Officials at the Oyster Creek Nuclear Power Plant in Lacey Township say an electrical issue was to blame for a temporary shutdown Sunday afternoon.

Oyster Creek nuclear plant (Excelon)

A spokeswoman says the problem was in the system that controls steam pressure at the facility.  All equipment performed as designed during the automatic shutdown.

The defective piece governs steam pressure that spins the turbine, according to spokeswoman Suzanne D'Ambrosio and Neil Sheehan of the Nuclear Regulatory Commission (NRC).

The reactor protection system has trip mechanisms when steam pressure exceeds recommended levels on the high side or the low side. What caused the regulator to fail is still under investigation, Sheehan said.

NRC officials harbored no "immediate concerns" over the problem or the actions taken by operators, Sheehan said. However, NRC will review Exelon's plans for repairs that precede any re-start.

Staff members will examine the problem and make any repairs that are necessary to bring the plant back online as soon as possible. NRC and plant operators recently resolved issues related to four unplanned shutdowns within a 7,000-hour period.

Oyster Creek, the oldest working commercial nuclear generating station in the U.S., is scheduled to begin decommissioning toward closure starting in 2019.