05000280/LER-2003-005
| Event date: | |
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| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 2802003005R00 - NRC Website | |
SURRY POWER STATION
Unit 1 05000 - 280 1.0 DESCRIPTION OF THE EVENT On March 31, 2003, the NRC issued Inspection Report 50-280/03-07 and 50-281/03-07 documenting the Triennial Fire Protection Inspection at Surry Power Station. The inspection identified an unresolved item (URI) related to a fire in the Unit 1 Emergency Switchgear Room (ESGR). The URI documented that certain Unit 1 ESGR fire scenarios and the postulated fire damage could result in the loss of reactor coolant pump (RCP) seal cooling, RCP seal package damage, and subsequently a seal loss of coolant accident. This issue was unresolved pending completion of a significance determination.
As part of the significance determination process (SDP) related to the URI, NRC personnel visited Surry in October 2003. During that visit, additional information was gathered by the NRC, and the NRC's preliminary SDP Phase 111 assessment was discussed. This NRC assessment used the RCP seal leakage model documented in Topical Report WCAP-15603, Rev. 1-A, titled "WOG 2000 Reactor Coolant Pump Seal Leakage Model for Westinghouse PWRsn. The NRC's Safety Evaluation of this Topical Report, dated May 20, 2003, requires consideration of a 20% probability that hot seals may result in an increased leakage up to 182 gpm per pump if seal cooling is lost for more than 13 minutes. In contrast to this WCAP-15603, Rev. 1-A model, the current Appendix R analyses for Surry assume the RCP seal leakage is 21 gpm for up to 70 minutes. This leakage value is based on WCAP-10541, Rev. 2, titled "Reactor Coolant Pump Seal Performance Following a Loss of All AC Power" (November 1986), which considered full-scale test results. The Appendix R, Section 1111.2.13 requirement to maintain pressurizer level during plant shutdown is met assuming the 21 gpm seal leakage value.
Based on review and consideration of the WCAP-15603, Rev. 1-A RCP seal leakage model, it was determined that assumption of that model's RCP seal leakage for greater than 13 minutes would result in an inability to maintain pressurizer level during plant shutdown, thus not satisfying the 10CFR50 Appendix R, Section 1111.2.b requirement. At the time of this determination, Unit 1 was operating at 100% power and Unit 2 was at cold shutdown. Following this determination, an eight-hour non-emergency report to the NRC was made at 1736 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.60548e-4 months <br /> on November 3, 2003 in accordance with 10CFR50.72(b)(3)(ii)(B). Similarly, this report is being submitted pursuant to 10CFR50.73(a)(2)(ii)(B) for a condition that resulted in an unanalyzed condition that significantly degraded plant safety.
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS One of the interim measures put in place was periodic thermal imaging to detect hot spots on energized equipment identified to be critical with respect to a fault of the type NIAC Fccm 366A 0-2001) FACILITY NAME (1) � DOCKET T � LER NUMBER 6) �
SURRY POWER STATION
� SECOF_NTIAL I REViSCIN NUMBER � NLIABER Unit 1 � 05000 - 280 2003 — 005 -- � postulated In the Appendix R Unit 1 ESGR fire scenarios of concern. As noted in Section 4.0, existence of hot spots could be a precursor of electrical equipment degradation or potential failure. The baseline results from the thermal imaging found no abnormalities in the temperature of the critical equipment.
Furthermore, a preliminary probabilistic risk assessment (PRA) has been performed which indicates that the risk of core damage from fires in the ESGR leading to RCP seal leakage beyond the RCS makeup capacity are less than 3E-6 per year. This contribution to risk is considered small in accordance with NRC Regulatory Guide 1.174.
Given these considerations, the interim measures and actions discussed in Sections 4.0 and 5.0, and the fact that an ESGR fire did not occur, this condition resulted in no significant safety consequences or implications, and the health and safety of the public were not affected at any time.
3.0 CAUSE WCAP-15603, Rev. 1-A was distributed to Dominion by Westinghouse Owners Group (WOG) letter WOG-03-340, dated July 7, 2003. This distribution was to Dominion representatives on the WOG Management Committee, the WOG Systems & Equipment Subcommittee, and the WOG Risk Management Subcommittee. Review of this information concluded that it was appropriate for consideration with respect to Surry's PRA modeling. However, given the nature of the WCAP, it was not viewed as applicable from a deterministic perspective, including in Appendix R analyses.
Therefore, the Appendix R analyses were not revised to reflect the WCAP-15603, Rev. 1-A model.
Note that the WOG is reviewing the Surry circumstances and the application of WCAP-15603, Rev. 1-A in Appendix R analyses. A preliminary indication from the WOG is that the use of the WCAP-15603 model in a deterministic manner is a misapplication of a bounding PRA model that was developed to support risk-informed applications. We will monitor the WOG's review activities for potential impact on the actions already taken or planned.
4.0 IMMEDIATE CORRECTIVE ACTION(S) Upon determination that the NRC's Safety Evaluation for WCAP-15603, Rev. 1-A applied a RCP seal leakage value of 182 gpm per pump during an Appendix R fire/loss of RCP seal cooling event, a Plant Issue/Deviation was issued. The Deviation was issued because the 182 gpm value exceeds the 21 gpm rate assumed in the current Appendix R analyses and would result in an inability to maintain pressurizer level during plant shutdown.
FACILITY NAME (1)
SURRY POWER STATION
DOCKET
05000 - 280 LER NUMBER PAGE (3) OF 5 p 2003 — 005 — � 00 1 4 The charging pump cross-connect was considered inoperable with respect to 10CFR50 Appendix R due to these circumstances. Technical Requirements Manual (TAM) requirements were applicable and specified that a fire watch be implemented within 14 days and that inoperable equipment be restored to operable status within 60 days.
The TRM required actions for charging pump cross-connect inoperability were entered at 1720 hours0.0199 days <br />0.478 hours <br />0.00284 weeks <br />6.5446e-4 months <br /> on November 3, 2003. The TRM-required fire watch was established at 1720 hours0.0199 days <br />0.478 hours <br />0.00284 weeks <br />6.5446e-4 months <br /> on November 4, 2003, and the 14-day action was exited.
In addition to applying the TRM requirements, the following interim measures were also implemented on November 4, 2003:
- To prevent a fault of the type postulated in the Appendix R Unit 1 ESGR fire scenarios of concern, periodic thermal imaging was initiated to detect hot spots on energized equipment identified to be critical. Existence of hot spots could be a precursor of electrical equipment degradation or potential failure.
- A Fire Safety Alert was issued identifying the need for increased monitoring of fire risk in the ESGR and requiring a Transient Fire Loading Permit (approved by Safety and Loss Prevention with Operations Department Manager concurrence) for transient combustibles being brought into the ESGR. Permit approval required a continuous fire watch with portable fire fighting equipment.
- Once per shift walkdowns of the ESGR by Operations personnel were instituted to ensure no condition existed that could contribute to the start or spread of a fire.
The thermal imaging and Operations walkdowns interim measures remained in place until a justification for continued operation (JCO), discussed in Section 5.0, was approved and implemented. The Fire Safety Alert interim measures will remain in place until a revision to the fire protection administrative procedure is made to address transient combustible controls commensurate with the significance of the fire area.
5.0 ADDITIONAL CORRECTIVE ACTIONS A JCO to ensure restoration of RCP seal cooling within 13 minutes was developed and approved on November 8, 2003. The JCO includes a temporary modification (tagging of numerous components in a specified position) and administrative controls (to open two valves as directed by the Main Control Room). In the event of a fire in the ESGR, the administrative control actions would be taken to complete alignment of the RCP seal injection fiowpath from the unaffected unit through the charging pump cross-connect to the RCP seals on the affected unit. The JCO measures reestablish compliance with the requirements of 10CFR50 Appendix R, Section 111.L. Following completion of the necessary training, the JCO was implemented on November 10, 2003, and the 60-day TRM action was exited.
FACILITY NAME (1)
SURRY POWER STATION
DOCKET � LER NUMBER p � PAGE (3) NumRER � 6.0 ACTIONS TO PREVENT RECURRENCE A request for engineering assistance (REA) will be developed to address permanent resolution of this Appendix R concern regarding loss of RCP seal cooling. The JCO, currently in place, will remain in place until permanent resolution is defined and implemented.
7.0 SIMILAR EVENTS None.
ILO MANUFACTURER/MODEL NUMBER
Not applicable.
9.0 ADDITIONAL INFORMATION The Unit 2 fire modeling and analysis is ongoing. It is anticipated that Unit 2 will be similarly affected. The corrective actions discussed in Sections 4.0 and 5.0 were implemented on both Units 1 and 2.