TEPCO (Tokyo Electric Power Company) has started removing fuel rods from a storage pond at the Unit 4 reactor building of Tsunami-hit Fukushima Daiichi Nuclear power station in Japan.
The first of the fuel-rod assemblies at the plant’s No. 4 reactor building was transferred from an underwater rack on the fifth floor to a portable cask. This step is an early milestone in decommissioning the facility amid doubts about whether the rods had been damaged and posed a radiation risk.
22 unused fuels will be moved to the cask a task which is planned to be completed by November 19. After being filled with fuel, the cask will be closed with a lid, and following decontamination, will be taken down to ground level and transported to the common spent fuel pool on a trailer. It is planned to take approximately one week from placing the fuel into the cask at the spent fuel pool to storing it in the common pool. The entire removal of all fuel inside the Unit 4 spent fuel pool is planned to take until the end of 2014.
“The operation is an important step toward decommissioning Fukushima Dai-ichi, which would take 30-40 years,” TEPCO President Naomi Hirose said in a video message on the company’s website. Explaining the three main decommissioning tasks at the site – extraction of spent fuel, removal of fuel debris, and the ultimate decommissioning of the facility – he announced that today’s “extraction process represents the beginning of a new and important chapter in our work.”
The Unit 4 reactor was offline at the time of the March 2011 disaster. So, its core didn’t melt as Units 1-3 did. But hydrogen explosions blew the roof and walls off the Unit 4 building and weakened the structure, leaving it vulnerable to earthquakes.
Tepco planned to remove 22 assemblies from the pool, which contains 1,331 spent fuel assemblies and 202 unused assemblies .
Japan’s Nuclear Regulation Authority assigned an inspector to oversee the removals, in addition to its existing staff at the plant, and is using video monitoring of the removal.
It is vital that the casks are watertight so the rods have no contact with air – which risks overheating and possible contamination.
Tepco said the company has 36 workers in six teams working two-hour shifts for the encasement process alone.
Some people have voiced concerns over the possibility that the containers used to move the fuel could somehow fall and break. Plant chief Akira Ono, however, has said that Tepco is familiar with the removal process and believes it won’t pose any grave danger..
