Tokai JCO Criticality Accident
Report 10/18/99 19:20
According to the Science and Technology Agency, the hose used to pour in boric acid liquid into the precipitation tank on Oct. 1, 99 was drawn from a fire truck from outside the conversion facility. After pouring the liquid into the precipitation tank, the hose was left on the ground as it was, and still remains there. It was revealed at the second "Uranium Conversion Plant Accident Investigation Committee" of the Nuclear Safety Committee that this hose was contaminated. Three points along the abandoned hose was measured. The radiation count of the three points in the order of the distance are, beginning with the point closest to the facility:
(1) 1.7 Bq/cm2 Alpha Radioactivity, 170 Bq/cm2 Beta Radioactivity
(2) 0.2 Bq/cm2 Alpha Radioactivity, 18 Bq/cm2 Beta Radioactivity
(3) 0.08 Bq/cm2 Alpha Radioactivity, 9.8 Bq/cm2 Beta Radioactivity
The date of the measurement was not reported. There is a possibility that the water had flown backwards, and that contaminated water from the precipitation tank had leaked from the hose.