TEPCO to restart Kashiwazaki-Kariwa reactor Monday

TEPCO restarted the reactor on January 21 for the first time in 13 years and 10 months, but brought it to a cold shutdown two days later as an alarm about five and a half hours after the reactivation indicated a power system failure in equipment that moves control rods.

The issue persisted even after components were replaced.

The plant operator explained Friday that the issue had been caused by an error in the alarm's settings.

It plans to postpone the start of the reactor's commercial operations by about three weeks to March 18.

An investigation found no equipment abnormalities but identified rare instances of delayed electric current flow in one of the three cables, which were detected as abnormalities and set off the alarm.

The company changed the alarm settings and confirmed normal current flow in all control rods.

TEPCO said it plans to raise the pressure inside the reactor gradually after restarting it, and begin power generation and transmission on February 16.

It will then halt the reactor temporarily on February 20 or later to check for abnormalities, before conducting a final inspection, getting confirmation from the Nuclear Regulation Authority and putting the unit into commercial operations on March 18.

"We can't rule out the possibility of (additional) minor issues," plant chief Takeyuki Inagaki told a press conference on Friday.

"We will proceed with work step by step and respond to any problems appropriately."

The latest issue was the fourth major glitch related to the reactor's control rods since last year.

A similar problem discovered right before the reactor's initial restart delayed the reactivation by a day.

All seven reactors at the Kashiwazaki-Kariwa plant are boiling water units, the same type used at the company's Fukushima No. 1 plant, which suffered a triple meltdown following the March 2011 major earthquake and tsunami that mainly hit northeastern Japan.

The Kashiwazaki-Kariwa reactors were halted in March 2012.

In 2017, the plant's No. 6 reactor passed the NRA's safety screening needed for its restart.

After a period in which the plant was under an effective operational ban due to flaws in antiterrorism measures, TEPCO gained the approval of the local community for the reactivation last December.