Smoke billowed from a building at Japan’s crippled nuclear power plant Friday as emergency crews worked to reconnect electricity to cooling systems and spray more water on the overheating reactors at the tsunami-ravaged facility.
Four of the troubled Fukushima Dai-ichi plant’s six reactors have seen fires, explosions or partial meltdowns in the week since the tsunami. While the reactor cores where energy is generated are a concern, Japanese and U.S. officials believe a critical danger are the pools used to store spent nuclear fuel: fuel rods in one pool were believed to be at least partially exposed and in danger of leaking radiation.
Friday’s smoke came from No. 2 reactor, and its cause was not known, the nuclear safety agency said. An explosion had hit the building on Tuesday, possibly damaging a crucial cooling chamber that sits below the reactor core.
More urgent, Japan’s chief government spokesman said, was the adjacent No. 3 reactor. Fuel rods there may have been partially exposed, and without enough water, the rods may heat further and possibly spew radiation. Frantic efforts were made Thursday to douse the unit with water, using helicopters and firetrucks, and authorities prepared to repeat the effort Friday.
“Dealing with No. 3 is our utmost priority,” Chief Cabinet Secretary Yukio Edano told reporters.
In the week since the massive earthquake and tsunami, Japan’s government and the utility that runs Fukushima have struggled to contain the plant’s cascading troubles.
Edano said Friday that Tokyo is asking the U.S. government for help and the two are discussing the specifics. “We are coordinating with the U.S. government as to what the U.S. can provide and what people really need,” Edano said.
The U.S. and Japan, close allies, have offered differing assessments over the dangers at Fukushima in recent days. U.S. Nuclear Regulatory Commission Chairman Gregory Jazcko said in Washington Thursday that it could take days and “possibly weeks” to get the complex under control. He defended the U.S. decision to recommend a 50-mile (80-kilometer) evacuation zone for its citizens, wider than the 30-mile (50-kilometer) band Japan has ordered.
Crucial to the effort to regain control over the Fukushima plant is laying a new power line to the plant, allowing operators to restore cooling systems to the reactors. The operator, Tokyo Electric Power Co, missed a deadline late Thursday but said Friday workers hoped to complete the effort, first reconnecting No. 1 reactor.
There was some good news earlier Friday. Radiation readings at the troubled nuclear plant have consistently followed a downward path through Friday morning, according to Nuclear and Industrial Safety Agency measurements taken roughly 1 kilometer west of the plant’s No. 2 reactor.
The agency said the radiation reading at 5 a.m. Friday came to 279.4 microsievert per hour, compared with 292.2 microsievert per hour at 8:40 p.m. Thursday, shortly after the Self-Defense Forces discharged water from fire trucks in an attempt to cool an apparently overheating spent fuel pool.
In an unprecedented move, up to 64 tons of water was discharged by helicopters and fire trucks of the SDF as well as a water cannon truck of the Metropolitan Police Department into the pool at the No. 3 reactor.
The mission is continuing Friday as part of the effort to avert any massive release of radioactive materials into the air from the pool, while efforts to restore the lost cooling function by reconnecting electricity to the plant through outside power lines have accelerated, according to the government.
The spent fuel pools at the power station lost their cooling function after the quake and tsunami struck last Friday. It is also no longer possible to monitor the water level and temperature of the pools of the No. 1 to 4 units.
Among the six reactors, the No. 1, No. 2 and No. 3 reactors that were operating at the time of the quake halted automatically, but their cores are believed to have partially melted as they lost their cooling functions after the quake.
The buildings housing the No. 1, No. 3 and No. 4 reactors have been severely damaged by apparent hydrogen blasts, and the No. 2 reactor’s containment vessel suffered damage to its pressure-suppression chamber at the bottom.
Prime Minister Naoto Kan expressed his gratitude to SDF personnel and police officers who were engaged in the daunting mission despite high radiation levels, saying at a government taskforce meeting, ‘‘I thank them for carrying out such dangerous operations.’‘
No grave health hazard has so far been reported among SDF and police officers who were involved.
Hidehiko Nishiyama, an agency spokesman, said efforts to bring electricity back to the plant by using outside power lines could be completed by Saturday to recover the lost cooling functions at the No. 2 reactor building, which he said takes priority over other the troubled reactors as it cannot be doused since the roof of its building is still intact.
TEPCO also plans to install a temporary power source in an area of the plant where the radiation level is low.
As for the remaining reactors that along with the No. 4 unit were under maintenance when the quake occurred, TEPCO officials said that it would be ‘‘some time’’ until the No. 5 and No. 6 units reach a dangerous situation
