In a San Onofre Unit 1 Preliminary Notification issued in September 1980, it was reported that, during testing, the licensee had identified a problem with the design of the diesel generator sequencing circuitry. This problem occurred when a safety injection signal was blocked, in accordance with the LOCA procedure following safety injection initiation. Under these circumstances, a subsequent loss of offsite power could not produce automatic resequencing of safety injection loads onto the diesel generator-supplied buses. This problem was the same one
that was raised as Technical Issue No. 4 in NUREG-0138[1] and was considered by the staff to be resolved on all operating plants. However, in view of the occurrence at San Onofre, it was believed that there was a deficiency in the process.
This issue is covered in this section under Issue 17, "Loss of Offsite Power Subsequent to a LOCA."
[1] NUREG-0138, "Staff Discussion of Fifteen Technical Issues Listed in Attachment to November 3, 1976 Memorandum from Director, NRR to NRR Staff," U.S. Nuclear Regulatory Commission, November 1976.
Page Last Reviewed/Updated 07/23/2025