CRITICALITY ACCIDENT AT A TOKAI URANIUM CONVERSION FACILITY
Uranium criticality should not be allowed to take place anywhere other
than nuclear reactors. The only exception where criticality is intentionally
produced is a nuclear warhead.
As a matter of fact, an uncontrolled nuclear fission chain reaction near
a big city could cause a disaster quite similar to what would result from
a nuclear war.
Taking into consideration IPPNW's view that a nuclear disaster would
be a final epidemic, and that there would be neither cure nor medical response,
we believe it our social responsibility to have a full insight into Japan's
present situation in which the criticality accident was caused and to propose
fundamental reforms of our systems to prevent such formidable accidents.
How the accident occurred
The facility in which the accident occurred is a private nuclear fuel plant
(JCO,
Ltd.) , where enriched UF6 gas is converted into UO2 powder for further
processing. The processing allowance is 718 tons UO2 powder uranium/year.
The following working procedures were carried out in an ordinary building
without any heavy shelter.
1. At 16:00 hour, September 29, 1999, 2.3 kg of enriched uranium (18.8%
highly
enriched uranium source to produce nuclear fuel for a fast breeder test
plutonium-reactor) was dissolved in a stainless bucket containing 18 litters
nitric
acid by hand. 4 buckets of the solution containing the total amount of 9.2
kg of uranium were poured into a settling basin (50 centimeters in diameter,
70 centimeters in depth, protected by water coolant) through an observation
hatch with a funnel. At this moment, the amount of uranium235 in the basin
reached much higher level than the calculated critical mass of 2.4 kg, but
criticality did not occur. The work was suspended overnight. As it was found
later, the administration staff of the factory were well aware that such
an act would be against the national rules and regulations.
2. At 10:37 hour, September 30, 1999, the moment the uranium solution of
seventh bucket was poured into the basin, with uranimum235 totaling 16.1
kg, the criticality occurred. Three workers near the basin were immediately
irradiated by neutrons. The amount of blood 24Na determined later showed
that irradiation was about 17Sv.
Symptoms of three irradiated workers by the National Institute of Radiological
Sciences are reported as follows:
September 30
A; male 35 years: Hypertension, bloodshot, severe diarrhea, consciousness
disturbance, hypertrophy of the submaxillary gland, leukocyte count = 13,000,
lymphocyte 1.6%, fever.
B; male 39 years: Hypertension, consciousness disturbance, leukocyte count
= 13,000, lymphocyte 2.0%, fever.
C; male 55 years: Consciousness normal, leukocyte count = 13,700, lymphocyte
5.8%, no fever.
October 1
A; leukocyte count = 26,900, lymphocyte 0.6%.
B; leukocyte count = 19,000, lymphocyte 0.9%.
C; leukocyte count = 6,700, lymphocyte 14.2%.
3. 10 minutes after the accident, the factory manager realized that the
criticality
accident had occurred and gave evacuation orders to all the workers. We
should take notice of the fact that the administration staff of the factory
had enough knowledge of criticality to understand the situation. At 11:45
hour, one hour after accident, the local government issued an evacuation
order to the residents living within 350m of the site. All the villagers
residing outside the 350m radius were asked to stay indoors.
4. About 6:00, October 1, 1999, the hard work of removing coolant water
surrounding the settling basin had been finished. The coolant water caused
neutrons to reflect into the basin and keeping the criticality occurring
inside the basin overnight. As it was confirmed by the neutron monitoring
data obtained in a facility several
kilometer away from the accident site, the criticality had been going on
for about 20 hours. From then on, neutron monitor recorded zero level of
radioactivity.
5. On October 3, 1999, it was announced that the criticality had been over,
and the village except the accident site was declared safe by both the central
and local governments. However, neither precise systematic data employed
in deciding on the safety nor the members who decided on the safety were
reported to the general public. At first the local government announced
that no radioactivity from possible secondary fission materials was detected
anywhere in the village outside the accident site. But, a very small amount
of131 I , which was the main suffering agent in Chernobyl Disaster, was
later detected in soil 1km away from the accident site.
Background of the Accident
1. The type of a nuclear fuel plant which should not be allowed to run in
light of the present nuclear technology is actually operating in Japan.
Both Japan's Nuclear Safety Commission and Nuclea Power Commission are responsible
for allowing such a plant to continue to operate.
Judging from the fact that we have experienced the occurrence of the
uranium criticality anywhere other than reactors in Japan, it may not be
too much to say that these Commissions are the organizations which have
not worked well so far. The very presence of the Nuclear Safety Commission
means that nuclear disasters must be avoided by all means because of their
irreversible nature. Therefore, this accident clearly showed the Nuclear
Safety Commission's incompetency.
However, even now, Japan's nuclear industry is actively operating under
the security guideline mandated by this incompetent Commission. Japan's
present situation surrounding nuclear industry can be said to be in a kind
of a nuclear anarchy. This is mainly brought about through the greediness
of big industries and corruption of Japan's bureaucracy.
2. The direct cause of the present criticality accident is extreme carelessness
on the side of all the employees of this plant, in addition to their ignoring
the basics of nuclear physics and nuclear technology. However, we should
not consider it as mere lack of knowledge. If we take it for granted that
many employees have enough knowledge of radioactivity and the critical mass
of uranium, it follows that their daily work is carried out, with such basic
rules ignored on purpose.
A considerable number of Japanese people who are in corporations or organizations
and working according to rules and regulations are likely to have difficulty
in associating concept with reality. Therefore, reeducating workers of nuclear
industry with a view to just cramming knowledge does not seem so promising
in terms of the prevention of such nuclear accidents.
3. The plant was capable of processing at most 700 tons of enriched uranium
per year. It is quite possible that such an irresponsible factory has not
been very strict in guarding the stockpile of enriched uranium. We might
call this situation a violation of the non-proliferation treaty. Neverthless,
no information available on the inspection of storage in nuclear fuel factories
which have enriched uranium stockpile has been issued publicly.
Reformation
1. Because any nuclear disaster such as criticality may not only cause irreversible
damage on citizens' lives but also constitute a grave menace to peaceful
international relationship. Therefore, the present incompetent administrative
system of nuclear power in Japan should fundamentally be reformed. Administration
is not to be monopolized by technocrats . Representatives from citizens,
farmers, fishermen, physicians and medical technologists should be invited
to the Nuclear Security Commission and Nuclear Power Commission. Representatives
from all the political parties in the Diet should also play an active role
in the Commissions.
2. Any argument supporting the safety of nuclear power is sure to entail
some doubt or objection. In Japan, nuclear accidents through human factors
seem to be inevitable in future.
The project of utilizing plutonium fuel in Japan must be stopped. Furthermore,
so long as human beings depend on nuclear power, the nightmare of nuclear weapons and wars utilizing plutonium which is produced in reactors persists.
This means that immediate global development of new harmless energy technology
such as effective utilization of solar energy must be launched at once,
as well as a resolution calling on this effort should be presented to the
United Nations.
3. The shortcoming the employees of the factory, where the present criticality
accident occurred, have in common is the lack of sensitivity to dangerousness
of chain reaction of nuclear fission. They seemingly have not heard of stories
about the development of atomic bombs, nuclear bombing at Hiroshima and
Nagasaki, and global damages caused by nuclear tests. Otherwise, so many
people could not have overlooked such careless daily operating procedures
in handling enriched uranium. We are afraid that this factory is not alone
in operating under careless and loose procedures.
As one of ten fundamental principles, the Hague Agenda for Peace and
Justice for the 21th century proposed that peace education should be compulsory
at every school in the world. The tragic history of nuclear weapons should
be taught in every country including Japan. We hope our website of timeline
of nuclear weapon would contribute to the world peace-education.
(October 14, 1999)