Palo Verde unit 1 has recovered from an emergency declaration prompted by arcing in a turbine building load center last week.
On Tuesday night, the reactor near Phoenix issued an unusual event declaration after a report of an explosion, according to an NRC event report. The unit dropped to 58 percent power from full power. According to the report, the incident did not actuate any engineered safety features, although it did cause the loss of one main feedwater pump and the loss of an electrical load center. Plant and NRC representatives told news agencies the load center cabinet was located on the turbine side of the plant, and the explosion was caused by arcing inside it.
Firefighters on site confirmed that the electrical malfunction did not cause a fire, the NRC reported, and the plant terminated the unusual event at 11:15 p.m., about three hours after it started. The NRC made the incident report public on Friday because of the Independence Day holiday, plus its usual 24-hour delay in publishing event reports.
Owned by seven southwestern utilities – with Arizona Public Service holding the largest, 29.1 percent stake – Palo Verde operates three Combustion Engineering System 80 pressurized water reactors. Generating 3,810 megawatts, the site is the largest producer of nuclear power in the U.S.