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Workers' Radiation Exposure at Japan's Nuclear Facilities

(April 2004 - March 2005)

In July, the Nuclear and Industrial Safety Agency (NISA) released data relating to worker radiation exposure and the management of radioactive waste at nuclear facilities for the 2004 fiscal year. The data covers nuclear power reactors, nuclear fuel related facilities and radioactive waste facilities.

During this period, trial operations commenced at Tohoku Electric Power Company's Higashidori reactor (BWR 1,110 MW). The collective dose at nuclear power plants (NPP) was 78.23 person-sieverts. This was lower than the previous year's figure of 96.87 person-sieverts. This was because in 2003 there were lots of problems at boiling water reactors. However, the exposure at pressurized water reactors actually increased by 4.26 person-sieverts in 2004.

All 402 people who received doses in the 15-20 milli-sievert range were sub-contractor workers. The highest dose was 19.4 milli-sieverts at Fukushima I. By contrast, figures published by the Radiation Dose Registration Center (part of the Radiation Effects Association) are much higher. This is because these figures take into account the fact that some people worked at more than one nuclear power plant. According to these figures, 776 people received doses in the 15-20 milli-sievert range and one person received a dose in the 20-25 milli-sievert range.

Subcontractor workers received 96% of the total dose. The highest dose to a power company employee was 10.7 milli-sieverts. This was at the Sendai NPP in Kyushu.

It was pointed out at the April 2002 Conference of Contracting Parties to the Convention on Nuclear Safety that worker exposure in Japan was the highest in the world. In August 2004 NISA published Japan's National Report for the Conference of Parties held in April 2005. This report was expected to include comments on improvements made so far. In fact, the basic position presented in the report is that exposure is "well within the prescribed dose limit". The only specific proposal for reducing collective dose for workers is through the introduction of "Rules on Fitness-for-Service". In simple language, this means that by relaxing the requirement to repair defects the amount of high-exposure work will be reduced. It would appear that the only idea NISA has to reduce worker exposure is to reduce reactor safety requirements.

Mikiko Watanabe (CNIC)

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