05000362/LER-2013-001
| San Onofre Nuclear Generating Station (Songs) Unit 3 | |
| Event date: | |
|---|---|
| Report date: | |
| 3622013001R00 - NRC Website | |
On October 23, 2012, during engineering walkdowns, the hydraulic fluid in the level sight glass of the San Onofre Nuclear Generating Station (SONGS) Unit 3 Train A Emergency Diesel Generator (EDG) [EK] Engine #2 governor [65] actuator was found with an abnormal color (purple) and higher than normal indicated level. On November 27, 2012, during subsequent investigation, additional reliable and substantive information including physical evidence was identified that supported a reason to believe (at that time) that tampering may have caused the abnormal condition. This event was reported as a one-hour notification to the NRC in accordance with 10 CFR 73, Appendix G, 1(a)(3) - Reportable Safeguards Events: Any event in which there is reason to believe that a person has committed or caused, or attempted to commit or cause, or has made a credible threat to commit or cause an interruption of normal operation of a licensed nuclear power reactor through the unauthorized use of or tampering with its machinery, components, or controls including the security system. Subsequently, while tampering could not be confirmed, it also could not definitively be ruled out as a possible cause. As such, this followup 60-day written report is being submitted in accordance with 10 CFR 73, Appendix G, Subpart I.
B. INITIAL CONDITIONS
Unit 3 was shutdown and defueled at the time of discovery on November 27, 2012, as well as during the period of time that the hydraulic fluid was potentially contaminated (October 21 - 23, 2012). There were no additional inoperable structures, systems, or components that contributed to the event. Unit 2 has been shutdown since January 10, 2012, and was unaffected by this event.
C. BACKGROUND INFORMATION
On October 23, 2012, during engineering walkdowns of the Unit 3 Train A EDG to assess the progress of maintenance work, personnel observed abnormal conditions of the fluid in the sight glass for the EDG 3A Engine #2 governor actuator. The fluid was a purplish color and the level of fluid was higher than normal.
All other Unit 2 and 3 EDGs were walked down and the governor actuator hydraulic fluid levels and color of each were verified normal. An assessment was initiated to determine the cause or causes of the abnormal color and fluid level in the EDG 3A governor actuator. This assessment included testing, document reviews, and personnel interviews.
The contaminated hydraulic fluid was subsequently confirmed by chemical analysis to be used engine coolant (i.e., had been run through an engine). It was also determined that the contamination occurred during the period of time between October 21 and October 23, 2012, based on the fact that Operations performs normal shift walkdowns of the EDG governor and observed the hydraulic fluid color and level to be satisfactory on October 21, 2012. Prior to this walkdown, EDG 3A had been placed in an inoperable condition for a scheduled maintenance outage.
D. APPARENT CAUSE
An apparent cause evaluation is in progress.
Immediate actions were to initiate an assessment of the event, inspect other credited safe shutdown equipment to verify appropriate state of readiness, and reinstate security access controls for the EDG 3A room. Hydraulic fluid in all engine governors was sampled and the affected mechanical governors were replaced. Interim actions included installation of leak-tight enclosures over the governor housings. These actions provided corrective measures to address potential causes of the event. Additional actions will be addressed upon completion of the assessments.
F. SAFETY ASSESSMENT
This event did not affect plant operation or safety, since EDG 3A was out of service and not required to be operable during the period of time the governor actuator hydraulic fluid was potentially contaminated. Pre- operational checks and testing would have identified the abnormal condition prior to placing the EDG in service.
Unit 3 has been shutdown since January 31, 2012, due to an unrelated event. Unit 2 has been shutdown since January 10, 2012, and was unaffected by this event.
G. ADDITIONAL INFORMATION
There have been no similar events in the past three years at SONGS.