Workers decontaminate a road in a special reconstruction district in the town of Futaba, Fukushima Prefecture, in October. | FUKUSHIMA MINPO

February 26, 2021

Traffic was lighter on the Joban Expressway in the Futaba district in Fukushima Prefecture during the New Year holiday, with people avoiding traveling back to see their relatives due to the novel coronavirus pandemic.

Roadside signs show the radiation levels of areas near the no-go zones put in place after meltdowns in 2011 at the Fukushima No. 1 nuclear plant, reflecting the fact that, even after 10 years, Fukushima residents are unable to return to their homes.

The no-go zones, which are considered uninhabitable for the foreseeable future due to high radiation levels, stretch through six Fukushima towns and villages: Tomioka, Okuma, Futaba, Namie, Katsurao and Iitate. Parts of those zones are now designated as special reconstruction districts, where the government will concentrate its decontamination efforts so that residents can return to their homes in the future.

A decade after the tsunami-triggered nuclear disaster, decontaminating the areas damaged by the fallout is a crucial part of the reconstruction that will pave the way for evacuees to come back to their homes and resume the life they had before the disaster.

But two figures of radiation exposure levels — 20 millisieverts a year and 1 millisievert a year — that the government provides as safety criteria are causing confusion among residents, triggering criticism of what could be called a double standard.

One of the criteria for the government to lift evacuation orders is whether the area’s annual cumulative radiation level has become 20 millisieverts or below, based on a recommendation from the nongovernmental International Commission on Radiological Protection.

When there is a nuclear disaster similar to that at the Fukushima No. 1 nuclear power plant, the ICRP recommends that annual radiation exposure should be limited to between 20 to 100 millisieverts immediately after the disaster. It then recommends the exposure is lowered to between 1 to 20 millisieverts during the reconstruction period.

As the minimum recommended exposure level right after a disaster, the 20 millisieverts mark became the radiation level yardstick for the central government to order the evacuation of a certain area after the nuclear meltdowns.

Meanwhile, the government has set up a long-term decontamination goal of reducing the radiation levels of contaminated areas to an annual 1 millisievert and below. This is to keep a lifetime exposure level below 100 millisievert — the level at which it starts to affect one’s health.

Therefore, the government stipulated the annual 1 millisievert exposure level in its reconstruction policy plan for Fukushima approved by the Cabinet in July 2012. The Environment Ministry aims to keep radiation levels in the special reconstruction district under 1 millisievert as a long-term goal.

However, the no-go zones had been above 50 millisieverts on an annual basis immediately after the nuclear meltdowns. The radiation level is on the decline with natural attenuation of radioactive cesium as well as weathering effects, but there are still patches with high radiation levels.

Even within the no-go zones, there is no easy way to carry out decontamination. Typically it is done by mowing lawns, raking up fallen leaves, washing down roads and other surfaces with a high-pressure water hose, and wiping off the walls and roofs of buildings and housing.

“It’s not easy to bring down radiation levels to 1 millisievert or below just with decontamination,” said an Environment Ministry official in charge.

In Article 1 of the radiation decontamination legislation established after the nuclear disaster, it is stipulated that the purpose of decontamination is to “minimize the health risks of radioactive exposure as much as possible.”

Despite the criteria for easing evacuation orders and the long-term goal on bringing down radiation levels, it is unclear how the government can lower radiation levels to 1 millisievert after evacuation orders are lifted for no-go zones.

The two figures are creating a confusion among local residents, who are torn between the desire to return to their homes and concerns over the radiation level.

“I won’t feel safe until annual radiation levels are below 1 millisievert,” one resident said, while another said, “Can you say for sure that an annual exposure of 20 millisieverts won’t affect our health in the future?”

https://www.japantimes.co.jp/news/2021/02/26/national/fukushima-radiation-criteria/