21 Décembre 2014
December 21, 2014
THE ASAHI SHIMBUN
OKUMA, Fukushima Prefecture--Tokyo Electric Power Co. removed the last four nuclear fuel assemblies that remained in the No. 4 reactor building of the crippled Fukushima No. 1 nuclear power plant from its storage pool on Dec. 20.
The No. 4 reactor was offline at the time of the March 11, 2011, Great East Japan Earthquake and tsunami. However, an explosion occurred in the building four days later, seriously damaging it.
After the accident, experts pointed to the risk of nuclear fuel in the pool melting from insufficient cooling and releasing a large amount of radioactive materials. However, the threat has been mitigated with the removal of the last assemblies.
On Dec. 20, TEPCO allowed the media to watch the removal work.
Workers pulled up from the pool a cask containing the last four unspent nuclear fuel assemblies. They plan to transfer it to the No. 6 reactor building, which sustained relatively minor damage in the disaster, within a few days after decontaminating the outside of the cask.
The transfer will mean that all of the nuclear fuel in the No. 4 building has been removed from the building as scheduled by year-end.
The pool had held a total of 1,535 nuclear fuel assemblies, which consisted of 1,331 spent and 204 unspent nuclear fuel assemblies.
TEPCO started the removal of those assemblies from the pool in November 2013 after installing a new roof and a crane on the building. The removal of spent nuclear fuel assemblies concluded in November this year.
There will be no work in the No. 4 reactor building for the time being. TEPCO will be engaged in efforts at the No. 1, No. 2 and No. 3 reactor buildings and in dealing with the growing volume of contaminated water partly resulting from efforts to keep the reactors from overheating.
(This article was written by Yu Kotsubo and Hiromi Kumai.)
Tokyo Electric Power Co. (TEPCO) removed the final four fuel rods from the spent fuel pool in the No. 4 reactor building at the Fukushima No. 1 nuclear plant on Dec. 20 -- one year ahead of schedule.
The timeline for the spent fuel removal project was moved up due to worries over whether the No. 4 reactor building -- heavily damaged by a hydrogen explosion following the March 2011 Great East Japan Earthquake and tsunami -- could withstand earthquakes.
The No. 4 reactor was undergoing a regular inspection when the disasters struck, so the fuel was not in the core at the time. A total of 1,535 fuel rods were inside of the unit's nuclear fuel pool -- 1,331 of which were spent fuel, and 204 were unused -- the highest number among all of the four damaged reactors at the Fukushima plant.
TEPCO began the operation to remove the extremely radioactive spent fuel in November 2013, and finished transferring them to a separate pool in November of this year before subsequently beginning removing the unused fuel. A TEPCO representative commented, "We'd like to use this experience with reactor No. 4 as a model for the other reactors."
While contaminated machinery from the time of the accident remains inside the No. 4 reactor building, removing it remains a low priority and there are no plans to do so yet.
Meanwhile, residents of six areas evacuated following the meltdowns will be allowed to stay overnight in their homes for the holiday season. Residents are usually only permitted to visit during daylight hours.
According to the government's nuclear emergency response headquarters, overnight stays will be allowed for the 30-day period from Dec. 20 through Jan. 18 for residents from the village of Iitate, the city of Minamisoma, the town of Kawamata and the village of Katsurao; for the 9-day period from Dec. 27 through Jan. 4 for residents from the village of Kawauchi; and for the 15-day period from Dec. 24 through Jan. 7 for residents from the town of Naraha.
Some 9,880 households and 26,740 residents are eligible for the holiday overnight stay program. Meanwhile, residents from those areas designated "difficult-to-return zones," where yearly radiation levels are above 50 millisieverts, are not eligible.
December 20, 2014
Tepco said Saturday it has finished removing all fuel rods from the spent-fuel pool in the shattered reactor 4 building at the Fukushima No. 1 nuclear plant, in a rare piece of positive news from the decommissioning process.
A total of 1,535 fuel rod assemblies, comprising 1,331 deemed at risk and 204 that were unused, have been transferred to other buildings following a yearlong process by Tokyo Electric Power Co., the beleaguered operator of the wrecked plant.
According to Tepco, this will reduce the risk of the spent fuel rods being exposed in the event of a new earthquake or a major accident.
“Completion of the removal work is a milestone and I feel deeply about it,” plant chief Akira Ono told reporters, while stressing that the decommissioning of Fukushima No. 1 remains an extremely lengthy process.
The overall cleanup and dismantling of the plant, an operation that is expected to take decades, has been delayed by a relentless on-site buildup of toxic radioactive water.
Reactor 4 avoided a core meltdown when the tsunami spawned by the March 11, 2011, earthquake ripped through the No. 1 plant, as the unit was offline for a regular inspection and all of its fuel was stored in the pool on the upper level of the building.
But the building was torn apart by a hydrogen explosion just days later as the enormity of the nuclear crisis was only just becoming apparent. The over 1,500 fuel rod assemblies that continued to be stored at the top of the devastated structure had remained a major source of concern, in Japan and overseas.
Tepco hopes to begin extracting the fuel from the reactor 3 spent-fuel pool in the next fiscal year beginning in April, and to begin the same operation at reactor 1 during fiscal 2017. But it is unknown whether the work will follow that schedule given the sky-high radiation levels that continue to plague reactors 1 through 3, which each suffered core meltdowns, and which put the levels clocked in reactor 4 in the shade.