A Japanese uranium processing company and six staff all pleaded guilty on Monday to charges of negligence resulting in death as the trial opened into Japan's worst nuclear accident. The pleas were entered at the initial hearing at the Mito District Court. Among the six staff who pleaded guilty was Kenzo Koshijima, 54, the former head of JCO Co, the plant in Tokaimura, in Ibaraki Prefecture, 140 km (90 miles) northeast of Tokyo where he accident occurred in September 1999.