The JCO facility converted uranium hexafluoride into enriched uranium dioxide fuel. This served as the first step in producing fuel rods for Japan's power plants and research reactors. [14] Enriching nuclear fuel requires precision and has the potential to …

2021年5月7日 · In 1999 the Japanese nuclear industry suffered a significant nuclear accident in Tokai-mura in Ibaraki, Japan. It happened in a nuclear fuel processing facility. To understand Ibaraki's criticality accident, we first briefly explain the uranium enrichment process at the Tokaimura plant.

conversion building (auxiliary plant) at the uranium conversion facility of JCO Company Limited in Tokaimura, Ibaraki Prefecture, Japan. A solution of . enriched uranium (18.8% 235U by mass) in an amount reportedly several times more than the specified mass limit had been poured directly into a precipitation tank,

On September 30, 1999, a criticality accident occured at the Tokai nuclear fuel plant, Tokai-mura, Ibaraki Prefecture, Japan. The plant, operated by JCO Co. Ltd., a 100% subsidiary of Sumitomo Metal Mining Co. Ltd. , converts enriched uranium hexafluoride (UF 6) to uranium dioxide (UO 2) for use in nuclear fuel. Criticality accidents involve a ...

On September 30, the enterprise began processing uranium for the Joyo reactor with raw materials enriched to 18.8%. The three workers loaded seven buckets of uranyl nitrate into the sump. It was almost seven times more than the maximum allowed.

The accident was caused by bringing together too much uranium enriched to a relatively high level, causing a "criticality" (a limited uncontrolled nuclear chain reaction), which continued intermittently for 20 hours.

At approximately 10:35 a.m. on September 30th, 1999, workers at the JCO nuclear fuel processing plant poured a seventh batch of 18.8% enriched uranyl nitrate solution, along with Uranium-235, into a precipitation vessel. The goal of this process is to convert the isotopically enriched uranium hexafluoride into uranium dioxide fuel.

NRC also issued a temporary inspection procedure to NRC resident inspectors at the two high-enriched uranium facilities and the two gaseous diffusion plants, to focus immediate attention on the suspected contributing causes.

The buckets, unloaded by two Japanese technicians contained uranium highly enriched in fissile U-235 isotope. By exceeding more than seven times the amount permitted by safety standards, they caused an early chain reaction that cost their lives.

18% enriched uranium, with a minimum critical mass of 46 kilograms (kg). The enrichment of the U02 scrap was reported to be 18.9% enriched in the isotope uranium-235 (U-235). It has been reported that workers caused a criticality accident, an uncontrolled chain reaction, when they placed 16 kg, instead of 2.4 kg, of enriched uranium in a tank of