Human Factor Analysis of JCO Criticality Accident

Abstract:

The criticality accident that occurred on September 30, 1999 at a uranium processing plant in Tokai-mura was an unprecedented nuclear accident in Japan, not only because it caused deaths of two workers due to radiation casualty but also because it called for evacuation and sheltering indoors to nearby residents. The accident was not directly caused by failures or malfunctions of hardware but by workers’ unsafe action deviated from the approved procedure. It was a typical organizational accident in that several organizational factors worked behind. This article is to analyze various causal factors that lead to the accident, including situational factors of workers’ unsafe action that triggered the accident, operational and business management of the company, and nuclear safety regulation by the government. It also discusses problems of emergency response after the accident.