Modelling of the contamination transfer in nuclear reactors: The OSCAR code - Applications to SFR and ITER
Résumé
Predicting the radioactive contamination of nuclear reactor circuits is a significant challenge for plant designers and operators. The major stakes are to decrease personnel exposure to radiations, to optimize plant operation, to limit activity of wastes and to prepare decommissioning. To address this challenge, the French strategy has been focusing on performing experiments in test loops representative of Pressurized Water Reactor (PWR) conditions, measuring the PWR contamination and developing a simulation code known as OSCAR. The OSCAR code has been developed by the CEA in collaboration with EDF and AREVA NP for more than 40 years. It has resulted from the merging of two former codes PACTOLE for Activated Corrosion Products (ACPs) and PROFIP for fission products and actinides. Thus, the OSCAR code has been designed to simulate the contamination transfer in the PWR Reactor Coolant System (RCS). The main transfer processes involved for ACPs are corrosion-release, erosion, deposition, dissolution/precipitation, convection, purification, neutron activation and radioactive decay. The OSCAR code calculates the space-time distribution of activities in solid and liquid phases in the PWR RCS and auxiliary systems. It is a modular code and it can easily integrate new models.In the same way, ACPs in the primary heat transfer system of the International Thermonuclear Experimental Reactor (ITER) and in the primary system of Sodium Fast Reactors (SFRs) can be a major concern as contributors to the source term of potential released activities to the environment in case of accident and to the occupational radiological exposure during the normal operation. Although the design and operating conditions of these reactors are different from those of PWRs, an application of the OSCAR code to SFRs, so-called OSCAR-Na, and another one to ITER, so-called OSCAR-Fusion, have been developed to treat the behaviour of corrosion products thanks to the modularity of the OSCAR code.After a general presentation of the OSCAR code, this contribution will describe the modelling of the ACP transfer common to the different types of nuclear reactors (discretization into control volumes and media, metallic elements, transfer mechanisms, mass balance equations) and then the specificities of OSCAR-Fusion and OSCAR-Na (in particular the corrosion model of OSCAR-Na). Finally, issues and RetD needs will be presented.
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