Temperature transient analysis of gas circulator trip test using the HTTR

Safety demonstration test using the High Temperature Engineering Test Reactor (HTTR) are in progress to verify the inherent safety features, to improve the safety design and the technologies for High Temperature Gas-cooled Reactor (HTGRs). The coolant flow reduction test by tripping one or two out of three gas circulators is one of the safety demonstration test. The reactor power safely brings to a stable level without a reactor scram and the temperature transient of the reactor-core is very slow. Through the safety demonstration test, the two dimensional temperature analysis code (TAC-NC code) was improved. The results of this study can be applied to development for not only the commercial HTGRs but also the Very High Temperature Reactor (VHTR) such as one of the Generation IV reactors. This paper describes the validation of the TAC-NC code using the measured value of the test by tripping of one and two out of three gas circulators at 30% (9MW) performed in 2003. The TAC-NC code could evaluate accurately the temperature transient within 10% during the test. Also, it was confirmed that the temperature transient by tripping all gas circulators is very slow and that the HTGR has high inherent safety features. (author)