Japan: Teams race to restore cooling functions at nuclear reactors - March 19, 2011
Cooling 3rd reactor of Fukushima Daiichi nuclear-power complex by Japan self defence force at Mar.18, 2011
Teams race to restore cooling functions at nuclear reactors
Saturday 19th March, 04:07 PM JST
Japan on Saturday continued efforts to contain the quake-triggered crisis at a nuclear power plant, with Tokyo Electric Power Co trying to bring electricity back to its crippled nuclear reactors in the hope of restoring their cooling functions, while firefighters again threw water to cool down overheating spent fuel pools.
Connecting a power line to the No. 2 reactor of the Fukushima Daiichi power plant is expected to be completed during the day.
Restoring a stable source of electricity is a key step to prevent further deterioration of the situation by cooling down the reactor cores or water in the spent fuel tanks.
After smoke was detected from the No. 3 reactor building on Wednesday, Self-Defense Forces, firefighters and others have engaged in an unprecedented mission to spray massive amounts of water at the damaged building so that the spent fuel pool located inside would fill with water, which is vital to prevent radioactive release.
The Tokyo Fire Department, including disaster relief specialists of its ‘‘hyper rescue’’ team, discharged 60 tons of water early Saturday and resumed the work in the afternoon and continued shooting water for seven hours. But the firefighters are believed to have left the water cannon truck unmanned apparently out of concerns over the radiation level in the area.
The Tokyo Fire Department said the dose that workers were exposed to so far was not ‘‘at a level that would affect health.’‘
Meanwhile, a Ground Self-Defense Force helicopter flew over the troubled Daiichi plant Saturday morning to check the changes in temperatures at its reactors using thermography, the Defense Ministry said.
The CH47 chopper also examined what effect the water sprayed on the reactor had in cooling the spent fuel pool, it said.
In the afternoon, Defense Minister Toshimi Kitazawa told a press conference that the examination found the surface temperatures at the No. 1 to No. 4 reactors remained at 100 C or lower and that their conditions remain stable.
Prime Minister Naoto Kan instructed Kitazawa to keep monitoring around the plant.
A rise in water temperature, usually to 40 C, causes the water level to fall, thus exposing the spent nuclear fuel rods, which could then heat up further, melt and discharge highly radioactive materials in the worst-case scenario, experts say.
According to the plant operator Tokyo Electric, the maximum earthquake intensity measured at the nuclear power plant was 507 gals at the No. 3 reactor building, smaller than 600 gals the nuclear plant is required to withstand. The data is a provisional figure.
The Nuclear and Industry Safety Agency has raised the severity level of the crisis-hit reactors to 5 from 4 on an international scale Friday, the same level as the Three Mile Island accident in the United States in 1979.
Among the six reactors at the Fukushima Daiichi Nuclear Power Station, the No. 1, No. 2 and No. 3 reactors, the only ones operating at the time of the magnitude 9.0 quake, halted automatically, but the cores are believed to have partially melted as the reactors lost cooling function after the quake.
The buildings housing the No. 1, No. 3 and No. 4 reactors have been severely damaged, leaving fuel pools there uncovered, and the No. 2 reactor’s containment vessel suffered damage to its pressure-suppression chamber below.
The No. 5 and No. 6 reactors were under maintenance at the time of the quake. It is now possible for these reactors to cool spent fuel by circulating water in the storage pools.