February 23, 2016

No Takahama reactor restart delay after loose bolt found to be source of leak

http://ajw.asahi.com/article/behind_news/social_affairs/AJ201602230044

THE ASAHI SHIMBUN

OSAKA--The radioactive water leak discovered recently at the Takahama nuclear power plant in Fukui Prefecture was caused by a loose bolt in the piping system and won't delay the planned restart of a reactor, its operator said Feb. 22.

The Kansai Electric Power Co. plant in the town of Takahama is currently undergoing procedures to restart its No. 4 reactor.

The discovery of the pool of contaminated water delayed the startup test at the reactor by a day, to the night of Feb. 22, but it is set to resume operations on Feb. 26 as scheduled.

Some 34 liters of radioactive water were found leaking near the purification equipment installed in the auxiliary structure of the No. 4 reactor building on Feb. 20 during a test to send water down the primary coolant pipe connected to the reactor.

When Kansai Electric examined the fault, they discovered that one of the four bolts attaching a valve to the pipe leading to the purification equipment was loose. The operator believes that water running through the pipe at a higher pressure than when the reactor is in operation had also contributed to the leak.

The bolt was tightened manually and although records stated that the procedure was completed in accordance with protocol, the operator said that it may not have been sufficiently tightened due to the limited space in the area.

Following the discovery of the leak, Kansai Electric examined all similar valves of the No. 4 reactor installed in about 80 locations and went on to conduct the startup test on Feb. 22.

Once the operator confirms that the control rods are functioning in the eight-day test, they will remove them and restart the reactor on Feb. 26.

The valves installed on the No. 3 reactor, which resumed operation on Jan. 29, were also checked for defects. The reactor will start commercial operation on the same day the No. 4 reactor restarts, if all goes according to plan.

Kansai Electric notified the Nuclear Regulation Authority and the Fukui prefectural government of the latest leak just one hour after the discovery, but took six hours to announce the matter publicly.