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Evaluation of the PAR Mitigation System in Swiss PWR Containment using the Gothic Code
- Conference Paper
The installation of Passive Autocatalytic Recombiners (PARs) in the containment of the operating nuclear power plants is increasingly based on three-dimensional studies that accurately predict the hydrogen pathways and local accumulation in containment and examine the hydrogen risk mitigation effects of the PARs. The GOTHIC code is applied in this paper to study the effectiveness of the PAR mitigation system to be installed in the NPP Gösgen in Switzerland, with reference to a limiting scenario with fast release of a mixture of hydrogen and steam. The PARs (box-type from AREVA) are modeled in GOTHIC via built-in components located according to a layout prepared by the PAR vendor. The PAR modeling approach is qualified simulating two experimental tests performed in the frame of the OECD/NEA THAI project. Two different sets of plant calculations are presented. The first, pre-qualification, calculation uses the information available from AREVA for the PAR recombination rate and efficiency. The second, post-qualification, calculation implements the recommendations obtained from the validation study, which led mainly to a limitation of the PAR efficiency. Both the calculations show that the recombiners cannot prevent the formation of a stratified cloud of hydrogen (10% molar concentration) but they can mitigate the hydrogen accumulation once formed. When a large number of recombiners are installed, the global behavior towards the combustion risk does not depend on the details of the single PAR behavior. The hydrogen ignition risk can be fully mitigated in a time frame ranging from 15 to 30 min after the fast release, depending on the parameters chosen for modelling the PAR efficiency Show more
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Organisational unit03725 - Prasser, Horst-Michael
Notespaper no. 21277
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