16 Avril 2015
April 16, 2015
The average radiation exposure of workers removing radioactive contamination from the Fukushima nuclear disaster has been 0.5 millisieverts a year, according to an April 15 announcement from the Radiation Effects Association (REA), which is managing workers' radiation exposure.
It was the first release of such information from the REA, and it covered around 26,000 workers. The highest yearly radiation exposure for any of the workers was 13.9 millisieverts, and the Ministry of Health, Labor and Welfare says, "We have been able to see that the health limit of 50 millisieverts of exposure per year was abided by."
The radiation exposure of decontamination workers is required to be recorded by ministry order, and businesses involved in the work have been registering their records with the REA. The data released by the REA covered areas including the special decontamination areas under direct management by the national government.
In the data, the highest average exposure for a yearly quarter was 0.8 millisieverts, for January through March in 2012. April through June that year saw an average of 0.4 millisieverts, and for the quarters afterwards up to December 2014, the averages were between 0.2 and 0.3 millisieverts. The number of decontamination workers covered by the data was 11,058 for 2011 and 2012, and 20,564 for 2013. The average yearly exposure for both the 2011 through 2012 period and for 2013 was 0.5 millisieverts per worker.
According to the Ministry of Health, Labor and Welfare, the average radiation exposure for nuclear plant workers not involved with the Fukushima cleanup is one millisievert, twice that of the decontamination workers.
THE ASAHI SHIMBUN
Cleanup crews around the crippled Fukushima No. 1 nuclear power plant were exposed to an average dose of 0.5 millisievert of radiation per year, well below the government safety standard, a report shows.
Released April 15 by the government-affiliated Radiation Effects Association, the report said the maximum dose for decontamination workers was 13.9 millisieverts per year, while the average dose was half the mean exposure level for ordinary nuclear plant workers of 1 millisievert.
Decontamination work is currently under way in broad areas near the Fukushima plant, which experienced a triple meltdown in the 2011 earthquake and tsunami disaster.
The association surveyed individuals who had been involved in state-led decontamination work between 2011 and 2013.
According to the report, no cleanup workers exceeded the health ministry's annual exposure limit of 50 millisieverts during the study period.
The report said 11,058 individuals were engaged in decontamination work around the Fukushima plant in 2011 and 2012. The highest exposure level of 13.9 millisieverts was detected during the period for one worker, with the average radiation dose being 0.5 millisievert.
In 2013, 20,564 people were engaged in the cleanup work and were exposed to a maximum radiation level of 6.7 millisieverts. The average exposure for 2013 was 0.5 millisievert per year.
The association also released preliminary readings for each quarter.
According to the data, cleanup crews received an average radiation dose of 0.8 millisievert between January and March 2012. The figure was relatively high compared with other quarters because the government conducted decontamination in areas with higher radiation levels on a trial basis during the period.
However, the health ministry said the number of workers surveyed is different from the total number of cleanup personnel reported by the Environment Ministry, which could mean the association failed to record radiation doses of all individuals working around the Fukushima plant.
The decontamination workers cleaning up the hot zone around the Fukushima No. 1 power plant received as much as 13.9 millisieverts of radiation from 2011 to 2013, well within government-mandated levels, the Radiation Effects Association said in its first report on the subject.
The average cumulative dose was 0.6 millisievert among the 26,382 workers tasked with decontaminating 11 municipalities in Fukushima Prefecture tainted by fallout from the March 2011 core meltdowns, said the association, which is in charge of managing their radiation exposure.
The Health, Labor and Welfare Ministry’s present limit for decontamination workers is 50 millisieverts a year and 100 millisieverts over five years.
According to the association’s tally, the cumulative radiation received by 22,015 workers, or 83.4 percent of the total, was 1 millisievert or lower, but 34 workers, or 0.1 percent, received a dose of over 10 millisieverts.
The association reported on Wednesday that a group of 6,037 people, or 22.9 percent, worked on different projects, with seven of them completing seven assignments. Their average radiation dose came to 2.6 millisieverts for workers who engaged in six different decontamination projects.
Exposure levels were higher for decontamination workers in municipalities in the northern part of Fukushima, including the village of Iitate and the city of Minamisoma, with the average in 2012 standing at 0.8 millisievert.
The number of decontamination workers in the northern municipalities was about half the number in the southern ones, including the village of Kawauchi.
Some 15.4 percent of the total in 2013 were aged 60 to 64. Most were men, with women only accounting for 2.6 percent.
Quarterly records show that the number of decontamination workers is climbing and totaled 17,988 in the July-September quarter of 2014, according to the association.
The average radiation dose peaked at 0.8 millisievert in January-March 2012 but leveled off to 0.2 to 0.3 millisievert after October-December 2012.
The association is commissioned to keep records of worker radiation doses in a database linked to general contractors and other companies that undertake the decontamination work. Since 2014, the database has covered at least 99 percent of the workers, according to the association.
Separately, a Fukushima Labor Bureau survey of 1,152 companies in charge of the decontamination work found some 800 violations of safety and sanitary regulations had been committed, including the failure to measure aerial radiation levels and have workers carry dosimeters.
If violations of labor regulations are included, nearly 70 percent of the companies committed violations, according to the bureau of the ministry.
According to the Environment Ministry, which is supervising the decontamination effort, some 12,000 people work on the cleanup every day. Work is complete in four of the 11 municipalities, and the ministry aims to finish the rest by March 2017.
April 15, 2015
Apr. 15, 2015 - Updated 23:12 UTC+2
A survey shows that radiation exposure was below the legal limit for workers engaged in the decontamination effort after the Fukushima Daiichi accident in 2011.
The Radiation Effects Association gathers radiation data for people engaged in government-run projects of soil decontamination and radioactive waste disposal.
The association announced on Wednesday the results of the survey on more than 26,000 people who worked before 2014.
This is the first time exposure levels for workers in the decontamination effort have been made public.
Association officials said no worker's exposure reached the legal limit of 50 millisieverts a year.
They said the average exposure was 0.5 millisieverts a year.
They also said that in 2013, 14.6 percent of workers were exposed to an annual dose of more than one millisievert. One millisievert is the annual permissible level for the general public.
Health ministry officials said they will continue to supervise operators undertaking the work so that radiation exposure can be properly managed.