Operator Southern California Edison reported the problem to the government, and the company said in a statement Thursday that it was promptly corrected.
The violation stems from a four-day Nuclear Regulatory Commission inspection in May during which officials reviewed records, observed activities and interviewed personnel, the AP article states.
According to the agency, the company failed to develop procedures to monitor electronic devices related to security, although the NRC withheld most details about the problem.
Edison Senior Vice President Pete Dietrich says changes have been made so “it doesn’t happen again.”
The plant, located between Los Angeles and San Diego, has been closed since January because of excessive wear to tubes that carry radioactive water, the AP article reports.