Following the discovery of a water coolant leak, the planned restart of the No. 3 reactor at Shikoku Electric Power Co.'s Ikata Nuclear Power Plant in Ikata, Ehime Prefecture, is expected to be delayed from its planned date of July 26 to next month.
On July 17, Shikoku Electric and the Ehime Prefectural Government announced that a water leak had been confirmed in connection with a coolant-cycling pump at the reactor. According to the utility, the leak was due to a problem with a shaft seal meant to prevent leaks, and the seal will have to be replaced. A standard maintenance check is said to take about a week, so the replacement will postpone the reactor's reactivation to August.
Shikoku Electric and other sources say that at about 11:20 a.m. on July 16, a problem was detected by a meter in the central control room during a test run of the coolant pump. Attempts were made to rectify the problem but it persisted, and it was confirmed that, as of 9:20 a.m. on July 17, several liters of water had leaked from one of the three shaft seals into an area that normally has almost no water flow.
The shaft seal is composed of two carbon disks, and a gap that formed between the disks is thought to be the reason for the leak.
The leaked water has been collected and put in a tank in the reactor's containment vessel, and there is said to have been no radiation leak or other environmental effects. Shikoku Electric reported the incident to the Nuclear Regulation Authority (NRA) on July 17, but says it does not intend to conduct new checks on any parts besides the faulty seal.
The No. 3 reactor passed the NRA's safety check in July 2015, and in April this year pre-reactivation checks began. However, problems have cropped up just ahead of the planned reactivation. In addition to the leak, accident-response drills on July 14 and 15 were discontinued after workers suffered heat stroke, prompting orders for the drills to be carried out again.