Thermal load control methods for the HTTR-IS nuclear hydrogen production system

Sato, Hiroyuki  ; Ohashi, Hirofumi ; Sakaba, Nariaki ; Nishihara, Tetsuo ; Kunitomi, Kazuhiko 

One of the key technology requirements to achieve the non-nuclear grade hydrogen plants is the development of control methods mitigating the effect of IS process abnormal transients on the reactor operation. The control methods are developed to stabilize the steam generator helium gas outlet temperature increase and to prevent the unstable flow in the natural circulation loop. The simulation results show that the steam generator water temperature can be decreased by interfacing the actuation of the air cooler inlet shut-off valve with the actuation of the diverter valve. Furthermore, the air cooler outlet shut-off valve is activated as the pressure difference approaches zero between the steam generator bottom and the down comer. It is demonstrated that the control methods developed enable the continuation of the nuclear reactor operation during IS process abnormal conditions without operator intervention.