05000282/LER-2009-008, Regarding Unanalyzed Condition Due to an Inadequate Fire Barrier
| ML100470751 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 02/11/2010 |
| From: | Schimmel M Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-PI-10-007 LER 09-008-00 | |
| Download: ML100470751 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor |
| 2822009008R00 - NRC Website | |
text
FEB P P 2010 L-PI-? 0-007 10 CFR 50.73 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Unit 1 Docket 50-282 License No. DPR-42 LER 1-09-08, Unanalvzed Condition due to an Inadequate Fire Barrier Northern States Power Company, a Minnesota corporation (NSPM) herewith encloses Licensee Event Report (LER) 1-09-08. The LER describes an inadequate fire barrier that was identified during a review of Prairie lsland Nuclear Generating Plant's safe shutdown compliance assessment and was previously reported in accordance with 10 CFR 50.72 on December 14,2009.
Summary of Commitments This letter contains no new commitments and no changes to existing commitments.
Mark A. Schimmel Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC Department of Commerce, State of Minnesota 171 7 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121
ENCLOSURE LICENSEE EVENT REPORT 1-09-08 3 Pages Follow
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION 9 2007)
LICENSEE EVENT REPORT (LER)
( S e e reverse for requ~red number of d ~ g ~ t s l c h a r a c t e r s for each block)
I FACILITY NAME Pra~r~e Island Nuclear Generat~ng Plant Unit 1 4 TITLE APPROVED BY OMB NO 3150-0104 EXPIRES 08/31/2010 Est~mated burden per response to comply wlth thls mandatory collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> Reported lessons learned are Incorporated lnto the llcenslng process and fed back to Industry Send comments regarding burden estlmate to the Records and FOlAlPnvacy Servlce Branch (7'-5 F52), U S Nuclear Regulatory Commlss~on, Washlngton, DC 20555-0001, or by Internet e-mall to ~nfocollects@nrc gov, and to the Desk Officer, Office of lnformat~on and Regulatory Affalrs, NEOB-10202. (3150-0066), Office of Management and Budget, Washington, DC 20503 If a means used to lmpose an ~nformat~on collect~on does not d~splay a currently val~d OMB control number, the NRC may not conduct or sponsor, and a person IS not requ~red to respond to, the ~nformatlon collect~on
- 2. DOCKET NUMBER 05000282 Unanalyzed Cond~t~on due to an Inadequate Fire Barrier
- 3. PAGE 1 of 3
- 5. EVENT DATE MONTH 12
- 6. LER NUMBER
- 12. LICENSEE CONTACT FOR THlS LER
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check all that apply) 20 2201(b) 20 2203(a)(3)(1) 50 73(a)(2)(1)(C) 5 0 73(a)(2)(~11) 20 2201(d) 20 2203(a)(3)(11) 50 73(a)(2)(11)(A) 50 73(a)(2)(v111)(A) 20 2203(a)(I) 20 2203(a)(4) 50 73(a)(2)(11)(B) 5 0 73(a)(2)(v111)(B) 20 2203(a)(2)(1) 50 36(c)(l)(l)(A) 50 73(a)(2)(111) 50 73(a)(2)(1x)(A) 20 2203(a)(2)(11) 50 36(c)(l)(11)(A) 50 73(a)(2)(1v)(A) 5 0 73(a)(2)(x) 20 2203(a)(2)(111) 5 0 36(c)(2)
El 50 73(a)(2)(v)(A) 73 71(a)(4) 20 2203(a)(2)(1v) 5 0 46(a)(3)(11) 50 73(a)(2)(v)(B) 73 71(a)(5) 20 2203(a)(2)(v) 5 0 73(a)(2)(1)(A) 50 73(a)(2)(v)(C)
OTHER 20 2203(a)(2)(v1) 50 73(a)(2)(1)(B) 50 73(a)(2)(v)(D)
Spec~fy In Abstract below or In NRC F V
- 9. OPERATING MODE Mode 1
- 10. POWER LEVEL 100%
DAY 14 YEAR NAME Kathryn Mews YEAR 2009
- 7. REPORT DATE TELEPHONE NUMBER (Include Area Code) 651.388.1121, extension 7384 2009 - 008 - 00 SEQUENTIAL NUMBER MONTH 02
- 8. OTHER FACILITIES INVOLVED REV NO FACILITY NAME FACILITY NAME DAY 11 DOCKET NUMBER DOCKET NUMBER
CAUSE
YEAR 2010 SYSTEM
- 14. SUPPLEMENTAL REPORT EXPECTED 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE).
O NO COMPONENT ABSTRACT (Limit to 1400 spaces, I e, approximately 15 single-spaced typewritten lines)
On December 14, 2009, Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, Identified that the power source to Safeguards Bus 16 was not protected per 10 CFR 50 Appendlx R requlrements In Fire Area (FA) 32. For a fire that occurs in FA32, fire induced damage to cable 1 C-333 could cause a spurious lockout of the 1 RY transformer source to Bus 16. Another source, the 02 Emergency Generator, was available to power Bus 16. However, cables affecting the operation of the D2 Emergency Generator exited a fire-protected cable tray and ran unprotected for a short distance before they ex~ted Fire Area 32. This condition was previously reported to the NRC as an unanalyzed condition (10 CFR 50 72(b)(3)(il)(B)) on December 14, 2009 due to the missing fire barrier.
The causal evaluat~on for this event determined that the apparent cause was inattention to detail and the lack of a detailed procedure to perform Appendix R circuit analysis. An hourly fire watch was previously in place for F~re Area 32 as a compensatory measure and will continue until the cable protection issue has been resolved.
Cables for the cred~ted power source to Safeguards Bus 16 will be provided the required fire protection to meet the safe shutdown requirements in National Fire Protection Association (NFPA) 805.
NRC FORM 366 (9-2007)
MANU-FACTURER YEAR
- 15. EXPECTED SUBMISSION DATE REPORTABLE TO EPlX MONTH DAY
CAUSE
SYSTEM COMPONENT MANU-FA CTURER REPORTABLE TO EPlX U.S. NUCLEAR REGULATORY COMMISSION (1 -2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
EVENT DESCRIPTION
On December 11, 2009, Unit 1 was operating at 100 percent power. It was identified that fire induced damage to cable 1 C-333 in FA32 could cause a spurious lockout of the 1 RY transformer', the alternate offsite power source to Safeguards Bus 1 6 ~,
which is credited to power equipment required to achieve safe shutdown in the event of a fire in Fire Area (FA) 32. Prior to this time, cable 1C-333 was not included in the FA32 analysis. It was noted that cables for the D2 emergency diesel generator3 are also routed though FA32, but the tray that they are routed through is protected with a thermal shield as approved in a NRC fire protection safety evaluation report dated May 4, 1983. Therefore a temporary procedure change was initiated to credit the D2 emergency diesel generator as a source to Bus 16.
On December 14, 2009 it was identified that cables for the D2 Emergency Diesel Generator exit the protected tray and run through the ceiling unprotected for approximately four feet in FA32. An automatic wet pipe sprinkler system is installed in the area with fire detection but there is not twenty feet free of intervening combustibles between the redundant power supplies to Bus 16 in FA32 as required by 10 CFR 50 Appendix R Section lll.G.2.b. Because the required degree of separation between power supplies to Bus 16 and the redundant safeguards train (Bus 15) was found to be missing, an 8-hour report (event number 45567) was made in accordance with 10 CFR 50.72.
EVENT ANALYSIS
Fire induced cable damage to cable 1 C-333 in FA32 could cause a spurious lockout of the 1 RY transformer, the alternate offsite power source to Safeguards Bus 16, which is credited to power equipment required to achieve safe shutdown in the event of a fire in FA32. Because a fire in FA32 could damage cables for Bus 16 and Bus 15, both trains of safe shutdown equipment, this condition is reportable as an unanalyzed condition under 10 CFR 50.73(a)(2)(ii)(B).
Without compensatory measures in place, this condition could have resulted in a loss of safety function (equipment required to achieve safe shutdown) in the event of a fire. Consequently, this event is reportable per 10CFR 50.73(a)(2)(v)(A) as a Safety System Functional Failure.
SAFETY SIGNIFICANCE
The unprotected condition of 1C-333 could have affected the credited offsite power source to Bus 16. Bus 16 is credited to power equipment required to achieve safe shutdown for Unit 1 in the event of a fire in FA32. A fire in FA32 could damage cables for both trains of safe shutdown equipment. FA32 has fire detection and an automatic wet pipe fire suppression system.
No fire occurred and there was no actual consequence to the public as a result of this unanalyzed condition.
' Ells System Code: FK 2
3 Ells System Code: EB Ells System Code: EK
U.S. NUCLEAR REGULATORY COMMISSION 1 2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
CAUSE
The Appendix R circuit analysis package did not include the sudden pressure switch trip (1 C-333 cable) due to inattention to detail and the lack of a detailed procedure to perform Appendix R circuit analysis. A contributing cause was that the sudden pressure trip switch is a unique feature of the offsite power transformers; most other 4KV breakers do not have a sudden pressure trip switch. However, there are several 4KV load breaker c~rcuit analysis packages that could have been referenced when performing the circuit analysis.
CORRECTIVE ACTION
An hourly fire watch was previously in place for Fire Area 32 as a compensatory measure and will continue until the cable protection issue has been resolved.
A procedure for Appendix R circuit analysis will be implemented. The procedure will include examples such as the unique feature of the offsite power transformers.
The site is transitioning to National Fire Protection Association (NFPA) 805, which is a performance-based, risk-informed licensing basis for fire protection. NFPA 805 endorses the use of state-of-the-art fire modeling techniques and fire probabilistic risk assessment tio determine the best solution to properly protect safe shutdown capability. Cables for the credited power source to Bus 16 will be provided the required fire protection to meet the safe shutdown requirements in NFPA 805.
PREVIOUS SIMILAR EVENTS
A review of the site's Corrective Action Program found two instances where cables were not included in their respective analysis fire areas. However, the equipment that the cables supported was not relied upon to be free of fire damage in those particular fire areas.
A review of LERs for Unit 1 and Unit 2 since 2006 identified LER 1-07-02 and LER 1-09-01 as being related to Appendix R non-compliance. These LERs reported unanalyzed conditions for fire areas due to non-compliance with Appendix R in the use of operator manual actions.