TOKYO - Radiation levels in areas affected by the accident at the Fukushima Daiichi nuclear plant operated by Tokyo Electric Power Company Holdings Inc. have fallen somewhat over the past 15 years due to natural decay and decontamination efforts.
However, forests and other areas remain contaminated to a level that would lead to designation as a radiation-controlled area under existing laws, even though residents are allowed to return nearby. Meanwhile, heavily contaminated zones are still designated "difficult-to-return areas" under an extralegal measure that has continued under the nuclear emergency declaration issued since the 2011 nuclear crisis.
A major problem is that the special law enacted after the accident concerning the handling of radioactive pollution introduced a new definition of "accident-derived radioactive materials," effectively treating nuclear accident-caused contamination as a separate category.
According to the "polluter pays" principle, TEPCO should decontaminate and restore all affected areas to their pre-accident state. However, the law has left contamination in forests and other areas outside its target untouched.
With cesium-137, which has a 30-year half-life and is the main source of current contamination, the pollution level will remain unignorable on a century scale.
Japan's Basic Environment Act established environmental standards for polluted materials, but it did not address contamination from radioactive substances prior to the Fukushima accident. Although the exemption for radioactive substances was removed in a 2012 revision, standards have not yet been established.
The government has stated that exposure is regulated at up to one millisievert per year, based on recommendations from the International Commission on Radiological Protection, so new standards are unnecessary.
The figure is a "dose limit," which is the maximum amount of exposure that the public can endure.
The government should promptly establish environmental standards for radioactive materials, including desirable levels of contamination. They should also create hazard maps showing compliance with these standards and provide them to residents as a basis for decision-making to avoid unnecessary exposure.
TEPCO's decommissioning roadmap states that it will remove melted fuel debris from three damaged reactors and complete decommissioning in 2051, 40 years after the accident.
However, even after 15 years, the condition inside the reactors remains unknown. A robotic arm has reportedly been inserted twice to remove debris from the No. 2 unit. But the total amount removed was only about 1 gram. Debris removal is difficult due to the extremely high radiation levels at the site, which can be lethal within minutes.
With an estimated 880 tons of debris, it is difficult to imagine that the cleanup will be finished in 40 years. Clearly, the plant will remain an accumulation site for radioactive waste for at least 100 years.
As 15 years have passed, the government has rolled out a policy to "maximize the use of nuclear power" as if the accident was over.
Regardless of the countermeasures taken after the Fukushima accident, risks of severe accident remain, and operating reactors produce radioactive waste with no clear disposal outlook. Let me ask a question once again: Is it necessary to generate electricity by a method that could render areas within 30 kilometers uninhabitable in the event of an accident?
(Tetsuji Imanaka, born in 1950, is a nuclear engineering specialist at Kyoto University who has worked on damage surveys of the former Soviet Union's Chernobyl nuclear accident and field investigations into the Fukushima accident.)
