Fukushima Now Part 1: The challenge of obtaining accurate air dose rate data in Fukushima
A citizens’ survey team has conducted air dose rate surveys in Fukushima Prefecture starting from May 2011 at a pace of once a year. The date of departure to conduct the survey differs from year to year, with it being a two-day period this year on June 7 to 8. It is not a well-organized survey based on a set plan, but certain tendencies can be seen throughout the six-year period. Each year, measurements are taken at fixed points along National Routes 114 and 393 going from Fukushima City to Iwaki City.
In the first year, we attempted to conduct a survey, using GPS skirting the 20km line of the evacuation zone starting from the government’s measurement point in Fukushima City, but got out-of-range indications on our mobile phones and had to settle for measurements every 3 kilometers. For the following year’s measurements, we brought a dedicated GPS unit, but measurment error was too large to identify the government’s sites. When we found landmarks, we photographed them for use in confirming our measurement points. That was good, but then they began prohibiting entry to the zones for which evacuation orders had been issued, and we became unable to enter the Tsushima district and other areas to take measurements where we had taken them the first year. Not only that, but traffic was cut off on the roadways, so to reach subsequent measurement points we were forced to detour for quite long distances. On the other hand, we were able to add some measurement points along the way. Of the seven points at which we were able to obtain measurements for all six years, four have been selected for the figure below. We used an Aloka TSC-171 survey meter, taking the average reading of three to five measurements (the number varied depending on the year). This is not the conventional way of taking measurements, but was done to prioritize the number of measurement points.
The readings declined greatly for the first two years, and this is thought to be the result of decontamination efforts. The higher reading at the Teko-oka Tunnel measurement point in the second year (dashed line in the figure) was the result of mistakenly taking the reading at the Iwaki-side entrance.
We became aware of having chosen the wrong entrance when we were processing the data after taking the measurements the second year. That even such a minor difference in location can result in such a major difference in readings gives a sense of the degree of complexity of radioactive contamination.
The area known as Kawafusa in Odaka-ku, Minamisoma, which we visited after completing our air dose rate survey, had been a settlement with 72 households prior to the accident, but only five of those have returned so far. The residents are receiving government assistance to dismantle their old houses, so many of them are leaving their property as vacant land. Also, the four former elementary schools in Odaka-ku have merged into one. Even so, only four students began school there this year, and the entire student body numbers only 60. This elementary school has a large, luxurious sports field covered with artificial turf from edge to edge. The sports fields at the other elementary schools are where each school’s decontamination waste has been landfilled.
Air dose rates have been similarly checked once a year at monitoring posts in Iitate Village. These have been conducted by the Iitate Village Photograph Exhibition Organizing Committee at the suggestion of a former CNIC director, Noboru Kobayashi. This committee was launched in an effort to promote the nationwide exhibition of panels made from a series of photographs taken by Kenichi Hasegawa, an Iitate resident, to keep the memory of the Fukushima nuclear accident from slipping away with time. There are two different sets of panels, Part 1 and Part 2, and the committee places requests with various localities to have them exhibited.
The surveys they are conducting were originally undertaken because some thought the readings at the monitoring posts established by the government did not reflect actual levels and they wanted to see what the reality was. Despite being busy, Mr. Kobayashi has been helping with these measurements. People have participated from as far away as Aomori. We visited Iitate this year on June 21 to 22. Below is a summary of the results and impressions at the time of the survey.
Measurements were made using five devices: two Aloka γ-ray measuring devices with a pocket survey meter, a Taugiken Tanpopo radiation counter, and two HORIBA Radi-3000 radiation monitors (in the table below, the average values of the five measurements have been converted to μSv/h). The figures derived from the measurements taken at the monitoring posts up to that time were about 20% lower than what the committee obtained with the measuring devices they brought in (even greater disparities were found in some places). Moreover, measurements taken short distances away showed much higher readings. These differences have decreased as decontamination proceeds.
The rate of returnees to Iitate is also about 10 percent, with extremely few of the younger generation returning. For a future imaginable to anyone, Mayor Sugano feels no need to limit the citizenry to its former residents and is soliciting people willing to settle there from across the nation. But will any new settlers show up? The biggest source of concern to the younger generation – radioactivity – is a problem for any young person and the mayor understands that well, so he seems to be grasping at straws. Beyond that, there are several unresolved issues such as ensuring employment, so it is difficult to imagine many people taking him up on his offer. For people to spend their youth in a high-radiation environment the likes of which we have never experienced before is, after all, not advisable. In view of our measurements, most people would agree wholeheartedly with that.
There are said to be plans to dismantle as many as 3,000 houses and buildings in Iitate in the future. This is because the government is providing the money to dismantle them. The dismantled houses and buildings will be reduced to ashes at incineration facilities being newly built in Warabidaira, south of Iwaki. Several repositories are being built to hold the incinerator ash and waste materials being brought to the incinerator from current temporary storage locations. The plan is to build more repositories as the amount of incinerator ash increases.
<Hideyuki Ban, CNIC Co-Director>