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The following is the text of a speech given by Hideyuki Ban (Co-Director), Citizens' Nuclear Information Center in Switzerland in April 2002. It is an updated version of a speech given in Bonn in June 2000 which was the original Report 34.

1. INTRODUCTION

Tokai-mura is a village with a population of 34,000 and 12,000 households (mura means Village and thus Tokai-mura means Tokai Village). The very first development of Japanese nuclear energy occurred in this village. On October 26, 1963, the first Japanese nuclear power plant began generating electricity. One third of the Village's population works for the nuclear industry. In addition, another one third of the residents are involved with Hitachi which is a conglomerate that extends its trade to nuclear power-related business. The remainder of the residents are not involved in the nuclear industry.

The criticality accident at JCO (a uranium conversion company) was the first one of its kind in Japan. It was also the first time that workers lost their lives due to a radiation exposure accident at a commercial nuclear facility. A number of residents in the vicinity of the accident site were exposed to radiation. It was the first time that local residents had been evacuated, and the first time that compensation was paid in the wake of such an accident. The accident had a great impact on the residents, changing their minds from active promotion to a desire for nuclear phase-out. Also, in response to this accident, a review was carried out on nuclear disaster measures, which led to the establishment of the emergency system with a new off-site center as its main project.

CNIC established the Comprehensive Review Committee of the JCO Criticality Accident, and has been conducting an investigation of the cause of the accident and the impact of the accident inflicted on the local citizens. The committee consists of 17 members, and we published a report in 2000. In February 2001, we carried out a public discussion with the Nuclear Safety Commission (NSC) on the causes of this accident. Currently, a second investigation on the impact on the residents is being carried out. At the same time, while continuing our fact finding mission into the causes of the accident, the members of the Committee monitor the trial of JCO and its employees in the gallery of the court.

2. THE BACKGROUND AND CAUSES OF THE ACCIDENT

2.1. The background

The accident began with a sudden flash of blue light at around 10:35 a.m. on September 30, 1999. Criticality was reached while workers were preparing uranyl nitrate solution. There were 124 workers at the JCO plant at the time of the accident. This figure includes the three workers who were directly involved in this process, and who were seriously exposed. Two of those three have died, one died on December 21, 1999, three months after the accident, and the other on April 27, 2000 from multiple organ failure caused by radiation exposure.

Despite the predictions of many, criticality continued for 20 hours. Criticality was finally contained in the early morning of October 1 due to an extremely dangerous operation carried out by JCO workers. The only resort left to them was to extract the coolant water surrounding the precipitation tank which contained the uranium solution. Even then, they only just managed to stop the chain reaction. The coolant water was acting as a reflector of neutrons which were contributing to the fission chain-reaction. According to an investigation after the accident, it is estimated that about 1 mg of uranium-235 had fissioned (2.5x1018 fissions) during those 20 hours.

The neutron monitors at the Naka Laboratory of the Japan Atomic Energy Research Institute, approximately 2km away from JCO, detected a large amount of neutrons released due to criticality at the plant. In addition, radioactive rare gases and radioactive iodine were released into the environment. Because the ventilation system was left on and not properly adjusted, radioactive gases were continually released for about a month until the plant was equipped with charcoal filters to absorb and block such gases.

The Tokai-mura municipal office voluntarily decided to evacuate approximately 180 people who were within a 350-meter radius of the JCO plant to a community center, 1.5-2km away from the plant, five hours after the accident. While the discussion on evacuation was going on, at around 2 pm an air dose of 0.75mSv/h (measured by gamma ray detectors) was recorded at one place in the area surrounding the accident site. However, at this stage, neutrons were not being measured. The evacuation of the 175 people started at 3 p.m. and was completed around 8 o'clock at night (about 10 hours after the accident). The evacuees stayed at the community center for over two days. Also, 310,000 people within a 10 km radius of the JCO plant were requested by Ibaraki Prefecture to stay indoors from the evening of the day of the accident (Sep. 30) till 3 p.m. the next day (Oct. 1). It is reported that the Prefectural government also made this order out of fear of the greater harm that would arise if criticality resumed.

2.2. Causes of the accident

2.2.1. The direct cause of the accident
The direct cause of the accident was that workers had poured uranyl nitrate solution containing 16.6 kg of uranium, with an enrichment level of 18.8%, into a precipitation tank in order to evenly homogenize the solution. The precipitation tank was not supposed to be used for homogenization. In addition, according to the government regulations, no more than 2.4 kg of uranium enriched to such a high concentration should be poured into a tank. Since there is an inherent danger of criticality at such facilities, the form, shape, and size of the containers must be designed with anti-criticality specifications to counter criticality even in the case of human error. This is called "geometrical control." The most significant error was that there was no geometrical control of this precipitation tank.

2.2.2. The underlying cause of the accident
JCO's main work consisted of reconversion of low-level enriched uranium from UF6 to UO2 for Light Water Reactors(LWRs). However, the company triggered the accident when it was preparing uranium for Joyo Fast Experimental Reactor(Joyo FR). Preparing uranium for Joyo was different from what JCO normally did because it required a process called "redissolution" in order to obtain the final product in the form of uranyl nitrate solution (process described below). However, business for Joyo made up only 1% of JCO's earnings and thus the company placed very little importance on training its employees for this process. The three employees directly involved with the process which led to the accident had no experience with redissolution and were not educated or informed on the risks of criticality. In addition, the company had not undertaken the particular process which led to the accident for three years.

Though JCO shared a large part of the market for reconversion in Japan with Mitsubishi Nuclear Fuel Co., it had been steadily losing sales due to the effects of increasingly severe competition, and also it was under immense pressure from the utility companies to lower prices. Table 1 shows that its sales plummeted from 3.25 billion yen in 1991 to 1.8 billion in 1998, while staff numbers were reduced from 162 in 1991 to 110 in 1998.

Table 1: Data on JCO

Year

1991

1995

1998

Staff

162

145

110

Engineers with college degree

34

33

20

Output (t)

552

495

365

Sales (million yen)

3,250

2,806

1,800

Source: NSC Subcommittee on JCO Criticality accident

Figure 1: JCO's uranium production for Joyo 

 

2.3. Safety assessment system by the Science and Technology Agency

The precipitation tank, the source of the accident, was the only equipment in the JCO Conversion Test Building that was not designed with geometrical control. Upon conducting a safety assessment for installation licensing of the plant, this lack of geometrical control was discussed within the Science and Technology Agency (STA). However, the agency decided to settle the matter by checking the mass control specified by JCO. In other words, STA was satisfied by simply checking the amount and the concentration of uranium that would be put into the precipitation tank. The agency's conclusion was that no criticality accident would take place if the employees would only abide by the specified amount.

The officer in charge of this assessment in the STA was a person seconded from the Power Reactor and Nuclear Fuel Development Corporation (PNC, now the Japan Nuclear Cycle Development Institute, JNC). Thus, the safety assessment was being carried out directly by a stakeholder.

In order to prepare a uranium solution for use in making fuel for the Joyo FR, the following process was undertaken at the JCO plant. U3O8 (Tri-uranium Oct-oxide) was dissolved once in order to be refined, then calcinated into uranium oxide, then dissolved once again with nitrate to provide uranium in the form of solution. (See Figure 2)

The second dissolution is called redissolution and the uranium reached criticality during this process. To be precise, the accident was triggered during the last process of redissolution when the employees attempted to homogenize the solution. Instead of transferring the concentrated nitric acid from a beaker to the storage column (itself an unapproved procedure) they transferred it directly to the precipitation tank. As mentioned above, the precipitation tank had no geometrical control. JCO insisted that they carry out this homogenization process to simplify the products' transportation procedures. Redissolution of uranium for Joyo required a high concentration of uranium (370g/liter). However, JCO did not install proper equipment for preparing a uranium solution of such a high concentration, and instead used equipment already existing in the plant.1 In order to avoid installing new equipment, a complicated and impractical manual was drawn up to carry out the process with existing equipment. This manual was approved by the STA. It is rather natural, then, that in efforts to simplify the process, the employees took procedures deviating from the impractical manuals and used equipment not designed for redissolution. The STA should have made the installation of equipment for redissolution a prerequisite before giving approval for JCO to carry out redissolution.

Figure 2: Process at the conversion test building

2.4. The Japan Nuclear Cycle Development Institute's responsibility

PNC made a contract with JCO, which was commissioned to purify the uranium dioxide or uranyl nitrate for Joyo FR. At the time of the accident, the workers were instructed to dissolve U3O8, imported from France, into the uranyl nitrate solution. The materials were transported from JNC to JCO, and then sent back to JNC in the form of the required product.

PNC was involved in the accidents at Monju in 1995 and at the Tokai Reprocessing plant in 1997. PNC was exonerated from serious responsibility for these accidents, but was made to change its name to JNC.

It is stated in the contract between JCO and JNC that JNC holds the responsibility and the power to control the process as need arises. It is also stated in the contract that JCO can make changes to the manufacturing process simply by consulting, and then receiving a verbal approval from JNC. Thus it is clear that JNC was aware of, and approved of the procedures taken at JCO. JCO has never followed the process approved by STA. JNC should have known this from the contract. There is, however, no evidence that JNC approved the use of the precipitation tank for homogenizing the uranium solution.

In addition, JNC was in a position in which it could have easily been aware of the dangerous procedures that were being taken at JCO. From these two points, it can be seen that JNC has responsibility for indirectly causing this accident by placing that particular order. However, there is no mention of JNC in the report of the government's investigation committee.

3. THE DISCONNECTED NUCLEAR FUEL CYCLE

When natural uranium is imported in the chemical form of UF6, it is enriched at the Rokkasho Uranium Enrichment Plant. The enriched UF6 for Pressurized Water Reactors(PWRs) is transported to Mitsubishi Nuclear Fuel Co.,Ltd, where the whole process from reconversion to fuel fabrication is carried out. On the other hand, UF6 for Boiled Water Reactors(BWRs) is transported to JCO, where the reconversion process is undertaken, and then UO2 is shipped to two nuclear fabrication facilities, JNF and Nuclear Fuel Industries, Ltd. Thus, there are only two reconversion plants in Japan. Due to the accident, JCO's operation license was cancelled. Therefore, a part of the nuclear fuel cycle is now stopped. Since electric companies have long-term contracts with uranium producers abroad, there is a move toward the resumption of the operation of JCO. However, at this point, there is no prospect of that. Currently, UF6 for BWRs enriched at Rokkasho is exported to the U.S. and companies manufacturing BWRs fuel are managing their production by depending solely on imported UO2.

Figure 3: Japan's nuclear fuel cycle

 

 

4. IMPROVEMENT ON THE EMERGENCY PLAN

It was Mr. Murakami, the mayor of Tokai-mura, who made the brave decision to evacuate village people. In the emergency plan at that time, he was supposed to wait for a decision by the emergency advisory body under the NSC. However, at the time that the mayor made his decision, such a body had not even been established. The Nuclear Safety Commission (NSC) itself responded slowly, and was hardly functioning at all.

From the lessons learned after the accident in December 1999, the Nuclear Disaster Prevention Law was established. This law specifies the system in which emergency evacuation is carried out under the authority of the Prime Minister's crisis management. Until the new system was established, mayors of municipalities were supposed to make a judgment after receiving advice from the NSC, but there was strong criticism of this system. In response to this criticism, it was decided that the central government would take responsibility for countermeasures in a case of a disaster. The law has made it mandatory for companies to prepare an accident countermeasure plan and to set up a disaster countermeasure section. It also calls for the strengthening of the role of the central government and a speedy reaction by it during a nuclear disaster. To meet this requirement, a so-called Off-site Center has been planned for construction near each nuclear facility. This law, however, requires countermeasures to be taken for the down-winders from one to 10km away only when the radioactive leak has reached 10,000 times the normal reading (air dose of 500micro Sv/h). This is a completely inadequate regulation for preventing the exposure of residents to radiation.

5. COMPENSATION FOR DAMAGES FROM THE ACCIDENT

Ibaraki Prefecture announced that direct damages from this accident have reached a total of 15.3 billion yen (U.S. $125 million) for 7000 cases (Table 2). Direct damages, for example, include compensation for the forced closure of businesses, and suspension of agricultural activities and fisheries. Perceived damage is not included in what is called "direct damages." In addition, real estate prices have not been evaluated and are still falling as are the prices of agricultural products.

Table 2: Damages inside Ibaraki Prefecture (at the end of October 2000)

Category

The amount of damages (million yen)

Commercial Industry

9,596

Agricultural, Livestock, Fishing Industry

2,504

Tourist Industry

1,472

Transportation Industry

211

Other Industries

750

Reduction of Tax Revenue (expected)

769

Total

15,302

JCO has paid all of the 15.3 billion yen compensation. However, JCO could not pay all of the money without assistance, and the parent company Sumitomo Metal Mining sold land and other assets to cover the costs. It is true that JCO has paid an unprecedented amount of compensation. However, this amount is only a portion of the total damage caused by the accident. No compensation has been paid to those who complain that their health has deteriorated.

6. RADIATION EFFECTS FROM THE ACCIDENT

6.1. Radioactive products

The radioactive gases were carried by the wind. A monitoring post approximately 7 km away from the JCO plant detected these gases. The wind direction altered four times, rotating a full 360 degrees during this period. The radioactive gases were directly heading towards the community center used for evacuation from 9 p.m. of the day of the accident till midnight. The government officials said that the exposure dose was low. However, monitors in Tokai-mura detected radiation more than 20 times higher than normal.

Since the filtering devices at the plant were insufficient, almost all the radioactive rare gases and iodine were released into the atmosphere, which included nine isotopes of krypton, nine isotopes of iodine, and six isotopes of xenon. Some of them and their daughters were detected in the environment. Looking at effects on human health, especially those of skin irritations caused by exposure to radiation, we should not ignore the beta-ray emitted from all of these isotopes which were released as a direct result of the criticality accident. JCO claims that there is no relation between beta rays and skin irritation, but there are grounds for thinking that the relationship is significant.

6.2. Radiation exposure of employees and residents

6.2.1. Exposure dose that was made public
The Nuclear Safety Commission reports in the government's investigation report that 664 people were exposed as a result of the accident (Table 3). Among local residents, there were 131 who were exposed to doses higher than the annual dose limit of 1 mSv, and 27 who were exposed to doses higher than 5 mSv. According to this report, no employee, other than the three directly involved in the accident, was exposed to doses higher than the annual dose limit of 50mSv for employees.

Table 3: Exposure Dose (Source: STA's Request Related on October 13, 2000)

Dose(mSv)

JCO Employees

Accident response task-force members

Citizens in the locality at the time of the accident

Total

<1

41

202

104

347

1=<-<5

82

51

104

237

5=<-<10

15

7

18

40

10=<-<15

6

0

6

12

15=<-<20

10

0

2

12

20=<-<25

8

0

1

9

25=<-<30

1

0

0

1

30=<-<35

2

0

0

2

35=<-<40

0

0

0

0

40-=<-<45

1

0

0

1

45=<-<50

3

0

0

3

TOTAL

169

260

235

664

(Figures don't include the 3 employees directly involved in the accident.)

It can be assumed that there was widespread exposure due to the fact that neutrons were detected at a laboratory approximately 2 km away from the JCO plant. Thus the number of exposed people reported by the government is just the tip of the iceberg. In addition, the exposure dose was reviewed twice and the numbers decreased with each review. The government succeeded in lowering the dose values by calculating effective doses. With this calculation, doses were lowered by basing the radiation weighting factor from neutrons on outdated information from The International Commission on Radiological Protection (ICRP) publication 26 (1977). For example, a dosimeter worn by one of the employees who took part in the coolant extraction detected 120 mSv. However, following the government's review of exposure doses, the final report said that this employee had received a dose under 50 mSv. (It was important for the government to keep the official report of exposure dose under 50 mSv since this is the annual exposure dose limit for occupational exposure.) However, Japan adopted in 2001 the radiation weighting factor specified in ICRP publication 60 (1990). As a result, despite their efforts in reducing the estimated doses, the government's final figures on exposure doses from the accident will increase two fold.

6.2.2. Propaganda by government to ignore the effects of the accident
The STA and the NSC are promoting the view that if the exposure dose is lower than 200 mSv, there is nothing to worry about. They claim that they are basing this argument on ICRP publication 60, paragraph 64 which discusses health effects from radiation exposure of Hiroshima and Nagasaki atomic bombs victims. However, they have taken what they need and have manipulated the information to back up their claims.

The Comprehensive Review Committee on the JCO Criticality Accident formed by CNIC conducted an investigation of local residents who were near to the JCO plant at the time of the accident2. The outcome of this investigation shows that many felt ill or had skin irritations after the criticality accident (Table 4 & Table 5).

Table 4: Correlation between the distance from the JCO site and the number of people experiencing physical abnormalities

Distance

(radius, m)

Abnormalities on the day of the accident1) (%)

Abnormalities experienced up to the time of survey2) (%)

Number of all respondents from the area (%)

350

6

(15.0)

15

(37.5)

40

(100.0)

350-500

41

(21.9)

78

(41.7)

187

(100.0)

500-1000

39

(15.7)

106

(42.6)

249

(100.0)

1000-1500

38

(11.9)

93

(29.2)

319

(100.0)

1500-2000

35

(9.0)

122

(31.5)

387

(100.0)

Total

15.9

(13.5)

414

(35.0)

1182

(100.0)

Notes:1)X2=19.768 d.f.=4 p<0.001 2)X2=31.209 d.f.=16 p<0.05

There were 129 people who experienced one symptom, 21 with two symptoms, and 9 with three or more symptoms immediately after the accident and until the next day. At the time of the survey (Feb.2000), there were 145 people who cited one of 20 items (see Table 5), 97 people who cited two items, 99 people with 3-5 items, and 73 people with 6 or more items. When the relation between the distance from the JCO plant in a straight line and the complaints of more than one physical abnormality were examined by chi-square test, significant differences were detected at the 1% level. When the correlation coefficient is examined, the distance from the scene of the accident to the residences and the physical abnormalities experienced on the day of the accident and also at the time of the survey have a statistically significant negative correlation.

 

Table 5: Do you or did you have any of the following symptoms? (In Feb.2000)

Symptoms

Persons

Ratio %

Nausea.

17

1.4

Headache.

68

5.8

Dizziness.

24

2.0

Rash or itching.

29

2.5

My body feels weak.

60

5.1

I get tired more easily.

70

5.9

I catch colds more easily.

51

4.3

I get a slight fever sometimes.

10

0.8

I readily get nosebleeds.

10

0.8

I have palpitations.

29

2.5

I have no appetite.

30

2.5

I can't sleep.

75

6.3

I have nightmares.

30

2.5

I suddenly have vivid flashbacks of the accident.

111

9.4

I'm afraid to approach the accident site.

214

18.1

I feel uneasy and irritable.

81

6.9

I can no longer concentrate.

45

3.8

I don't want to see any news about the criticality accident.

113

9.6

I've become lethargic.

44

3.7

I feel extremely anxious.

233

19.7

The committee carried out the second investigation on the local residents who responded to the first investigation. The committee found that some cases of physical abnormalities had increased. For example, nausea increased to 3.8% from 1.4%, headaches increased to 10.2% from 5.8%, dizziness increased to 5.8% from 2.0%, rash or itching increased to 5.8% from 2.5%, feeling weak increased to 7.7% from 5.1%, palpitations increased to 4.5% from 2.5%, etc. Local residents are still suffering from damages caused by the criticality accident.

7. INVESTIGATION OF EFFECTS ON LOCAL RESIDENTS

The mayor of Tokai-mura said that the villagers' perception of nuclear energy has dramatically changed. Before the accident, the villagers were proud of their village's status as "the Nuclear Village", but now, they feel that the word nuclear itself gives a negative impression of their village. It is symbolic that the wording of "the Nuclear Village" was removed from the village sign board after the accident (See the photo3).

A poll of the local residents of Tokai-mura was conducted in February 2000 by the Comprehensive Social Impact Assessment of the JCO Criticality Accident, initiated by CNIC. The results of our poll show that 63.7% are against any further development of nuclear energy (Table 6), and 53.1% felt that nuclear business in the village should be down-sized from now on (Table 7). The result of this poll was largely reproduced in the second poll conducted in February 2002.

 

Table 6: What do you think about the following opinion?
"Japan should not build any more nuclear power plants."

 

Counts

Ratio %

I agree.

489

41.4

I mildly agree.

263

22.3

I mildly disagree.

100

8.5

I disagree.

133

11.3

Don't know.

161

13.6

NA

36

3.1

Total

1,182

100.0

Table 7: What should be done with the many nuclear power facilities in Tokaimura?

 

Counts

Ratio %

They should continue operation as at present,

with attention to safety.

420

35.5

They should be gradually reduced.

233

19.7

Dangerous facilities should be shut down immediately.

395

33.4

Other

27

2.3

Don’t know

65

5.5

NA

42

3.5

Total

1182

100.0

 

 

 

 

 

 

 

 

 

 

According to the polls conducted by the Japan Public Opinion Poll Association, 80-90% of those polled were worried over the safety of nuclear energy.

The Japanese public is now actively interested in renewable energy sources, and wants to retreat from nuclear energy.

8. FINAL COMMENTS

All of what I have reported so far has been caused by the fission of just 1 mg of uranium-235. And this criticality accident at JCO foretells further such damages. According to the government's safety assessment, a criticality accident should not take place at the JCO Plant - yet the accident did occur.

As a result of the accident, the mindset of Tokai-mura changed greatly, and the number of people who want a shift from the nuclear-dependent village policy has increased. This is also shown in the opinion polls. Nationwide, too, there are more voices of concern about the dependence on nuclear energy and more opinions favoring nuclear phase-out.

Since the accident, there have been two referenda held in Japan. One was on the loading of MOX fuel4 at Kashiwazaki-Kariwa nuclear power plants, held in May 2001, and the other one was on the siting of a nuclear power plant in Miyama-town in Mie prefecture, held in November 2001. In Kashiwazaki-Kariwa, the voter turnout was 88.14%, of which 53.4% were opposed to the use of MOX in reactor No.3. The referendum in Miyamacho was originally set up by the promoters', but the opposition reached 67% with a 90% turnout, which lead to the rejection of the siting. In this way, we can see the shift of public opinion, which was brought about by the JCO criticality accident.

Photo: Sign board

References

1. Dissolution tank 24 liter; 100 gU/liter, Storage column 40 liter; 60 gU/liter, Precipitation tank 53 liter; 45 gU/liter, Product (uranyl nitrate) 6.5 liter; 370 gU/liter, (Uranium Processing Facility Criticality Accident Investigation Committee of the Atomic Safety Commission)
2. The investigation was carried out in Feb.2000. 946 households randomly chosen from residents of three zones (350 meter radius, 500~1000 m radius, 1~1.5 km radius and 1.5~2km radius of the JCO plant) were polled. Each household was provided three sheets and 1082 people from 692 households answered the questionnaires. The second investigation of the 692 households who answered the first questionnaire was carried out in Feb.2002 by the same committee. In the second investigation 1008 people out of 535 household responded.
3. Mainichi newspaper, November 18,1999
4. MOX fuel: Uranium Plutonium Mixed Oxide fuel. The agreement between the Governors of Niigata and Fukushima Prefectures, the Mayors and Tokyo Electric Power Company (TEPCO) regarding Japan's MOX program was cancelled after a scandal at TEPCO which occurred three years after the JCO criticality accident.



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