Tokyo Electric Power Company Holdings (Tepco) plans to postpone the restart, scheduled for Tuesday, of the No. 6 reactor at its Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture, sources familiar with the matter said Monday.
The plan comes after a problem was confirmed during a test to pull out control rods that suppress nuclear fission reactions in the reactor on Saturday. Although the problem has been resolved, the company apparently judged it necessary to exercise caution in the restart-related work.
Tepco found that an alarm designed to prevent unintended pullout did not become active during the test. An investigation revealed an error in the pullout prevention function settings.
After correcting the settings, the problem was resolved at 8:16 p.m. Sunday.
Later, the company checked whether the alarm functions properly for all control rods.