IAEA-BIOMASS-4 Testing of environmental transfer models using Chernobyl fallout data from the Iput River catchment area, Bryansk Region, Russian Federation Report of the Dose Reconstruction Working Group of BIOMASS Theme 2 Part of the IAEA Co-ordinated Research Project on Biosphere Modelling and Assessment (BIOMASS) April 2003 INTERNATIONAL ATOMIC ENERGY AGENCY The originating Section of this publication in the IAEA was: Waste Safety Section International Atomic Energy Agency Wagramer Strasse 5 P.O. Box 100 A-1400 Vienna, Austria TESTING OF ENVIRONMENTAL TRANSFER MODELS USING CHERNOBYL FALLOUT DATA FROM THE IPUT RIVER CATCHMENT AREA, BRYANSK REGION, RUSSIAN FEDERATION IAEA, VIENNA, 2003 IAEA-BIOMASS-4 ISBN 92–0–104003–2 © IAEA, 2003 Printed by the IAEA in Austria April 2003 FOREWORD The IAEA Programme on BIOsphere Modelling and ASSessment (BIOMASS) was launched in Vienna in October 1996. The programme was concerned with developing and improving capabilities to predict the transfer of radionuclides in the environment. The programme had three themes: Theme 1: Radioactive Waste Disposal. The objective was to develop the concept of a standard or reference biosphere for application to the assessment of the long term safety of repositories for radioactive waste. Under the general heading of “Reference Biospheres”, six Task Groups were established: Task Group 1: Principles for the Definition of Critical and Other Exposure Groups. Task Group 2: Principles for the Application of Data to Assessment Models. Task Group 3: Consideration of Alternative Assessment Contexts. Task Group 4: Biosphere System Identification and Justification. Task Group 5: Biosphere System Descriptions. Task Group 6: Model Development. Theme 2: Environmental Releases. BIOMASS provided an international forum for activities aimed at increasing the confidence in methods and models for the assessment of radiation exposure related to environmental releases. Two working groups addressed issues concerned with the reconstruction of radiation doses received by people from past releases of radionuclides to the environment and the evaluation of the efficacy of remedial measures. Theme 3: Biosphere Processes. The aim of this theme was to improve capabilities for modelling the transfer of radionuclides in particular parts of the biosphere identified as being of potential radiological significance and where there were gaps in modelling approaches. This topic was explored using a range of methods including reviews of the literature, model inter-comparison exercises and, where possible, model testing against independent sources of data. Three working groups were established to examine the modelling of: (1) long term tritium dispersion in the environment; (2) radionuclide uptake by fruits; and (3) radionuclide migration and accumulation in forest ecosystems. This report describes results of the studies undertaken by the Dose Reconstruction Working Group under Theme 2. The IAEA wishes to acknowledge the contribution of the Theme 2 Working Group Leader, K. Thiessen of the United States of America, to the preparation of this report. The IAEA Scientific Secretary for this publication was initially. K.-L. Sjoeblom and subsequently. C. Robinson of the Division of Radiation and Waste Safety. EDITORIAL NOTE The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. CONTENTS SUMMARY ............................................................................................................................... 1 1. INTRODUCTION ............................................................................................................ 3 1.1. Chernobyl accident and model testing..................................................................... 3 1.2. Objectives of the BIOMASS programme................................................................ 4 1.3. The objectives of the Iput scenario exercise............................................................ 4 1.4. Description of the Iput scenario .............................................................................. 5 1.5. Structure of the report.............................................................................................. 8 2. PARTICIPANTS AND MODELS ................................................................................... 8 3. SUMMARY OF MODEL APPROACHES.................................................................... 12 3.1. Modelling of atmospheric radionuclide deposition............................................... 12 3.2. Exposure due to groundshine ................................................................................ 13 3.3. Exposure due to cloudshine................................................................................... 14 3.4. Exposure due to inhalation.................................................................................... 14 3.5. Modelling the dynamics of 137Cs activity in soil................................................... 15 3.6. Modelling of plant contamination ......................................................................... 16 3.7. Modelling of agricultural countermeasures........................................................... 18 3.8. Modelling of the contamination of milk and beef with 137Cs................................ 19 3.9. Modelling of the radioactive contamination of natural products .......................... 21 3.9.1. Mushrooms and wild berries................................................................... 21 3.9.2. River and lake fish................................................................................... 21 3.10. The ingestion dose and whole body concentration of 137Cs .................................. 22 4. SELECTION OF MODEL PARAMETERS .................................................................. 23 4.1. Dose conversion factors for 137Cs ......................................................................... 23 4.2. Parameters of 137Cs migration in soil .................................................................... 25 4.2.1. Total inventory of 137Cs in soil................................................................ 25 4.2.2. Dynamics of mobile 137Cs in the root zone of plants .............................. 25 4.3. Selection of soil-to-plant transfer factors .............................................................. 27 4.4. Selection of parameter values for 137Cs transfer from feed to animal products (beef, milk, pork)................................................................................................... 28 5. DISCUSSION OF RESULTS......................................................................................... 29 5.1. Contamination of pasture and agricultural plants.................................................. 29 5.1.1. Leafy vegetables...................................................................................... 30 5.1.2. Potatoes ................................................................................................... 30 5.1.3. Cereals..................................................................................................... 31 5.1.4. Pasture (hay)............................................................................................ 31 5.2. Contamination of milk, beef and pork................................................................... 31 5.2.1. Milk......................................................................................................... 31 5.2.2. Beef ......................................................................................................... 32 5.2.3. Pork ......................................................................................................... 32 5.3. Effectiveness of agricultural countermeasures...................................................... 33 5.4. Contamination of products from the natural ecosystem........................................ 62 5.4.1. Mushrooms.............................................................................................. 62 5.4.2. Berries ..................................................................................................... 62 5.4.3. River and lake fish................................................................................... 63 5.5. Average daily intake of 137Cs by humans.............................................................. 63 5.6. Average 137Cs concentrations in humans .............................................................. 64 5.7. Estimates of internal and external effective dose and total dose........................... 64 5.7.1. Exposure to the initial radioactive cloud from Chernobyl ...................... 65 5.7.2. Effective doses from groundshine........................................................... 65 5.7.3. Inhalation dose from resuspension.......................................................... 65 5.7.4. Effective doses from ingestion................................................................ 66 5.7.5. Total doses.............................................................................................. 67 6. REASONS