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Tepco Begins Removal Of Fuel Assemblies At Fukushima-Daiichi

By David Dalton
18 November 2013

Tepco Begins Removal Of Fuel Assemblies At Fukushima-Daiichi
The operation to remove fuel assemblies has begun. Photo courtesy of Tepco.

18 Nov (NucNet): Tokyo Electric Power Company (Tepco) this morning began the delicate operation of removing fuel assemblies from the spent fuel pool at Unit 4 of the destroyed Fukushima-Daiichi nuclear power plant.

The company said that at 09:50 local time it had begun preparations for the fuel removal and that at 11:45 it began moving the transportation container to the spent fuel pool.

By 15:27 the container had been lowered into the pool and the first fuel assembly had been loaded onto the container, Tepco said.

“At 15:18 we started to pull up the first fuel assembly with a crane,” a Tepco spokesman said. He said spent fuel removal was a “significant, first major step towards decommissioning the facility”.

A recently installed crane is being lowered into the pool and hooked on to the assemblies to place them inside a cask.

It will take about two days to remove the first 22 fuel assemblies, Tepco said. The assemblies are four-metre long tubes containing pellets of uranium fuel.

Tepco said last week that there are 1,533 fuel assemblies in the pool, with 1,331 used and 202 unused, and their removal to long-term onsite storage is expected to take until the end of 2014.

Unit 4 at Fukushima-Daiichi was offline at the time of the earthquake and tsunami, and all spent fuel assemblies had been transferred to the spent fuel pool. The unused assemblies were being prepared to be inserted into the reactor when the disaster happened.

Removing fuel assemblies from a fuel pool is “a normal operation”, said Tepco, but because of damage caused by a hydrogen explosion at Unit 4 after the March 2011 tsunami and earthquake, the job entails a risk that is “clearly different from normal operations in terms of working environment”.

One particular issue is debris that has fallen into the pool and could not be completely removed because it sits between the fuel racks and the assemblies. Tepco said that to avoid this debris causing any damage to the fuel elements during removal, the process would proceed slowly and be carefully monitored.

Tepco said the removal of the fuel assemblies is necessary because they are sitting in a storage pool that is above ground and in a heavily damaged building that had to be stabilised before beginning the removal.

Tepco said that in December 2012 it conducted a seismic safety evaluation of the Unit 4 reactor building, which showed that even in the event of a major earthquake the earthquake resistance of the reactor building and the spent fuel pool is adequate.

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