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Tokai JCO Criticality Accident

Report [5]10/14/99 18:50

Radiation Was Indeed Leaking

Oct. 14

Radiation, such as iodine, has been leaking from the JCO facility into the atmosphere. As we have been pointing out since the early stage of the accident, the site of the accident and the surrounding environment has not been fully dissociated. Windows and doors of the facility were not sealed. In addition, the stack was left open and the ventilation system was left on. Thus radiation, in the form of gas, had been leaking into the atmosphere. Windows and doors were sealed up on Oct. 11, 12 days after the accident, and the ventilation system was shut off, however, the site is not completely sealed yet. It is outrageous that the Science and Technology Agency (STA) and Nuclear Safety Commission (NSC) connived at such situation and allowed radioactive materials to leak in such a manner for 12 days.

JCO announced on Oct. 11 that 21 Bq /m3 of Iodine 131 was measured from the atmosphere near the stack of the re-conversion facility where the accident took place. This is twice the amount of the regulated limit for the concentration of Iodine 131 (10 Bq/m3) in the atmosphere of the area outside the controlled vicinity of the site. (The full table of the regulated limits on the release of various nuclear materials can be faxed upon request.) Judging from the fact that the halflife of Iodine 131 is about 8 days, there is no doubt that a higher concentrated amount of Iodine 131 was released into the atmosphere immediately after the accident.

Iodine 133, which has a halflife of 21 hours, was measured from the atmosphere around the stack as well. It was reported that the measured amount was below the concentration limit of 80Bq/m3, however, since its halflife is extremely short, Iodine 133 must have been released with much higher concentration than the concentration of Iodine 131.

According to JCO's research, 0.044 Bq/m3 of Iodine 131 was measured from the atmosphere of the boundary of the JCO plant about 70 meters south west of the re-conversion facility. The same amount of Iodine 131 was found in the atmosphere outside the plant as well.

Far from taking measures to prevent radioactive materials from being released into the environment, such as sealing up the facility, JCO had left on the ventilation system and as a result, indirectly took part in aiding the atmosphere inside the facility to spill into the atmosphere.

The responsibility of JCO and STA is grave in allowing radiation to leak for 12 days in such a manner. A complete seal up of the precipitation basin and the re-conversion facility has yet to be achieved, and radiation is still leaking. CNIC is very concerned over how the site is going to be decommissioned.



Citizens' Nuclear Information Center
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Shinjuku-ku, Tokyo, 162-0065, Japan