CBRN event in Japan on Thu 11th September 2008

This is the final report on the radiation overexposure of a worker on September 11th, 2008 to establish the INES ratings.

On October 31st, 2008, a licensee in Ehime prefecture notified the Ministry of Education, Culture, Sports, Science and Technology (MEXT) that effective dose of the worker showed beyond annual dose limit of occupational exposure.

According to the report from the licensee, it was found that during the period of September, the exposure monitor of the worker showed effective dose of 52 mSv. He engaged in repair of cyclotron in the controlled area only on September 11th.

The company submitted a report to the MEXT on November 7th which is required by the Law concerning Prevention from Radiation Hazards due to Radioisotopes, etc. The report did not reveal any apparent measurement errors, though the cause of the overexposure was not clearly shown and some measurement errors had been suspected.

This rating was evaluated and finalized by MEXT with confirmation by the Radioisotope INES Evaluation Working Group under the MEXT held on December 18th, 2008.