The Tokyo Electric Power Co. will start operating a cooling system by the end of May for the Fukushima No. 1 nuclear plant's No. 1 reactor, the utility company said May 4.
The Tokyo Electric Power Co. will start operating a cooling system by the end of May for the Fukushima No. 1 nuclear plant's No. 1 reactor, the utility company said May 4.
The system will extract water from the containment vessel and cool it before sending it back in. TEPCO intends to have the system operational as early as late May, and it also plans to introduce similar systems to the No. 2 and No. 3 reactors by July.
At the No. 1 reactor, TEPCO says an operation called "water entombment" is under way, whereby the containment vessel, with the pressure vessel inside, is submerged in water.
The cooling system being developed will make use of pipes that have been used to inject nitrogen into the containment vessel, with the addition of new pipes that will remove hot water covering the nuclear fuel rods in the reactor core.
TEPCO said it would be difficult to restore the cooling system used in previous operations because the equipment is housed in a room that contains high levels of radiation.
Cooling will be conducted in two steps. First, water in the containment vessel will be pumped at 100 tons per hour to a heat exchanger installed near the equipment hatch of the reactor building.
The water will be cooled by transmitting heat to water coming from a different route. The heated water will then be pumped at 200 tons per hour to equipment beside the building where it will be cooled by a large fan.
This will enhance the cooling capacity considerably in comparison with the current water injection at rates of several tons per hour.
Installation of the air-cooling apparatus will begin May 8, and the installation of the heat exchanger and piping will start May 16. The work will be completed and the cooling equipment will become operational in late May at the earliest.
TEPCO intends to bring down the temperature of water in the reactor below 100 degrees a few days after the system is fully operational.
Installation of the heat exchanger involves difficulties, including installation of pipes in the reactor building where radiation levels are high. To reduce the levels of radiation, preparatory work was done May 4 to install an apparatus to eliminate radioactive substances suspended in the air in the building.
TEPCO was scheduled to put the apparatus into operation May 5 to ensure that workers can enter the building from May 8, whereupon measurement instruments in the reactor building will be repaired and inspected.
TEPCO said May 5 that two employees entered the No. 1 reactor building for the first time since March 12, when a hydrogen explosion damaged the facility.