05000306/LER-2012-002, Diesel Generators Inoperable Due to Missing Flood Control Barrier Seal

Diesel Generators Inoperable Due to Missing Flood Control Barrier Seal

ML12258A387
Person / Time
Site:	Prairie Island
Issue date:	09/14/2012
From:	Molden J Xcel Energy, Northern States Power Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-12-085 LER 12-002-00
Download: ML12258A387 (5)

LER-2012-002, Diesel Generators Inoperable Due to Missing Flood Control Barrier Seal

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3062012002R00 - NRC Website

text

@ Xcel Energym September 14, 2012 L-PI-12-085 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 50-30612012-002-00, Unit 2 Diesel Generators Inoperable Due To Missing Hazard Barrier On July 20, 2012, Prairie Island Nuclear Generating Plant (PINGP) Unit 2 was operating at 100% power. Diesel Generators (DGs) D5 and D6 were declared inoperable due to a missing hazard barrier that protects the D5lD6 building from High Energy Line Break (HELB) related flooding events (Event Notification System Number 48122). The hazard barrier is required to be installed with Unit 2 in Modes 1, 2, 3 and 4 when the Main Steam Isolation Valves (MSIVs) are open. Because the hazard barrier was removed, Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.1 Condition B was entered for both DGs and LC0 3.8.1 Condition E was entered for two DGs inoperable on the same unit. The flood control barrier seal was restored and the LC0 conditions were exited associated with D5 and D6 DGs.

A preliminary Licensee Event Report (LER) for this occurrence is attached.

Summary of Commitments This letter contains no new commitments and no changes to existing commitments.

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 1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121

ENCLOSURE LICENSEE EVENT REPORT 50-30612012-002-00 3 Pages Follow

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION I APPRoVEDBYOMBNO. 3150-0104 EXPIRES: 10131/2013 LICENSEE EVENT REPORT (LER)

(See reverse for required number of digitstcharacters for each block)

, the NRC may not conduct or sponsor, and a person is not required lo respond to, the information collection.

I I

I I

I I

I I

9. OPERATING MODE I

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check all that apply)

Mode 1

10. POWER LEVEL 100%

3. PAGE 1 OF 3

1. FACILITY NAME Prairie Island Nuclear Generating Plant Unit 2

5. EVENT DATE 50.73(a)(2)(vii)

[7 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A)

[7 50.73(a)(Z)(x)

[7 73.71(a)(4) 73.71(a)(5)

OTHER

4. TITLE Unit 2 Diesel Generators Inoperable Due To Missing Flood Control Barrier Seal 2, DOCKET NUMBER 05000 306 MONTH 07 I [7 20,2203(a)(2)(vi) 50,73(a)(2)(i)(B)

[7 50.73(a)(2)(v)(D)

Specify in Abstract below or in 12. LICENSEE CONTACT FOR THlS LER

6. LER NUMBER NAME Frank Sienczak DAY 20 YEAR TELEPHONE NUMBER (Include Area Code) 651.388.1 121 x4125

7. REPORT DATE YEAR 2012

8. OTHER FACILITIES INVOLVED 2012 - 002 - 00 SEQUENTIAL NUMBER FACILITY NAME FACILITY NAME YEAR 2012 MONTH 09 REV NO I On July 20, 2012, the Prairie Island Nuclear Generating Plant (PINGP) Unit 2 declared Diesel Generators (DGs) D5 and D6 inoperable due to a missing hazard barrier. The missing hazard barrier is required to be installed with Unit 2 in Modes 1, 2, 3 and 4 when the Main Steam Isolation Valves (MSIVs) are open.

DOCKET NUMBER DOCKET NUMBER DAY 14 I

1 I

I I I

14. SUPPLEMENTAL REPORT EXPECTED O YES (If yes, complete 15. EXPECTED SUBMISSION DATE).

0 NO Technical Specification Limiting Condition for Operation (LCO) 3.8.1 Condition B was entered for both DGs and LC0 3.8.1 Condition E was entered for two DGs inoperable on the same unit.

The Root Cause Evaluation (RCE) is still in progress and the final cause and corrective actions have not been determined. This information will be submitted in the supplemental report following completion of the RCE.

MANU-FA CTURER ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

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NRC FORM 366 (10-2010)

REPORTABLE TO EPlX SYSTEM

CAUSE

YEAR 2012 I

I COMPONENT REPORTABLE TO EPlX

15. EXPECTED SUBMISSION DATE

CAUSE

SYSTEM MONTH 10 COMPONENT DAY 17 MANU-FACTURER

EVENT DESCRIPTION LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (1 0-201 0)

CONTINUATION SHEET Prairie Island Nuclear Generating Plant (PINGP) Administrative Work Instruction 5AWI 8.9.0, Internal Flooding Drainage Control, Section 6.2.9 (Pipe Trench in D5lD6 Building) step a.3 states that "The concrete trench covers and the sealant between the trench covers and the surrounding floor must be in place whenever there is a possibility of a High Energy Line Break (HELB) in the Unit 2 Turbine Building." Section 6.2.10 (D5lD6 Diesel Generator Building) step c.2 states that "The sealed concrete trench covers must be in place whenever Unit 2 is in Mode 1, Mode 2, Mode 3, and Mode 4 when the Main Steam Isolation Valves (MSIVs) are open."

Contrary to 5AWI 8.9.0, on June 25, 2012, insulators removed sealant around a concrete pipe trench cover located in the D6 future inverter room under Work Order (WO) 437670 task 04 without implementing corn ensatory actions to prevent internal flooding from impacting the D5lD6 Diesel P

Ge~erators (DGs) in case of a HELB event. Although not recognized, this condition made D5 and D6 inoperable. Then on June 28, 2012, site maintenance removed the D6 future inverter room concrete pipe trench cover under Work Order (WO) 437670 task 02 without implementing compensatory actions to prevent internal flooding from impacting the D5lD6 DGs in case of a HELB event. The concrete pipe trench cover was re-installed on June 29, 2012, under Work Order (WO) 437670 task

03.

1. FACILITY NAME Prairie Island Nuclear Generating Plant Unit 2 On July 9,2012 the concrete pipe trench cover was removed under Work Order (WO) 437670 task

06. During a walkdown, on July 20, 2012 a station engineer identified that the trench covers and sealant were missing. At 1400, D5 and D6 DGs were declared inoperable and Limiting Condition for Operation (LCO) 3.8.1 AC Sources - Operating Condition B (One DG inoperable) and Condition E (Two DGs inoperable) were entered. This condition was reportable per 10 CFR 50.73(a)(2)(v)(A) as an event or condition that could have prevented the fulfillment of a safety function. On July 20, 2012 at 1505 hrs the concrete pipe trench cover and flood control barrier seal was restored and the LC0 conditions were exited associated with D5 and D6 DGs.

6. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO 2012 -

002

- 00

2. DOCKET NUMBER 05000 306

EVENT ANALYSIS

3. PAGE 2OF3 An analysis has determined that in the event of a Turbine Building HELB there is a potential for damage to other piping systems with unlimited water sources as a result of displacement of the failed high energy pipe (pipe whip). Depending on the location of the HELB, the Cooling Water (CL) system can be significantly damaged. In addition, the HELB environment can cause the Fire Protection (FP) sprinkler system to actuate depending on the location and size of the break. This results in HELB induced internal flooding. The Cooling Water and Fire Protection systems would then supply a continuous flow of water into the Turbine Building until operators take manual action to stop the flow.

The trench that runs between the Unit 2 Turbine Building and the D5lD6 building creates a flow path for flood water to enter the D5lD6 building. The trench covers in the D5lD6 building are in place as flood barriers to stop the water from entering into the building. This condition is reportable per 10 CFR 50.73(a)(2)(v)(A), an event or condition that could have prevented the fulfillment of a safety function; I 0 CFR 50.73(a)(2)(i)(B), operations or condition prohibited by Technical Specifications;

and, 10 CFR 50a73(a)(2)(ix)(A), single cause that could have prevented fulfillment of the safety functions of trains or channels in different systems. LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMiSS1ON (1 0-201 0)

CONTINUATION SHEET Ells System Code DG

SAFETY SIGNIFICANCE

1. FACILITY NAME Prairie Island Nuclear Generating Plant Unit 2 This issue had no nuclear, radiological, industrial, or environmental impact. Internal flooding of the Turbine Building and D5lD6 building did not occur, so the Structures, Systems and Components (SSCs) in the D5lD6 building were not affected and both DGs could have started and run if required.

In addition, off site power was available. Therefore, this event did not affect the health and safety of the public.

6. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO 2012 -

002

- 00

2. DOCKET NUMBER 05000 306

CAUSE

3. PAGE 3 OF 3 The Root Cause Evaluation (RCE) is still in progress and the final cause has not been determined.

This will be submitted in the supplemental report following completion of the RCE.

CORRECTIVE ACTION

The Root Cause Evaluation (RCE) is still in progress and the final corrective actions have not been determined. This will be submitted in the supplemental report following completion of the RCE.

PREVIOUS SIMILAR EVENTS

LER 50-28212010-001-00, "Unanalyzed Condition Due to Postulated High Energy Line Break On Cooling Water System," May 3, 2010