air-particulate matter concentration etc. The results obtained allowed for the mapping of the parameters studied which lead to useful conclusions. Dosimetric calculations for the population living around the power plants and the plants staff were also performed, based on the suggestions of [UNSCEAR, 1982].

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    Radon in the Living Environment,
    Athens, 19­23 April 1999

    THE EFFECT OF HUMIDITY ON THE RADON COUNTING EFFICIENCY OF INTEGRATED INSTRUMENTS


    N.P.Petropoulos, E.P.Hinis, S.E.Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780, Greece



    Abstract


    Four commercially available integrated radon concentration measurement instruments, produced by the same manufacturer in the period between 1996 to 1998, have been tested to study the effect of absolute humidity on the radon counting efficiency. All four devices use high efficiency dRAM cells semiconductor sensor chips for alpha particle detection. The chips are located inside a measurement chamber, which is separated from the ambient air by a filter. Ambient air is continuously or quasi-continuously pumped through this filter into the chamber, in order to prevent the input of radon decay products and other solid isotopes along with the incoming air stream. Any radon inside the chamber decays to 218Po, which becomes positively charged by ionisation effects. The 218Po progeny is being forced to the chip detectors by a high voltage electrical field. The alpha particles emitted by 218Po penetrate the detector and they are registered as electrical pulses. Single channel analysis processing ensures that pulses of different heights, due to other radon and/or thoron daughters present, are not registered. It is known that absolute humidity highly affects the charged fraction of the radon progeny; therefore, a humidity effect on the radon counting efficiency of such instruments is reasonably expected. Simultaneous tests for all four instruments were performed in the Radon Calibration Facility of our Laboratory (8.5 m3 air tight chamber) within a relative humidity (φ ) range between 30 to 90% at 20-25 ° C, with radon concentrations between 0.35 to 4.53 kBqm-3 . No significant differences between the indications of the humidity sensors of the Facility (external) and the radon instruments (internal) were observed. However, the internal sensors registered temperatures about 2-4 °C higher than the external. The absolute humidity (ω ) is evaluated by assuming steam as an ideal gas by the formula : ω = φ (18 pg)/(29pair), where φ is the relative humidity, pg the saturation pressure of the steam at the prevailing temperature and pair the ambient pressure. It is apparent that the absolute humidity has to be calculated using environmental values indicated by the instruments internal sensors when available. Figure 1 presents the humidity effect on the radon counting efficiency for one of the instruments tested. Such graphs were also plotted for each of the other three instruments. It is concluded that there seems to exist a linear correlation between absolute humidity and radon counting efficiency with a 0.7 correlation coefficient in the range experimented. However, it is believed that for an absolute humidity range wider than the one examined, the radon counting efficiency is dependent rather on the square of the absolute humidity.

    Instrument CF = A0 + A1 ω2 Correlation
    coefficient
    Residual
    mean square
    (%)
    A0 A1
    INSTR-1 2.40 0.69 0.65 18
    INSTR-2 1.62 0.63 0.71 20
    INSTR-3 1.45 -0.29 0.66 24
    INSTR-4 0.72 0.20 0.66 17
    Table 1: Calibration Factors (CF) of the instruments examined


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    Radon in the Living Environment,
    Athens, 19­23 April 1999

    BUILDING MATERIALS PHOTON ATTENUATION, NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATE


    N.P.Petropoulos, M.J. Anagnostakis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780, Greece

    Abstract




    High concentrations of natural radionuclides in building materials result in high dose rate indoors due to radon and thoron exhalation and the γ-rays emitted from them. Among the natural radionuclides contained in building materials, most attention has been given to 226Ra due to 222Rn exhalation and the subsequent internal exposure. In external dose calculations due to building materials it is usually assumed that there exists radioactive equilibrium among the radionuclides of both the uranium and thorium series. In the case of the radionuclides of the uranium series it is assumed that there exists radioactive equilibrium among the long lived radionuclides 238U, 226Ra and 210Pb. The above assumption is seldom checked mainly because of the difficulties in the γ-spectroscopic determination of 238U and 210Pb which is possible only by using low-energy photons, where intense self-absorption of the photons inside the sample exists. In this case the count-rate during a γ-spectroscopic analysis is highly affected by the intense self-absorption of the photons. For the determination of radionuclides emitting low-energy photons a method has been developed which needs as input among others the linear attenuation coefficient μ for the analysed material. This paper presents:
    1. Correlations in the form μ=f( ρ , E ) developed for the estimation of the linear attenuation coefficient μ(cm-1 ) as a function of the material packing density ρ (grcm-3 ) and the photon energy E (keV) for several materials of environmental importance, such as building materials.
    2. Gamma-spectroscopic analysis techniques used for the determination of 238U, 226Ra, 210Pb, 232Th and 40K in environmental samples, together with the results obtained from the analysis of building materials used in Greece and industrial by-products used for the production of building materials. Among the techniques reported one is based on the direct determination of 226Ra and 235U from the analysis of the multiplet photopeak at ~186keV.
    3. Results from radon exhalation measurements of building materials such as cement and fly-ash and building structures conducted in the radon chambers in our Laboratory.


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    Radon in the Living Environment,
    Athens, 19­23 April 1999

    BUILDING MATERIALS RADON EXHALATION RATE: ERRICCA INTERCOMPARISON EXERCISE RESULTS


    N.P. Petropoulos, M.J. Anagnostakis, and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780 Athens, Greece

    Abstract




    The Nuclear Engineering Section of the National Technical University of Athens undertook the organisation of a European building material radon exhalation rate intercomparison exercise in the framework of the European Research into Radon In Construction Concerted Action (ERRICCA). The intercomparison started in June 1998 and it was concluded in February 1999. Twenty participants from 13 countries took part. The exercise focused on the radon exhalation rate determination from a concrete slab, specially constructed to produce radon surface flux well below 10 mBqm-2s-1 . This paper describes the measurement results obtained using different instruments and methods in order to assess the "state-of-the-art" of low-level radon exhalation measurements, being performed around Europe. Results are compared to each other and they provide an indication of the collective precision of such measurements for low exhalation rates. The agreement, with a few exceptions, is satisfactorily good.

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    The Science of the Total Environment, Vol. 272, pp. 261-272, 2001

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS LIGNITE FIELD BASIN


    P.K. Rouni, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    The Megalopolis lignite field basin in southern Greece, with Megalopolis-A and B  lignite-fired power plants in operation (total 900 MW), has been repeatedly investigated during the past 25 years by the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA). The present work aims at an integrated radioenvironmental approach leading to the dose assessment to the public and to the plants staff. This approach includes systematic sampling of lignite and barren at the local lignite mines feeding the power plants and sampling of lignite, fly-ash and bottom ash at the power plants for the determination of the activity of the natural radionuclides 226Ra, 232Th, 40K, 234Th and 210Pb. Furthermore, the following measurements and samplings were conducted in 25 selected sites within 10km around the power plants: soil sampling for the determination of the above radionuclides, radon concentration and exhalation rate measurements, soil gas radon concentration measurements, dose measurements and calculations, determination of air-particulate matter concentration etc. The results obtained allowed for the mapping of the parameters studied which lead to useful conclusions. Dosimetric calculations for the population living around the power plants and the plants staff were also performed, based on the suggestions of [UNSCEAR, 1982].

     



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    Third International Symposium on Naturally Occuring Radioactive Materials
    Brussels 17-21 September 2001

    TECHNOLOGICALLY ENHANCED NATURAL RADIOACTIVITY OF FLY-ASH PRODUCED IN LIGNITE-FIRED POWER PLANTS AND THE ASSOCIATED RADIOLOGICAL IMPACT

    D.J. Karangelos, P.K.Rouni, N.P.Petropoulos, M.J. Anagnostakis, E.P.Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Coal- and lignite-fired power plants produce significant amounts of ashes, which are quite often being used as additives in cement and other building materials. In many cases coal and lignite present high concentrations of naturally occurring radionuclides, such as 238U, 226Ra, 210Pb, 232Th and 40K. Moreover, during the combustion process the produced ashes are highly enriched in the above radionuclides, thus characterized as Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM). The most important naturally occurring radionuclide in such power plant ashes is 226Ra, since it produces radon, which when exhaled contributes significantly to the dose received by workers and the public. An extensive research project for the determination of the natural radioactivity of lignite and ashes from Greek lignite-fired power plants is in progress in the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) since 1983. From the results obtained so far it may be concluded that 226Ra radioactivity of fly-ash may, in some cases, exceed the 1kBqkg-1 level, which is high compared to the mean 226Ra radioactivity of surface soils in Greece (25Bqkg-1). Furthermore, the radioactivity of 210Pb in fly-ash may reach the value of up to 4kBkg-1, depending on the sampling location inside the power plant. This paper presents: natural radioactivity results from the analysis of the lignite fed to and the ashes produced in Greek lignite-fired power plants, enrichment factors of natural radionuclides in the ashes and radon exhalation measurements from fly-ash collected at different stages along the emission control system. Enrichment factor results are being interpreted in relation to the physical properties of the investigated nuclides and the temperature and flow parameters in the flue gas pathway. Discarded ash deposition fields in the vicinity of the power plants are also investigated in terms of surface soil radon exhalation and soil gas radon concentration.

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    Archive of Oncology 2001;9(4):231-6

    DETERMINATION OF DEPLETED URANIUM IN ENVIRONMENTAL SAMPLES BY GAMMA-SPECTROSCOPIC TECHNIQUES

    M.J. Anagnostakis, E.P. Hinis, D.J. Karangelos, N.P. Petropoulos, P.K. Rouni, S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "VINCA", Belgrade, Yugoslavia

    Abstract


    The use of depleted uranium (DU) in military operations causes the contamination of the target area due to DU dispersion in the environment. Since the isotopic abundance of uranium in DU is different than that in nature, the only evidence of DU contamination is the disruption of the natural isotopic abundance of 238U and 235U. For the investigation of the existence of such a disruption, the accurate determination of 235U and 238U is necessary. The Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) uses high-resolution LEGe detectors and especially developed gamma spectroscopic analysis techniques for the determination of 238U, 235U and subsequently for the isotopic abundance of the uranium isotopes in the sample. Uranium 235 is determined from the analysis of the multiplet photopeak at 186 keV. DU may be detected with this technique provided that the 238U activity of the DU is higher than ~20% of that of 238U in the natural uranium of the sample. The analyses by NES-NTUA of surface soil samples collected well before the dispersion of depleted uranium in Kosovo, made evident that Kosovo is an area of high natural background, with a pronounced surface soil variation in natural uranium content, and 238U activity reaching values as high as 330 Bq kg-1. It was also observed that disturbance of radioactive equilibrium among the nuclides of the uranium series is quite often observed due to leaching and weathering, with the ratio of the activities of 238U and 226Ra ranging from 0.17 to 5.5. After the military operations in Kosovo, surface soil and vegetation samples as well as DU penetrators were analysed in NES-NTUA. Among the soil samples analysed it was found that some of those collected around a DU penetrator crater were contaminated by DU, with 238U activity exceeding 2 kBqkg-1, and ratio of 238U/226Ra exceeding the value of 10. In these soil samples, the natural isotopic abundance of the uranium isotopes was significantly disrupted; this allowed for an estimation of the isotopic abundance of 235U in the dispersed DU of about 0.2%, which agrees very well with relevant values found in the literature for DU penetrators. DU in the vegetation samples analysed was below detection limit. The analysis of DU penetrators led to the detection 238U, 235U and their daughters, and to an estimation of the dose-rate due to the gamma-rays emitted from the penetrator, which reached 6.5 μSvh-1 on the surface, sloping to background at the distance of about 40 cm.

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    Kerntechnik 68 (2001) 1-2

    EXPERIMENTAL INVESTIGATION OF THE REWETTING PROCESS AT PRESSURES OF 1-7 BAR

    E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract



    Several water experiments have been carried out to investigate the physical mechanisms relevant to the rewetting phenomena either at atmospheric conditions or in a steam environment. Yet, there seems to be a scarcity of experimental data for the low pressure range from 2 to 7 bar with parameters the liquid film flowrate and the subcooling. An experimental facility to simulate two-phase low-pressure water flow phenomena has been designed, constructed and employed to investigate the rewetting process of hot surfaces in a water-steam environment at pressures in the above range, as well as at atmospheric conditions; the facility is on-line interfaced to computers which control its operation and undertake all the data acquisition tasks. Furthermore, a numerical method to experimentally evaluate the wet front position along the rod was introduced. The present paper describes the experimental work aimed at studying the wet front propagation along a stainless steel fuel rod, in a top-flooding environment in the pressure range 1-7 bar, wall temperatures up to 550°C and at a liquid flowrate of 10-3m3min-1 at both saturated steam conditions and in atmospheric environment with water subcooling in the range 0-75K. The experimental results fitted well to an existing dimensionless rewetting correlation, together with world available vapour environment rewetting data extending its validity down to the pressure of 1 bar. Furthermore, the effect of the inlet water subcooling was introduced in to this correlation.

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    CCMS Workshop: "Risk Assesment of Chernobyl Accident Consequences"
    Kiev, 9-12 April 2002

    GEOGRAPHICAL MAPPING AND ASSOCIATED FRACTAL ANALYSIS OF THE LONG-LIVED CHERNOBYL FALLOUT RADIONUCLIDES IN GREECE

    N.P.Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Immediately after the Chernobyl accident, a soil-sampling programme was undertaken in order to detect and quantitatively analyse the long-lived radionuclides in the Chernobyl fallout. Soil samples (1242 in number) of 1 cm thick surface soil were collected in Greece, during the period from May-November 1986. The samples were counted and analysed using Ge detector set-ups. In an attempt to proceed to the mapping of the long-lived radionuclides detected, an in-house Unix-based Data Base/geographical information system (DBGIS) was developed. Prior to mapping multifractal analyses of the deposition pattern for each radionuclide detected were performed. In the present work an analysis of the results of the deposition of 137Cs, 134Cs, 144Ce, 141Ce, 125Sb, 110mAg, 106Ru, Ru, 95Zr and 54Mn are presented, together with relevant fractal analyses and the respective contour maps. The maximum detected values of the above mentioned radionuclides were 149±0.1, 76.1±0.1, 32.9±0.2, 46±2, 4.56±0.02, 7.98±0.02, 79.1±0.4, 337±2, 20.1±0.2 and 3.02±0.02 kBm-2, respectively. Furthermore, a statistical technique to compare contour maps was introduced and applied, to explain the differences, which appeared in the maps of the above-mentioned nuclides.

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    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    RADIOENVIRONMENTAL SURVEY OF THE MEGALOPOLIS POWER PLANTS FLY-ASH DEPOSITS


    D.J. Karangelos, P.K. Rouni, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


     

    The Megalopolis lignite field basin is located in the centre of the Peloponese peninsula in southern Greece. Two lignite-fired power plants are in operation in this region: Megalopolis-A (600MW – 3 units) since the early 70's and Megalopolis-B (300MW – 1 unit) since the early 90's. An extensive research project for the determination of the natural radioactivity of lignite and ashes from the Megalopolis power plants started in the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) in 1983. The project has evolved to an integrated radioenvironmental survey of the Megalopolis lignite field basin area. The present work aims at the presentation of the radioenvironmental survey of the fly-ash deposits in the vicinity of the power plants. The power plants produce over 2 million metric tonns of fly-ash annually, which is primarily disposed off in deposits located mainly at exhausted lignite mines. These deposits are in the form of ash layers several meters thick, which are then covered by a layer of soil. The disposed fly-ash has a 226Ra content which sometimes exceeds 1 kBqkg-1, which is very high compared to the mean 226Ra radioactivity of surface soils in Greece (25 Bqkg-1). Results regarding (a) γ-dose rate, (b) radon concentration in the ambient air, (c) soil radon exhalation rate and (d) soil gas radon concentration are reported from systematic field measurements at three deposit sites. Repeated measurements under various environmental conditions have been carried out, in order to estimate the variability of the radon related quantities. In addition, soil sampling of the surface and 0-80 cm layer has been conducted at the deposits to allow for the determination of the activity of natural radionuclides, namely 226Ra, 232Th, 40K, 234Th and 210Pb. The radiological characterization of the fly-ash deposits obtained through these results is compared to the natural radioactivity background in the wider Megalopolis area, using additional results of a previous similar survey by NES-NTUA [1]. It can be concluded that, from the radiological point of view, the Megalopolis fly-ash deposits do not differ significantly from the rest of the Megalopolis lignite field basin, despite the fact that most of the underground soil layers consist of fly-ash with high 226Ra content. A possible explanation for this might be that radon emanation from the fly-ash layer is as low as radon emanation from natural soil due to fly-ash crystallization process in the power plant furnace. This explanation is currently under experimental investigation in the NES-NTUA Laboratory. Furthermore, the comparison of results from different aged deposition fields concludes that aging and restoration processes in the deposition fields, such as tree cultivation and agriculture have a positive effect to radon related radiological parameters.

     

    [1] P.K.Rouni, N.P.Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E.Simopoulos, "Radioenvironmental survey of the Megalopolis lignite field basin", The Science of the Total Environment, 272(2001); 261-272.






    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    DISTURBANCE OF RADIOACTIVE EQUILIBRIUM IN THE ASHES PRODUCED IN LIGNITE FIRED POWER PLANTS


    D.J. Karangelos, N.P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Coal- and lignite-fired power plants produce significant amounts of ashes, which are quite often being used as additives in cement and other building materials. In many cases, coal and lignite present high concentrations of naturally occurring radionuclides, such as 238U, 226Ra, 210Pb, 232Th and 40K. Moreover, during the combustion process the produced ashes are enriched in the above radionuclides, thus characterized as Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM). The most important naturally occurring radionuclide in such power plant ashes is 226Ra, since it produces radon, which when exhaled contributes significantly to the dose received by workers and the public. An extensive research project for the determination of the natural radioactivity of lignite and ashes from Greek lignite-fired power plants is in progress in the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) since 1983. From the results obtained so far, it may be concluded that 226Ra radioactivity of fly-ash in some cases exceeds 1kBqkg-1, which is very high compared to the mean 226Ra radioactivity of surface soils in Greece (25Bqkg-1). Furthermore, the radioactivity of 210Pb in fly-ash may reach the value of up to 4kBqkg‑1, depending on the sampling location inside the power plant. This paper presents: natural radioactivity results from the analysis of the lignite fed to and the ashes produced in Greek lignite-fired power plants, and enrichment ratios of natural radionuclides in the ashes collected at different stages along the emission control system of the power plant. Enrichment ratio results are being interpreted in relation to the physical properties of the investigated nuclides and the temperature in the flue gas pathway. The different enrichment of the various nuclides of uranium series along emission control system, results to a disturbance of their radioactive equilibrium, which is more pronounced towards the end of the flue gas pathway. Furthermore, the fly-ash collected in several points along the emission control system of the power plant was investigated, in terms of radon exhalation rate.




    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    URANIUM-238 AND ITS DAUGHTER PRODUCTS IN GREEK SURFACE SOILS


    M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    High concentrations of natural radionuclides in the soil can result in high dose rates outdoors mainly due to external exposure. In dose calculations, the main radionuclides of interest are 226Ra, 232Th and 40K. Research till recent years has focused mainly into the evaluation of 226Ra concentration, due to radon exhalation from the ground, and due to its relatively simple determination through its gamma emitting decay products. Other radionuclides of the uranium series such as 238U and 210Pb, emitting low energy photons are not usually determined due to γ-spectroscopic difficulties, and for dosimetric calculations an assumption of radioactive equilibrium among the nuclides of the uranium (238U) series as well as the nuclides of the thorium (232Th) series is usually adopted. Among the nuclides of the uranium series, radioactive disequilibrium may exist, and this is the case of the relatively long-lived nuclides 238U (T½ = 4.47 109y), 226Ra (T½ = 1600y) and 210Pb (T½ = 22.2y) for several reasons, such as leaching, rock weathering, radon exhalation from the ground etc. Radioactive equilibrium may also be disturbed because of human activities, such as the existence of coal fired power plants and the resulting fly-ash fallout. An extensive research has been undertaken by the Nuclear Engineering Laboratory of the National Technical University of Athens (NES-NTUA) for the investigation of the natural and artificial radioactivity in greek surface soils. This research has resulted to the mapping of 226Ra, 232Th and 40K in greek surface soils, as well as the mapping of radionuclides of the Chernobyl fallout in Greece. The gamma spectroscopic determination of 238U and 210Pb, which emit low energy photons of 63.29keV and 46.5keV respectively, with very low yields, requires the use of detectors with high efficiency in the low region below 200keV, such as LEGe or XtRa detectors, and special techniques for self-absorption corrections inside the samples. Due to the time consuming and difficult determination of the low activities of 238U and 210Pb in environmental samples such as soil, only recently such results are found in the literature. In the framework of this research soil samples from allover Greece are analysed for 238U, 226Ra and 210Pb. From the samples analysed so far, the conclusion may be drawn that, when 226Ra concentration is much lower than about 25Bqkg-1, which is incidentally the mean value for 226Ra of greek surface soils, radioactive equilibrium is significantly disturbed, and the ratio 226Ra/238U may be as low as 0.3. In the case where 226Ra activity is much higher than 25Bqkg-1, radioactive equilibrium is again significantly disturbed with the ratio 226Ra/238U reaching values as much as 4. The above findings indicate that extreme values of 226Ra in surface soils may be the result of 226Ra leaching. This research is currently focused on the mapping of uranium at surface soils in specific locations in Greece, and on the investigation of its association with that of 226Ra. Concerning the concentration of 210Pb in surface soils, the analyses performed show that is was almost always higher than that of 226Ra, probably due to radon exhalation from the ground. Analyses of soil samples from deeper soil layers are also performed, in order to investigate the vertical profile of the radionuclides under study.




    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    SURVEY OF DEPLETED URANIUM CONTAMINATION IN SOIL AND VEGETATION USING γ-SPECTROSCOPY


    Z.S. Zunic
    Radiation Medicine Department, Institute of Nuclear Sciences "Vinca", PO Box 522, 11001 Belgrade, Yugoslavia
    D.J. Karangelos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept. National Technical University of Athens, 15780 Athens, Greece

    Abstract


    The use of depleted uranium (DU) in military operations results to contamination of the target area due to DU dispersion in the environment. Since uranium isotopes are naturally occurring radionuclides, DU is characterized as Technologically Enhanced Naturally Occurring Radioactive Material (TENORM). The determination of DU contamination in environmental samples is a difficult task because the isotopes of uranium 238U and 235U that exist in DU also exist in natural uranium, which is detected in almost all environmental samples as trace element. Since the isotopic abundance in DU is different from that in nature, the only evidence that environmental samples are contaminated by DU is the disruption of the natural isotopic abundance of 235U and 238U in the analysed sample. For the investigation of the existence of such disruption, the accurate quantitative determination of 235U and 238U is necessary. Because of the extremely long half-lives of the uranium isotopes and the low energy photons that they emit, their determination by gamma-spectroscopy requires the use of special detectors and techniques. The Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) uses high-resolution LEGe detectors and especially developed gamma spectroscopic analysis techniques for the determination of 235U and 238U and subsequently for the isotopic abundance of the uranium isotopes in the sample. The analysis of the multiplet photopeak at 186keV with the LEGe detector, leads -through its two components- to the determination of 235U. Since 235U and 238U already exist in the natural sample prior to contamination, DU may be detected with this technique if 238U in the DU is higher than the 1/5 of the 238U in the natural uranium in the sample. This technique is relatively easy to apply, compared to those that involve radiochemical analysis and it may be used for screening purposes and for mapping in DU target areas. From the analysis of surface soil samples from allover Greece and from areas of Kosovo, collected well before the dispersion of depleted uranium in the area, which have been performed in NES-NTUA it has become evident that the Kosovo area is a natural high background area with a pronounced surface soil variation in natural uranium content, and 238U activity reaching values as high as 360Bqkg-1. It was also observed that disturbance of radioactive equilibrium among the nuclides of the uranium series is quite often observed due to leaching and weathering, with the ratio of the activities of 238U and 226Ra ranging from 0.17 to 3.4. After the military operations in Kosovo, environmental samples from a DU target area were collected and analysed in NES-NTUA. The surface soil samples were collected in and around a DU penetrator crater, in a systematic way, to allow for DU contamination mapping. Samples were also collected and analysed from deeper soil layer to allow the investigation of DU vertical migration and from vegetation. Preliminary results from the analyses performed so far show that a few of the analysed soil samples were found contaminated by DU, with 238U activity exceeding by far 1kBq, and ratio of 238U/226Ra exceeding the value of 10. In these contaminated soil samples, the natural isotopic abundance of the uranium isotopes was significantly disrupted, and allowed for an estimation of the isotopic abundance of 235U about 0.2% which agrees very well with relevant values found in the literature for DU penetrators. Vegetation samples imported from Yugoslavia as well as other Balcan countries to Greece, were also analysed by gamma spectroscopy, but their content in DU was below the detection limit of 1Bqkg-1 for 238U.




    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    DATA LEADING TO THE INVESTIGATION OF A RELATION BETWEEN SEISMIC ACTIVITY AND RADON DAUGHTERS CONCENTRATION OUTDOORS


    D.J. Karangelos, N. P. Petropoulos, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    The continuous monitoring of radon daughters concentration outdoors has been a part of the Athens area environmental radioactivity monitoring program of the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) since the mid '80s. The monitoring system consists of a Sodium-Iodide (NaI) detector and appropriate electronics including a spectrum stabilizer suitable to compensate for spectrum shifts mainly due to large temperature variations. The radon daughter photons to be monitored are mainly those of 214Pb (352 keV) and 214Bi (609 keV). Both single channel analysis in regular time intervals and a spectrum collection over 24 hr intervals through a multi channel analyzer are employed. Data acquisition is computer driven and fully automated. Through this 15-year long operation of the system, observations were made that the radon daughters concentration outdoors was significantly increased for a time window of 5 to 8 days before a seismic event, probably due to precursory earth cracks. Furthermore, it has been heuristically concluded that (a) a radon daughters concentration increase has been detected before all earthquakes of magnitude >4.5R within a radius of 200 km from Athens (b) a radon daughters concentration increase has been detected before all earthquakes of magnitude >3.5R within a radius of 50 km from Athens and (c) no false positive increases have been detected so far. These heuristic conclusions suggested that an increase of radon daughters concentration outdoors might be an earthquake precursor for the area under study. Following this suggestion data collection was enhanced to record rainfall and total γ-background; both these parameters might indicate a probable false positive signal which has to be filtered out. Furthermore, adaptive control of sampling intervals was introduced so that every case of significant radon daughters concentration increase is represented with adequate statistics. This paper presents a first attempt for the analysis of such data. Data treatment involved mathematical methods for (a) subtracting the total γ-background from the signal (b) eliminating the rainfall effect on the signal and (c) discriminating the signal from noise. It was then attempted to correlate signal data with earthquake data such as magnitude and Athens to epicenter distance. The analysis results obtained indicate that this monitoring method gives a reliable indication for an earthquake within a reasonable time window. In addition, after establishing a proper monitoring network, the epicenter may be located with acceptable accuracy. A correlation between radon daughters concentration increases and earthquake magnitudes may be established after a network monitoring for a long time, despite the fact that experimental conditions towards this end are unpredictable and unfavorable. This precursory method may prove useful if combined with other similar tools. Research is under way to investigate whether excess radon daughters concentration is air transported from the epicenter site or it is due to increased soil radon exhalation at the monitoring station .




    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    REDUCING THE NATURAL RADIOACTIVITY BACKGROUND IN Ge DETECTOR SHIELDS


    A.Nikoglou, D.J. Karangelos, P.K.Rouni, M.J. Anagnostakis, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Gamma spectroscopy is a widely used technique for the qualitative and quantitative determination of gamma emitting radionuclides in a variety of samples. There are cases where the total activity of the radionuclides of interest in the analysed samples is extremely low. Typical such radionuclides are those of natural radioactivity in water samples, foodstuff, or even air-filters through which large volumes of air have been pumped for the determination of the radionuclides content in the air. Though Ge detectors used for such measurements of natural radionuclides are almost always equipped with very efficient detector shields, the existence of background radiation, due to the photons emitted from the environment outside the shield, the shield itself and the detector cryostat cannot be totally avoided or neglected. This background poses limitations to the lower limit of detection and the accuracy of the measurements performed, and should be minimized as possible. One important background contributor is the radon decay products, in and around the detector chamber, which is described as the interior of the detector shield. Among the radon daughters, the most important background contributors are 214Pb and 214Bi, which emit a total of five important photons with energies 295.22keV, 351.99keV, 609.32keV, 1120.28keV and 1764.51keV, which are often used for the 226Ra indirect determination. Besides the background fluctuations due to pure statistics, radon daughters concentration imply an additional background fluctuation. Gamma spectroscopy measurements in the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) are performed in the gamma spectroscopy laboratory, which is equipped with a wide variety of Ge detectors, the oldest being a 20 years old GeLi detector with 24% efficiency and the newest an XtRa detector with 107% efficiency. The laboratory has recently moved to the basement of a new building. From repeated and extensive background measurements in the new building, it was concluded that the detectors background was increased probably due to the building aging; furthermore unreasonable background fluctuations were experienced. Because of its high efficiency, the XtRa detector was subject to the most pronounced background changes. For this reason, a detailed investigation of the factors affecting the radon concentration inside the room and the detectors background was undertaken. The radon activity inside the room was monitored as a function of parameters such as ventilation and air conditioning inside the room, and it was found to vary from 40 Bqm-3 to as much as ~120Bqm-3, over a two years period. The best conditions for as low as possible radon concentration indoors were: no air-conditioning inside the room, natural ventilation through the open doors and the increase of the air circulation by using a shaft especially constructed for this purpose. Furthermore, an effort was undertaken to reduce the background due to the radon daughters inside the detectors chambers, using various techniques. Among them the most effective it proved to be:
    • nitrogen feed inside the chamber from the detector tank exhaust pipe, and
    • limiting the indoor air volume inside the chamber.
    The latter was accomplished with fitting inside the chamber a light aluminium construction, made from a very thin aluminium foil of high purity, which was filled with nitrogen. This construction almost completely fills the XtRa detector chamber, leaving space only for the samples to be analysed, thus significantly reducing radon environment inside the chamber. From the results obtained so far, it was concluded that this was the most efficient way to reduce the background, with a reduction factor of about 0.7, and almost vanishing the background fluctuations.




    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    ASSOCIATION OF THE CHERNOBYL FALLOUT ISOTOPES PATTERNS WITH THOSE OF RAINFALL IN GREECE


    M. Michelaraki
    Department of Climatology, Hellenic National Meteorological Service166 03 Athens, Greece
    P.F. Vrantzas, N.P.Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    A wide soil-sampling programme was undertaken right after the Chernobyl accident in Greece by the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA), in order to detect and quantitatively analyse the long-lived radionuclides in the Chernobyl fallout. Samples (1242) of 1cm thick surface soil were collected[1] all over Greece during the period from May to November 1986. The samples were counted and analysed using Ge detector set-ups. An in-house unix-based data base/geographical information system was developed for the detailed mapping of the ten radionuclides 137Cs, 134Cs, 144Ce, 141Ce 125Sb, 106Ru, 103Ru, 95Zr, 110mAg and 54Mn mainly deposited in Greece. Multi-fractal analysis has also been performed. This analysis has already been published ([2],[3]) and showed that there exist differences in the spatial distribution of the above radionuclides. These differences are primarily attributed to different deposition pathways and mechanisms and different arrival dates. In the present work, a statistical technique to compare contour maps is introduced and applied to explain the differences,in the fallout patterns of the above-mentioned radionuclides. As a result of this analysis, it was made clear that there are two main subsets of radionuclides (a): 137Cs, 134Cs, 144Ce, 141Ce 125Sb, 106Ru, 103Ru and 95Zr, and (b):110mAg and 54Mn, deposited in distinct ways. Furthermore, the weekly rainfall during the period from April 26th to May 30th was mapped. Multifractal analysis of the rainfall patterns has also been performed. The above two radionuclide subsets, were compared with the rainfall patterns using an introduced statistical technique. As a result, the pattern overlapping ratio was calculated and it was concluded that the 137Cs subset was deposited during the week May 3rd - 9th, 1986, while the 110mAg subset was deposited during the following week May 10th -16th, 1986.
    References
    1. Simopoulos, S.E. (1989). Soil sampling and 137Cs analysis of the Chernobyl fallout in Greece. International Journal of Radiation Applied Instrumentation, Part A: Applied Radiation Isotopes, 40, 607-613.
    2. Petropoulos, N.P., Hinis, E.P., & Simopoulos, S.E. (1996). 137Cs fallout in Greece and its associated radiological impact. Environment International, 22(Suppl. 1), 369-373.
    3. Petropoulos, N.P., Anagnostakis, M.J., Hinis, E.P. and Simopoulos, S.E. (2001). Geographical mapping and associated fractal analysis of the long-lived Chernobyl fallout radionuclides in Greece, Journal of Environmental Radioactivity, 53 (2001), 59-66.





    NRE VII, International Symposium
    May 20-24, 2002, Rhodes, Greece

    RADON-IN-WATER SECONDARY STANDARD PREPARATION


    D.J. Karangelos, N. P. Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Radon-in-water standard solutions are required for the calibration and quality control of instruments measuring Radon concentration in water samples. However, due to the short half-life of Radon, such standards are not widely available.This work presents a method developed at the NES-NTUA to generate Radon-in-water solutions of known concentration that can easily be applied in a laboratory with access to a Radon-in-air calibration facility. Air with the appropriate concentration of Radon is bubbled through deionized distilled water, giving a solution with the desired Radon concentration, as predicted by published Radon solubility data. Operating parameters have been suitably chosen so that volumes in the order of liters can be generated, with concentrations from less than 1 Bq/lt up to some tens of Bq/liter, depending on the Radon source used. The entire process takes less than 30 minutes, excluding the time for the original build-up of Radon in the reference Radon chamber.A series of experiments conducted to validate the method is presented, where the samples produced were measured using active instrumentation coupled to a Radon bubbler. The concentrations tested ranged from 3 to 17 Bq/lt. Performance in terms of precision and accuracy was found to be adequate. An example is also given, with this method applied to check the calibration of a Radon-in-water measuring apparatus based on a gas-transfer membrane.The method has been proven to be accurate enough for the solution produced to be usable as a secondary standard, traceable to within 10% of the calibration of the original Radon source. This fact, as well as other attractive features such as low running cost and ease of use, makes it appropriate for purposes such as quality control, intercalibration of instruments and laboratory intercomparison.




    Industry Technology Environment International Conference
    Moscow, 18-20 September 2002

    TECHNOLOGICALLY ENHANCED NATURAL RADIOACTIVITY OF FLY-ASH PRODUCED IN COAL BURNING POWER PLANTS AND THE ASSOCIATED RADIOLOGICAL IMPACT

    D.J. Karangelos, P.K.Rouni, N.P.Petropoulos, M.J. Anagnostakis, E.P.Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    Coal and lignite fired power plants produce significant amounts of ashes, which are quite often being used as additives in cement and other building materials. In many cases coal and lignite present high concentrations of naturally occurring radionuclides, such as 238U, 226Ra, 210Pb, 232Th and 40K. Moreover, during the combustion process the produced ashes are highly enriched in the above radionuclides, thus characterized as Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM). The most important naturally occurring radionuclide in such power plant ashes is 226Ra, since it produces radon, which when exhaled contributes significantly to the dose received by the workers and the public. An extensive research project for the determination of the natural radioactivity of lignite and ashes from Greek lignite fired power plants is in progress in the Nuclear Engineering Section of the National Technical University of Athens (NES-NTUA) since 1983. From the results obtained so far it may be concluded that 226Ra radioactivity of fly-ash may, in some cases, exceeds the 1kBqkg-1 level, which is high compared to the mean 226Ra radioactivity of surface soils in Greece, which is 25Bqkg-1. Furthermore, the radioactivity of the volatile 210Pb in the fly-ash may reach the value of up to 4kBkg-1, depending on the sampling location inside the power plant. The enrichment factor depends upon the specific nuclide physical properties as well as on other factors. In this paper it will be presented: natural radioactivity results from the analysis of the lignite's feeding and the ashes produced in greek lignite-burning power plants, enrichment factors of natural radionuclides in the ashes and radon exhalation measurements from fly-ash collected at different stages along the emission control system of the power plants. Similar results will be presented for building materials fabricated using fly-ash. Finally, an estimation of the radiological consequences due to the fly-ash releases in the vicinity of a lignite-burning power plant, and the use of fly-ash in building materials production will be presented.

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    First Workshop on Natural Radionuclides in Hydrology and Hydrogeology
    Luxembourg, 4-7 September 2002

    RADON-IN-WATER SECONDARY STANDARD PREPARATION IN A WIDE ACTIVITY CONCENTRATION RANGE

    D.J. Karangelos, N.P. Petropoulos, E.P. Hinis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    This work presents a method developed at the NES-NTUA to generate radon-in-water solutions of known concentration that can easily be applied in a laboratory with access to a Radon-in-air calibration facility. The method has been proven to be accurate enough for the solution produced to be usable as a secondary standard, traceable to within 10% of the calibration of the original Radon source. This fact, as well as other attractive features such as low running cost and ease of use, makes it appropriate for purposes such as quality control, intercalibration of instruments and laboratory intercomparison.

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    Journal of Environmental Radioactivity 61:257-269, 2002

    PHOTON ATTENUATION, NATURAL RADIOACTIVITY CONTENT AND RADON EXHALATION RATE OF BUILDING MATERIALS

    N.P. Petropoulos, M.J. Anagnostakis and S.E. Simopoulos
    Nuclear Engineering Section, Mechanical Engineering Dept., National Technical University of Athens, 15780 Athens, Greece

    Abstract


    High concentrations of natural radionuclides in building materials can result in high dose rates indoors, from both internal and external exposure. In dose calculations, the main radionuclides of interest are 226Ra, 232Th and 40K. Usually much attention is paid to 226Ra due to Rn-222 exhalation and the subsequent internal exposure. Other radionuclides of the uranium series such as 238U and 210Pb, emitting low energy photons are not usually determined and an assumption of radioactive equilibrium is made. The above assumption is seldom checked mainly because of the difficulties in the γ-spectroscopic analysis of low energy photons. For the determination of radionuclides emitting low-energy photons, in samples like building materials where intense self-absorption of the photons exists, a method for self-absorption correction has been developed. The method needs as input the linear attenuation coefficient μ for the material under analysis. This paper presents:

    1. Correlations in the form μ=f(ρ,E) developed for the estimation of the linear attenuation coefficient μ (cm-1), as a function of the material packing density (g cm-3) and the photon energy E (keV), for building materials as well as other materials of environmental importance.
    2. Gamma-spectroscopic analysis techniques used for the determination of 238U, 226Ra, 210Pb, 232Th and 40K in environmental samples, together with the results obtained from the analysis of building materials used in Greece, and industrial by-products used for the production of building materials. Among the techniques used, one is based on the direct determination of 226Ra and 235U from the analysis of the multiplet photopeak at ~186 keV.
    3. Results from radon exhalation measurements of building materials such as cement and fly-ash and building structures conducted in the radon chambers in our Laboratory.


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