Testing of Models for Predicting the Behaviour of Radionuclides in Freshwater Systems and Coastal Areas
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Testing of Models for Predicting the Behaviour of Radionuclides in Freshwater Systems and Coastal Areas Report of the Aquatic Working Group of EMRAS Theme 1 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 Aquatic Working Group under Theme 1. The IAEA wishes to acknowledge the contribution of the Working Group Leader, L. Monte of Italy and J. Brittain of Norway (Editing) to the preparation of this report. The IAEA Scientific Secretary for this publication was D. Telleria of the Division of Radiation, Transport and Waste Safety. CONTENTS SUMMARY ............................................................................................................................... 1 CHAPTER 1. INTRODUCTION ......................................................................................... 4 1.1. Background.................................................................................................... 4 1.2. Scenarios for model intercomparison ............................................................ 5 CHAPTER 2. WASH-OFF OF CHERNOBYL 90SR AND 137CS DEPOSITION FROM THE PRIPYAT FLOODPLAIN ................................................................. 8 2.1. Introduction.................................................................................................... 8 2.2. Main characteristics of the models ................................................................ 9 2.3. Results and discussion................................................................................. 11 2.4. Conclusions.................................................................................................. 15 CHAPTER 3. INTERCOMPARISON OF MODELS FOR PREDICTING THE BEHAVIOUR OF 137CS AND 90SR OF CHERNOBYL ORIGIN IN THE DNIEPER-SOUTHERN BOUG (DNIEPER-BUG) ESTUARY ......................... 17 3.1. Introduction.................................................................................................. 17 3.2. Main characteristics of the models .............................................................. 20 3.3. Results and discussion................................................................................. 23 3.4. Conclusions.................................................................................................. 25 CHAPTER 4. MIGRATION OF TRITIUM IN THE LOIRE RIVER ............................... 26 4.1. Introduction.................................................................................................. 26 4.2. Main characteristics of the models .............................................................. 26 4.3. Results and discussion................................................................................. 28 4.3.1. Analysis of the models’ results (blind test) ................................... 28 4.3.2. Improvements of the models and new tests................................... 37 4.3.3. Further exercise: models inter-comparisons for a hypothetical realistic pulse-type release............................................................. 42 4.4. Conclusions.................................................................................................. 50 CHAPTER 5. RADIOACTIVE CONTAMINATION OF THE TECHA RIVER BY 90SR, 137CS AND 239,240PU (SOUTH URALS, RUSSIA)..................................... 52 5.1. Introduction.................................................................................................. 52 5.1.1. Exposure of the population............................................................ 54 5.1.2. Countermeasures............................................................................ 55 5.1.3. Current sources of the radionuclide input to the Techa River....... 56 5.2. Main characteristics of the models .............................................................. 56 5.2.1. Model CASTEAURv0.1................................................................ 57 5.2.2. Model TRANSFER-2.................................................................... 58 5.2.3. Model CASSANDRA.................................................................... 58 5.2.4. Model GIDRO-W .......................................................................... 59 5.2.5. Model RIVTOX............................................................................. 60 5.3. Model results................................................................................................ 60 5.3.1. Model CASTEAUR....................................................................... 60 5.3.2. Model TRANSFER-2.................................................................... 64 5.3.3. Model CASSANDRA.................................................................... 65 5.3.4. Model GIDRO-W .......................................................................... 69 5.3.5. Model RIVTOX............................................................................. 69 5.4. Discussion.................................................................................................... 74 5.4.1. Comparison of the model calculations with empirical data: radionuclides in water.................................................................... 74 5.4.2. Comparison of the model calculations with empirical data: radionuclides in bottom sediments ................................................ 76 5.4.3. Intercomparison of the tested models and empirical data ............. 79 5.5. Conclusions.................................................................................................. 82 CHAPTER 6. MODELLING 226RA SELF-CLEANING IN THE HUELVA ESTUARY ........................................................................................... 83 6.1. Introduction.................................................................................................. 83 6.2. Main characteristics of the models .............................................................. 85 6.3. Results and discussions................................................................................ 86 6.4. Conclusions.................................................................................................. 89 CHAPTER 7. SIMULATION OF 90SR WASH-OFF FROM THE CONTAMINATED PRIPYAT RIVER FLOODPLAIN USING COMMERCIALLY AVAILABLE SOFTWARE ................................................ 90 7.1. Introduction.................................................................................................. 90 7.2. Main characteristics of the models .............................................................. 90 7.2.1. Model set-up procedures................................................................ 91 7.3. Results, discussion and conclusions ............................................................ 93 CHAPTER 8. CONCLUSIONS.......................................................................................... 97 REFERENCES....................................................................................................................... 100 APPENDIX I. SCENARIO DESCRIPTIONS .................................................................. 103 I.1. Wash-off of Chernobyl