United States Nuclear Regulatory Commission - Protecting People and the Environment

Resolution of Generic Safety Issues: Issue 44: Failure of Saltwater Cooling System (Rev. 1) ( NUREG-0933, Main Report with Supplements 1–34 )


While operating at 100% power on March 10, 1980, San Onofre Unit 1 experienced a complete loss of the salt water cooling system. The event involved an unlikely triple failure and desiccant contamination of the instrument air system was found to be the major contributing cause of one of the failures.

After issuance of the case study (AEOD/C204)1055 on the San Onofre event, AEOD recommended499 further review and/or requirements in four specific areas: (1) single failure vulnerability of cooling systems; (2) inservice test programs; (3) contamination of plant air systems; and (4) plant technical specifications.


The NRR response500 to AEOD indicated that two of the four recommendations had already been implemented, i.e., the single failure analysis was included in SEP Topic IX-3 and inservice testing was within the scope of the review of licensee IST programs. With regard to the AEOD recommendation on plant technical specifications, NRR determined that the existing LCO for salt water cooling systems in the standard technical specifications was adequate and no further action was comtemplated. Thus, the only remaining generic concern of this issue was the safety system vulnerability to common cause failures from contamination of the instrument air system. A specific issue (Issue 43) was previously identified for the generic review and resolution of concerns for contamination of instrument air systems. Thus, the remaining generic concern of Issue 44 was determined to be covered in Issue 43.

Page Last Reviewed/Updated Thursday, March 29, 2012