- Tepco continues search for melted fuel at bottom of reactors
- Once fuel is located, development of removal system begins
Five years after the triple meltdown at Tokyo Electric Power Co.’s Fukushima Dai-Ichi nuclear plant north of Tokyo, decommissioning and cleanup continue. The following is a short question and answer on the situation at the site of the worst atomic disaster since Chernobyl.
What is the current state?
Tepco, as the utility is known, continues to search for the fuel that melted through the bottom of the three reactor chambers after the March 11, 2011, earthquake and tsunami knocked out the facility’s cooling system. Due to the dangerously high radiation levels in the reactor buildings, humans can’t enter. While the company has used cosmic ray photographs and computer models to estimate the approximate location, advanced robots must be used to find it.
Water management is another pressing issue. About 150 metric tons of water -- less than the amount of water in one lane of an Olympic-sized swimming pool -- flow into the reactor building daily from the nearby hills. The water mixes with the melted fuel, becomes contaminated and is pumped into tanks on the site. Tepco will begin operating a frozen soil barrier surrounding the wrecked buildings to keep out water after the Nuclear Regulation Authority endorsed its plan last week.
How do they get the melted fuel out?
Once robots developed by Hitachi Ltd. and Toshiba Corp. locate the melted fuel, planning can begin to remove it. Leading the development of the removal system is the International Research Institute for Nuclear Decommissioning, a group of 18 Japanese companies and organizations formed in 2013 to support Fukushima’s decommissioning.
Depending on the location of the melted fuel, a robotic arm and crane system could retrieve the melted fuel debris through the roof of the reactor or through the side, according to Hirofumi Kinoshita, chief project manager for Hitachi’s Fukushima nuclear business department.
This approach would be drastically different than what was done at Chernobyl, which was buried in a concrete sarcophagus with no attempt to remove the fuel.
How much will the Fukushima disaster cost?
The nuclear accident and its fallout will ultimately cost more than 11 trillion yen ($97.3 billion), according to a study by Japanese college professors including Kenichi Oshima, a professor of economics at Ritsumeikan University.
Tepco has spent 444.2 billion yen decommissioning reactors 1 to 4 as of December, according to company spokeswoman Yukako Handa. Water management and reactor stabilization will cost more than 1 trillion yen in the 10-year period ending March 2025, according to Tepco.
What happens next?
Tepco will remove used fuel rods -- which are separate from the melted fuel -- that remain in containment pools of water in the top floors of reactors No. 1, 2 and 3 where they were stored before the accident. Tepco will begin removing the spent rods in the No. 3 reactor within about two years with a robotic claw system. Removal in the No. 1 and No. 2 reactors won’t begin until 2020 at the earliest.
The entire decommissioning process, including finding and removing the melted fuel at the bottom of the reactors, will take another 30 years to 40 years, according to Tepco.
What has changed?
A new nuclear regulatory body, known as the Nuclear Regulation Authority, was established in 2012 to replace a predecessor criticized for ignoring warnings before the Fukushima disaster and having cozy ties with operators. The NRA judges whether facilities meet safety guidelines for restart.
All of Japan’s nuclear reactors were eventually shut for safety checks following the Fukushima disaster. While four of the nation’s 43 operable reactors have restarted so far under post-Fukushima safety rules, a local court has subsequently issued an injunction preventing two of the recently restarted reactors from operating because of safety concerns.
The government still sees nuclear energy playing an important part in its energy mix and has set a target for atomic energy to make up a quarter of its electricity supply by 2030.