05000282/LER-2012-005-01, Regarding Diesel Generators Inoperable Due to Exhaust Fire

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Regarding Diesel Generators Inoperable Due to Exhaust Fire
ML13207A099
Person / Time
Site: Prairie Island 
(DPR-042)
Issue date: 07/25/2013
From: Jeffery Lynch
Northern States Power Co, Xcel Energy
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-13-026 LER 12-005-01
Download: ML13207A099 (6)
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LER-2012-005, Regarding Diesel Generators Inoperable Due to Exhaust Fire
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(iv)(B)(6)
2822012005R01 - NRC Website
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text

(l Xcel Energy JUt 2 5 2013 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Unit 1 Docket 50-282 Renewed License No. DPR-42 L-PI-13-026 10 CFR 50.73 Licensee Event Report (LER) 50-282/2012-005-00, Unit 1 Diesel Generators Inoperable Due To Exhaust Fire Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), herewith encloses a revised LER 50-282/2012-005-01 for this occurrence.

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

L:~~

Site ~~i:~ident, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:

Administrator, Region Ill, USNRC Project Manager, Prairie Island Nuclear Generating Plant, USNRC Resident Inspector, Prairie Island Nuclear Generating Plant, USNRC Department of Commerce, State of Minnesota 1717 Wakonade Drive East

  • Welch, Minnesota 55089-9642 Telephone: 651.388.1121

ENCLOSURE LICENSEE EVENT REPORT 50-282/2012-005-01 4 Pages Follow

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES: 10/3112013

{10-2010)

, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Prairie Island Nuclear Generating Plant Unit 1 05000 282 1 OF 4
4. TITLE Unit 1 Diesel Generators Inoperable Due To Exhaust Fire
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER I SEQUENTIAL I REV MONTH DAY YEAR YEAR NUMBER NO MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 08 14 2012 2012 -

005 -

01 07 25 2013

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

Mode 1 D

20.2201(b)

D 20.2203(a)(3)(i)

D

50. 73(a)(2)(i)(C) 0
50. 73(a)(2)(vii)

D 20.2201(d)

D 20.2203(a)(3)(ii)

D

50. 73(a)(2)(ii)(A)

D

50. 73(a)(2)(viii)(A)

D 20.2203(a)(1)

D 20.2203(a)(4)

D

50. 73(a)(2)(ii)(B)

D

50. 73(a)(2)(viii)(B)

D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D

50. 73(a)(2)(iii)

D

50. 73( a)(2)(ix)(A)
10. POWER LEVEL D

20.2203(a)(2)(ii)

D 50.36(c)(1 )(ii)(A) 0

50. 73(a)(2)(iv)(A)

D

50. 73(a)(2)(x) 100%

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

D

50. 73( a)(2)(v)(A)

D 73.71(a)(4)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

D

50. 73(a)(2)(v)(B)

D 73.71 (a)(5)

D 20.2203(a)(2)(v) 0

50. 73(a)(2)(i)(A)

D 50.73(a)(2)(v)(C)

D OTHER D

20.2203(a)(2)(vi)

D

50. 73(a)(2)(i)(B)

D

50. 73(a)(2)(v)(D)

Specify in Abstract below or in 12. LICENSEE CONTACT FOR THIS LER NAME I

TELEPHONE NUMBER (Include Area Code)

Frank Sienczak 651.388.1121 x4125 MANU-REPORTABLE MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX X

EK DG F010 y

14. SUPPLEMENTAL REPORT EXPECTED 15.EXPECTED MONTH DAY YEAR 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE).

NO SUBMISSION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On August 13, 2012, at 1048 COT, 01 Diesel Generator (DG) was declared inoperable due to a sustained flame on the control side turbocharger exhaust extension. 02 DG was run on August 14, 2012, to determine if a common cause failure was present. At 0312 COT on August 14, 2012, 02 was declared inoperable due to an exhaust leak with a visible flame on the control side turbocharger exhaust extension. The flame on 02 DG was detected at the same location as the flame that rendered 01 inoperable. With both DGs inoperable, this required Unit 1 to be placed in Mode 3 (Hot Standby) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 (Cold Shutdown) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per Technical Specifications (TS) 3.8.1 Condition F. While shutting down the unit, there was an auto actuation of the Auxiliary Feedwater system.

The direct cause of this event is that inadequate compression and gasket material on the 01 and 02 exhaust extension resulted in excessive oil and hot gas leakage causing fires on 01 and 02 exhaust.

NRC FORM 366 (10-2010) LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (10-201 0)

CONTINUATION SHEET

6. LER NUMBER
3. PAGE YEAR SEQUENTIAL REV Prairie Island Nuclear Generating Plant Unit 1 05000 282 NUMBER NO 2 OF4 2012 -

005 01

EVENT DESCRIPTION

On August 13, 2012, Prairie Island Nuclear Generating Plant (PINGP) Unit 1 was operating at 100%

power with electrical Bus 1 R-YN [BU]3 Out of Service (OOS) for preventive maintenance.(This bus provides power from 1 RY [XFMR]4 transformer to Bus 13 and 14 (secondary plant pumps and loads) when 1M transformer is not available while the main generator is off line.)

At 0939 COT, a planned entry into Technical Specification (TS) 3.8.1 Condition B was made to perform a monthly 01 Diesel Generator Monthly Slow Start Surveillance Test. At 1048 COT, a sustained flame was observed on the control side turbocharger exhaust extension. The flame did not last longer than 15 minutes, and no damage to 01 was observed as a result of the flame. 01 was subsequently shutdown and declared inoperable. The unit remained in TS 3.8.1 Condition B 14 day Limiting Condition for Operation (LCO).

Subsequent investigation by maintenance determined that there appeared to be a gasket leak on the turbocharger exhaust extension. 01 was tagged out of service for repairs. Work was then initiated to replace the exhaust manifolds and turbocharger exhaust extension gaskets on both sides of the engine.

On August 14, 2012, at 0243 COT, 02 Diesel Generator (DG)1 was run to determine if a common cause failure was present. At 0312 COT, 02 was also declared inoperable due to an exhaust leak with a visible flame on the control side turbocharger exhaust extension (the same location as the 01 exhaust leak). The fire did not last longer than 15 minutes, and fire damage was limited to exhaust manifold insulation, 02 was not damaged.

Bus 1 R-YN work was then expedited to restore it to a normal lineup. However, 01 repairs had not been completed, and with both DG inoperable, Unit 1 was required to be placed in Mode 3 (Hot Standby) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 (Cold Shutdown) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per TS 3.8.1 Condition F.

Power was reduced to approximately 15% per operating procedure 1C1.4, "Unit 1 Power Operation." Due to the preventative maintenance on Bus 1 R-YN, Bus 13 and 14 could not be transferred to 1 R and would be lost when taking the generator offline in accordance with the Unit 1 Shutdown Procedure 1C1.3. The resultant loss of power to Bus 13 and 14 would result in a loss of all Condensate pumps and a subsequent loss of Main Feedwater. The abnormal operating procedure 1C1.4 AOP 1, "Rapid Power Reduction Unit 1,"was entered, which directed reducing generator output below 1 00 MWe and inserting a manual reactor trip. The LCO time limit expired prior to restoring either 01 or 02, and the unit was taken offline without 1 R-YN power available to Bus 13 and

14. This resulted in a unit shutdown without all the normal non-safeguards power available to the secondary systems and an auto start of Auxiliary Feedwater. 02 was subsequently restored on August 14, 2012, at 1808 COT, which negated the requirement to place U1 in Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

1 EllS System Code DG 2 EllS System Code BA 3 EllS System Code BU 4 EllS System Code XFMR LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

CONTINUATION SHEET

6. LER NUMBER
3. PAGE YEAR SEQUENTIAL REV Prairie Island Nuclear Generating Plant Unit 1 05000 282 NUMBER NO 3 OF 4 2012 -

005 01 On August 14, 2012, at 1025 COT, the decision was made to manually trip Unit 1 at 15% power and allow auto start of Auxiliary Feedwater (AFW)(BA)2 for heat sink. This decision was based on the anticipated 1 RY source to buses 13 and 14 would not be available after taking the unit offline. Unit shutdown procedure assumes that this power will be available and that the turbine generator can be taken offline and main feedwater can be transferred to AFW in a controlled manner.

EVENT ANALYSIS

Each DG, as a backup to the normal standby AC power supply, is capable of sequentially starting and supplying the power requirements of one of the redundant sets of engineered safety features for its reactor Unit. In addition, in the event of a station blackout (SBO) condition, each DG is capable of sequentially starting and supplying the power requirements of the hot shutdown (Mode 3) loads for its unit, as well as the essential loads of the blacked out unit, through the use of manual bus tiebreakers interconnecting the 4160V buses.

Based on engineering evaluations the small fire seen during this event would not have an effect on the ability of 01 and 02 to respond to an emergency condition. 01 and 02 would have been able to perform their intended safety functions. The fire would not result in a failure to start, load/run, or run.

This event is reportable per 10 CFR 50.73(a)(2)(i)(A), the completion of any nuclear plant shutdown required by the plant's Technical Specifications; 10 CFR 50.73 (a)(2)(vii) any event where a single cause or condition caused at least one independent train or channel to become inoperable in multiple systems or two independent trains or channels to become inoperable in a single system designed to mitigate the consequences of an accident; and 10 CFR 50.73 (a)(2)(iv)(A) any event or condition that resulted in manual or automatic actuation of any of the systems (10 CFR 50.73 (a)(2)(iv)(B)(6) PWR auxiliary feedwater).

SAFETY SIGNIFICANCE

This issue had no radiological, industrial, or environmental impact. Station management reported this event to the NRC on August 14, 2012, forTS shutdown based on both DGs being declared inoperable requiring a unit shutdown. There was a safety system functional failure in that both DGs were inoperable. Loss of both DGs represents a loss of redundancy in the availability of electrical power systems. However, during this time-frame, off site power was available and capable of supplying power to the systems required to shutdown the reactor and decay heat removal. Based on the electrical lineup a valid automatic system actuation signal started the AFW system. The AFW system also serves as part of the Engineered Safety Features (ESF) Systems. The AFW System delivers high pressure water to the steam generators following an interruption of the main feedwater flow, maintaining the steam generators as the primary heat sink. Therefore, this event did not affect the health and safety of the public. LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

CONTINUATION SHEET

6. LER NUMBER
3. PAGE YEAR SEQUENTIAL REV Prairie Island Nuclear Generating Plant Unit 1 05000 282 NUMBER NO 40F4 2012 -

005 01

CAUSE

The cause of this event can be attributed to the yielding of the exhaust manifold bolts. This resulted in a loss of compression on the exhaust manifold and extension gaskets. The loss of compression leads to an increase in oil and exhaust gas leakage. The insulation installed around the exhaust joint was wrapped 360 degrees around the extension allowing oil to accumulate on the insulation blanket. The increased exhaust gas leakage heated up the oil to reach the ignition point and eventually catch on fire.

CORRECTIVE ACTION

Immediate actions (lA) taken was to replace the gaskets and re-torque for both 01 and 02.

The final corrective actions to prevent reoccurrence were the installation of the new Garlock gaskets and the Belleville washer system for both 01 and 02.

PREVIOUS SIMILAR EVENTS

In March 2009, September 2011, and in April 2012 exhaust leaks had been identified on 01 OG.

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