An accident that exposed five workers to radiation at the Oarai Research & Development Center of the Japan Atomic Energy Agency (JAEA) during a check of radioactive materials has raised serious suspicions of sloppy safety management at the facility.
Of the five who were exposed to radiation during the June 6 incident, a worker in his 50s was found with 22,000 becquerels of plutonium-239 in his lungs. He is expected to suffer internal radiation exposure of 1.2 sieverts over a period of one year and 12 sieverts over the course of 50 years. This exposure is certain to greatly exceed the annual limit of 0.05 sieverts for workers involved in handling radiation, making the JAEA incident the worst internal radiation exposure accident in Japan.
Plutonium emits alpha rays that can attack and damage nearby cells. While medication to help discharge radioactive materials from the body has been administered to the five workers, concerns have been raised over the increased risk of cancer. Long-term treatment, including psychological care, is essential for these workers.
The incident occurred at the fuel research building where research and development of fuel for fast nuclear reactors and other materials had been carried out. The facility was set to close down, and the five workers were examining the radioactive material inside a storage container that had not been opened for 26 years. A plastic bag holding the radioactive material burst open when they were about to remove the bag from the container, and the material was discharged.
It is a known fact that internal plutonium exposure seriously affects people's health. Despite this common knowledge, the work to inspect the container was done on an open workbench. Furthermore, the five workers were wearing half-face masks that covered only the lower half of their faces.
The internal exposure could possibly have been avoided if a sealed workbench and full-face masks had been used.
There is an understanding -- taken for granted in the nuclear business -- that safety management deserves extreme care. But it appears this was lacking.
Nuclear structures operated by the JAEA are aging, and the organization plans to decommission 44 of the 89 facilities it owns. But it is unacceptable to proceed with decommission projects without a sense of caution just because they are designated post-research cleanup work.
After it was learned that the JAEA failed to inspect a number of devices at its Monju prototype fast-breeder reactor in Fukui Prefecture, the Nuclear Regulation Authority two years ago recommended that the JAEA be replaced as the operator of the trouble-plagued reactor. The latest incident reveals that the reactor operator has not learned a lesson from that time.
The JAEA needs to take this accident seriously as the organization is responsible for taking measures against potential accidents.