TEPCO Submits Plan For Fuel Removal At Unit 3 Fukushima Daiichi
TEPCO submitted plans to the NRA for spent fuel removal from unit 3. This included more detail on how they intend to install a cover and remove transit casks from the building.
The defueling building cover bridges the original reactor building, putting the load on the existing scaffolding system and an accessory building.
This structure avoids contact with the reactor well, known to have high radiation levels. TEPCO did not mention any measures to prevent radiation issues from the fuel canal between the reactor and the spent fuel pool. They also do not mention anything about worker exposures or how human work would be conducted. Estimated radiation levels in the area are as high as 1 sievert/hour.
The fuel casks would be moved out of the pool to the left side as seen in the diagram. This would allow them to be lowered to an area near the original garage and hoist entrance. The defueling building will have a new floor suspended over the original reactor building similar to the defueling building of unit 4.
A new crane, made to fit the narrow defueling building will be installed. The lifting mechanism can lift up to 50 tons. Since this crane will be new in design it will likely need NRA inspection and testing before it can be used. TEPCO also outlined the features of the fuel hook they intend to use to grasp assemblies to remove them to the transit cask.
The new transit cask only holds 7 fuel assemblies. TEPCO does not mention why a smaller cask may be used. It could be due to weight limits of the defueling building design.
TEPCO leaves many questions unanswered but it appears they may have at least begun the review process with NRA to proceed with fabricating the new equipment. Removal of small debris, closer inspection of the fuel assemblies and decision on how to handle damaged fuel will still need to be worked out.
Original TEPCO document (in Japanese)
http://www.tepco.co.jp/cc/press/betu14_j/images/140625j0301.pdf
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