Ducts are laid in the No. 1 reactor building of the Fukushima No. 1 nuclear power plant on May 5. (Tokyo Electric Power Co.)
Tokyo Electric Power Co. will soon begin installing a new cooling system for the No. 1 reactor at the crippled Fukushima No. 1 nuclear power plant, a step toward achieving cold shutdown, which means bringing reactor core temperatures under 100 degrees.
The new system, equipped with pumps that can send in 100 to 200 tons of water per hour, is expected to considerably enhance the cooling capacity.
Currently, the reactor is being cooled with a provisional system that injects 8 tons of water per hour.
TEPCO said radioactivity levels in the No. 1 reactor building fell below the target of 0.01 becquerels per cubic centimeter on May 7, two days after a filtering device was set up to remove radioactive materials in the air.
Workers were expected to enter the building as early as May 8 to start preparations for installing the new cooling system.
The new system will extract water from the containment vessel and cool it before sending it back in. The containment vessel, with the pressure vessel inside, is being submerged in water.
In the No. 1 reactor building, high radiation levels of 10 to 40 millisieverts per hour on average were recorded after radioactive materials were released due to a hydrogen explosion on March 12.
On May 5, workers entered the No. 1 reactor building for the first time since the explosion damaged the facility, to install ventilation ducts.
Previously, only robots were able to enter the building due to high radiation levels.
TEPCO also plans to install new cooling systems for the No. 3 and No. 2 reactors by the end of July, but obstacles remain.
At the No. 3 reactor, the temperature at the lower part of the pressure vessel rose in May after staying at around 110 degrees in April. It hit 150.3 degrees as of 11 a.m. May 7.
TEPCO plans to switch to new water-injection piping, saying water may be leaking from a damaged part of the existing piping.
At the No. 2 reactor, the suppression pool connected to the containment vessel is believed to have been damaged.
The damaged part would have to be sealed with concrete before the new cooling system is installed.
(This article was written by Tatsuyuki Kobori and Hidenori Tsuboya.)