Thin film samples: a new methodology for investigating the mechanisms of fission gas releases from nuclear fuel during a
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Thin film samples: a new methodology for investigating the mechanisms of fission gas releases from nuclear fuel during a LOCA Guillaume Brindelle1, 2, Gianguido Baldinozzi2, Hélène Capdevila1, Lionel Desgranges1, Yves Pontillon1 1 CEA, DEN, DEC, F-13108 Saint-Paul-Lez-Durance, France 2 CNRS, SPMS, LRC CARMEN, CentraleSupelec, F-92295, Châtenay-Malabry, France ABSTRACT Accurately predicting fission gas releases (FGR) from high burn-up fuels during offnormal conditions, such as a loss-of-coolant accident (LOCA), is an important, major challenge. A significant step forward would be to identify and assess the basic mechanisms causing this FGR. A helpful way of better understanding these basic mechanisms is to separate these effects and to perform irradiations on materials simulating the nuclear fuel. Mesoporous or dense CeO2 and UO2 samples (with thin film geometry) were selected for these studies as materials representative of irradiated fuels. A basic mechanism to obtain a better understanding of FGR is described and a new methodology using thin film samples is developed to test the validity of this mechanism. INTRODUCTION Fission gas release (FGR) is a key phenomenon that must be accurately assessed for fuel rod design and licensing under both normal and off-normal conditions. It constitutes important input data in terms of both the radioactive source term with regard to the consequences of a nuclear accident on the environment, and the driving force behind fuel damage. Correctly predicting its release under these conditions is an important R&D goal in order to fully understand the impact of FGR during an accident scenario, such as a loss-of-coolant accident (LOCA). A significant step forward would be to identify and assess the basic mechanisms causing this FGR. One of the most usefull ways to do that is to monitor the FGR kinetic together with the determination of the areas of the fuel pellet impacted by this release. The experimental facility, the samples and the common results obtained from the experiments will be described, followed by details of the innovative, new methodology used in this study.
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EXPERIMENT Description of the annealing test facility The whole annealing test facility, called MERARG (French acronym for Fission Gas Release Study by Annealing Facility) is shown in Figure 1. This facility is operated in one of the hot cells at the LECA-STAR laboratory at CEA, Cadarache. A detailed description of the characteristics of this experimental loop has already been published [1], and only the key features are summarised below. The key components are the induction furnace located in a shielded hot cell, the gamma spectrometry device (a p-doped Ge crystal detector) specifically for online measurements, and a glove box to store the gases for furthe
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