Bringing outside electrical power could be a major relief helping cool down dangerously overheated reactors. Also, Japanese authorities raise the severity rating of the nuclear crisis.
The Tokyo Electric Power Co. hopes to reconnect power as early as Saturday to a dangerously overheating nuclear power plant damaged by last week's earthquake and tsunami, Japanese state broadcaster NHK said today.
The power company, also called Tepco, is working to restore power to the six nuclear reactors at the Fukushima Daiichi power station about 140 miles northeast of Tokyo. A new power supply could help run pumps to cool the reactors and their associated spent-fuel ponds, a challenge that's been growing harder ever since the massive magnitude 9.0 earthquake and resulting tsunamis knocked out power and damaged auxiliary cooling pumps.
The International Atomic Energy Agency initially reported yesterday that a new power cable had been connected to reactor 2, which suffered a serious explosion Monday that breached its primary containment vessel, but the U.N. agency corrected its report later to say only that efforts to connect the power were continuing. Another priority is for restored power is reactor 3, which suffered an explosion of its own and which is fueled by a more hazardous combination of uranium and plutonium oxide.
Also Friday, Japan's Nuclear and Industrial Safety Administration announced at a news conference that it has raised its severity rating Fukushima Daiichi plant problem from level 4 to level 5 on the International Nuclear and Radiological Event Scale. That elevates it from an "accident with local consequences" to an "accident with wider consequences." The Three Mile Island accident was rated level 5; the accident at Chernobyl reached topped the severity with a level-7 "serious accident," according to the IAEA (PDF).
On Friday, workers used fire trucks for a second day to douse reactor 3 with water to try to replace what's been evaporating from the hot nuclear fuel. Uncooled and uncovered fuel can release radioactive materials into the surrounding air.
Tepco had been trying to connect the power line Wednesday, but radiation risks postponed the work.
The situation at the reactors is dire. A fire earlier this week forced most of the plant's staff to evacuate, complicating efforts to stabilize temperatures. Today, highly unusual efforts to keep the fuel from overheating included spraying 30 tons of water from trucks and dropping several loads of water from a helicopter.
The power line means cooling reactors with electrical pumps will be much easier. Japanese state broadcaster NHK reported today that the tsunami damaged the main pumps, so makeshift ones will be used instead.
Tepco already had resorted to cooling reactors 1, 2, and 3 with seawater, another last-ditch move because seawater is highly corrosive. Reactors 4, 5, and 6 had been shut down before the quake because of an inspection, but they, too, are a problem because of hot fuel in their spent-fuel ponds. Reactor 4's pond was the site of a serious fire already.
Corrected 2:48 a.m. Friday with new information from IAEA that the power line has not yet been connected and updated with NISA's higher severity rating.