Employees at JCO Co.'s uranium-reconversion plant in Tokaimura, Ibaraki Prefecture, directly heated steel buckets containing nitric acid and powdered uranium using a portable electric cooking stove, it has been learned. Following the nation's worst nuclear accident at the plant on Sept. 30, it was found that employees had followed an illegal manual when processing nuclear fuel. The manual recommended using the cooking stove to speed up the dissolution of the uranium.The government had not approved the use of the buckets or the cooking stove in the processing of nuclear fuel.