Tokyo Electric Power Co. said the tsunami generated by last month’s earthquake was as high as 15 meters at its crippled nuclear station, which has been leaking radiation since the surge knocked out backup power systems.
The utility provided its first assessment of the height of the tsunami since the March 11 quake, after criticism from the government and evacuees that it was slow in responding to the disaster. The base of the station is about 10 meters (33 feet) above sea level.
“Most of the area around the reactor buildings and turbine housings was swamped,” the utility known as Tepco said in a statement late yesterday.
Almost one month on from the disaster, Tepco is still using emergency equipment to try to cool reactors damaged at the Fukushima Dai-Ichi station north of Tokyo after mains electricity was knocked out. The company is trying to prevent further explosions after blasts damaged containment structures, releasing radiation into the air and sea.
Tepco plans to start transferring high-level radioactive water in a trench at the station’s No. 2 reactor to a condenser.
“We aim to drain the contaminated water away immediately as the level has risen to less than one meter below the top of the trench,” said Teruaki Kobayashi, the head of the company’s nuclear maintenance group, today in Tokyo.
About 60,000 metric tons of contaminated water lies in the basements of turbine buildings and trenches around the No. 1, 2 and 3 reactors, the company said last week. Tepco needs to drain the water to restore reactor cooling systems in the turbine buildings.
Tokyo Electric plans to complete the release of low-level radioactive water into the sea from a waste treatment facility at the plant today, Jun Nakagawa, a spokesman for the utility, said by phone from Tokyo.
The company plans to use the space for storage for more contaminated water.
“Work to restore the cooling systems is lagging behind because it’s taking longer than expected to drain radioactive water from the basements,” Hironobu Unesaki, a nuclear engineering professor at Kyoto University, said yesterday.
The utility plans to begin using a remotely controlled helicopter to investigate conditions at the nuclear station today, a day behind schedule because of bad weather, Naoki Tsunoda, a spokesman for the utility, said yesterday.
Tepco said on April 8 that the station, which has six reactors and is about 220 kilometers (137 miles) north of Tokyo, wasn’t further damaged by a magnitude-7.1 aftershock on April 7.
The March 11 magnitude-9 earthquake, Japan’s strongest on record, and tsunami left more than 27,700 dead or missing as of 10 a.m. Tokyo time yesterday, according to Japan’s National Police Agency. The government estimated the damage at 25 trillion yen ($295 billion).
Almost 85,000 people in Fukushima remain in evacuation centers after leaving the area around the nuclear power plant or because their homes were destroyed in the tsunami, according to the prefectural government’s website.
Fifteen engineers were able to return to the nuclear plant site after the April 7 quake. They continue to pump nitrogen into one of the reactors, part of an effort to prevent hydrogen explosions at the plant, Tokyo Electric said.
There have been no indications of plant damage at Fukushima Dai-Ichi or changes in radiation levels following the aftershock, Takashi Kurita, a company spokesman, said April 8.
At Tepco’s Fukushima Dai-Ni power plant, located to the south of the Dai-Ichi station, the tsunami surge reached as high as 7 meters, damaging a heat exchanger, without reaching the turbines or reactors. The station has been in cold shutdown since the disaster.
The company’s stock has fallen 80 percent since March 10, the day before the disaster. The shares rose 80 yen, or 24 percent, to 420 yen on April 8, their biggest gain since 1974.