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Tokai Accident Reports

The following reports have been gathered from various organisations:

 

Japan's Nuclear Criticality Accident

By Steven Dolley, Research Director, Nuclear Control Institute, October 4, 1999

When and where did the accident take place?

An inadvertent nuclear chain reaction, or so-called "criticality accident," began at 10:35 AM local time on Thursday, September 30 at the JCO Co. Ltd. Conversion Test Building at Tokaimura, Japan, about 75 miles northeast of Tokyo. The chain reaction, which gave off intense heat and radiation, could not be stopped until 18 hours later.

The accident began when workers were converting enriched uranium into oxide powder for use in preparing fuel for the Joyo experimental fast breeder reactor. This reactor is part of Japan's plutonium-production program. The uranium was enriched to 18.8% U-235, far higher than the 3 to 5% enriched uranium used as fuel in Japan's conventional nuclear power reactors. Breeder fuel, whether enriched uranium or plutonium, is far more susceptible to criticality accidents than power-reactor fuel.

What happened?

It appears that workers deliberately circumvented safety measures to save time. A solution of uranyl nitrate was transferred into a large-volume precipitation tank, rather than the smaller, cylindrical container required by regulations. According to JCO Inc. official Yutaka Tatsuta, one of the injured workers reported that some 16 kilograms of uranium solution had been poured into the precipitation tank, nearly eight times more than its criticality safety limit of 2.4 kilograms.

Workers reported seeing a blue flash and then started to feel ill. According to one report, "the area was wrapped in a haze of blue smoke." Workers told plant staff that "they saw a blue flame rising from the fuel." Kenji Sumida, a member of Japanese government's Nuclear Safety Commission, concluded, "I know this is difficult to believe, but I think that we have no choice but to recognize this accident as having been critical." The criticality continued for about 18 hours until the water that was moderating the flow of neutrons and allowing the chain reaction to continue was drained and the tank was flooded with boron, a neutron absorber.

How much radiation was released?

At one point, radiation levels near the plant were 15,000 times above normal background. A total of at least 49 people were contaminated with radiation, including 39 JCO staff, seven residents, and three firefighters who transported the injured workers. Two of the workers received such high doses of radiation that they are not expected to survive.

What emergency measures were taken?

Police blocked off a 250-meter radius around the facility. The local village government requested evacuation within 350 meters of plant; more than 150 people were affected. Residents beyond this perimeter were requested (several reports said "ordered") to stay indoors. Reportedly more than 310,000 people were affected. School children couldn't return home and were required to remain inside at their schools. Late Thursday afternoon, rain began falling in Tokai, and residents were warned to stay out of the rain, and not to ingest rainwater or well water. An all-clear was issued around 7 AM the next morning (Friday, October 1).

Who is responsible for this accident?

There is plenty of blame to go around. According to reports, workers in the facility deliberately ignored the criticality limit of 2.4 kilograms, and had poured solution containing between 14 and 16 kilograms of enriched uranium into the container prior to the accident. This illegal method was standard operating procedure, practiced for over two years and codified in a secret company manual that contradicted Japanese law and was never shown to government safety regulators. These regulators must accept responsibility for not detecting this major safety violation.

Japan's Yomiuri newspaper reported that the plant was an experimental facility and the workers thus may have been operating without appropriate safety measures, including protective gear and remote control systems, normally required in larger commercial facilities. After the accident began, it took JCO Inc. nearly an hour to notify local Tokai authorities, despite a safety agreement requiring immediate notification of any accident, regardless of how serious.

Is this Japan's first serious nuclear accident?

The Tokai criticality incident is the latest in a series of major accidents in Japan's breeder-reactor and plutonium-fuel program. In December 1995, the Monju demonstration fast breeder reactor leaked nearly a ton of liquid sodium coolant, which caught fire when it came into contact with air. Officials of PNC, the company that built and operated Monju, attempted to cover up the extent of the accident by doctoring and destroying evidence. In 1997, a waste-storage reprocessing plant at the Tokai facility burned and exploded, leading to another cover-up attempt. PNC has since been reorganized by the government into the Japan Nuclear Cycle Research Institute (JNC) as a result of these accidents and cover-ups.

Has this sort of accident happened elsewhere?

France's nuclear safety institute DSIN said the Tokai accident was the 60th criticality accident since 1945, 33 of which occurred in the United States and 19 in the former Soviet Union. Two-thirds of these accidents occurred at research centers. There had never been a criticality accident previously reported in Japan.

What steps can be taken to prevent such accidents in the future?

The local government has ordered JCO to halt all uranium-processing activities until safety can be assured, and the national government has undertaken a safety review. However, past assurances of safety in the Japanese breeder and plutonium program have proven unfounded. When the Tokai facility was licensed in 1983, its operators assured Japanese government regulators that "critical fission chain reactions could not occur."

The Monju breeder's sodium leak and fire, the Tokai reprocessing plant's waste explosion and fire, and the Tokai criticality accident all have resulted from Japan's program to produce and use plutonium fuel and to develop fast breeder reactors. Not only is plutonium fuel far more expensive than conventional, low-enriched uranium fuel (the fuel of choice in almost all the world's nuclear power reactors), it is also far more dangerous. Plutonium and highly enriched uranium are also suitable for use in atomic bombs. As the latest accident shows, regulatory reforms have failed to improve the safety culture in Japan's breeder plutonium program.

The surest way for Japan to prevent such accidents in the future is to shut down its breeder and plutonium fuel programs and to concentrate on safe operation of its nuclear power reactors using low-enriched uranium fuel. At present, Japan is planning to introduce plutonium into their reactors in the form of so-called "mixed-oxide" (MOX) fuel. MOX fuel potentially increases both the probability and severity of nuclear power reactor accidents.

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Accident possibly Level 5 - More than 100 Terabecquerals of fallout

From Magpie Country Nukes Headliner, a nuclear issues news briefing from Japan, editor: Dr K. Hosokawa. E-mail: hosokawk@cc.saga-u.ac.jp Website MagpieNews 5th October 1999

Several groups of independent scientists have carried out survey around the JCO Tokai plant, mainly in the 350m zone. Radioactive fallout of cesium-137, iodine-131, strontium-91 have been confirmed. Also sodium-24, which was produced by neutron radiation by the accident, has been extensively detected both by STA and indenpendent groups.

The following is an edited version of a tentative calculation of the amount of fission products release by the JCO Tokai accident. MagpieNews is grateful to CNIC and Dr Jin Takagi for their kind permission of citation. There are also a couple of graphs on the Japanese webpage of CNIC, indicating neutron dose rate. Dr Takagi says that these graphs are tentative ones, based on provisional calculations based on the limited date available at the moment.

Of the uranium poured into the precipitation basin (= "sediment tank" as reported in the previous MagpieNews) that caused the criticality accident, CNIC assumes that roughly 1-10grams of uranium 235 underwent fission, and 1E+16 to 1E+17 Bq (becquerel) of fission products were produced. Assuming the radio active materials released at Chernobuyl was roughly 1E+19 Bq, the Tokai release may amount to 1/1000 to 1/100 of that.

If 1/100 of the produced fission products (radioactive materials) was released, based on the assumption that all the radioactive gas was released and some of the other radioactive materials were released as well, then the amount of radioactive materials during the JCO Tokai accident was 1E+14 to 1E+15 Bq , i.e. one hundred teraBq to one thousand teraBq.

According to IAEA International Nuclear Event Scale (INES), an accident involving a release of this much radioactivity is categorized as Level 5. STA announced that the Tokai accident was Level 4. In reality, however, it is a Level 5 accident.

CNIC assumes that an amount of radioactive materials corresponding to the amount produced in the facility were released to the outside of the facility, and that the radioactive materials with short halflives have already attenuated. However, it is certain that no small amount of radioactive materials are still left inside the precipitation basin.

It has been reported that the gamma ray emitted from the remaining radioactive materials are kept inside because the JCO company put a shield consisting of layers of aluminum around their premises. However, this shield is an unreliable tentative treatment, and there are serious doubts for its efficiency. There is a possibility that some of the remaining radioactive materials are still being released at the moment, and the possibility of such materials being released in the future cannot be denied.

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Tokai accident site still emitting radiation above safety limits

Greenpeace, Tokaimura, Oct 4, 1999

Levels of radioactivity in an area of the town of Tokaimura remain well above background levels despite statements made by the Japanese government that they are now normal, following Thursday’s nuclear accident at a uranium processing plant, 110km north of Tokyo.

Measurements taken by a Greenpeace team at around 4pm on Sunday on a public road (Genken Road) which runs next to the contaminated plant at a distance of 30 metres, revealed the level of radioactivity in the middle of road to be 0.54 micro sieverts per hour, which is five times background levels of 0.1. Measurements taken today recorded a level of 0.4 micro sieverts per hour, suggesting levels of radioactivity were slowly falling.

Following the accident, which released large amounts of radiation, every resident within 350 metres of the plant was evacuated. On Saturday the government lifted the exclusion order after Chief Secretary to the Cabinet, Hiromu Nonaka stated: “We have confirmed that the radiation levels, even in the area 350 metres from the plant have returned to normal.”

Greenpeace team leader Diederik Samsom, a nuclear engineer and qualified radiation protection officer from Holland, said: “The high level of radioactivity we measured on Sunday was in the middle of Genken road, which had been reopened to the public by Japanese authorities some 24 hours earlier. The Japanese government needs to close this road to the public while radiation levels remain significantly higher than background levels. If this had been a public road in Holland or Germany it would have been closed off to the public.”

At a distance of 100 metres from the plant the radiation levels, measured on Sunday, were up to two and a half times background levels and fell to background levels at 200 metres. Other measurements taken on other public roads around the site but at a further distance (500-600 metres) from the contaminated plant, found levels of radioactivity at background or normal levels.

One of the causes for the elevated levels outside of the site boundaries is the extraordinarily high levels of gamma and beta radiation being emitted from the uranium and fission products contained within the contaminated building which lies only 30 metres from a public road. A desperate attempt has been made by the Japanese authorities to stop the radiation from reaching the public by constructing a three-metre high wall of bags filled with aluminium fluoride and cement blocks on the exterior wall of the plant.. Another possible contribution to the radiation levels might also come from contamination of the area by fission products released during the accident. Greenpeace is undertaking further sampling to assess the possibility.

Greenpeace is concerned about the progress made with the removal of the remaining radioactive material. All attempts to enter the building to start the clean-up have failed up to now and very little is known about the clean-up strategy. Greenpeace is demanding full disclosure by the Japanese authorities of its clean-up plans. “The government has been shown to make numerous mistakes in this tragic story, from approving safety manuals to a complete failure in emergency planning. The government has to explain its continued failures in radiation protection,” said Greenpeace Japan executive director Sanae Shida.

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International Atomic Energy Agency Briefing

This Greenpeace report is based on a verbal briefing given by the IAEA's Abel Gonzalez, head of radiation protection. His briefing was based on official information passed to the IAEA through the Japanese authorities.

The IAEA says the most likely scenario is thought to be:

A situation where one dissolver tank with one feeder going into it. Uranium hexaflouride (UF6) is dissoved in nitric acid, then precipitated to produce uranyl nitrate. Instead of putting in 2.4 kg they put in 16 kg and at one enrichment level of 18.8 percent. The other key factor is that this is done at quite high temperature, and so there is an external jacket around the tank containing water. The three key parameters that may have played a role in accident are 1. the quantity of uranium put in the tank; 2. an unknown factor -- the volume of acid in the tank; and 3. the status of the water jacket.

The water jacket is significant because it acts as neutron reflector; eventually to stop the reaction, they removed the water. Over a period of 17 hours what occured was a series of "criticality excursions", ie criticality, a flash of radiation, move to sub-critical, go critical again etc and so on for 17 hours. The authorities don't know how many excursions there were. There were NO chemcial explosions. Another scenario/possible explantion is that there were 2 tanks with two feeder pipes, and that the wrong concentration of uranium was put into the wrong tank. The IAEA/Japanese authorities could not rule out this being a possible scenairo. The significance of this scenario is that somehow large amounts of uranium were into a small tank rather than a larger receiving vessel. If too much uranium was put in the wrong tank, this would explain why criticality occured.

The radiation exposures: The authorities confirm there were 3 workers in the "conversion test building". 2 of them received at least 8000 millisvts - that is confirmed information. It is possible that it could have been over 10.000 msv which is potentially fatal. The thrid worker received approx 3000 msv but this is unconfirmed. There were 36 other workers on site; their invdividual doses are not known at this stage but it is believed that they all exceeded 20 millisievert limit. (International occupational standard) The authoirties are unable to give any indication of the range of dose workers received. Three emergency workers were also over-exposed, no indication of range. Sevev residents also received doses over 1 millisievert.

The IAEA's provisional classification on INES (int nuke event scale) is 4. The authorities say that all the doses came from the irradiation flushes (ie during criticality excursions) -- with a high component of neutron radiation even at site boundary . Authorities say actual release of radioactive material (as opposed to an extremely intense radiation field created by the criticality excursions) was small and that mainly noble gases (mainly xenon) were released. The IAEA characterises it as "a very serious safety breach". They think there are probably both design and operational safety breaches.

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Japanese Disaster Points to Need for Public Protection Overhaul
says Nuclear Free Councils

This is a press release on 4th October from theUK Nuclear Free Local Authorities

In the aftermath of the Tokai nuclear plant disaster which hit Japan last Thursday Nuclear Free Local Authorities (NFLAs) again called for a review of UK nuclear emergency planning.

The accident at the Tokai Plant located in a heavily built up area, involved the implementation of evacuation of nearby households, sheltering from radioactive fall out of a 310,000 population in a 10km radius area, schools
and factory closures, contaminated food controls, motor traffic restrictions, rail cancellations, and mass screening of thousands of people to check for contamination. Japan's Government Chief Cabinet Secretary last Thursday described the nuclear accident at the Tokai uranium processing plant as an "...unprecedented crisis of the nation."

Commenting on the Tokai accident, an NFLA spokesman said: "The scale of the emergency response required in Japan shows current UK nuclear site emergency planning is inadequate. In the UK detailed emergency planning is only required for at most a few kilometers around nuclear sites. The precise area is determined between a plant operator and the safety regulator, the Health and Safety Executive (HSE). They decide what they think is a 'reasonably foreseeable' nuclear accident. But this approach is deeply flawed. The consequences of real nuclear accidents are far more extensive than those which the nuclear
industry and the HSE are capable of foreseeing. We need an approach to emergency planning grounded on experience, not theory."

Before the Tokai disaster NFLAs argued for more extensive emergency planning in response to a UK Health and Safety Commission (HSC) consultation earlier this year. The HSC consulted local authorities on draft Radiation (Emergency Preparedness and Public Information) Regulations (REPPIR) for the implementation of European requirements for
responding to radiological emergencies.

NFLAs criticised the draft REPPIR for being too weak because:

* plans must be confined to 'reasonably foreseeable radiation emergencies' and not unpredictable, or merely possible emergencies however catastrophic: yet Chernobyl was not 'reasonably foreseeable' and consequently no emergency
plan is required for major nuclear accidents;

* the actual assessment of what is reasonably foreseeable is carried out principally by those who create the risk;

* the statutory definition of a radiation emergency is one where a radiation dose five times greater than the permitted maximum is predicted;

* the public to be provided with prior information (so that they may be forearmed against an emergency) are geographically defined by the concept of the 'reasonably foreseeable radiation emergency': others in a wider geographical area that might be assisted by prior information, in the event of a worse accident than is 'foreseeable', will not be advised in advance and will accordingly be less well prepared;

* nuclear transportation is excluded from the regulations; and

* incorrectly, the HSC proposals breach the EU Euratom Treaty, by exempting Ministry of Defence nuclear hazards from the regulations.

NFLAs therefore argue that:

* plans should address emergencies that are capable of causing major impacts;

* the statutory definition of a radiation emergency should be one where a radiation dose in simple excess of the permitted maximum public dose itself is likely;

* the characterisation of the emergencies for which the plans should provide should not be left to the self-interested technocratic judgement of those who create them but should involve a strong independent element which allows
for public perception and discussion of the risks to play its proper part;

* all transport operations for civil nuclear power and fuel cycle operations and military nuclear weapons and propulsion operations should be subjected to hazard assessment. Local authorities should be involved though their representative associations in the preparations of any generic emergency transport plan and should be consulted over the need for specific
local authority plans on frequently-used transport routes;

* the public to be provided with prior information should not be confined to the area of a 'reasonably foreseeable' emergency but should include all those who could be affected; and

* the HSE should confer with the Legal Service of the European Commission which takes the view that the requirements of Directives, which provide for the protection of the public against radiation, do not exclude nuclear hazards of military origin.

Further Information: Stewart Kemp (W) 0161 234 3244
(H) 0114 266 7656
(M) 07771 930196

* Nuclear Free Local Authorities *
* Town Hall *
* Manchester M60 2LA UK *
* Email: nfznsc@gn.apc.org *
* Website: http://www.gn.apc.org/nfznsc/ *

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Is the Tokai accident over ?

From Magpie Country Nukes Headliner, a nuclear issues news briefing from Japan.
E-mail: hosokawk@cc.saga-u.ac.jp Website MagpieNews 6th October 1999

No way! First of all, nobody knows what is the physical condition inside the buildin g in which the criticality took place. The radiation (now mainly gamma) leve l is too high so that there is no access for the time being.

At least we are 100% certain that there is a good lot of fission products (i .e. radioactive materials) in that building, namely what JCO calls the Re-conversion Test Building.

This means at least two things:

* We do not know whether there is physical destruction of the building structure through which the fission products can escape into atmosphere.

* A large number of workers prepared for radiation exposure is needed for liquidation of the site.

There is an alternative, of course, of doing no liquidation work and just shield the entire building with concrete and/or some other material, i.e. construction of a Chernobyl-type sacrophagus although the size is much smaller. At the moment, the site has been walled with a make-shift shield of piled sa ndbags actuallyu containing alminium powder that absorbs neutrons and dry concrete that blocks gamma.

The following is an inventory of fission products detected within 3km of the accident site. The figures were taken from newspapers and TV reports, and has been compiled by CNIC (Citizens' Nuclear Information Center).

* strontium-91 --- 0.021Bq/m3 in air, 900m southeast of the site
* strontium-91 (krypton-91) --- unknown amount, location not specified
* iodine-131 --- 54.7Bq/kg from mugwort leaves, 100m from the site
* iodine-133 (krypton-91) --- unreported amount, 100m from the site
* cesium-137 --- unreported amount, 7 locations
* sodium-24 --- 64Bq/kg, 300m west from the site
* sodium-24 --- 1.7Bq/kg, 3km west from the site
* xenon-139 --- from the vomit of the exposed workers
* krypton-91 --- from the vomit of the exposed workers

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Radiation exposure of population higher than government estimates

Greenpeace press release Tokyo, Oct 7, 1999

The numbers of people who suffered radiation exposure during the nuclear accident at the Tokaimura uranium plant was almost certainly higher than government estimates of forty nine people due to the high levels of neutron radiation, coupled with the slow evacuation of the area, Greenpeace said today, based on results of an investigation around the site.

Releasing the monitoring results in Mito city and Tokyo today, Greenpeace said that it had found evidence of radioactive fallout.Greenpeace also found high radiation levels on a public road near the plant on Sunday -- 24 hours after the all-clear was given by the government -- and compelling evidence of high levels of neutron radiation. Neutron radiation is the most penetrating and one of the most dangerous forms of radiation.

"Greenpeace undertook this survey in order to provide some independent assessment of the levels of radiation and the extent of contamination resulting from the Tokaimura accident," said Greenpeace Japan executive director, Sanae Shida. "Our results raise further serious questions about the Japanese government's nuclear safety and emergency planning procedures and the safety of the nuclear industry in general."

Greenpeace said that during the critical accident period, which lasted some 20 hours, high levels of neutron radiation (1) appear to have irradiated the environment up to a distance of at least 500 metres from the site of the accident. (This conclusion is supported by radiation modelling carried out by the environment group, Citizens Nuclear Information Centre- CNIC). This undoubtedly would have affected the hundreds of people who traveled on a nearby main road, were in the more than 170 houses, on a golf range and on agricultural land .

Neither the owner of the plant, JCO, nor the Japanese authorities used neutron detectors until six and a half hours after the accident. However Greenpeace was able to estimate the full radiation doses by analysing household salt samples obtained from residents living around the plant. When salt is bombarded with neutron radiation, the radioisotope sodium (natrium) 24 is created. The amount of this radioactive isotope present in the salt can then be used to calculate the intensity of neutron radiation emitted during the accident.

"Just as the table salt was bombarded with neutrons so were all the people within range of the accident site", said Diederik Samsom, a nuclear engineer and qualified radiation protection officer, who led the Greenpeace investigation.

"It was known 10 minutes after the accident that this incident was a criticality event (nuclear chain reaction). Evacuation from the surrounding area to avoid the penetrating neutron radiation should have been immediate. Instead it was almost four and a half hours before the evacuation order was announced."

The Greenpeace research team also found elevated levels of Iodine 131 and Iodine 133 in plant and soil samples around the plant. This shows that the accident resulted in radioactive fall-out. Iodine-133 has a short half life and therefore cannot have come from any other source. However, the lack of non-volatile radioactive elements in the samples (such as Cerium-144) suggests that the actual release from the accident was limited to the gaseous and volatile substances.

"It seems that a worse case scenario was avoided in this case. But this was more the result of good luck than good management. If the tank containing the uranium had ruptured, the situation would have undoubtedly been considerably worse," said Samsom. "Nevertheless, there was fall-out and the public around the site needs to know what were and are the exact levels. Our sampling showed there is a need for more research. It's now up to the authorities to extend their sketchy
reporting to a full-scale assessment of contamination levels in the area around the plant."

Greenpeace also urges the government to conduct a long-term health monitoring programme of all people who were in the vicinity of the plant during the accident. The first step should be immediate registration of all people likely to have been exposed to radiation.

"The accident demonstrates the lack of a safety culture within the nuclear industry globally, and illustrates the inherent hazards of
nuclear technology," said Greenpeace International nuclear campaigner, Shaun Burnie. "This is not an isolated incident. Yesterday, 29 workers were exposed to elevated radiation levels as a result of a leak of radioactive material at the Wolsung nuclear power plant in South Korea. The Japanese and other governments must change their energy policies by ending nuclear programmes, including fast breeder reactors, and moving into energy efficiency and renewable energy."

Notes:

1 8 milliSieverts (mSv)/hour at fence 1 mSv/hour at 175 metres from plant 0.05 mSv/hour at 500 metres

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Greenpeace Monitoring Results - 7th October

The Accident

The criticality accident involved the fission of uranium in a watery solution. Approximately 16kg of uranium including 18.8% in the isotope U-235 inside a steel vessel went critical.The results of the fission are more or less the same as in a reactor: fission products, activation products (from the strong neutron field) and transuranics (including plutonium) - but without the shielding that exists in a nuclear power plant.It is still uncertain what the actual yield of the 'tank-reactor' was during 17 and half hours but latest estimates say that approx 2-3 grams uranium was fissioned.

The resulting amount of plutonium from this would be rather small but not insignificant. However, our analysis shows that, since the tank is still intact, heavy elements like plutonium are not released in the environment during the accident. There is a risk that this could happen during the 'removal' operation of the tank, but so far, only the gaseous and volatile elements have left the tank. The tracers showing this phenomenon are found around the site: Iodine, Cesium and some strontium.

Background radiation levels

Greenpeace began measuring radioactivity around the Tokaimura site on the late afternoon of Sunday October 3rd late afternoon Within hours we discovered that background radiation levels were not "back to normal" as stated by the Japanese government but in fact were up to five times higher, at 0.54 microSieverts per hour. The sampling team from Greenpeace Netherlands, and Germany as well as Japan, measured these levels approximately forty metres from the source of the
radiation - the building in which the uranium had gone critical on Thursday 30th September. This happens to be a public highway, including pavement where people walk and cycle.

The levels found would not be acceptable for a public space in either Germany or the Netherlands for example, in fact levels at perimeter fences in Germany if they exceed 1.3 times background (background being 0.1microSieverts), it would mean immediate closure of the area. In the case of Tokaimura and the governments response, the area was officially declared safe by Saturday evening October 2nd, though during most of Saturday there were no restrictions or warning signs to people entering the area, particularly along Genken road, which runs along the main wall of the plant. Levels of background radiation on Saturday were certainly higher than those measured by Greenpeace on Sunday. Once again therefore the government and in particular the Science and Technology Agency failed to protect public health and instead sought to descalate the
seriousness of the accident.

Fallout

The Japanese government stated after the accident that there had been no radioactive fallout. Once again they were wrong in their assessment, and once again they allowed people back into the area most directly contaminated before conducting a comprehensive environmental assessment.

Greenpeace sampled soil and plant material from around the JCO uranium fuel conversion facility. Samples were taken during Sunday 3th and Monday 4th, and sent for analysis at the Department of Radio-Chemistry, at the University of Rikkyo, in Tokyo. Levels of Iodine-131 and Iodine-133 were detected, and calculating back to the period at the end of the accident, around 04.30am on Friday, the levels were 1182 Becuerels per kilogram. Iodine isotopes such as these have very short half lives and therefore will soon decay, due to their activity, they also are probably hiding or masking other radioactive isotopes such as Cesium-137, which is a major isotope in terms of public health. The levels measured have led Greenpeace to the
following conclusions:

· there was radioactive fallout - including Iodine-131 and 133;

· these are volatile substances that would have been released from the uranium facility in the form of a fine gas or aerosol. Upon entering the environment, especially since for a period of the accident it was raining, the material landed on the ground in the immediate vicinity of the plant, within hundreds of metres, but probably within a few kilometres. Wider dispersion is possible, but Greenpeace has no measurements of this.

· Undoubtedly released were so-called noble gases, Xenon and Krypton. These would have dispersed into the atmosphere relatively quickly in an easterly and southerly direction. These are beta emitters and would eventually be distributed throughout
the northern hemisphere - approximately 12 months. Given the amount of nuclear material involved, 16kg uranium, it is unlikely that the amounts released were large, though only when more details are released on the actual activity, and grams and kilograms fissioned will calculations be possible. No measurements were conducted by Greenpeace for these isotopes - though Greenpeace has conducted large scale Krypton-85 monitoring around the la Haguye reprocessing plant in Normandy, France. There levels of Krypton - because all of it is released into the atmosphere, have been measured up to 400,000 Becquerels per cubic meter. Background is around 1.2 Bq/m cubed. This is all due to reprocessing of nuclear waste spent fuel including
hundreds of tons from Japan - Tokyo Electric, Kansai Electric, Kyushu, etc.

What does this mean ?

Levels measured demonstrate that this was not a release like Chernobyl. Most of the activity remains inside the vessel, at least
95% we estimate. A comprehensive environmental monitoring program is essential to accurately understand the dispersion and level of fallout. In terms of public health, there is no threshold below which radiation is considered safe. However, levels measured do not pose an immediate health risk to people but more likely will effect public health over the longer term. It is impossible to say what the actual effect will be. As for contamination of farm land and crops around the plant, that has occurred, harvesting of crops was halted and therefore none should enter the food chain. Full compensation to the farming
community is absolutely essential, and should be paid for by the central government.

Neutron radiation

The other major component to Greenpeace's radiation monitoring was to seek to identify levels of neutron radiation emitted during the accident. Such radiation, which is deeply penetrating, travels in a straightline from source for hundreds of meters, passing through almost everything, but losing energy the longer it travels, and the more objects it passes through. Greenpeace's method for measuring was to seek to identify isotopes that had been activated by neutron radiation. Specifically in the first few days after the accident it is possible to measure for the radioactive isotope Sodium 24, this is created when the isotope Sodium-23 is activated by neutrons. To obtain samples, Greenpeace obtained samples of domestic table salt from two
houses around the JCO uranium facility. This salt used for cooking received the full neutron release during the accident. Only one sample was large enough, 2kg to measure in the laboratory in Rikkyo University. The levels measured on Monday night, 4th-5th October, were then calculated back to the end of the nuclear accident, Friday 4.30AM, by simple multiplication based upon the half life decay period of sodium24, (15 hours). The calculations made gave a figure of 6280Bq/kg, with an error margin of plus/minus 319Bq.

Using this figure we can calculate the neutron yield or flux energy released during the 20 hours of the criticality. This then has been cross referenced with the actual measurements made by the Japanese authorities around the facility in terms of micro-sieverts per hour.

On the basis that neutron radiation traveled at least 500 meters from the accident site, Greenpeace believes that within at least this area hundreds of people would have been exposed to harmful neutron radiation. This compares with the Japanese governments assurance that 49 people were exposed to radiation.

According to Professor Wolfgang Koehning, radiation biologist at University of Muenster in Germany, who analysed Greenpeace's figures, exposure to people in the neighbourhood was about 20 millisieverts, this compares with a maximum recommended yearly rate of 1 millisievert for the general public. Within this range of exposure, many people will have received a dose less than this, perhaps half their annual dose. On the other hand, a number of people may have received a dose
of many times their annual dose, tens and tens of years even. Actual neutron dose could be even considerably higher according to Professor Koehning.

Neutron radiation is considered harmful to the building block of life human DNA cells, damage to which can seriously increase the risk of cancer and other health effects.

Thus the people living in the immediate vicinity of the accident, as well as workers in the fields, and people passing through the area, for the many hours before evacuation were all exposed to neutron radiation. In addition the evacuation procedure was a disorganized mess, with people still in the 350 zone some seven or more hours after the initial criticality. In fact the zone was never completely evacuated, so people were exposed to the full 20 hours of neutron radiation. In addition the zone was not large enough, with people receiving a radiation dose at 400, 500 metres and more.

The effects of the neutron radiation will have to be monitored for the entire exposed population for at least the next thirty years. Blood cancers, leukemia, will only show up in the first ten years, longer-termed induced cancers will take longer to show. This will require a full-scale public health monitoring regime set up by the Health Ministry and the Regional Government. Japan has the most experience in the world in doing this having monitored for more than fifty years the radiation victims of the Nagasaki and Hiroshima atomic bombings.

What can you do

For those concerned about the consequences of the Tokai accident, please contact the following numbers for further details.

If you are a foreign national living in Japan, you have a particular opportunity to help prevent future accidents in Japan. Western nuclear trading states, especially Britain, France, Belgium the Netherlands, Australia, Canada and the United States, all assist Japan's nuclear development. In particular, Greenpeace is battling to stop the UK, France and Belgium from providing any more weapons-usable plutonium to Japan. Over 30 tons of this dangerous nuclear material is due to be shipped back to Japan over the next ten years. Already Japan has 5 tons of plutonium stockpiled at facilities around the country, most of which is not by coincidence at Tokaimura.

Please ask for an explanation from these countries as to why they support Japan's nuclear program, especially its plutonium program, and urge them to stop before Japan suffers a more serious accident than that which occurred at Tokaimura on September 30th.

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