The utility had intended to start removing the fuel rods from the unit’s packed cooling pool as early as Friday.
The test was requested by the Japan Nuclear Energy Safety Organization. The government-affiliated agency called for an initial test that would include transporting a protective fuel cask from the No. 4 storage pool to another pool in a different building about 100 meters away, to provide more stable conditions for cooling spent fuel, the sources said.
The agency has already inspected the equipment to be used in the operation on behalf of the Nuclear Regulation Authority. It has also urged Tepco to have its work evaluated by a group of Japanese and overseas experts formed by the International Research Institute for Nuclear Decommissioning, a Tokyo-based organization founded by Japanese government agencies, nuclear facility manufacturers and electric power companies.
Of the four reactors in use at the time of the March 2011 disasters, only the No. 4 unit avoided meltdown because it had been defueled for maintenance and all its rods were sitting in its spent fuel pool.
The building housing the No. 4 reactor and the storage pool, however, was hit by fires and a hydrogen explosion after the station lost power, disrupting the pool’s cooling system. More than 1,300 spent fuel assemblies and more than 200 fresh ones, including some containing plutonium-infused mixed-oxide fuel, remain in the pool.
A crane has been installed to carry a protective cask into and out of the pool. The spent fuel will be placed in the cask and moved to a nearby storage pool by trailer.
The work at unit 4 will mark a new stage in the decommissioning process for the four damaged reactors.
In the meantime, efforts continue to secure the massive amount of highly radioactive water accumulating at the plant from the perpetual cooling operations at the reactors. Ground water creeping into the premises has been compounding the problem, with leaky storage tanks raising public fears of ocean contamination.