Modelling Radiation Exposure and Radionuclide Transfer for Non-human Species Report of the Biota Working Group of EMRAS Theme 3 Environmental Modelling for RAdiation Safety (EMRAS) Programme FOREWORD Environmental assessment models are used for evaluating the radiological impact of actual and potential releases of radionuclides to the environment. They are essential tools for use in the regulatory control of routine discharges to the environment and also in planning measures to be taken in the event of accidental releases; they are also used for predicting the impact of releases which may occur far into the future, for example, from underground radioactive waste repositories. It is important to check, to the extent possible, the reliability of the predictions of such models by comparison with measured values in the environment or by comparing with the predictions of other models. The International Atomic Energy Agency (IAEA) has been organizing programmes of international model testing since the 1980s. The programmes have contributed to a general improvement in models, in transfer data and in the capabilities of modellers in Member States. The documents published by the IAEA on this subject in the last two decades demonstrate the comprehensive nature of the programmes and record the associated advances which have been made. From 2003 to 2007, the IAEA organised a programme titled “Environmental Modelling for RAdiation Safety” (EMRAS). The programme comprised three themes: Theme 1: Radioactive Release Assessment ⎯ Working Group 1: Revision of IAEA Technical Report Series No. 364 “Handbook of parameter values for the prediction of radionuclide transfer in temperate environments (TRS-364) working group; ⎯ Working Group 2: Modelling of tritium and carbon-14 transfer to biota and man working group; ⎯ Working Group 3: the Chernobyl I-131 release: model validation and assessment of the countermeasure effectiveness working group; ⎯ Working Group 4: Model validation for radionuclide transport in the aquatic system “Watershed-River” and in estuaries working group. Theme 2: Remediation of Sites with Radioactive Residues ⎯ Working Group 1: Modelling of naturally occurring radioactive materials (NORM) releases and the remediation benefits for sites contaminated by extractive industries (U/Th mining and milling, oil and gas industry, phosphate industry, etc.) working group; ⎯ Working Group 2: Remediation assessment for urban areas contaminated with dispersed radionuclides working group. Theme 3: Protection of the Environment ⎯ Working Group 1: Model validation for biota dose assessment working group. This report describes the work of the Biota Working Group under Theme 3. The IAEA wishes to acknowledge the contributions of the Working Group Leaders, B. Howard and N. Beresford (both of the United Kingdom), as well as J. Vives i Batlle (United Kingdom) and T. Yankovich (Canada) to the editorial preparation of this report. The IAEA Scientific Secretary for this publication was initially M. Balonov and subsequently D.M. Telleria both of the Division of Radiation, Transport and Waste Safety. CONTENTS SUMMARY ............................................................................................................................... 1 CHAPTER 1. INTRODUCTION.............................................................................................. 2 CHAPTER 2. MODEL DESCRIPTIONS................................................................................. 3 2.1. Common elements .............................................................................................. 3 2.1.1. Dosimetry ............................................................................................. 3 2.1.2. Transfer................................................................................................. 4 2.1.3. Reference organisms ............................................................................ 5 2.1.4. Assessment structure............................................................................ 5 2.2. Atomic Energy Canada Limited (AECL) approach ........................................... 5 2.3. RESRAD-BIOTA............................................................................................... 6 2.4. ERICA (Environmental Risk from Ionising Contaminants – Assessment and Management) ............................................................................................... 6 2.5. FASSET (Framework for the Assessment of Environmental Impact)............... 7 2.6. England and Wales Environment Agency R&D128 (EA R&D128) ................. 8 2.7. LIETDOS-BIO ................................................................................................... 8 2.8. DosDiMEco........................................................................................................ 8 2.9. ECOMOD........................................................................................................... 9 2.10. EDEN 2 (Elementary Dose Evaluation for Natural Environment) .................. 10 2.11. CASTEAUR ..................................................................................................... 11 2.12. EPIC DOSES3D............................................................................................... 12 2.13. FASTer ............................................................................................................. 13 2.13.1. Transfer to herbivores and carnivores ................................................ 13 2.14. D-MAX............................................................................................................. 16 2.15. LAKECO-B...................................................................................................... 18 2.15.1. Transfer module.................................................................................. 18 2.15.2. Dose module....................................................................................... 20 2.16. SÚJB approach................................................................................................. 22 CHAPTER 3. COMPARISON OF UNWEIGHTED ABSORBED DOSE RATES.......... 23 3.1. Introduction ...................................................................................................... 23 3.2. Description of the exercise ............................................................................... 23 3.3. Statistical analysis methodology ...................................................................... 24 3.3.1. Exploratory data analysis................................................................... 25 3.3.2. Normality tests....................................................................................25 3.3.3. Calculation of reference data and scoring of each approach for performance........................................................................................ 28 3.3.4. Issues in results interpretation ............................................................ 28 3.4. Results .............................................................................................................. 29 3.4.1. Identification of outliers ..................................................................... 29 3.5. Discussion......................................................................................................... 36 3.5.1. Effect of number of daughter products............................................... 37 3.5.2. Effect of soil/sediment depth and target position............................... 38 3.6. Conclusions ...................................................................................................... 46 CHAPTER 4. COMPARISON OF PREDICTED WHOLE-BODY ACTIVITY CONCENTRATIONS........................................................................................... 48 4.1. Exercise description.......................................................................................... 48 4.2. Application of the participating models ........................................................... 48 4.2.1. AECL approach.................................................................................. 48 4.2.2. RESRAD-BIOTA............................................................................... 49 4.2.3. ERICA ................................................................................................ 50 4.2.4. FASSET.............................................................................................. 50 4.2.5. DosDiMEco........................................................................................ 51 4.2.6. ECOMOD (Russia)............................................................................ 51 4.3. Results .............................................................................................................. 51 4.4. Statistical analyses............................................................................................ 65 4.4.1. Evaluation of statistical analyses........................................................ 66 4.5. Discussion......................................................................................................... 68 4.6. Conclusions ...................................................................................................... 70 CHAPTER 5. FRESHWATER SCENARIO: PERCH LAKE ........................................... 72 5.1. Scenario description......................................................................................... 72 5.2. Application of models to the scenario .............................................................