Facility had high sulfate concentrations in the steam generators

Nov. 1, 2002 -- Palo Verde Unit 1 crews manually tripped the reactor during a restart procedure because of high sulfate concentrations in the steam generators, Arizona Public Service (APS) reported.

The Arizona utility told the Nuclear Regulatory Commission (NRC) that it had to trip the Unit 1 reactor from approximately 19% rated thermal power on Thursday. Operators had been in the process of restarting the unit after a planned maintenance and repair outage.

APS characterized the trip as an uncomplicated reactor trip and said the unit was at normal temperature and pressure prior to the trip.

Unit 1 was stable at normal operating temperature and pressure in Mode 3, and APS said that the trip did not adversely affect the safe operation of the plant or the health and safety of the public.

Operators are still looking into the cause of the buildup of sulfates and did not yet have an estimated restart date.