Dossier :

Update 18 October 1999

Update 14 October 1999

Update 11 October 1999

Update 8 October 1999

Update 7 October 1999

Update 6 October 1999

Update 5 October 1999

Update 4 October 1999


18 October 1999


WISE-Paris, 18 October 1999
Last modification at 18h00, Paris time

o At a press conference on 15 october, JCO admitted that a " limited amount " (20 Bq/m3, twice the allowed quantity) of radioactive iodine-131 had been released into the atmosphere after the accident via the ventilation system of the building in which the criticality accident occurred. Prefecture and STA knew about the iodine release, but they took no measures considering the escaping quantity of radioactivity would be negligible. Concentrations of 0.04 Bq/m3 of I-131 were detected 50 m southwest of the building (the monitoring point is still within the JCO premises).

o The STA inspection of the JCO plant (which is legally prescribed) on 3 october 1999 was the very first one in 10 years to be carried out. It was also revealed that STA had conducted no site inspection either at Tokai Reprocessing Plant (operated by JNC) or at Rokkasho-mura Enrichment Plant (operated by JNFL) over six years. STA claims they were too busy.

o One member of the first team who approached the building to take photographs of the pipe systems they were going to work on, according to a JCO statement, was initially dosed with 20 mSv. Now it is revealed that the workers wore 2-digit type neutron recorders (the meter is reset to "00" when the count is over 99). The "20 mSv" actually were 120 mSv (neutron plus gamma, mostly consisting of neutron dose.) The fact was reported by STA on 15 october 1999 to the accident investigation unit of NSC. In the same report, STA confirmed that the number of the exposed persons now reached 69. This figure does NOT include the general public who had stayed very close to the plant for over 5 hours in neutron shower before they were evacuated. Dr Komei Hosokawa of Saga-University estimates that some 100 to 150 people were significantly exposed to neutron radiation.


14 October 1999


WISE-Paris, 14 October 1999
Last modification at 19h00, Paris time

o According to news reports, at the time of the accident, there was not even any hot line between the prefectural government and Tokaimura's town hall. Tokai officials had to rely on busy public telephone lines when they tried to obtain radiation monitoring data from the prefectural authorities after the accident.

o Experts and scientists at a symposium held at Kyoto Seika University on 4 October 1999, said the government should be accountable for the nuclear accident at the uranium-processing plant in Tokai, Ibaraki Prefecture. They also expressed concern that the company as well as the government might be withholding information or releasing incorrect information about the nation's worst nuclear disaster. Seika University President Hajime Nakao said the fact that the country is continuing with plans to put the Joyo fast-breeder reactor back online makes him think that the government wants the ability to build nuclear arms.

o On 14 October 1999, the visit of three IAEA experts in Japan comes a day after the Japanese Government admitted a ventilator at the plant had been mistakenly left operating for 12 days, allowing radioactive particles to leak into the atmosphere. The ventilator was only turned off on Monday 11 October 1999, three days after high levels of the radioactive substance iodine 131 were detected around the plant. Radiation levels at the accident site at Tokaimura are still dangerously high, so it is unclear how close the IAEA team will get.

o As part of the reorganization of central government ministries and agencies, which will begin in 2001, the Nuclear Safety Commission (NSC) will operate under a newly created Cabinet office, with enhanced independence - being an advisory body, the NSC has no licensing authority - as will be the case with the Nuclear Energy Commission. The two commissions now belong to the Prime Minister's Office.


11 October 1999


WISE-Paris, 11 October 1999
Last modification at 19h00, Paris time

o CNIC revised its estimation of the quantity of U-235 that underwent fission to "up to several tens of milligram of U-235". The Japanese Government's Nuclear Safety Commission (NSC), according to the daily Asahi, claims that the figure would be in the order of 0.001 mg (10E-6 grams).

o NSC confirmed in an official report to the Government that the criticality in the Tokai accident continued for 17.5 hours; the judgement is based on neutron dose monitoring by different institutions.

o The number of exposed people continues to increase, and reached 63 as of 9 October 1999.

o Six workers who worked on the cooling circuit of the accidented tank have received neutron+gamma radiation beyond the 100 mSv emergency limit prescribed by IAEA. NSC decided to take that measure "beyond the law". Workers should operate under an special limit of 200 mSv, said one member of the NSC.

o Sumitomo Metal Mining company, of which JCO is a 100% subsidiary, now intends to totally withdraw from the nuclear fuel business. This means that quite a few of the Japanese nuclear reactors will have to find overseas suppliers for nuclear fuel assemblies (conventional uranium fuel). For instance, Kyushu Electric Power Company depends for 70% on JCO uranium fuel, and is severely affected by the suspension (and permanent shut down, which is now likely) of JCO operations.

o The European Parliament voted for a total review of " all the nuclear facilities worlwide " by the IAEA. They require controls and check-up at the Tokaimura plant and ask the japanese officials for revised safety procedures. Hirofumi Nakasone, the new head of the Science and Technology Agency (STA) accepted IAEA experts to come to " increase transparency and recover international confidence "


8 October 1999


WISE-Paris, 8 October 1999
Last modification at 17h00, Paris time

o According to Japan Atomic Industrial Forum, the JCO's Tokai plant is able to process 715 ton uranium for light-water reactor fuel , and three tons of uranium for FBR fuel. The conversion of fuel for Joyo was the first operation of that kind in three years and only began on September 22. JCO employs 154 persons.

o "While there may be some cracks, since we have not been able to enter the site, the plant does not appear to be destroyed from the outside," the STA told the IAEA. It added that it was not sure how much radiation may have escaped from the building.

o The environmental group Greenpeace investigated materials from around the site -- including soil from around the accident site as well as salt (which is a neutron flow indicator) from the homes of local residents -- and concluded the government lifted its evacuation advisory too soon. According to Greenpeace, neutron radiation seems to have irradiated the environment at least 500 meters from the accident site, which would have reached a major nearby street and more than 170 homes as well as a golf course and farmland.

o The approach of spokesmen for the companies involved seemed similarly focused on the need to provide swift reassurance and emphasised the culpable role of workers without examining that of managers, even those on the spot, let alone those higher up in the JCO company and its parent corporation, Sumitomo Metal Mining.

o The insurance program designed to cover damage from nuclear accidents is not likely to compensate people for lost sales of agricultural products because of the Tokaimura nuclear accident, sources said on thursday 4 october. Sales are expected to decline in Tokaimura and neighboring municipalities in Ibaraki Prefecture. Nor is the insurance program likely to cover the entire cost of other losses stemming from the nation's first accident involving nuclear criticality. These include losses related to the suspension of railroad services and temporary closure of private firms. The insurance system makes it mandatory for operators of nuclear facilities to buy insurance against possible accidents. Further, it allows the use of taxpayers' money--subject to Diet approval--to pay compensation if the responsible operator is not capable of paying for all damages, reported the daily Asahi Shimbun.

o Prime Minister Keizo Obuchi claims that during the accident, governmental bodies, including the defense agency, the national police agency and the fire and disaster management agency have been directed by himself, to make concerted efforts to secure the safety of residents and to prevent the radiation hazard from expanding.

o "We did not foresee that the situation could intensify and that is why we were late in responding," said Hiromu Nonaka, a government spokesman. "We have to acknowledge that we were lax."


7 October 1999


WISE-Paris, 7 October 1999
Last modification at 20h00, Paris time

o The Tokai-mura uranium was of French military origin :
The uranium which originated the criticality accident at Tokaimura on 30 septembre was of French origin, confirmed JCO Co spokesman, Norimichi Mori, to the French daily Le Monde. French sources indicated that the 18,8% enriched uranium was exported in december 1997. The 420 kg of uranium had been enriched by COGEMA in its military enrichment plant in Pierrelatte (shut down in 1996). The deal had been organized by the German nuclear fuel broker NUKEM. COGEMA stressed directly after the accident that it had no agreement with JCO Co. In fact COGEMA's client is JNC Co, operator of the Joyo experimental fast breeder reactor, which subcontracted the conversion work to JCO.

o The following is an overview of fission products detected within 3 km of the accident site. The figures were taken from newspapers and TV reports, and have been compiled by CNIC. (Citizens' Nuclear Information Center, Tokyo:
- strontium-91 : 0.021 Bq/m3 in air, 900 m southeast of the site
- strontium-91 (krypton-91) : unknown amount, location not specified
- iodine-131 : 54.7 Bq/kg from mugwort leaves, 100 m from the site
- iodine-133 (krypton-91) : unreported amount, 100 m from the site
- cesium-137 : unreported amount, 7 locations
- sodium-24 : 64 Bq/kg, 300 m west from the site
- sodium-24 : 1.7 Bq/kg, 3 km west from the site
- xenon-139 : from the vomit of the exposed workers
- krypton-91 : from the vomit of the exposed workers

o According to insider reports, STA officials are going to rank the Tokai accident at Level 5 instead of Level 4 on the International Nuclear Event Scale (INES), in other words as severe as Three Mile Island accident 1979.


6 October 1999


WISE-Paris, 6 October 1999
Last modification at 20h00, Paris time

o The mayor and the Governor of Ibaraki Prefecture jointly met the Prime Minister Obuchi on Monday (4 Oct). They firmly requested the suspension of JCO's operations, and also stated that new legislation to guarantee safety in nuclear plants should be introduced.

o In the mean time the mayor of Tokai-mura issued an order of total suspension of the operation of JCO Tokai plant (all the work inside its Tokai facility) on the basis of the Safety Agreement between the company and the village administration. This is the first time in Japan in which a local government made use of this sanction power based on the nuclear safety agreement with a plant operator. It was also decided that the Tokai nuclear fuel reprocessing plant, of which the operation has been suspended since the March 1997 explosion and fire, would not restart for the time being. The reporcessing plant was about to restart. Its operator is Japan Nuclear Fuel Cycle Development Institute (JNC), former PNC.

o On 6 October 1999, according to Kyodo News Agency, the Science and Technology Agency (STA) has decided to revoke the business license of JCO Co due to the "seriousness of the accident".

o According to Reuters, on 6 October 1999, a police spokesman said that about 200 investigators raided JCO's headquarters in Tokyo and its office in Tokai-mura, searching for causes and responsibilities for the accident. It has been reported that STA and the Ibaraki Prefecture Police are involved in the investigations

o Kyodo quoted government sources as saying that the authorities have confirmed during their investigations that JCO had changed the government-approved procedure manual and used the illegal one as "standard procedure." JCO officials have admitted the firm illegally revised a government-approved manual to allow workers to use buckets instead of a pump to transfer a uranium solution to a tank. It has been revealed that the three JCO workers, who were hospitalized due to massive radiation exposure, had not been wearing their film badges to measure radiation dose. This is another serious violation of the safety regulations.

o The responsability of the Tokai local government is also put into question since it did not conduct a nuclear emergency exercise for the last eight years.

o The Government's emergency response headquarter has been resolved, and now a Nuclear Accident Investigation Committee is to be set up. The PM's office ordered an ad hoc inspection in all nuclear facilities, including power plants, all over Japan.

o A number of public meetings and protest actions are being organized all over the country by NGOs, trade unions and concerned citizens.

Update 2

5 October 1999


WISE-Paris, 5 October 1999
Last modification at 20h00, Paris time

Note : Changes may occur in the chronology of events, especially concerning the setting up of a first 200 m radius safety area and the later evacuation of the people living as far as 350 m from the facility. Also, it remains unclear what happened on 30 September 1999 between 12h41 and 15:00, a crucial time period.

o At 11h15 (40 minutes after the start of the event, time laps after accident start indicated in the format +0:40) on 30 September 1999, JCO mentioned the possibility of a criticality accident in its first notification of the event to the Science and Technology Agency (STA).

o At 11h33 on 30 September 1999 (+0:58), JCO informed Tokaimura's municipality of an accident that occured in their facility.

o At 12h30 on 30 September 1999 (+1:55), the head of the Prime Minister's office receives the first report on the accident. It takes almost one hour before he takes action. At the same time, Tokai's officials broadcast information about the accident via the local radios and ask people to stay indoors.

o At 12h41 on 30 September 1999 (+2:06), the police define a 200 m radius area around the site and prevent any vehicle from entering.

o In beetween, the Chemical Warfare Unit (which belongs to Ground Self-Defense Forces) stationned at Omiya, Saitama prefecture, is mobilized and sent to Tokaimura. "However, the unit is unable to cope with this kind of nuclear accident", the Chief Cabinet Hiromu Nonaka said, according to the daily Yomiuri Shimbun.

o At 15h00 on 30 September 1999 (+4:25), Tokaimura municipality issues an evacuation evacuation request area for residents in the the area inside the 350 m radius of the plant.

o At 15h30 on 30 September 1999 (+4:55), the actual order to evacuate was issued to about 150 residents from 50 households in a 350 meter radius around the plant (actually not really in a circle but rather the supposed downwinders). They were brought with 9 bus to the 1,5 km near-by Funaishikawa Community Center.

o At 16h00 on 30 September (+5:25), STA and JAERI (Japan Atomic Energy Research Institute) experts staff are on site and start measurements. Traces of cesium-138 are detected on the ground inside the complex of JAERI, located next to the accident site.

o STA and several groups of independant scientists have carried out sampling around the JCO Tokai plant, mainly in the 350 m area zone. Radioactive fallout of cesium-137, iodine-131, strontium-91 and sodium-24 have been (extensively for sodium-24) confirmed.

Update 1

4 October 1999


WISE-Paris, 4 October 1999
Last modification at 20h00, Paris time

o The dosis, re-evaluated on the basis of blood analysis, received by the three men exposed to the highest levels were respectively 17 Sv (age 35), 10 Sv (age 39), 3 Sv (age 54). The dose calculations are based on sodium-24 concentrations, not only in the blood but also in the vomit of all three men. The 35-year man was transferred to the Tokyo University Hospital, arriving there at 16h30 on Saturday. Doctors were preparing for either umbilical cord blood or haematogenous tissues transplantation, rather than bone marrow transplantation.

o 18 workers who carried out the work inside the facility to destroy the cooling water system around the precipitation tank - operation carried out in order to get the water out which functioned as moderator during the accident - received doses estimated between 20 mSv and 103 mSv. The legal limit for workers in Japan is 50 mSv per year. In case of emergency, the limit is exceptionally 100 mSv for a single operation.

o As the daily Asahi Shimbun reported, based on information by an inside source, the production process had been hastened by the employess under pressure by the plant management.

o On 2 October 1999, at 18h30 the Japanese government issued a "Safety Declaration" stating that there would be no contamination in the 350 m radius zone and lifted the evacuation.

o On 4 October 1999, it is announced that various samples of a common local herb had been collected by citizens in the area on 2 October 1999, measured by the Research Reactor Institute of Kyoto University, were found contaminated with 23 to 54 Bq/kg Iodine-131.

o The uranium enrichment level was specified as 18.8% U-235.

o The liquid uranyl nitrate is transported to the Joyo site, some 20 km from Tokai, and converted into UO2 there.

o The exact events which led to the desaster are still unclear. We have screened many different accident accounts. None of them seem to make sense from A to Z. We prefer to wait for further confirmation before indicating any details. However, the following points seem to be conclusive:

- the accident took place in a precipitation tank;
- the operator action involved manual introduction of uranium;
- the operators were under stress by plant management to speed up the process;
- the operators were not or insufficiently trained and were working outside internal and regulatory manuals;
- the licensing procedure of the installation did not require the qualification against criticality accidents and there was no procedure for the event of a criticality accident;
- there was no neutron counter at the installation; it has been brought in from another part of the facility; its presence could have greatly accellerated the identification of a criticality accident and therefore the protection of workers and the public.

o Preliminary calculations on the emissions of radioactivity, carried out by Dr. Jinzaburo Takagi, a nuclear chemist and founder of the Citizens' Nuclear Information Center (CNIC), suggest that the accident should be rated level 5 rather than level 4.

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