Level 2 problem at Sendai No.1

August 8, 2015

Cooling system pump at Sendai nuclear plant stopped due to faulty vibration meter

http://mainichi.jp/english/english/newsselect/news/20150808p2a00m0na007000c.html

SATSUMASENDAI, Kagoshima -- One of three cooling system water pumps at the Sendai Nuclear Power Plant's No. 1 reactor, now being prepared for reactivation, was halted after staff noticed an unusual vibration meter reading, Kyushu Electric Power Co. announced on Aug. 7.

According to Kyushu Electric, the pump is inside the No. 1 reactor's containment vessel, and the meter measures the vibration of the pump shaft. At 10:22 a.m. on Aug. 7, a worker in the central control room confirmed that the vibration meter was displaying a lower than usual value. At 6:30 p.m. workers stopped the pump, inspected it and found that the pump's vibration meter was defective. They replaced a part of the vibration meter.

The pump was started at full operation on Aug. 4, to raise the temperature and pressure of cooling water for the reactor. The utility says the incident will not affect its schedule for restarting the No. 1 reactor on Aug. 11.

Since July, Kyushu Electric is classifying problems that occur at the No. 1 reactor on a five-level scale from 0 to 4, and it has decided it will announce problems of level 2 or higher, which could impact the restart schedule. The pump trouble was the first such announcement, and was a level 2 problem.