Improved instrument setpoints for extended surveillance intervals

San Onofre Nuclear Generating Station (SONGS) units 2 and 3 have both entered a nominal 24-month fuel cycle. The technical specifications for the following systems previously included requirements for the performance of preventive maintenance (PM) at 18-month intervals: (1) reactor protection system (RPS); (2) engineered safety features actuation system (ESFAS); (3) remote shutdown system (RSD); and (4) accident monitoring system (AMS). To avoid the need for an otherwise unnecessary unit shutdown, an evaluation was initiated by Southern California Edison (SCE) to determine if the surveillance intervals for technical specification PM could be extended to support the 24-month fuel cycle. The evaluation has been completed for the first three systems listed above (the AMS evaluation is still in progress). This evaluation showed that the extension of the maintenance interval to 24 months (nominal) could be safely accomplished. The two key areas of drift and setpoint analysis are covered in detail in this paper