Sensitivity analysis of xenon reactivity temperature dependency for HTTR LOFC test by using RELAP5-3D code

Honda, Yuki; Fukaya, Yuji   ; Nakagawa, Shigeaki  ; Baker, R. I.*; Sato, Hiroyuki  

A high-temperature gas-cooled reactor (HTGR) has superior safety characteristics. A loss of forced cooling (LOFC) test using a high-temperature engineering test reactor (HTTR) has been carried out to verify the inherent safety of an HTGR when forced cooling is diminished without reactor scram. In the test, an all-gas circulator was tripped with an initial reactor power of 9 MW and re-criticality was shown. This study focuses on developing a point kinetics method with RELAP5-3D code for an LOFC accident. There is a large temperature difference between the inlet and outlet of the core in an HTGR, and the temperature fluctuation range has been large in several accidents. We analyze the temperature dependency of xenon-135 reactivity and show that the temperature dependency of xenon-135 microscopic absorption cross-section affected the re-criticality time of the LOFC test.