DEVELOPMENT AND EXPERIENCE OF FULL SYSTEM DECONTAMINATION FOR THE FUGEN NUCLEAR-POWER STATION .2. RESULTS OF FULL SYSTEM DECONTAMINATION

In 1989 and 1991, the Japanese first and second campaigns of full syst em decontamination were performed successfully in each loop of two ind ependent core cooling systems of FUGEN as an operating nuclear power s tation. Dilute chelate reagent, Kuridecon-203 (KD-203) was used in 0.1 % from 0.05% for the decontaminations at 120 degrees C for 24h. ''Puri fying decontamination'' method, in which injection of reagent and puri fication of decontaminant are carried out simultaneously, was applied to control KD-203 concentration low and to restrain dose rate of the s ystem during the decontaminations. 6.6 and 7.8 man-Sv were saved and 7 to 8 TBq of Co-60 were removed through the decontaminations. No negat ive influence for materials composed of the cooling circuits was obser ved in the visual inspection and in-situ materials tests carried out d uring the decontaminations. There is no incident derived from the camp aigns for more than five year's operation. Dose rate of the primary co oling system has not reached to the pre-decontamination level yet afte r four year's operation.