by Yomiuri Shimbun
A final report to be issued by the Nuclear and Industrial Safety Agency over the 1999 criticality accident in Ibaraki Prefecture will state that the government and the former Nuclear Fuel Development Corp. (Donen) should share responsibility for the disaster, sources said Sunday.
In the accident at the JCO Inc. uranium fuel-processing plant in Tokaimura in the prefecture, two JCO employees were killed and more than 660 people living nearby exposed to radioactive fallout.
The report is to be compiled by a panel of the agency chaired by Hideki Nariai, a professor emeritus at Tsukuba University.
Donen has since been renamed the Japan Nuclear Cycle Development Institute.
The agency studied trial documents disclosed in March 2003 after the Mito District Court found JCO executives responsible for the accident.
The ruling rejected claims by the defense that the government's sloppy safety checks and Donen's irresponsible award of a project to JCO were to blame, but the agency said their responsibility should be pointed out, according to the sources.
The agency will submit the report to the International Atomic Energy Agency.
The accident occurred when three JCO employees mixed uranium with nitric acid by pouring 16.8 kilograms of a uranium solution into a sedimentation tank, ignoring a JCO regulation prohibiting the use of more than 2.4 kilograms of uranium at one time to prevent a criticality, a limited uncontrolled nuclear chain reaction.
According to the report, the process was introduced by JCO at the request of Donen in 1986.
The process was designed to equalize the density of solution for each product, but since more uranium than the amount regulated was often used, experts, including those from Donen, knew special measures had to be taken to prevent a criticality.
However, the experts never discussed such measures, the report says.
In 1984, the government approved fuel processing at the JCO facility, but the government's safety inspections only focused on the manufacturing process of powdered uranium, a main product, and left the production process of uranium solution unchecked, the report says.
Since the equalization process was introduced in 1986, inspectors often overlooked the lack of measures to prevent accidents, the report says.
Copyright 2005 The Yomiuri Shimbun