Assessment of amount and concentration of tritium in HTTR-IS system based on tritium behavior during high-temperature continuous operation of HTTR

Dipu, A. L.; Ohashi, Hirofumi ; Hamamoto, Shimpei  ; Sato, Hiroyuki  ; Nishihara, Tetsuo 

The tritium concentration in the high temperature engineering test reactor (HTTR) was measured during the high temperature continuous operation for 50 days. The tritium concentration in the primary helium gas increased after startup and reached a maximum value. It then decreased slightly over the course during the normal operation phase. Decrease of concentration of tritium in primary helium gas during the normal operation phase could be attributed to the effect of tritium chemisorption on graphite. The tritium concentration in the secondary helium gas showed a peak value during the power ramp up phase. Afterwards, it decreased gradually at the end of normal power operation. It was assessed that the concentration and total quantity of tritium in the secondary helium cooling system for the HTTR-Iodine Sulfur (IS) system can be maintained below the regulatory limits, which means the hydrogen production plant can be exempt from the safety function of the nuclear facility.