Abstract
The HTTR (High Temperature Engineering Test Reactor), which has thermal output of 30MW, coolant inlet temperature of 395°C and 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 accident. Safety demonstration tests using the HTTR are underway in order to demonstrate such excellent inherent safety features of the HTGR. The reactivity insertion test demonstrates that rapid increase of reactor power during withdrawal of the control rod is restrained by only the negative reactivity feedback effect without operation of the reactor power control system, and the kemperature transient of the reactor is slow. A one-point core dynamics approximation with one fuel channel, one fuel temperature coefficient and one moderator coefficient could not simulate accurately the reactor power behavior. On the other hand, an original new method using some temperature coefficients for regions in the core was very effective. It is crucial to evaluate this method precisely to simulate a performance of HTGR with showing excellent inherent safety features under the reactivity initiated incident by control rod withdrawal error. Moreover, all experimental data of reactivity insertion tests and analytical results are released.
