Sendai Nuclear Unit Restart Suspended Amid Equipment Trouble

Kyushu Electric Power Co.’s restart of Sendai 1—the first Japanese reactor to begin operation under new safety standards after the Fukushima disaster—hit a technical hiccup last week, prompting the company to halt ramp up of power output.

The utility said on Aug. 21 that it had suspended increasing output at the unit after an alarm alerted operators to a problem with a condensate pump on the secondary system. A later investigation revealed that seawater had entered one of the pumps.

The problem occurred as the unit was being ramped up to 75% of output. The unit restarted generating power on Aug. 14 after being idled for four years.

Inspection results released on Aug. 25 showed five tubes in condenser A had been contaminated by seawater. The company now plans to make repairs—including “putting stoppers on the five tubes”—and increase output from Aug. 27 onwards.

As a precautionary measure, it will also plug 64 tubes around the five tubes, noting that those only represent 0.5% of the 13,000 tubes in condenser A.

The first of 43 operable Japanese nuclear reactors that are mostly expected to start coming back online over the coming months and years, Sendai-1 is also the first to operate under new standards put into effect in July 2013 by the Nuclear Regulation Authority (NRA). The agency established in the aftermath of the Fukushima disaster suspended Sendai-1′s operation four years ago—since May 2011. Japan’s last operating reactor, Ohi-1, was shut down in September 2013.

On Aug. 17, the NRA began conducting pre-service inspections on the Takahama-3 unit owned by Kansai Electric Power Co. The reactor had been certified to meet the new safety standards on Feb. 12. Construction work plans for equipment and facilities at the plant were approved on Aug. 4.

The unit may resume operation around mid-November, some industry observers project. Inspections are not expected to take less time than they did for Sendai-1, Kansai Electric officials told reporters on Aug. 18.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)

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