The Nuclear Industrial and Safety Agency (NISA) has published the collective radiation dose incurred in the 2007 fiscal year (April 2007 to March 2008) by people working at nuclear power plants, including Fugen and Monju. The collective dose was 78.27 person sieverts, an increase of 10.64 person sieverts compared to the previous year.
The increase resulted from the need to carry out inspections and repairs in response to many problems arising in aging reactors, including problems with control rods.
Compared to the previous year, the collective dose incurred working on pressurized water reactors (PWR) increased by 6.08 person sieverts. This included an increase of 3.80 person sieverts at Sendai Nuclear Power Plant (Kyushu Electric) and 3.39 person sieverts at Takahama (Kansai Electric). The collective dose incurred at boiling water reactors (BWR) increased by 4.67 person sieverts, including an increase of 3.21 person sieverts at Fukushima II (Tokyo Electric), 2.84 person sieverts at Shimane (Chugoku Electric) and 2.16 person sieverts at Onagawa (Tohoku Electric).
All 360 people who received doses in the 15 - 20 milli-sievert (mSv) range were subcontractor workers. A further 3 subcontractor workers received doses in excess of 20 mSv, the highest individual dose being 21.1 mSv at Takahama (Kansai Electric). The highest dose for an employee of an electric power company was 11.4 mSv at Shimane.
The data published by NISA does not take into account the fact that many people work at more than one site. According to the Radiation Dose Registration Center for Workers (Registration Center), which calculates the total dose received by individuals at all work places, 709 workers received doses in the 15 - 20 mSv range and 5 workers received doses in the 20 - 25 mSv range. The Registration Center does not distinguish between work carried out at nuclear power plants, or between power company employees and subcontractors. However, it is a fair assumption that all the workers who receive high radiation doses at nuclear power plants are subcontractor workers. In any case, the overwhelming majority of radiation exposure at nuclear power plants is incurred by subcontractor workers, who receive 96% of the collective dose.
The workers compensation case of Tadashi Kiyuna, who died of malignant lymphoma after receiving a total dose of around 100 mSv in a period of 6 years and 4 months, is continuing (see NIT 120). The Ministry of Health, Labour and Welfare has held four closed expert committee meetings, but no decision has yet been made. The expert committee is considering the details of Kiyuna's work, medical issues including a theory that the condition is caused by a virus, and accumulated case studies. On September 11, citizens concerned about worker radiation exposure at nuclear power plants submitted a petition signed by over 150,000 people throughout Japan and demanded that Kiyuna's workers compensation claim be swiftly accepted.
Mikiko Watanabe (CNIC)