14 Avril 2013
April 12, 2013
A rat causing a power outage by short-circuiting a temporary switchboard. Another blackout occurring as workers install antirat nets. Holes in the linings of huge sunken reservoirs leaking radioactive water.
Tokyo Electric Power Co.’s crippled Fukushima No. 1 nuclear power plant has run into a string of problems the past few weeks that highlight its precarious state more than two years after three of its six reactors melted down in the wake of a devastating earthquake and tsunami.
A makeshift system of pipes, tanks and power cables meant to carry cooling water into the melted reactors and spent-fuel pools inside shattered buildings remains highly vulnerable, Nuclear Regulation Authority Chairman Shunichi Tanaka acknowledged Wednesday.
“Fukushima No. 1 is still in an extremely unstable condition. There is no mistake about that,” Tanaka said at a weekly meeting of the regulatory body’s leaders. “We cannot rule out the possibility that similar problems might occur again. Whenever a problem occurs, it halts the plant’s operations and delays the primary goal of decommissioning the plant.”
The problems have raised doubts about whether the plant can stay intact through a decommissioning process that could take 40 years, prompting officials to compile risk-reduction measures and revise decommissioning plans. The regulatory watchdog said Wednesday it would add a ninth on-site inspector in order to better oversee the plant.
Just over the past three weeks, there have been at least eight accidents or problems at the plant, the NRA said.
The spate of problems started March 18, when a rat got into an outdoor switchboard — which was sitting on a pickup truck — powering the jury-rigged cooling system and several other key parts of the plant, causing a short-circuit and blackout that lasted 30 hours in some areas of the plant. Four storage pools for fuel rods lost cooling during the outage, causing Tepco to acknowledge that it had added backup power only to the reactors, despite repeated concerns raised over a pool meltdown.
The cause of the outage wasn’t clear at the time, but Tepco later released a photo of the electrocuted rat, which had fallen on the bottom of the switchboard housing. The most extensive outage since the crisis started after the March 2011 disasters caused more Fukushima residents to even consider evacuation.
Two weeks later, a new water processing machine designed to remove most radioactive elements temporarily stopped after a worker pushed a wrong button. The next day, one of the fuel storage pools lost power again for several hours when part of a wire short-circuited a switchboard while an operator installed antirat nets. Tepco reported three other minor glitches on the same day, including overheating of equipment related to boron injection to the melted reactors.
Regulators acknowledge that rats and snakes are abundant at the plant, and Tepco has started to take steps to protect pipes and cables from rat gnawing. Replacement of parts and equipment to those of higher quality and long-term use is in progress.
In the latest development, three of the plant’s seven sunken reservoirs are leaking. Tepco reported the first leak early Saturday, hours after the plant’s second power outage. Within days, it was learned that three reservoirs were leaking, paralyzing the plant’s storage plans for contaminated water.
Tepco says none of the about 120 tons of radioactive water that leaked was believed to have reached the ocean. Experts suspect the radioactive water has been leaking from the plant since early on in the crisis, citing high contamination in fish caught just off the plant.
The contaminated water is a headache for the plant, and by far the most serious of the recent problems because of its potential impact on water management and the environment.
The tanks are crucial to the management of contaminated water used to cool melted fuel rods at the plant’s wrecked reactors. They have since stabilized significantly, but the melted fuel inside must be kept cool with water, which leaks out of the reactors’ holes and ruptures and flows into basement areas.
“The contaminated water situation is on the verge of collapse,” Tanaka said. But he said there was no choice but to keep adding water, while trying to seek ways to minimize the leaks and their risks.
To address local outrage over the recent problems and Tepco’s failure to detect problems earlier, company President Naomi Hirose traveled to Fukushima and apologized Wednesday for the problems. He promised to expedite the construction of steel containers and move all the water there from the sunken reservoirs, at the request of industry minister Toshimitsu Motegi.
The reservoirs, all built by Maeda Corp., come in different sizes, including one the size of an Olympic swimming pool and similar to an industrial waste dump.