Reality of Fukushima cleanup hits Japan
By Daniel Leussink
OKUMA, Japan - Two years after an accident at the Fukushima Daiichi Nuclear Power Plant triggered the worlds' worst nuclear crisis since Chernobyl, decommissioning is set to begin. The threat of extremely hazardous radioactive contamination from the plant - which suffered a triple meltdown and hydrogen explosions - forced tens of thousands of farmers, families and elderly to evacuate from their homes.
The greatest danger has passed since those dark days. In December 2011, the Japanese government declared that the plant had reached a safe state of "cold shutdown". That was nine months after the March 11 magnitude 9 earthquake set the
accident in motion at this nuclear plant 250 kilometers north of Tokyo.
Radioactive contamination levels on site remain extremely high, making the decommissioning of the plant a Herculean task for plant operator Tokyo Electric Power Company (Tepco). The conditions at reactors 1, 2 and 3 remain too severe for workers to enter. Decommissioning is going to take more than a quarter of a century, says Tepco.
"It will take a considerable amount of time before this site will become history," plant manager Takeshi Takahashi told foreign journalists on the second floor of the main anti-earthquake building at the tsunami-hit plant. Bunk beds were lined up against the walls of the room so that it could also be used for staying overnight.
"What we need to do is isolate, remove and store the damaged and broken nuclear fuel safely," said the 56-year-old Takahashi. "This work will take 30 to 40 years to complete."
The task of decommissioning the plant is in the hands of the company that has been battered by the nuclear crisis and dozens of subcontractors who have taken over parts of on-site construction work. It will start at reactor 4, which was not in operation at the time of the accident. The spent fuel pool still holds 1,533 fuel rods. It became exposed to the atmosphere after the upper part of the reactor building was blown off following the hydrogen explosions in reactors 1 and 3.
Tepco is planning to move the undamaged fuel rods from the pool to a newly constructed common fuel pool in an operation that is expected to start in November and take a year to complete. The nuclear rods will remain in the common pool for four or five years before being placed in safer dry casks being built at a site further away from the sea front.
The common pool, capacity 6,800, already holds 6,300 rods. Therefore Tepco is planning to move out some of these rods once the construction of the dry casks is finished to make space for the rods from the pool in reactor 4.
Tepco faces the unprecedented job of having to remove the melted nuclear fuel - including the highly toxic MOX fuel (a mix of plutonium and uranium) from reactor 3 - from the damaged reactors as part of the decommissioning. This work is expected to begin around 2022.
The exact location inside the reactors of the melted fuel remains unclear, according to Asahi Shimbun. It is expected to be scattered within the pressure vessel, containment vessel and piping system of the reactors.
On Wednesday morning, Tepco showed the reactors to the foreign journalists, who were driven around them in a tour bus and allowed to take a look inside the new common pool constructed for the spent fuel rods.
The radiation levels at the plant will be declining in the future. Especially if more and more radioactively contaminated rubble is removed around and inside the reactors as part of the decommissioning of the plant and more of the isotopes contaminating the site reach their half-life.
A huge, squashed construction crane with an arm used to reach up to the roof of the 60-meter high reactor buildings and overturned cars are still abandoned around the area near the ocean side - visible scars from the fight Tepco workers put up in order to stabilize the plant. Here, the radiation levels spiked up rapidly and are still extremely high.
A Tepco spokesperson measured a radiation level of 1,710 microsieverts per hour inside the tour bus on the ocean side outside the turbine building of reactor 3, equal to 14.989,8 millisieverts or 14.9 sieverts per year. If radiation levels do not decline during the course of a year, workers risk taking in 300 times the legal annual radiation dose limit for people at nuclear facilities.
A Tepco spokesperson measured a radiation level of 1,070 per hour at a measure point on the mountainside near reactors 1 and 2, equal to 9,379 millisieverts or 9.3 sieverts per year. That would be 187 times the annual legal limit.
The Japanese government has set this limit at 50 millisieverts per year and 100 millisieverts over five years, according to Asahi Shimbun. The annual limit of 50 millisieverts in Japan is the same as the legal annual dose limit for nuclear workers in the United States. The radiation dose at the main gate of the plant was 5.0 microsieverts per hour.
Perhaps the most dangerous job at the plant will be to decommission reactor 3. Hiroshige Kobayashi, manager of the Fukushima Daiichi Construction Office of Kajima Corporation, and his colleagues are using a large, remotely controlled crane to remove highly contaminated rubble and debris from what he calls the operator floor - the top part including the spent fuel pool - of reactor 3.
"It is a fact that the radiation levels in reactor 3 are high, so what we do is manage the dose [of our exposure]," said 45-year-old Kobayashi.
"We're planning to use remote controlled technologies," he said, adding that this includes technologies he has not experienced before, such as GPS and laser. "Our method for trying to reduce our [exposure] dose is by trying to conduct our work while keeping as much distance as possible."
For Tepco, a goal for the spring of this year includes the endoscopic inspection of the interiors of the reactor containment vessels. After surveying inside the containment vessels of reactors 1 and 2, the company found radiation levels high enough to kill a human within one hour, reported the Asahi Shimbun on February 21. Up to 11 sieverts per hour was detected inside reactor 1 and up to 73 sieverts per hour was detected inside reactor 2.
Tepco also sent Quincy - a remotely controlled exploration robot with a price tag of US$6 million - into reactor 1. It went missing in October 2011.
"Radiation is something that has no color and no smell," said manager Kobayashi. "We always have to be aware that the threat of radiation is something scary. We're talking about it between ourselves in our safety meetings so that we can enhance our safety awareness."
Daniel Leussink is a Dutch writer who has been based in Tokyo since 2007.
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