Repository performance assessment and advanced fuel cycle models for input to decision making of options for nuclear was
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Repository performance assessment and advanced fuel cycle models for input to decision making of options for nuclear waste and resource management J.S.Small1, C.H.Zimmerman2, D.R.Parker2, C.Robbins3, A.E.Bond1, G.A.Stevens1 1 Nexia Solutions Ltd., Warrington, UK 2 Nexia Solutions Ltd., Sellafield, UK 3 Grallator Modelling, Simulation, & Software, Derbyshire, UK ABSTRACT A methodology and computer software is described which can be used to track the inventory of radionuclides as they are affected by various nuclear, physical and chemical processes during reactor, storage, effluent and disposal phases of the nuclear fuel cycle. Such a model is required to provide an assessment of economic, environmental and societal performance indicators which underpin decisions regarding options for the use and management and nuclear materials. An example generic deep repository model is described which can be used to provide an indicator of environmental performance of vitrified high level waste and UO2 and mixed oxide (MOX) spent fuels. The assessment models highlight the significance of the I-129 fission product which necessitates the use of appropriate dose assessment models to be considered for each process step of the nuclear fuel cycle in order that a complete environmental assessment of process options can be determined. INTRODUCTION Decisions regarding the management of nuclear resources and associated wastes require an appropriate assessment of various Economic, Environmental and Societal (EES) impacts of options for the disposition of nuclear materials. A complete set of EES indicators must be selected and considered taking account of the opinions of stakeholders, and where possible a justifiable and transparent comparison of indicators provides a basis to evaluate the optimum management option. Indicators of environmental impact are generally quantifiable, most typically in the form of performance assessment (PA) dose models of the repository disposal of radioactive waste. Such models when considered in isolation may however give an incomplete analysis of the impact of various processing and transfer steps that may be involved. This paper introduces how fuel cycle modelling software (ORION) can be used to keep account of the time evolution of nuclear materials to determine the distribution of radionuclide inventory to storage, waste and effluent streams. Assessment tools to provide a full analysis of the environmental impacts of process effluent streams and of the low, intermediate and high level waste (LLW, ILW, HLW) storage and disposal are being developed. A full analysis of the environmental impact of nuclear management scenarios will be presented in the future. Here we present, as an example, a generic PA model to assess the impacts resulting from the groundwater pathway from repository disposal of vitrified HLW and UO2 and MOX spent fuels. Results considering the effects of model and parameter uncertainty in wasteform performance and in the near-field, geosphere and biosphere models are discussed.
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