Tokyo, Nov 18 (IANS): The operator of the crisis-hit Fukushima Daiichi nuclear power plant Monday began removing nuclear fuel from a storage pool at the Number Four reactor building.
The building was severely damaged by a hydrogen explosion following the March 11, 2011 earthquake-triggered tsunami that knocked out the plant's key cooling systems.
Workers at the stricken facility in Japan's northeast began the year-long mission of removing the highly radioactive uranium and plutonium rods from the storage pool as an essential step towards the eventual decades-long decommissioning process of the entire battered complex located 240 km northeast of Tokyo, Xinhua reported.
The plant's operator, Tokyo Electric Power Co. (TEPCO), embarked on the tricky mission which will see them remove around 1,500 assemblies of nuclear fuel, 1,331 of which are considered to be highly radioactive spent fuel, with the remaining assemblies being unused.
The individual radioactive rods are grouped together in assemblies which must be extracted from the storage pool where they were being kept when the tsunami battered the plant.
TEPCO said that over the next two days it was aiming to remove around 22 of the assemblies, with the entire process expected to take more than a year.
The first 22 units would be transferred into a special steel container through Monday night, the utility said, with workers then using cranes to lift the steel container out of the pool and move it to another storage pool located 100 metres away.
The initial process must be conducted underwater to ensure that no radioactive materials escape into the atmosphere and experts have said that although the process has been performed thousands of times before the tsunami struck, as part of the plant's regular procedures, debris in the pool from the hydrogen explosion could hamper the workers' efforts.
Japan's Nuclear Regulation Authority (NRA) chairman Shunichi Tanaka was quoted by local media Monday as saying that the work required "extreme care and judgment" because the pools are littered with small pieces of rubble as a result of the hydrogen explosion.
"The fuel has to be handled very carefully," Tanaka said. "There is a need to make sure that a fuel assembly is not pulled out from the fuel rack by force when it gets stuck because of the rubble."
Tanaka added that it was possible that "small fissures may get bigger" when fuel is taken out and leaks radioactive gas as a result - an opinion reinforced by the utility itself, along with independent nuclear experts.
TEPCO and nuclear experts concurred that the potential to find previously undetected damage to the fuel assemblies caused by the explosion existed and this could present a massive obstacle to the process, as any damaged assemblies removed from the water could potentially release huge amounts of radiation into the atmosphere before being brought under control.
Levels of radiation at the pool are already at the point where six teams of six workers each will work in two-hour shifts to remove the assemblies to ensure that they are not exposed to extended periods of radioactivity, the utility said Monday.
TEPCO has been plagued by problems since the March disaster and has been grappling to contain a massive daily influx of contaminated water in hastily built storage tanks on the premises.
Some of the tanks have sprung leaks, causing toxic water to flow freely into the adjacent Pacific Ocean. In one instance a tank was overfilled with water by workers, causing radioactive water to spew over the tank's top.
Human error was also responsible for a worker mistakenly removing a pipe connected to a desalination treatment system used to treat water housed to keep melted fuel cool, causing more than seven tons of radioactive water to leak from the pipe for around 50 minutes.
Also, a vital pump used to inject water to cool nuclear fuel inside the Number One turbine building was switched off due to a worker mistakenly pressing a stop button on a switchboard.
In addition to the cooling of nuclear fuel being temporarily suspended in two of the complex's containment units, the decontamination of radioactive gases was also halted due to the error, TEPCO said.
Nuclear watchdogs, in light of such instances of professional ineptitude by workers at the stricken facility, are particularly wary of the utility's current endeavours as the potential for massive radioactive leaks, should something go wrong, is extremely high.
The overall decommissioning of the plant is expected to take around 40 years with the removal of all nuclear fuel from the Number Four reactor building being completed by the end of next year, TEPCO said Monday.