At 4 other N-plants, control rods fell off

   In addition to Hokuriku Electric Power Co.’s Shika Nuclear Power Plant No. 1 reactor (Ishikawa Pref.), accidents in which control rods of nuclear reactors fell off during regular inspections took place in five more reactors at four other nuclear power plants, electric power companies announced one after another on March 19 and 20.

   Unlike the Shika plant No. 1 reactor, these reactors reportedly did not reach criticality. Power companies failed to report these cases to the government on the grounds that they were not required to do so because the accidents did not cause emergency shutdowns of reactors.

   Such accidents took place at Chubu Electric Power Co.’s Hamaoka Nuclear Power Plant (Shizuoka Pref.) No. 3 reactor in 1991, Tohoku Electric Power Co.’s Onagawa Nuclear Power Station (Miyagi Pref.) No. 1 reactor in 1988 and No. 3 reactor in 2003, Tokyo Electric Power Co.’s (TEPCO) Fukushima No. 2 Nuclear Power Plant (Fukushima Pref.) No. 3 reactor in 1993, and TEPCO’s Kashiwazaki-Kariwa Nuclear Power Station (Niigata Pref.) No. 1 reactor in 2000.

   The power companies explained that those accidents had been caused by human errors in the operating valves that drive the control rods.

   Following the 1993 accident at Fukushima No. 2 Plant, TEPCO revised the operating procedure but failed to inform other plants of the accident or the revision.

   If all power companies had shared such information, the criticality accident at Shika plant could have been prevented.

   Hokuriku Electric Power Co. had a criticality accident in 1999 at its No. 1 reactor at the Shika nuclear power plant, but the company concealed this for eight years. This was revealed on March 15, and the company is facing severe public criticism.

   The government role of supervising nuclear power plants is now being called into question.                            - Akahata, March 20 & 21, 2007