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The OSCAR code: a simulation tool to assess the PWR contamination for decommissioning

Abstract : Knowing the contamination state of the end-of-life nuclear reactor systems by Long-Lived RadioNu-clides (LLRNs) is a key stage for the decommissioning process. Indeed, the initial state is necessary to optimize the decommissioning works and to manage the radioactive waste as well. To address this issue, the contamination state is usually characterized using different types of techniques: in-situ gamma spectrometry, gamma camera scanning, dose rate measurements, , ,  measurements of samples obtained by smears or scrapings and then chemical separation processes, scaling factor approach… To reduce the amount of these measurements and thus the Occupational Radiation Ex-posure (ORE) and the decommissioning costs, a method is to assess the level of contamination by simulation. Furthermore, at the design stage of a new reactor, its decommissioning has to be taken into account and a simulation tool, such as the OSCAR code, can predict the radioactive source term at the end of life of a future reactor. The OSCAR code (Outil de Simulation de la ContAmination en Réacteur - tOol of Simulation of Con-tAmination in Reactor) has been developed by the CEA in collaboration with EDF and Framatome since the 1970s. The OSCAR code simulates the production and transfer of Activated Corrosion Products (ACPs) and Actinides and Fission Products and (AFPs) in the reactor systems and thus calculates the masses and activities of radionuclides deposited inside piping and heat exchangers of different circuits. As the OSCAR code has been originally devoted to mainly an industrial objective, which is the reduction of the Occupational Radiation Exposure (ORE) for operating PWRs, it deals with the main ACPs, 60Co, 58Co, 54Mn…, which are short-lived radionuclides. Nevertheless, it also cal-culates LLRNs of interest for decommissioning, such as 55Fe, 63Ni, 90Sr, 239Pu…, most of which are difficult to measure. The OSCAR code is validated through on-site measurements, including the EMECC campaigns, an operational experience feedback unique in the world, that consist of measur-ing the gamma surface activities mainly of the PWR primary system but also of auxiliary systems. After a presentation of the features and modeling of the OSCAR code, the paper will present some OSCAR simulation results of long-lived ACPs and AFPs deposited inside PWR circuits and their comparison with measurements. Perspectives of the OSCAR code on the decommissioning pro-grams will also be discussed.
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Submitted on : Thursday, November 18, 2021 - 12:30:05 PM
Last modification on : Saturday, November 20, 2021 - 3:43:37 AM

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  • HAL Id : cea-03434535, version 1

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Frederic Dacquait, J-Baptiste Genin, Jerome Francescatto, Gilles Benier, Gaëlle Galassi, et al.. The OSCAR code: a simulation tool to assess the PWR contamination for decommissioning. DEM 2021 – International Conference on Decommissioning Challenges:, Sep 2021, Avignon, France. pp.Oral T04 / 054. ⟨cea-03434535⟩

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