TOKYO -- Five workers at a state-run nuclear research facility near Tokyo have been exposed to dangerous levels of radioactive material, raising allegations of poor management and safety compliance that could significantly set back efforts to rebuild the Japanese public's trust in nuclear technology.
The exposure occurred Tuesday at the Japan Atomic Energy Agency's Oarai Research & Development Center, when a plastic bag covering a container for powdered nuclear material tore open during an inspection, according to the agency. The material entered the lungs of at least four of the five workers.
Up to 22,000 becquerels of plutonium 239 was detected in the lungs of one man in his 50s, alongside other isotopes. Americium was detected in the lungs of three others. The fifth worker is thought highly likely to have suffered internal exposure as well. The most heavily affected worker faces radiation exposure of 1.2 sieverts over the course of a year and 12 Sv over 50 years. The legal limit for workers handling radioactive material is 0.1 Sv over five years.
"I have never heard of a case of internal exposure this severe," Shunichi Tanaka, chairman of Japan's Nuclear Regulation Authority, said at a news conference Thursday.
"To handle radioactive material carefully is essential," Tanaka said, calling on the JAEA's management to "seriously reflect" on the incident. The NRA, formed following the March 2011 meltdowns at the Fukushima Daiichi power plant, has repeatedly taken the agency to task for mistakes and neglect, including skipped inspections at the Monju fast-breeder reactor in Fukui Prefecture.
The agency's insufficient attention to safety "doesn't seem to be getting much better," Tanaka said.
Poor planning for the inspection work resulting in Tuesday's incident may have played a role. The Oarai laboratory handles materials used as fuel for experimental reactors, including plutonium and uranium. A number of inspections, including of fuel storage containers, were being carried out in a short time, rather than spread out and conducted regularly, and the procedures used were apparently not well established. Nor was the work conducted in a sealed environment. The NRA will send its own inspectors to the site to get a firmer handle on what went wrong.
The facility has said it did not foresee the plastic bag tearing and radioactive material scattering as it did. The bag and container within were in long-term storage, and are thought to have been supervised improperly.
Shortcomings in the annual safety training required for workers handling radioactive material have also emerged. While the five workers exposed were wearing protective face masks, they seem to have been fastened carelessly, leaving gaps through which the material was inhaled. "We need to check whether the masks were worn properly," said Nobuhiko Ban, an NRA commissioner.
The five exposed workers have been taken to the National Institute of Radiological Sciences, and will be held at least until Saturday for treatment and observation. They have been rinsed to remove any lingering material, and have been given medicine to expel material absorbed by the body, the agency said Wednesday.
While this will help clear particles taken up by the blood, removing material remaining in the lungs is more difficult. "We don't expect damage to lung function right away," said Makoto Akashi, a senior official at the body overseeing the institute. "We will need to keep track of their progress over time."
The accident could push the NRA to rethink how it regulates government institutes working on next-generation nuclear technologies, which have been left largely to their own devices over the past several years.
The JAEA operates more than 10 research facilities around Japan. Each of them is organized differently, and operates under different safety procedures based on the type of research being done. This makes regulating these laboratories a good deal more difficult than overseeing commercial nuclear operations, which use only two types of power-generating reactor.
Therefore, the NRA has not set detailed rules or operating procedures for the handling of radioactive material at these labs. "Operations are left up to the facility," according to the regulator. Instead of policing laboratories, time and resources have been focused on screening commercial nuclear facilities to let them resume power generation. Several plants have been given the regulatory go-ahead, and the government aims to have around 20% of Japan's power come from nuclear plants by 2030.
But this strategy seems to have created conditions ripe for accidents. Convincing a leery public that nuclear power and technology can be operated safely will now require not just oversight of power plants, but detailed rules and safety measures for laboratories conducting basic research and training staff as well.