The Environment Ministry released a road map on Jan. 26 for decontaminating areas around the Fukushima No. 1 nuclear power plant, hoping to provide encouragement for residents forced to flee the radioactive fallout from the accident.
The Environment Ministry released a road map on Jan. 26 for decontaminating areas around the Fukushima No. 1 nuclear power plant, hoping to provide encouragement for residents forced to flee the radioactive fallout from the accident.
"I hope the evacuees will be able to return to their homes as early as possible," Environment Minister Goshi Hosono told reporters.
But not all evacuees received a timeline for when they might eventually be allowed return to their homes. Given the enormity of the decontamination project, the road map showed that the most dangerous areas will be virtually abandoned for the time being and that much of the plan could end up depending largely on natural decreases in radiation levels.
According to the document, the central government will be directly involved in decontamination work in the no-entry zone within a 20-kilometer radius of the nuclear plant and the "planned evacuation zone" extending beyond that radius in the northwest direction.
In areas with annual radiation doses below 50 millisieverts at a height of 1 meter above ground, work should be completed by March 2014 to reduce the level to 20 millisieverts or less, making those areas habitable, according to the road map.
The ministry, however, decided that it would be difficult to achieve that reduction goal in areas with annual doses exceeding 50 millisieverts.
The Environment Ministry used a three-way zoning structure based on radiation levels to determine priority for decontaminating land plots other than forests--including residential land for about 60,000 households, farmland, commercial and industrial estates.
For "zones being prepared for the lifting of the evacuation order," with annual doses of 20 millisieverts or less, explanatory meetings will be held for evacuees from those areas as early as this month on steps for their return home.
Owners and occupants of privately owned land will be asked to approve workers’ entry into and decontamination of their properties.
The efforts will start in areas with annual doses of 10-20 millisieverts, where a sizable reduction can be expected and the reduction goal is 10 millisieverts or less. A stricter reduction target of 1 microsievert per hour (corresponding to 5 millisieverts per year) or less will apply to schools.
Decontamination work, including soil removal, will begin in July and hopefully be finished by December 2012, according to the road map. That time frame may provide an indication of when the evacuation order will be lifted.
Owners’ approval will be sought and decontamination efforts will start in June for areas with annual doses below 10 millisieverts.
Under the road map, decontamination will be finished by March 2013 in areas between 5 and 10 millisieverts and by March 2014 in areas between 1 and 5 millisieverts.
March 2014 is also the target date for completing decontamination in the "no-residence zones," or areas with annual doses between 20 and 50 millisieverts. The target for dose reduction there is 20 millisieverts or less per year.
But for the "no-return zones," where annual doses exceed 50 millisieverts, the road map provided no specific schedule for decontamination work, leaving room for abandonment of efforts as an option. Only pilot decontamination programs will be conducted in those zones.
A report by International Atomic Energy Agency investigators who visited Japan in October advised Japanese authorities to "maintain their focus on remediation activities that bring the best results in reducing the doses to the public."
An expert advisory panel to the administration of Prime Minister Yoshihiko Noda also said there should be a rationally defined order of priority for decontamination work.
The latest road map, which placed the foremost priority on areas with intermediate annual doses of between 10 and 20 millisieverts, has drawn on those recommendations.
However, Tokyo has made little progress in discussions with local governments over where to build intermediary storage facilities for contaminated soil and other radioactive waste. The central government envisages building the intermediary storehouses in the no-return zones where full-scale decontamination efforts have been postponed. A schedule for decontamination work there will only be mapped out next year at the earliest.
"We have let it be known, in an objective manner, that the situation has become more difficult for people from the no-return zones (to return home)," Hosono said.
The postponement of decontamination efforts in the no-return zones may be intended to make it clearer that those zones are reserved for intermediary storage facilities.
The Environment Ministry also does not fully understand the effectiveness of different decontamination methods in different locations.
Existing decontamination measures sometimes fail to reduce radiation levels on asphalt and tiled roofs because washing them with detergent and water does not always eliminate radioactive substances that have slipped into small openings.
"Repeated decontamination work has only limited effects," said Soichiro Seki, a senior ministry official. "Once decontamination work is done, there is no way but to wait for a spontaneous decrease. There is no miracle wand for decontamination."
The ministry hopes to draw on pilot projects to investigate the extent to which radiation levels can drop.
Although the results of the pilot programs are not yet available, decontamination is already being prepared in areas of relatively low radiation levels so that evacuees can return home as early as possible.
By contrast, decontamination may not be an urgent priority in the no-return zones, where the central government may either buy up or temporarily lease land plots in the future.
Another question concerns radiation exposure to workers directly involved in decontamination efforts.
The government hopes about 30,000 people will be involved in the work, but their health control poses a major issue. Radiation protection using vests containing lead or other metals is not practical for work because they each weigh several kilograms.
The basic policy stated in the latest road map set a "long-term goal" of dose reduction to 1 millisievert or less per year, or to levels before the nuclear disaster started on March 11 last year.
The government projects that doses will be halved in the first two years, but that forecast takes into account a natural decrease. Decontamination will account for only just over 10 percent of the reduction.
Given the current technological level, the only approach available, once all decontamination work described in the road map is completed, is to sit back and wait for radioactive substances to decrease spontaneously.
The Environment Ministry hopes the public release of the road map will help local governments accelerate decisions on choosing locations for temporary storage for contaminated soil. But it remains to be seen whether the passive approach to rely on spontaneous decay alone after spring 2014 can gain the understanding of local residents.
(This article was compiled from reports by Harufumi Mori, Shinichi Sekine and Takashi Sugimoto.)