Japan Nuclear Watchdog Flags Document Mishandling at Tepco

A Tokyo Electric Power Co. employee mishandled confidential security documents at Japan’s biggest nuclear power plant, according to the nation’s atomic watchdog, in the latest security breach to affect a facility that’s close to getting approval to restart.

Tepco shares fell as much as 10%, the biggest intraday decline since April. The Nuclear Regulation Authority published a document Thursday saying a Tepco employee at the Kashiwazaki Kariwa plant removed papers from a designated storage area, made copies and locked them in another desk. The NRA said the severity level of the incident, which occurred in June, was the lowest on its four-point scale.