05000306/LER-2008-001, Unanalyzed Condition Due to Both Trains of Component Cooling Being Susceptible to a Postulated High Energy Line Break
| ML082730905 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 09/29/2008 |
| From: | Wadley M Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-PI-08-078, LER 2-08-01 LER 08-001-00 | |
| Download: ML082730905 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3062008001R00 - NRC Website | |
text
Xcel Energy" September 29, 2008 L-PI-08-078 10 CFR 50.73 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Unit 2 Docket 50-306 License No. DPR-60 LER 2-08-01, Unanalyzed Condition Due to Both Trains of Component Cooling Being Susceptible to a Postulated High Energy Line Break Northern States Power Company, a Minnesota corporation (NSPM) herewith encloses Licensee Event Report (LER) 2-08-01. The LER describes a condition where both trains of the component cooling water system were susceptible to a single failure caused by a postulated high energy line break in the Turbine Building. NSPM notified the NRC of this event, as required by 10 CFR 50.72(b)(3)(ii)(B) on July 31, 2008.
Please contact us if you require additional information related to this event.
Summarv of Commitments This letter contains one new commitment and no changes to existing commitments:
NSPM will supplement this LER if the evaluation of the cause of the as-found condition uncovers any significant new information on the cause or identifies any significant
additional corrective actions
Michael D. Wadley f
Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota 1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121
Document Control Desk Page 2 Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC Department of Commerce, State of Minnesota
ENCLOSURE LICENSEE EVENT REPORT 2-08-01 3 Pages Follow
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9 2007)
LICENSEE EVENT REPORT (LER)
(See reverse for requ~red number of d~g~tslcharacters for each block)
I.
FACILITY NAME Pra~r~e Island Nuclear Generat~ng Plant Unit 2 APPROVED BY OMB NO 3150-0104 EXPIRES 08/31/2010 Estimated burden per response to comply wlth thls mandatory collectlon 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 Into the llcensrng process and fed back to Industry Send comments regarding burden estlmate to the Records and FOIAIPrlvacy Servlce Branch (T-5 F52), U S Nuclear Regulatory Comrn~ss~on, Washlngton, DC 20555-0001, or by Internet e-mall to ~nfocollects@nrc gov, and to the Desk Officer, Office of lnformatlon and Regulatory Affalrs. NEOB-10202, (3150-0066), Office of Management and Budget, Washington, DC 20503 If a means used to lmpose an lnformatlon collect~on does not dlsplay a currently valld OMB control number, the NRC may not conduct or sponsor, and a person IS not requtred to respond to, the lnformatlon collectlon
- 2. DOCKET NUMBER 05000306
- 4. TITLE Unanalyzed Cond~t~on Due to Both Trains of Component Cooling Susceptible to a Postulated High Energy Line Break
- 3. PAGE 1 of 3
- 5. EVENT DATE
- 9. OPERATING MODE 1
- 10. POWER LEVEL 100
- 6. LER NUMBER
- 7. REPORT DATE MONTH 7
- 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) 50 73(a)(2)(vli) 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) 5 0 73(a)(2)(11)(6) 50 73(a)(2)(v111)(6) 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)(ll)(A) 50 73(a)(2)(1v)(A) 50 73(a)(2)(x) 20 2203(a)(2)(111) 50 36(c)(2) 50 73(a)(2)(v)(A) 73 71 (a)(4) 20 2203(a)(2)(1v) 50 46(a)(3)(11) 50 73(a)(2)(v)(B) 73 71 (a)(5) 20 2203(a)(2)(v) 50 73(a)(2)(1)(A) 50 73(a)(2)(v)(C)
OTHER 20 2203(a)(2)(v1) 50 73(a)(2)(1)(6) 50 73@)(2)(v)(D)
Spec~fy In Abstract below or In NRC F w
366A
- 12. LICENSEE CONTACT FOR THlS LER
- 8. OTHER FACILITIES INVOLVED YEAR MONTH 09 FACILITY NAME FACILITY NAME DAY 31 DOCKET NUMBER DOCKET NUMBER 2008 - 001 - 00 SEQUENTIAL NUMBER DAY 29 YEAR 2008 NAME Jeff Kiv~, Pr~nc~pal Regulatory Compliance Engineer REV NO YEAR 2008 TELEPHONE NUMBER (Include Area Code) 651.388.1121 REPORTABLE TO EPIX YEAR ABSTRACT (Limit to 1400 spaces, i e, approximately 15 smgle-spaced typewritten hnes)
On July 31, 2008, Prairie Island Nuclear Generating Plant (PINGP) Unit 2 was operating at 100 percent power. At 1345 CDT Prairie Island staff declared both trains of the Unit 2 component cooling water (CC) system inoperable due to the discovery that a postulated Unit 2 high energy line break (HELB) in the Turbine Building could fail a CC line that would affect both trains of the Unit 2 CC system. With both trains of CC declared inoperable, PINGP staff entered Technical Specification (TS) Limiting Condition for Operability (LCO) 3.0.3. PINGP staff isolated the CC line in the Turbine Building at 1612 on July 31, 2008, which returned Unit 2 CC to operable status.
The as-found condition was an original design issue uncovered during walkdowns in support of turbine building CC system seismic qualification. The long term corrective action will be to reroute the piping away from break areas or identify an alternate source of cooling, such that CC can be removed from the Turbine Build~ng.
NRC FORM 366 (9-2007)
MANU-FA CTURER COMPONENT SYSTEM
- 14. SUPPLEMENTAL REPORT EXPECTED 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE).
O NO
CAUSE
CAUSE MANU-FACTURER DAY
- 15. EXPECTED SUBMISSION DATE REPORTABLE TO EPIX SYSTEM MONTH COMPONENT
EVENT DESCRIPTION LICENSEE EVENT REPORT (LER)
U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
CONTINUATION SHEET On July 31, 2008, Prairie Island Nuclear Generating Plant (PINGP) Unit 2 was operating at 100 percent power. At 1345 CDT Prairie Island staff declared both trains of the Unit 2 component cooling water' (CC) system inoperable due to the discovery that a postulated Unit 2 high energy line break (HELB) in the Turbine Building could fail a CC line that would affect both trains of the Unit 2 CC system. With both trains of CC declared inoperable, PINGP staff entered Technical Specification (TS) Limiting Condition for Operability (LCO) 3.0.3. PINGP staff isolated the CC line in the Turbine Building at 1612 on July 31, 2008, which returned Unit 2 CC to operable status. Unit 2 remained at 100 percent power throughout the event.
EVENT ANALYSIS
I. FAClLlN NAME Prairie Island Nuclear Generating Plant Unit 2 The CC system is required to mitigate a HELB, but the CC line that was susceptible to a Unit 2 HELB supplies cooling to Unit 2 sample coolers. While this line can remain isolated at power, there is no automatic isolation of this line (e.g., on a safety injection signal) and any CC inventory loss out of this line would eventually affect both trains of the CC system. This condition was identified in support of turbine building CC system seismic qualification. Turbine building loads can be lined up to either unit CC system, but were aligned to Unit 2 CC at the time of discovery.
- 6. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO 2008 -
001
- - 00
- 2. DOCKET 05000306 This condition was a susceptibility of two trains of Unit 2 CC to a consequential failure from a postulated Unit 2 HELB. A postulated HELB break location was identified that would have been expected to break a nearby CC line to Unit 2 sample coolers. Since a Unit 2 HELB could directly result in the loss of both trains of Unit 2 CC (a system that is required to meet the single failure criterion), in this configuration the Unit 2 CC system did not meet the single failure criterion. Thus, this condition is reportable per 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition. No actual loss of function occurred as a result of this condition (neither the postulated HELB nor the consequential CC line break actually occurred). Thus, this event is not reportable per 10CFR 50.73(a)(2)(v).
- 3. PAGE 2 of 3
SAFETY SIGNIFICANCE
A This condition resulted in a potential for a postulated HELB at a specific break location to cause a break in a CC line. Once a leak in the CC system is isolated or repaired, the system can be refilled and returned to service. Loss of CC due to a pipe rupture is addressed in plant operating procedures, which provide operators immediate and subsequent action steps to mitigate the consequences of a event. Thus, this event did not affect the health and safety of the public and the safety significance of this event is considered minimal.
1 Ells System Code: CC
CAUSE LICENSEE EVENT REPORT (LER)
U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
CONTINUATION SHEET The as-found condition was the result of an original design issue that was uncovered during walkdowns in support of turbine building CC system seismic qualification. Northern States Power Company, a Minnesota corporation (NSPM) is evaluating the cause of the as-found condition and will supplement this LER if any significant additional information relating to the cause is uncovered.
- 1. FACILITY NAME Prairie Island Nuclear Generating Plant Unit 2
CORRECTIVE ACTION
The susceptible CC line in the Turbine Building was isolated in the Auxiliary Building.
- 2. DOCKET NUMBER 05000306 The planned corrective action is to modify the cooling source to the cold lab and turbine building sample coolers to reroute or eliminate CC lines from the Turbine Building. If the cause evaluation identifies any additional significant corrective actions, NSPM will supplement this LER.
PREVIOUS SIMILAR EVENTS
- 6. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO 2008 -
001
- - 00 Review of LERs for Unit 1 and Unit 2 since 2006 found no similar events.
- 3. PAGE 3 of 3