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Tokai JCO Criticality Accident

Report [21]12/7/99 12:10

CNIC Sets Up an Independent Investigation Committee on JCO Criticality Accident.

CNIC held a press conference on December 2nd, and announced that we have set up an independent investigation committee on the JCO criticality accident and have invited a number of independent researchers. This committee, Committee for Comprehensive Social Impact Assessment of JCO Accident, will not only assess the technical aspects of the accident, but will assess the economics as well as security issues of nuclear power industry and the current nuclear power policies as well. Together with this announcement, we submitted open questions to the government's own investigation committee of the accident. The questions are listed below.

Open Requests to the Uranium Conversion Facility Plant Criticality Accident Investigation Committee of the Nuclear Safety Commission

Your committee is rushing to release a final report on the JCO criticality accident by the end of this year. However, further important investigations and analysis on the scale of the accident have not been carried out since your fifth meeting where you released the estimated radiation dose received by the local residents based on an assumption that about 1mg of uranium fissioned in the criticality accident. We believe that those estimated figures were based on many uncertain data and factors. We demand a fuller investigation and analysis of the scale and the level of released radiation dose.

1) Regarding the uranium solution left in the precipitation tank.
a. Collect and analyze a second sample from the uranium solution left in the precipitation tank and release all data on the results. When collecting the second sample, the solution must be stirred, or a sample from the top, the middle, and the bottom must be collected in order to gather a sample that represents a uniform concentration.
b. Release all data on nuclides that were found from analyzing the first sample collected on October 20th.

2) Regarding the analysis of activated metal
a. Analyze and release all data on activated metal, especially the stainless steel beaker, the stainless steel bucket, and many other metal samples that must be in the conversion building.
b. Release complete data on the model of neutron dispersion which was used to analyze the activation of stainless steel net located outside the conversion building.

3) Regarding the neutron dose figure
a. Release all data from the two area radiation monitors located in the conversion building.
b. Release all data from all area radiation monitors outside the conversion building (excluding the already released data from the monitor in the powder storage room of the process building No.1).

4) Regarding the estimation on the energy distribution of neutrons
To reevaluate the adequacy of the calculations made on the assumption that there was one 40cm thick wall between the precipitation tank and the rem counter located near the window on the second floor of the Japan Nuclear Cycle Development Institute.

5) Regarding the leakage of radioactive particles
To confirm that the scrubber, HEPA filter, and other filters are functioning, and measure the amount and the types of radioactive materials, and to ultimately confirm if there were any leakage by measuring the amount of radioactive materials that reached the filters. Release all data on this analysis.

6) Licensing for the operation and modification of a conversion building
a. Release all application forms, supplemental materials, and diagrams needed for the licensing to operate a conversion building and the licensing for the innovation of the installation of a conversion building.
b. To release all materials that were examined during the safety evaluation of the conversion building of the JCO plant.



Citizens' Nuclear Information Center
Akebonobashi Co-op 2F-B, 8-5 Sumiyoshi-cho,
Shinjuku-ku, Tokyo, 162-0065, Japan