The nuclear plant accident that occurred Monday in Mihama, Fukui Prefecture, is a shocking reminder that the nation's nuclear safety inspection system is flawed. Four maintenance workers in a building housing steam turbines were killed and seven others were injured, some critically, when high-temperature steam blew off from a ruptured condenser pipe. In terms of the number of deaths, it was the worst accident in the history of the nation's nuclear power program.

This is the second time in Japan that a nuclear accident has claimed the lives of workers. In 1999, two men died of radiation exposure at a nuclear-fuel reprocessing facility in Tokaimura, Ibaraki Prefecture. At the time, residents in the vicinity were ordered to evacuate to avoid possible exposure to radiation.

Fortunately, no radiation leaks occurred this time because the pipe that ruptured is not directly connected to the reactor. The cause of the damage has yet to be determined. A thorough investigation is required, all the more because similar accidents could occur in other light-water nuclear plants or in thermal power plants that likewise generate electricity by steam turbines.