Study on optimization of FFD/FFDL system and RTCB plant operation; Thechnique of collecting fission gas using the cover gas cleanup system in JOYOs

Sumino, Kozo ; Aoyama, Takafumi ; Nagai, Akinori

The cover gas radioactivity in the reactor vessel increases when a fuel pin failure occurs or RTCB (Run to Cladding Breach) testing is performed. The activity must be reduced to minimize the personnel exposure and to maintain the reserve capacity of the waste gas system in which the residual fission gas is stored. The CGCS (Cover Gas Cleanup System) was installed in the JOYO primary cover gas system to collect and remove the fission gas. The cryogenic charcoal bed cooled by the liquid nitrogen selectively adsorbs the krypton and xenon due to the adsorption ratio difference. The collection ratio for xenon and krypton was measured using fission gas in the fuel failure simulation test and a standard helium diluted non-radioactive gas. As a result, the collection ratio was confirmed to be more than 90% for xenon and more than 80% for krypton by six hours operation of CGCS. It was confirmed that the CGCS has a capability to remove the fission gas effectively.