|
Press Releases
1999/10/05
| ACCIDENT AT THE TOKAI-MURA FUEL CONVERSION PLANT
|
October 5, 1999
Science & Technology Agency
On September 30, a criticality accident occurred at the Conversion
Testing Facility of J.C.O. Co., Ltd in Tokai-mura. The accident seems to
have happened during the process of manufacturing fuel for Experimental
Fast Reactor "Joyo", when three workers, in violation of the rules, had
been dealing with the solution containing 16kg of uranium (18.8% enrichment)
and pouring the solution into the precipitation tank. The tank has a cooling
jacket which contained water. Calculations showed that the water in the
cooling jacket acted as a neutron reflector, causing the criticality to
continue. In order to bring the situation under control, the water in the
cooling jacket was flushed by opening the valve in the line that sends water
into the jacket, breaking the line, and by gas blowing, and the criticality
became significantly low around 6:00 a.m., October 1. Furthermore, in order
to eliminate the possibility of recriticality, borate solution was poured
into the tank around 8:30 a.m., which terminated the criticality.
Three workers had been exposed to a large amount of neutron radiation, and
were taken to the Mito National Hospital first, and then transferred to
the National Institute of Radiological Sciences, where they received careful
medical treatment. Later, two of them who were heavily injured were transferred
to the Tokyo University Hospital, to receive operation. Other than these
three workers, 46 people (36 workers of J.C.O and other companies, 7 local
people, and 3 firefighters) were exposed to radiation, though the dose level
was not serious. Furthermore, every effort is being made to conduct the
measurement of external doses of the local public, so that their health
is assured and their concern is mitigated.
Thus, in the morning of October 1, the radiation level in the area returned
to the normal level, and the Nuclear Safety Commission confirmed the safety
based on the analysis of radiation data and their trends. At 3:00 p.m.,
October 1, the Government declared that it had confirmed the termination
of criticality. Accordingly, the post-accident decision to shelter the population
within the radius of about 10 kilometers was lifted. And whether the evacuation
of residents within 350 meters could be lifted was examined carefully, based
on dose rate data and trends of radiation data of soil and well water around
the facility. At 6:30 p.m., October 2, the evacuation was lifted, since
it was judged appropriate to do so, after shielding the radiation at points
near the facility where radiation level was still high.
We are therefore no longer in an emergency situation, and from now on, we
will take actions necessary for understanding the radiation situation inside
the facility, decontamination, and investigation into the cause of the accident.
The Japanese Government will manage the situation with all its might, striving
to ensure the promotion of nuclear research, development and utilization.
Such efforts, we believe, will lead to gaining international confidence.
Top of this page
|
