Tokyo, Saitama residents say ‘no’ to living near Fukushima soil
The flower bed in Shinjuku Gyoen National Garden where decontaminated soil from Fukushima Prefecture will be reused
February 25, 2023
Residents of Tokyo and Saitama are up in arms at an Environment Ministry plan to reuse decontaminated soil from Fukushima Prefecture in their midst, including a major park in the capital’s Shinjuku district.
They formally submitted requests on Feb. 24 asking to suspend the plan to distribute the soil that was formerly contaminated from radioactive fallout due to the 2011 triple meltdown at the Fukushima No. 1 nuclear power plant.
The plan, announced in December, is aimed at reducing the volume that would go to the final storage site.
One potential test site is Shinjuku Gyoen National Garden in the heart of Tokyo.
At a meeting on Feb. 24 between about 50 local residents and Environment Ministry officials, a request was submitted asking to cancel the plan as well as holding explanatory meetings about the project.
After the meeting, one of the residents, Kunikazu Hirai, 70, said, “We are angry at the danger of having soil that was once contaminated with radiation brought right next door to us.”
According to Environment Ministry officials, there were about 1.2 million visitors to Shinjuku Gyoen National Garden in fiscal 2021, although annual visitors numbered about 2 million prior to the novel coronavirus pandemic.
The two other candidate test sites are the National Institute for Environmental Studies in Tsukuba, Ibaraki Prefecture, and the National Environmental Research and Training Institute in Tokorozawa, Saitama Prefecture.
All three sites are managed by the Environment Ministry and officials believe that consent of local residents is not needed to proceed with their plan.
However, Saitama residents not only attended the Feb. 24 meeting with Environment Ministry officials but also submitted their own request to stop the project.
The unpopularity of the plan is understandable. A proposal to reuse soil in two municipalities in Fukushima Prefecture went nowhere after local residents raised strong opposition.
Only soil decontaminated to levels below 8,000 becquerels per kilogram will be used in the trial runs.
The plan for Tokyo calls for reusing the soil in a flower bed in an area of Shinjuku Gyoen National Garden that would be off-limits to the public. The flower bed would be 10 meters by 3 meters with a hole dug 1 meter deep.
A plastic sheet will be placed in the hole before about six cubic meters of decontaminated soil covers it. A 50-centimeter layer of soil will be placed on top of the decontaminated soil.
The water collected in the sheet will be moved to an adjacent tank and measured for radiation levels. If the levels are under government standards, the water would be released into the sewage system.
The Environment Ministry held an explanatory meeting on Dec. 21, but only 28 people showed up, in large part, because notification of the scheduled meeting was given at the last minute.
Shinjuku Mayor Kenichi Yoshizumi said while the project was completely in the hands of the central government, he expressed dissatisfaction at the explanation and documents presented by the Environment Ministry, which he called “difficult to understand.”
Tokorozawa residents raised objections at an explanatory meeting held in their community in January, and Mayor Masato Fujimoto said it would be difficult for the project to proceed if residents were opposed.
Kenichi Oshima, a professor of environmental economics at Ryukoku University in Kyoto, said the ministry likely wanted to conduct the trial in Tokyo to attract more attention and gain understanding.
But he added, “What has to be paid attention to is not to create a dispute between various regions by having the central government pressuring localities with comments such as, ‘Are you saying you will not cooperate to help Fukushima Prefecture?’”
Japan’s Nuclear Regulation Authority concerned about risks of radioactive leaks from facility near Tokyo
November 23, 2018
The Japan Atomic Energy Agency said Wednesday that some of the low-level radioactive waste stored underground at a facility near Tokyo may leak from its containers due to inadequate disposal procedures.
The government-backed agency keeps 53,000 drums of low-level radioactive waste, or about 10,600 kiloliters, in a concrete pit in the basement of a building of the Nuclear Research and Science Institute in the village of Tokai, Ibaraki Prefecture.
Some of the waste did not undergo the proper water removal process when placed in the pit, and leakage and corroded containers in the pit were found during inspections between 1987 and 1991, according to the agency.
The nuclear research body planned to inspect the drums over the next 50 years to check for leakage. But the Nuclear Regulation Authority said at a meeting Wednesday that the agency needs to check them more quickly.
The agency should inspect all the drums within five years, Shinsuke Yamanaka, an NRA commissioner, said at the meeting.
The agency currently inspects the drums visually once a year but will now begin to lift and check them individually.
According to the agency and the NRA, the low-level radioactive waste is placed at the facility, built sometime from around 1964 to 1976, for disposal.
The agency said it did not properly conduct the process of removing water and other materials in some cases during the 1960s.
https://www.japantimes.co.jp/news/2018/11/22/national/low-level-radioactive-waste-stored-tokai-research-facility-near-tokyo-may-leak-agency-says/#.W_mJgvZFzIV
Possible safety regulation violations at Ibaraki Pref. nuclear facility led to accident: NRA
In this photo provided by the JAEA, the stainless steel radioactive material container involved in the June 6, 2017 accident is seen soon after the plastic bags inside burst, exposing five workers to powdered plutonium and uranium oxides, at the Oarai Research & Development Center in Oarai, Ibaraki Prefecture.
Staff likely failed to follow safety regulations at a nuclear research facility in Ibaraki Prefecture where five workers were exposed to radioactive materials in June, a Nuclear Regulation Authority (NRA) inquiry has revealed.
While just after the accident the Japan Atomic Energy Agency (JAEA) stated that there was no way that such a serious incident could have been predicted, the NRA’s on-site investigation has revealed that, regardless of whether the accident could have been predicted, the facility staff were working without conducting proper safety procedures.
The accident occurred at the JAEA Oarai Research and Development Center in Oarai, Ibaraki Prefecture, at roughly 11:15 a.m. on June 6, when a worker opened a stainless steel container to inspect the powdered nuclear fuel materials within. The plastic bag inside the container ruptured, exposing the worker and four other staff to plutonium and other radioactive materials. The container had been sealed in 1991, and not opened once since.
“There was no way to know the state of the vessel’s contents, so the work was done extremely carefully,” the JAEA had initially explained. It had also stated that the workers had been aware that the plastic bag around the materials had degraded over the 26 years it was in storage. The JAEA had also been aware since January of a similar case at another facility where the plastic bag in a container had swelled up.
However, the recent inquiry found that the workers at the Ibaraki facility decided that the item on the inspection safety checklist stating “risk of explosion, rupture or dispersal” was non-applicable before beginning their task, which their supervisor also approved. Furthermore, though there were five sealed workstations in the room, the workers chose to open the container at a simple, unsealed workstation instead. No work plan had been put together prior to the task.
“If the workers had used a sealed workstation, it is clear that this accident could have been prevented,” lamented a JAEA representative.
Also, after the accident, it took three hours to set up a temporary decontamination tent for the effected workers. The survey found that the building where the incident occurred was not equipped with the materials necessary to construct the decontamination tent, and no drills for the setup had ever been carried out. In addition, a shower meant to wash away radioactive materials was also found to be broken.
“When handling plutonium, we cannot afford to make inexperienced or groundless decisions,” declared NRA Chairman Shunichi Tanaka at a regular meeting of the authority on July 5. “(The JAEA’s) safety culture is lacking.”
https://mainichi.jp/english/articles/20170707/p2a/00m/0na/013000c
Scrapping Tokai facility will cost 1 trillion yen and take 70 years
The Tokai reprocessing site in Tokai village, Ibaraki Prefecture
The planned decommissioning of the Tokai spent nuclear fuel reprocessing plant in Ibaraki Prefecture will take 70 years and cost taxpayers about 1 trillion yen ($8.9 billion), according to the Japan Atomic Energy Agency.
The JAEA submitted its estimate to the Nuclear Regulation Authority on June 30 for approval.
By any measure, it will be a Herculean task to dismantle the facilities in the village of Tokai. Whether it will be possible to remove the high-level radioactive waste liquids and materials according to schedule is by no means certain.
Under the JAEA plan, the immediate task will be to assess the level of on-site contamination, decontaminate facilities and implement measures to secure safety of the site and workers, including enhancing earthquake-resistance of the facilities. That alone would take 10 years.
At the same time, the agency said it would start work to vitrify about 400 cubic meters of high-level radioactive waste liquids, a by-product of the reprocessing process.
Total costs during the first 10 years were calculated to come to 217 billion yen. Over the subsequent 60 years, the JAEA said it planned to demolish the facilities and decontaminate buildings at a total estimated cost of 770 billion yen.
That figure was broken down as follows: 250 billion yen to process the radioactive waste materials; 380 billion yen to dispose of the waste; and 140 billion yen to dismantle the facilities.
The NRA will first check safety and other issues before reaching a decision. If it gives the nod, the JAEA will start the project.
France is among countries that already have experience with dismantling reprocessing facilities, but it would be the first time to do it in Japan.
The Tokai reprocessing facilities were constructed at a total cost of 190 billion yen. It started full-scale operations in 1981, and has reprocessed 1,140 tons of spent nuclear fuel since then.
In 1997, the plant was rocked by an explosion at its bituminization facility to solidify waste.
Decommissioning of the Tokai plant was decided in 2014.
http://www.asahi.com/ajw/articles/AJ201707010038.html
Ibaraki plutonium exposures baffle Japanese nuclear experts
Experts probing the cause of the plutonium-inhalation accident involving five employees at a fuel research facility in Ibaraki Prefecture are trying to determine whether failures in safety equipment or procedures allowed the deadly powder to escape its container.
The accident might have been caused by the long-term buildup of helium emitted by the plutonium, one expert says.
The accident took place at around 11:15 a.m. Tuesday when five men from the Plutonium Fuel Research Facility at Oarai Research & Development Center were taking stock of a radioactive substance in an old storage container. This process usually involves placing the container into a special machine that adjusts the air pressure to prevent the material inside from being blown into the air.
Masked, gloved and donning other protective gear, a worker in his 50s along with a coworker standing by, removed the sealing bolts of a stainless steel container and opened the lid only to see a black powder burst forth.
“The plastic bags were thick and we did not expect them to burst,” said an official at Japan Atomic Energy Agency, the facility’s operator. “I have no idea why (the plutonium powder) flew out of the container,” another said.
The powdery substance had originally been encased in a plastic container double-wrapped in plastic. It was then placed inside a stainless steel container sealed with six bolts. The container had not been opened since 1991, and held about 300 grams of uranium oxide and plutonium oxide that had been used in past experiments, JAEA officials said.
“The container may have been filled with helium (which can be emitted by plutonium) from extended storage, and that may have increased the pressure inside it,” according to Kazuya Idemitsu, an expert on nuclear fuel engineering and a professor at the Graduate School of Engineering at Kyushu University.
Although masks were covering the workers’ noses and mouths, radioactive material was detected inside the noses of three of the exposed employees.
The agency said Wednesday that internal radiation exposure was detected in four of the five workers and that a fifth is suspected as well.
Up to 22,000 becquerels of plutonium were detected in the lungs of the worker in his 50s who opened the lid. Based on that figure, the agency estimates his body has likely has 360,000 becquerels of material inside it overall, they said Thursday.
Under current labor standards, that translates into 1.2 sieverts over a year, and perhaps a 12 sieverts over 50 years, the officials said.
The government allows designated nuclear workers to be exposed to a maximum of 0.05 sievert per year, or 0.1 sievert over five years.
“This is an unusually high amount of radiation. We must carefully look into whether the workers took proper steps,” Nobuhiko Ban, an expert on radiological protection and a member of the Nuclear Regulation Authority, said at an NRA meeting Wednesday.
Plutonium decay can continuously damage cells in the body so it is imperative to make sure workers don’t inhale it, Ban acknowledged.
The main threat from internal plutonium exposure this is bone cancer.
“There are very limited cases of treatment for internal exposure to plutonium in Japan,” Kazuhiko Maekawa, an expert on the subject, said.Gen Suzuki, an expert on radiation epidemiology and professor at the International University of Health and Welfare, said the amount of radiation in their bodies can vary based on the size and character of each particle of plutonium.
March 1997: Radioactive material leaks after a fire and explosion at the Ibaraki branch of now-defunct Power Reactor and Nuclear Fuel Development Corp., later absorbed by Japan Atomic Energy Agency. Thirty-seven employees were exposed.
September 1999: A self-sustaining chain reaction is triggered by the use of mixing buckets at uranium processing firm JCO Co. in the village of Tokai, Ibaraki Prefecture. The accident eventually kills two of three employees, after tainting more than 600 residents.
June 2006: A suspected case of plutonium inhalation occurs at Japan Nuclear Fuel’s reprocessing plant in the village of Rokkasho, Aomori Prefecture, but a check for internal exposure turns out negative.
July 2008: A worker at Global Nuclear Fuel Japan Co. is exposed to uranium in Yokosuka, Kanagawa Prefecture, followed by the exposure of four workers to a uranium-tainted liquid a month later.
March 2011: Three workers stepped in to a puddle during the meltdown crisis at the Fukushima No. 1 power plant, exposing two to high radiation.
May 2013: Thirty-four researchers at JAEA’s Japan Proton Accelerator Research Complex (J-PARC) in Tokai are exposed to an exotic soup of isotopes during an experiment.
http://www.japantimes.co.jp/news/2017/06/08/national/ibaraki-plutonium-exposures-baffle-japanese-nuclear-experts/#.WTuQ9jekLrd
Ibaraki nuclear research facility under scrutiny after accident; gas suspected in rupture
OARAI, Ibaraki — A nuclear research facility here has come under scrutiny after workers were exposed to radiation while checking radioactive materials that had remained in storage for 26 years.
One of the workers exposed to radiation in the accident at the Oarai Research & Development Center of the Japan Atomic Energy Agency (JAEA) on June 6, identified as a male in his 50s, was found with up to 22,000 becquerels of plutonium-239 in his lungs, raising fears he could develop cancer or suffer other health problems.
According to the JAEA, the total level of radioactive materials that entered the man’s blood, bones, organs and other parts of his body was estimated at 360,000 becquerels, based on the amount detected in his lungs.
Problems with safety management at the agency had already been pointed out, and focus is likely to turn toward whether the work at the time of the accident was appropriate.
The agency said that when the worker opened the bolted lid of a steel container during a check, the plastic bag inside ruptured, scattering dust containing uranium and plutonium. Two other workers were next to the worker at the time, assisting in the check.
The some 300 grams of dust was produced when fuel was created for the onsite Joyo experimental fast reactor, which first reached criticality in 1977. It had been placed in a polyethylene container, enclosed in two plastic bags, and then placed in a steel container, where it had been stored since 1991. There were no records to show that the container had been opened before, officials said.
The latest check was being conducted after the Nuclear Regulation Authority had pointed out problems with the management of fuel at another JAEA facility. The JAEA had planned to check 21 steel containers containing uranium and plutonium dust. The accident on June 6 occurred during a check of the first of these containers.
Why did the plastic bag rupture? Kazuya Idemitsu, a professor in the Laboratory of Energy Materials Science at Kyushu University, commented, “Over time, the atomic nuclei of uranium, plutonium and other such substances break down, releasing helium nuclei (alpha rays). When stored over a long time, helium gas would build up, and it’s possible that the pressure inside the container rose, resulting in the rupture.”
Sources close to the JAEA also acknowledged this possibility, with one commenting, “It may not have been a good idea to use a polyethylene container, which had a possibility of rupturing, for storage over a long period.”
On June 7, the Ibaraki prefectural and Oarai municipal governments conducted an on-site inspection of the Oarai Research & Development Center under a nuclear safety agreement. Seventeen officials viewed the inside of the analysis room where the accident occurred through a monitor, and examined the concentration of radioactive materials in expelled air.
Masaaki Kondo, a safety coordinator at the prefectural nuclear power safety division, commented, “We confirmed that the damage did not spread.” The Mito Labor Standards Inspection Office and prefectural police are investigating the cause of the accident and whether the work that led to it was appropriate.
https://mainichi.jp/english/articles/20170608/p2a/00m/0na/018000c
22,000 becquerels of plutonium-239 and 220 becquerels of americium-241 found in lungs of nuclear facility worker
‘No one has inhaled this much plutonium’: 5 staff exposed to radiation in Japan lab accident
Japanese authorities are unsure about the medical prognosis for five staffers who inhaled toxic plutonium after mishandling it at the Oarai Research and Development Center outside Tokyo.
“As far as I can remember, no one has inhaled plutonium at this level,” said Ishikawa Keiji, a security official at the Japan Atomic Energy Agency (JAEA) which oversees the lab, cited by the Jiji Press news agency.
The accident occurred at 11:15am on Tuesday in the analysis room of the facility dedicated to researching improved nuclear fuel for its fast reactors.
One of the five men opened a metallic cylinder where the fuel, a mixture of uranium and plutonium, is stored before and after experiments. In the process, the double plastic wrapping inside which the radioactive material is kept ripped, and the toxic substance burst into the air.
Shunichi Tanaka, chairman of the Nuclear Regulation Authority (NRA), which has frequently criticized the JAEA for the conditions at its facilities, said “workplace complacency” was possibly to blame.
The NRA said the workers had never experienced a similar plastic rip before, and as a result, did not feel the need to complete their research in a tightly sealed environment.
The researcher responsible for opening the box, described as a man in his 50s, had 22,000 becquerels of plutonium-239 detected in his lungs, and the other four between 2,200 and 14,000 becquerels.
Officials said the five staff have not yet complained of health problems with one assuring that “the amount is not enough to cause acute radiation damage,” according to the Japanese newspaper The Asahi Shimbun.
The longer-term predictions were less definitive, however.
“Detection of 22,000 becquerels is a situation that cannot be easily brushed aside. It is no small amount, although it may not be life-threatening,” said Nobuhiko Ban, an NRA radiological protection specialist, quoted by The Asahi Shimbun.
The five have been injected with a substance that speeds up the discharge of radioactive materials and remain under observation at the National Institutes for Quantum and Radiological Science and Technology.
The NRA has previously said that JEAA was “unfit” to operate an accident-plagued prototype reactor at Monju and has also faced accusations of poor handling of radioactive materials at another site.
But a use for Japan’s large plutonium stockpile must be found, and there are currently plans for utilizing MOX fuel – a mixture of plutonium and uranium, such as that involved in the latest accident – to power conventional reactors instead of the low-enriched uranium that they were designed for.
https://www.rt.com/news/391283-japan-nuclear-accident-plutonium/
‘No one has inhaled this much plutonium’: 5 staff exposed to radiation in Japan lab accident
Japanese authorities are unsure about the medical prognosis for five staffers who inhaled toxic plutonium after mishandling it at the Oarai Research and Development Center outside Tokyo.
“As far as I can remember, no one has inhaled plutonium at this level,” said Ishikawa Keiji, a security official at the Japan Atomic Energy Agency (JAEA) which oversees the lab, cited by the Jiji Press news agency.
The accident occurred at 11:15am on Tuesday in the analysis room of the facility dedicated to researching improved nuclear fuel for its fast reactors.
One of the five men opened a metallic cylinder where the fuel, a mixture of uranium and plutonium, is stored before and after experiments. In the process, the double plastic wrapping inside which the radioactive material is kept ripped, and the toxic substance burst into the air.
Shunichi Tanaka, chairman of the Nuclear Regulation Authority (NRA), which has frequently criticized the JAEA for the conditions at its facilities, said “workplace complacency” was possibly to blame.
The NRA said the workers had never experienced a similar plastic rip before, and as a result, did not feel the need to complete their research in a tightly sealed environment.
The researcher responsible for opening the box, described as a man in his 50s, had 22,000 becquerels of plutonium-239 detected in his lungs, and the other four between 2,200 and 14,000 becquerels.
Officials said the five staff have not yet complained of health problems with one assuring that “the amount is not enough to cause acute radiation damage,” according to the Japanese newspaper The Asahi Shimbun.
The longer-term predictions were less definitive, however.
“Detection of 22,000 becquerels is a situation that cannot be easily brushed aside. It is no small amount, although it may not be life-threatening,” said Nobuhiko Ban, an NRA radiological protection specialist, quoted by The Asahi Shimbun.
The five have been injected with a substance that speeds up the discharge of radioactive materials and remain under observation at the National Institutes for Quantum and Radiological Science and Technology.
The NRA has previously said that JEAA was “unfit” to operate an accident-plagued prototype reactor at Monju and has also faced accusations of poor handling of radioactive materials at another site.
But a use for Japan’s large plutonium stockpile must be found, and there are currently plans for utilizing MOX fuel – a mixture of plutonium and uranium, such as that involved in the latest accident – to power conventional reactors instead of the low-enriched uranium that they were designed for.
https://www.rt.com/news/391283-japan-nuclear-accident-plutonium/
High level of radiation found in lungs of nuclear facility worker
OARAI, Ibaraki — A worker at a research and development (R&D) center here has been found to have a high level of radioactive material — up to 22,000 becquerels — in his lungs following exposure to radiation, the center said on June 7.
The discovery came after five workers at the Oarai Research & Development Center, which belongs to the Japan Atomic Energy Agency, were exposed to radioactive materials on June 6.
Radioactive materials are difficult to expunge from the human body, and it is thought that the level of internal exposure in this case will be 1.2 sieverts in one year, and 12 sieverts over 50 years.
The five workers have been taken to the National Institutes of Radiological Sciences in Chiba Prefecture, where they are undergoing examinations.
At a Nuclear Regulation Authority (NRA) meeting on June 7, a committee member said the workers’ situation is “not mild.”
According to organizations such as the NRA, one of the five workers was found to have up to 22,000 becquerels of plutonium-239 and 220 becquerels of americium-241 in his lungs. Two other workers were discovered to have 12 becquerels and 130 becquerels of americium-241 in their lungs, respectively. All five workers were administered medicine designed to reduce the radiation dose of the internal exposure.
The five workers were all wearing protective clothing and face masks at the time of the radiation exposure, the R&D center said. It is currently being investigated whether or not there were any problems at the time the incident happened.
Plutonium and americium are both harmful to human bodies as they emit alpha rays.
http://mainichi.jp/english/articles/20170607/p2a/00m/0na/018000c
Four workers exposed to radioactive materials at Ibaraki nuclear facility
Four workers suffered internal radiation exposure due to inhalation of a large amount of plutonium during an inspection at a nuclear research facility in Ibaraki Prefecture on Tuesday, the operator of the facility said Wednesday.
In the wake of what appears to be an unprecedented internal radiation exposure accident, the state’s nuclear safety regulator and local labor authorities inspected the scene to see if there were any flaws in safety management.
The accident occurred at the fuel research building of the Japan Atomic Energy Agency’s Oarai Research & Development Center when a bag covering a container for nuclear fuel materials, including powder samples of plutonium and uranium, tore during inspection on Tuesday.
Up to 22,000 becquerels of plutonium 239 were detected in the lungs of a male worker in his 50s. Up to 14,000 becquerels of radioactive materials were found in the three other workers, officials of the Japan Atomic Energy Agency said.
The Nuclear Regulation Authority said the worker with the higher reading has been exposed to an extreme amount of radiation and the situation is considered grave.
While none of the workers have complained of health problems so far, an official with the facility’s operator said it “cannot rule out the possibility of future health effects.”
The agency assumes that the amount of radiation exposure of the male worker in his 50s translates to up to 12 sieverts over 50 years, well above the legal limit set for workers who deal with radiation.
For its part, the labor office said that it estimates the man with the highest exposure to radiation has exceeded the annual limit of radiation exposure, which is 50 millisieverts a year and 100 millisieverts in five years.
Plutonium is known to emit alpha rays over a long period, damaging surrounding organs and tissues. If it is deposited into the lungs, it could increase the risk of developing cancer
The five workers have been transported to the National Institute of Radiological Sciences and given medication to help discharge radioactive materials from their bodies.
“I saw such a (high) figure for the first time,” said Makoto Akashi, a senior official at the National Institutes for Quantum and Radiological Science and Technology, referring to the reading of 22,000 becquerels. The institute oversees the National Institute of Radiological Sciences.
“It is very clear from a scientific viewpoint that the internal exposure to radiation would increase the risk of cancer (for the workers),” Akashi said.
“I have never heard of such a large amount as a reading for internal exposure to radiation,” Shunichi Tanaka, who heads the NRA, told a separate news conference.
The workers wore masks but could have inhaled radioactive material from the small gaps between the masks and their faces.
Kunikazu Noguchi, an expert on radiological protection and associate professor at Nihon University, said it is hard to conclude the impact of the 22,000 becquerels, as the actual amount of radioactive substances he inhaled is still unknown.
“It is possible, however, that the worker could have been exposed to more radioactive materials than the legally allowable maximum limit,” Noguchi said. He said it is necessary to get to the bottom of the incident, especially whether workers followed guidelines, as it is hard to imagine a plastic bag containing nuclear substances could tear in such a facility as the Oarai center.
Worker at Ibaraki facility has up to 22,000 becquerels of plutonium in lungs
TOKYO – Five workers have suffered internal radiation exposure, with one found with up to 22,000 becquerels of plutonium in his lungs, following an inspection accident at a nuclear research facility in Ibaraki Prefecture on Tuesday, the operator of the facility said Wednesday.
In one of the worst accidents involving internal radiation exposure in Japan, up to 5,600 to 14,000 becquerels of plutonium 239 have been detected from the other three workers, the Japan Atomic Energy Agency said.
The accident occurred at the fuel research building of the agency’s Oarai Research & Development Center when a bag covering a container for nuclear fuel materials, including powder samples of plutonium and uranium, tore during inspection.
A labor standards inspection office in Ibaraki conducted an inspection Tuesday and Wednesday at the building, while the Nuclear Regulation Authority, the nuclear safety watchdog, also dispatched an inspector to the scene to check whether there were any violations of safety regulations.
The agency estimates that the amount of radiation exposure of the man with the highest level translates to up to 12 sieverts over 50 years.
The labor office believes that the man in his 50s has exceeded the annual limit of radiation exposure of 0.1 sievert in five years set for those who handle radioactive materials.
Plutonium is known to emit alpha rays for a long period, damaging surrounding organs and tissues. If it is deposited into the lungs, it could increase the risk of developing cancer.
The Japan Atomic Energy Agency has said the operation by the workers was carried out as usual.
Nuclear Regulation Authority Chairman Shunichi Tanaka said of the incident at a press conference, “Perhaps (the workers) have become too accustomed to plutonium. I urge careful handling.”
“As (a level for) internal radiation exposure it’s an amount unheard of,” he said.
“We shouldn’t downplay the situation,” said NRA Commissioner Nobuhiko Ban, a specialist in radiological protection.
While none of the workers has complained of health problems so far, an official of the facility operator said it “cannot rule out the possibility of future health effects.”
The five workers have been transported to the National Institute of Radiological Sciences and given medication to facilitate the discharge of radioactive materials from their bodies.
Since radioactive materials were found on hands and faces of four of the five workers, they have been decontaminated, said an official of the National Institutes for Quantum and Radiological Science and Technology, an umbrella organization of the National Institute of Radiological Sciences.
The workers wore masks to cover their mouths and noses but could have inhaled the radioactive materials from the small gaps between the masks and their faces.
The Japan Atomic Energy Agency has previously come under criticism for lacking safety awareness, following revelations of a massive number of equipment inspection failures at its Monju prototype fast-breeder nuclear reactor in Fukui Prefecture.
The Japanese government decided to decommission Monju last year after it has barely operated over the past two decades despite its envisioned key role in the country’s nuclear fuel recycling policy.
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