Radioactive Fallout in Norway from the Chernobyl Accident
Total Page:16
File Type:pdf, Size:1020Kb
NO94 00041 NRPA Report 1994:2 Radioactive fallout in Norway from the Chernobyl accident Studies on the behaviour of radiocaesiums in the environment and possible health impacts Per Strand Statens ' strålevernsir mvciiian Radiation Protection Authoritv Postboks 55 • X-1 345 Østerås • Norwav NRPA Report 1994:2 Radioactive fallout in Norway from the Chernobyl accident Studies on the behaviour of radiocaesiums in the environment and possible health impacts Per Strand Strand P. Radioactive fallout in Norway from the Chernobyl accident. Studies on the behaviour of ladiocacshm» in the environment and possible health impacts. NRPA Report 1994:2. Østerås: Norwegian Radiation Protection Authority, 1994. Keywords: Chernobyl accident. Long term behaviour of tadiocacsium. External and internal doses. Countenncasures. Health effects. Abstract: The Chernobyl accident had considerable consequences for Norway. Except for the areas in the former USSR, around Chernobyl, Norway received fallout which gave amoung the highest contamination levels. The natural and semi- natural ecosystems will produce food products with high activity levels of radiocaesium for several rWrnini^m Cost-effective countermeasures were implemented, and they reduced the doses considerable, especially for critical groups. Doses received over the next 50 years will probably cause cancer in 500 persons. Strand P. Radioaktivt nedfall i Norge etter Tsjemobylulykken. Undersøkelse av radiocesiums oppførsel i miljøet og mulige helsekonsekvenscr. StrålevemRapport 1994:2. Østerås: Statens strålevern, 1994. Sprik: engelsk. Nøkitloid: Tsjemobylulykken. Overføring av radioceshim. Eksterne og interne doser. Mottiltak. Hclseeffekter. Bayme: Tsjemobylulykken medførte betydelige konsekvenser for Norge. Med unntak av områdene rundt Tsjernobyl i det tidligere Sovjetunionen, fikk Norge de mest forurensede landområdene. Utmarksområdene vil produsere nærings- midler med høyt radioaktivt innhold i mange tiår fremover. Det er gjennom ført tiltak som har vært meget kostnadseffektive og som har redusert stråle dosen til befolkningen betraktelig, spesielt blant kritiske grupper. Dosen mot tatt over de neste 50 år vil trolig forårsake kreft hos 500 personer i Norge. Head of project: Per Strand. Norwegian Radiation Protection Authority, P.O.Box 55, N-1345 Østerås, Norway. Erik-Anders Westerlund, Environmental Protection Department. 152 pages. Published 1994-01-01. Printed number 300 (94-01). Cover design: Graf, Oslo. Printed by: Griiner & Jebsen A/S, Østerås. Orden to: Norwegian Radiation Protection Authority, P.O.Box 55, N-1345 Østerås, Norway, telephone +47 67 14 41 90, fax +47 67 14 74 07. ISBN 82-7633-034-7 ISSN 0804-4910 2 PREFACE The present work was part of Norwegian Radiation Protection Authority's work on assessing the possible consequences in Norway caused by the Chernobyl accident. It was conducted in close cooperation with the Agricultural University of Norway. Field studies have been performed several places in Norway and involved cooparation with veterinaries, farmers, reindeer hunters, doctors, and agronomists among many. The study owes much to the Norwegian system LORAKON which operates nationwide for monitoring radioactivity in food and in the environment. I am deeply indebted to Dr. med Jon Reitan and Professor Knut Hove for their encouragement and support in all the aspect of my work on this thesis. I would also like to express my sincere thanks to Ms Lisbeth Brynildsen, Dr. ing. Ole Harbitz, Professor Brit Salbu and Ms Tone Selnæs for their collaboration and support. Many persons have given their contributions to the work presented in this thesis, and I wish to thank my colleagues at the Norwegian Radiation Protection Authority, especially Ms Anita A. Sørli, Professor Terje Strand, Mr Torolf Berthelsen, Mr Leiv Berteig, Ms Elin Bøe and Mr Erik-Anders Westerlund. Director Ole Harbitz and Director of Division Anders Westerlund made it possible for me to allocate time for finishing work. I want further to express my gratitude to Mr Tor Wang and Ms Anne Marie Helle with whom I have had a close collaboration with in the field work. A special thank to Ms Kari Thunem who has typed and retyped my manuscript several times without any complains. The research was financially supported by Ministry of Agricultural and the Norwegian Food Control Authority. Oslo, June 1993 Per Strand 3 CONTENTS PREFACE 2 SYNOPSIS OF INDIVIDUAL PAPERS 5 1. BACKGROUND 10 2. INTRODUCTION 11 2.1 Radioactive Fallout 11 2.1.1 Nuclear Weapons Tests 12 2.1.2 The Chernobyl Accident 13 2.2. Movement of Radioisotopes in the Environment 15 2.2.1 Radioisotopes'Behaviour in Soil and 15 Contamination of Plants 2.2.2 Uptake by Animals 16 2.2.3 Long Term Behaviour of Radiocaesium 17 in Semi-Natural Ecosystems 2.3 Countermeasures 17 2.3.1 Countermeasures for Reducing External Radiation 18 2.3.2 Countermeasures for Reducing Doses following Inhalation 18 2.3.3 Countermeasures Applied to the Food Chain 18 2.4 Estimations of Radiation Dose 19 2.5 Health Effects 21 2.5.1 Cancer 23 2.5.2 Genetical Effects 23 2.5.3 Correlation between Dose and Effects 24 3. AIMS OF THE STUDY 25 4. MATERIALS AND METHODS 26 4.1 Sampling 26 4.2 Measurements 26 4.2.1 Food and Environmental Samples 27 4.2.2 External Dose Measurements 27 4.2.3 Transfer Factors 27 4.2.4 Effective Ecological Half-Life 27 4.2.5 Measurements on People 28 4.3 Dietary Survey 28 4.4 Dose Calculations 28 4 4.5 Epidemiological Studies 28 5. RESULTS 30 5.1 Transfer of Radioactivity from Fallout to Man 30 5.1.1 Semi-Natural Ecosystem 31 5.1.2 Long Term Behaviour of Radiocaesium in Semi-Natural Ecosystems 32 5.2 Countermeasures and Cost-Benefit Analysis 34 5.3 Radiation Doses and Health Effects 35 6. GENERAL DISCUSSION 38 6.1 Behaviour of Radiocaesium in the Environment 38 6.1.1 Radiocaesium behaviour in Soil and Uptake to Plants 38 6.1.2 Uptake of Radiocaesium by Animals 40 6.1.3 Long Term Behaviour of Radiocaesium in Semi-Natural Ecosystems 41 6.2 Cost-Benefit Analyses of Countermeasures 43 6.2.1 Justification of Implementing Countermeasures 43 6.2.2 Optimizing 44 6.3 Dose Assessment and Possible Health Consequences 46 6.3.1 Dose Assessment 46 6.3.2 Possible Consequences for Health 48 7. CONCLUSION 51 REFERENCES 53 INDIVIDUAL PAPERS l-X 59 5 SYNOPSES OF INDIVIDUAL PAPERS This review is based on ten individual papers, which are summarized below. The papers will later be referred to by their Roman numerals. I Hove K, and Strand P: Predictions for the Duration of the Chernobyl Radiocaesium Problem in Non-Cultivated Areas Based on a Reassessment of the Behaviour of Fallout from Nuclear Weapons Tests. In: Flitton S, Katz EW (Eds): Environmental contamination following a major nuclear accident. IAEA-SM-306 1:215-223, Vienna 1990. Result from the 1960s, environmental studies on fallout from nuclear weapons tests indicated lengthy effective ecological half-lives for radiocaesium. Most Norwegian soils have a relatively low clay content and therefore the caesium remains available for plant uptake for many years. The effective ecological half-life for the soil-plant- sheep system was estimated to be about 20 years. The transfer of radiocaesium from the two types of fallout to lamb, goat milk, white cheese and fungi were of a similar order. II Selnæs T. D and Strand P.: Comparison of the uptake of Radiocaesium From Soil to Grass After Nuclear Weapons Tests and the Chernobyl Accident. The Analyst . 117, 493-496, 1992. In two selected sampling sites, the uptake of radiocaesium both from the nuclear weapons tests and the Chernobyl accident was studied. Soil profiles and vegetation samples were measured. For L17Cs from Chernobyl, 85 % was found in the upper 5 cm of soil while the l17Cs from nuclear weapons t.sts was more evenly distributed down the profile, about 55 % being found between 3 and 12 cm. The transfer factor from soil to plant was found to be 0.41 _+. 0.07 nrkg'1 for the weapons "7Cs, and 0.40 ±_ 0.22 nrkg'1 for Chernobyl L17Cs. There was no significant difference in the uptake of the two types of fallout. By comparison with samples taken on the same spot in the 1960s, it was shown that physical decay of ''"Cs and, to some extent the vertical transport of n'Cs in the soil, were the major factors in decreasing the activity levels in grass. Using the data from the years after the nuclear weapons tests and adding to the data from 1989, an effective ecological half-life of about 13 years was calculated for the soil-plant system. III Strand P, Brynildsen L. I., Harbitz O and Tveten U. Measures Introduced in Norway after the Chernobyl Accident. A cost-benefit analysis. In: Flitton S, Katz EW (Eds): Environmental contamination following a major nuclear accident. IAEA-SM-306 2:191-202, Vienna 1990. 6 Following the Chernobyl accident in l'W(>, radioactive fallout was deposited over large areas of Scandinavia and Central Europe. In Norway, the long term contamination was almost entirely due to radiocaesium and countermcasures were called for to limit the potential radiation dose to the population. The countermeasures employed were interdiction of certain foodstuffs, ploughing, and addition of chemicals to soils to reduce plant uptake, changing slaughter time, use of a caesium-binding chemical to reduce gut uptake by food animals, reducing activity levels in food animals by special feeding of the animal for a certain period of time depending on the activity level, and interdiction of food products. It were also aimed to reduce the intake of radioactivity to people by giving dietary advice. The cost of the countermeasures (including interdiction of food) was about NOK 185 million. NOK 50 million and NOK 60 million, in 1986, 1987 and 1988 respectively.