Fission gas release under fast transient and LOCA conditions: Analytical devices implemented at Commissariat a l'Energie Atomique

R and D programs in support to general policy about exploitation of nuclear energy, developed in France these past years, highly promote studies about reactor safety on normal operating conditions as well as in accidental conditions. More recently, increasing interest for Fission Gas Release (FGR) studies in LOCA and fast transient conditions enabled starting of many research programs in CEA and particularly in Nuclear Energy Directorate (DEN). Within this context, the Fuel Studies Department (DEC) acquired an important theoretical as well as experimental experience. In order to achieve this competence, the Department equipped itself with specific technical facilities set up in very high activity hot cells, in particular at the CEA Grenoble. The researchers of the Department have a set of thermal treatment devices, including a vacuum furnace and a controlled atmosphere one (helium, air). These devices are associated to on line quantitative gamma spectrometry and gas chromatography coupled with a mass spectrometer, in order to measure emitted gas. The greatest asset of such an installation is to ensure a high analytical experiments rate, and as a consequence to make parametrical approach of planned studies easier. This is perfectly illustrated by two programs that are occurring this year, linked to LOCA and fast transient. In these cases, parametric analysis of fuel types, of their micro-structures (including MOX fuel), of burn-up influence, of thermal sequence imposed on the fuel sample was realized. Even though the reproduction of LOCA and/or fast transient conditions, occurring in nuclear power reactors, is only partial with this type of facilities, the realized tests enable to identify and quantify many physical parameters. This capability brings out important mechanisms promoting FGR, and permits to set up physical laws. (author)