KARIWA, NIIGATA PREF. ¨C Tokyo Electric Power Company Holdings (Tepco) announced Friday it will restart the No. 6 reactor at its Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture on Monday.
Tepco restarted the reactor on Jan. 21 for the first time in 13 years and 10 months but shut it down hours later following an alarm indicating, about five and a half hours after the reactivation, that a power system failure had occurred in equipment that moves control rods. The issue persisted even after equipment components were replaced.
The plant operator explained Friday that the issue was caused by an error with 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 Feb. 16. It will then halt the reactor temporarily on Feb. 20 or later to check for abnormalities, before conducting a final inspection, obtaining 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 said at a news 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 found 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 as those at the company¡¯s Fukushima No. 1 plant, which suffered a triple meltdown following the 2011 Great East Japan 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 Nuclear Regulation Authority¡¯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 consent of the local authorities for the reactivation last December.
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