抄録
A HTTR (High Temperature Engineering Test Reactor), which has a thermal output of 30 MW, a coolant inlet temperature of 395°C and a coolant outlet temperature of 850°C/950°C, is a first high-temperature gas-cooled reactor (HTGR) in Japan. The HTGR has a high inherent safety potential to accidents. The safety demonstration tests such as the reactivity insertion and the coolant flow reduction tests using the HTTR are underway in order to demonstrate such excellent inherent safety features of HTGRs. These tests demonstrate that the rapid increase or decrease in the reactor power is restrained by only the negative reactivity feedback effect without an operation of the reactor power control system, and the temperature transient of the reactor is slow. A one-point core dynamics approximation with one fuel channel model could not simulate accurately the reactor power behavior. On the other hand, an original new method using region temperature coefficients and a connection between some fuel channel models and whole core component model for calculating radial heat transfer in the core is adopted. It is crucial to evaluate this method precisely to simulate a performance of HTGR with showing excellent inherent safety features under the reactivity incident by gas circulator tripping error.
