Japanese media are reporting that just before midday June 6 workers at a nuclear research facility in Ibaraki, Japan were exposed to radiation after a bag containing nuclear materials broke.
One report said the five workers were inspecting a container of nuclear fuel materials, among which was plutonium and uranium, at the nuclear research facility in Oarai in Ibaraki. Three of the five have been exposed to high levels of radiation, which was detected in their nostrils, a sign they had inhaled radioactive materials, among them plutonium.
The accident took place in a lab researching new kinds of fuel for experimental fast breeder reactors, according to Japan Atomic Energy Agency (JAEA). One news report stated that after an experiment in the lab, the five workers had been in charge of inspecting a vessel containing nuclear fuel. One worker had opened the lid of the container when some of the 300g of plutonium and uranium contained inside a plastic bag inside the container blew out. It is believed that the bag had somehow already been breached.
Masataka Tanimoto, a JAEA spokesman, was quoted as saying that the man who opened the container, who is in his 50s, was shown to have high levels of plutonium exposure in his lungs.
Initial reports suggested that the level of exposure, at 25 becquerels, was too low for any serious health risk. A later update stated that the worker in his 50s was found to have 22,000 becquerels of plutonium in his lungs. The other four were shown to have levels of plutonium ranging from 2,200 becquerels to 14,000 becquerels in their lungs. Additionally, all five had high levels of americium-241.
There was no mention about the impact on the immediate community, such as evacuations of local residents and so on.
In Yoshida's Dilemma I discuss a similar accident in 1999 at the Tokai nuclear research facility, also in Ibaraki Prefecture.
On that occasion three workers at the facility had been charged with meeting an unusual order of highly enriched uranium fuel, also for use in an experimental “fast breeder” reactor. Such reactors generate electricity while producing more fuel than it consumes by transforming uranium-238 into plutonium-239.
The specialty fuel they were concocting involved the dissolution of over 16 kg of uranium enriched to 18.8 percent – a concentration around six times higher than that used at conventional nuclear power stations. But the JCO company that operated the facility and its workers violated procedures and apparatus set by the regulatory authorities, preparing the enriched fuel in seven metal buckets and tipping them all into a precipitation tank. Just one bucket would have been sufficient for the batch being made and as the last one was emptied of its contents, workers reported seeing “a blue flame rising from the fuel.”
A chain reaction had started and was sustained in the tank for over 20 hours. It took more than an hour for the facility to report the accident – which was a clear breach of protocol that required operators to report accidents of this severity immediately.
Two of the workers, Hisashi Ouchi and Masato Shinohara, died from the radiation doses received, which were reportedly about 16,000 mSv – more than twice the dose considered to be fatal. Dozens more staff, some of whom stopped the reaction by draining the water from the tank and flooding it with neutron absorbing boron, received high but not immediately life-threatening doses while around 310,000 residents were confined to their homes due to concerns about elevated radiation levels near the facility. Nobody told them that the bucket short-cut had sent harmful and powerful neutrons scorching through the facility and into their homes.
It subsequently came to light that the facility had been a hotbed of illegal practices for the best part of a decade. One Greenpeace official commented the facility had the "safety standards of a bakery."
Only time will tell of this most recent incident was also the result of poor safety standards, though one Associated Press report said the chairman of the Nuclear Regulation Authority, Shunichi Tanaka, had blamed work routine complacency as a possible cause and that the NRA has started investigating possible violations of safety standards at the facility.
Either way, it seems destined to add further fuel to the argument of those who are against nuclear energy in Japan, not least of all because Japan's only fast breeder reactor, the plutonium-burning Monju reactor in Fukui, which has a poor safety record since opening in 1995, is to be closed down and decommissioned.
Addendum: Overnight news of this latest incident report that the doses received by the three workers were not high enough to be of significant detriment to health, though the exact amount of exposure increased significantly over the course of the day.
One Nuclear Regulatory Agency official, Nobuhiko Ban, who is a specialist in radiological protection, was quoted as saying that 22,000 becquerels of exposure "is a situation that cannot be easily brushed aside."
"It is no small amount, although it may not be life-threatening," he said. "There will be a need to confirm if the work procedures were appropriate.”
No radioactive materials leaked outside of the centre, according to the NRA.
Meanwhile, international criticism continues of Japan’s continuing extraction of plutonium as part of its spent-fuel recycling program. Japan already possesses a cache of almost 50 metric tons of weapons grade plutonium, estimated to be enough to make 6,000 warheads similar to the one that flattened Nagasaki on Aug. 9, 1945. Around 7 tons of that total is stored within Japan and calls are increasing for Japan to stop increasing that stockpile through its spent-fuel recycling program. The Oarai research and development centre, which is located about 60 km north of Tokyo, is a facility largely dedicated to nuclear fuel development using plutonium.