05000483/LER-2010-005-01, Regarding Emergency Diesel Generator a Shutdown During 24 Hour Surveillance

Regarding Emergency Diesel Generator a Shutdown During 24 Hour Surveillance

ML103560324
Person / Time
Site:	Callaway
Issue date:	12/21/2010
From:	Diya F Ameren Missouri
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
ULNRC-05752 LER 10-005-01
Download: ML103560324 (10)

LER-2010-005, Regarding Emergency Diesel Generator a Shutdown During 24 Hour Surveillance

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
4832010005R01 - NRC Website

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WAmeren MISSOURI December 21, 2010 u.s. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:

ULNRC-05752 Fadi M. Diya Vice President Nuclear Operations Ameren Missouri Callaway Plant T 573.676.6411 F 573.676.4056 10 CFR 50.73(a)(2)(i)(B) 10 CFR 50.73(a)(2)(v)(A) 10 CFR 50.73(a)(2)(v)(B) 10 CFR 50.73(a)(2)(v)(D)

DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2010-005-01 EMERGENCY DIESEL GENERATOR "A" SHUTDOWN DURING 24-HOUR SURVEILLANCE On May 28, 2010 Callaway Plant submitted Licensee Event Report (LER) 2010-005-00 in accordance with 10 CFR 50.73(a)(2)(i)(B), 10 CFR 50.73(a)(2)(v)(A), 10 CFR 50.73(a)(2)(v)(B), and 10 CFR 50.73(a)(2)(v)(D) to report an event in which the "A" emergency diesel generator at Callaway failed and automatically shut down during a 24-hour surveillance run.

The enclosed supplemental Licensee Event Report, LER 2010-005-01, is submitted to revise the causes and corrective actions for the same condition.

This letter does not contain new commitments.

Enclosure s. incereiy, ~

~UU Fadi M Diya Vice President, Nuclear Operations Junction CC & Hwy 0 PO Box 620, MC CA-460 Fulton, MO 65251 AmerenMissouri.com

ULNRC-05752 December 21, 2010 Page 2 cc:

Mr. Elmo E. Collins, lr.

Regional Administrator U.S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 820 1 NRC Road Steedman, MO 65077 Mr. Mohan C. Thadani (2 copies)

Senior Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8Gl4 Washington, DC 20555-2738 Mr. lames Polickoski Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8BlA Washington, DC 20555-2738

ULNRC-05752 December 21,2010 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4200 South Hulen, Suite 422 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

LEREvents@inpo.org (must :;l'rH.lthc \\VOI{I) version 01' the [,I*.H 10 this addrc:;s)

Electronic distribution for the following can be made via LER ULNRC Distribution:

A. C. Heflin F. M. Diya C. O. Reasoner III D. W. Neterer L. S. Sandbothe S. A. Maglio S. L. Gallagher T. L. Woodward (NSRB)

T. B. Elwood D. E. Dumbacher (NRC)

B. D. Brooks (WCNOC)

Ms. Diane M. Hooper (WCNOC)

Mr. TilTI Hope (Luminant Power)

Mr. Ron Barnes (APS)

Mr. Tom Baldwin (PG&E)

Mr. Wayne Harrison (STPNOC)

Ms. Linda Conklin (SCE)

Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)

Missouri Public Service Commission Records Center (INPO)

NRC FORM 366 (10-2010)

U.s. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

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

1. FACILITY NAME Callaway Plant Unit 1

4. TITLE

2. DOCKET NUMBER 05000483

13. PAGE 1

OF 7 Emergency Diesel Generator A Shutdown during 24 Hour Surveillance

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV MONTH FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

DAY YEAR FACILITY NAME DOCKET NUMBER 03 30 2010 2010 - 005 -

01 12 21 2010

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) o 20.2201(b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 1 o 20.2201 (d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) o 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B)

...... 0 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A) o 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)

10. POWER LEVEL o 20.2203(a)(2)(iii) 0 50.36(c)(2) l8I 50.73(a)(2)(v)(A) 0 73.71 (a)(4) o 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) l8I 50.73(a)(2)(v)(B) 0 73.71 (a)(5) o 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER 100%

o 20.2203(a)(2)(vi) l8I 50.73(a)(2)(i)(B) l8I 50.73(a)(2)(v)(O)

Specify in Abstract below or in

1. FACILITY NAME

2. DOCKET Callaway Plant Unit 1 05000483 YEAR 2010

6. LER NUMBER I

SEQUENTIAL I NUMBER 005 REV NO.

01

3. PAGE 3

OF grid via the A train 4160-V AC safety-related bus NBO 1 such that offsite power was available to the train A 4160-V AC safety-related bus. Offsite power was being supplied to the B train 4160-V AC bus NB02 via the normal supply breaker for that bus.

3.

EVENT DESCRIPTION

The event addressed by this LER is a failure of the A EDG to continue to run during performance ofa surveillance (24-hour run) on March 30, 2010.

The 24-hour run was begun with a slow start of the A EDG at approximately 0125 on March 30,2010. Nothing unusual was observed at that time. The EDG load was subsequently ramped up to six megawatts such that full load was achieved at approximately 0145. There were no alarms or indication present while the EDG continued to run.

Shortly after 1800, the Reactor Operator (RO) observed both megawatts and voltage lowering, so some slight adjustments to power and voltage were made. Load and voltage parameters were maintained within the required range.

At 1808, alarms unexpectedly came on for an automatic diesel shutdown. The following annunciators came in:

Main Control Board Annunciator:

20D - DG NE01 TROUBLE 20B - alarmed and cleared on under voltage/under frequency Local annunciators:

6D - ENGINE TROUBLE SHUTDOWN 7A - GENERATOR UNDERFREQUENCY 7D - GENERATOR PROTECTIVE RELAY Flags dropped locally for Protective Relays:

NE107 132 DG REVERSE POWER NE107 130 DG UNIT SID TARGET RELAY NE107 124 1DG VOLT HZ NE107 186 1DG LOCK OUT RELAY The Field Supervisor inspected the A EDG. He saw no apparent cause for the trip. A System Engineer came on site at approximately 1915 and conducted a walk down of the XNB01 transformer, the NB03 capacitor bank, the diesel generator output breaker, and the diesel room.

There were no flags dropped on NB0111, the diesel generator output breaker. There were no other lockouts on the NBO 1 bus and no indications of any faulted equipment with lockouts.

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE Callaway Plant Unit 1 05000483 YEAR I

SEQUENTIAL I REV NUMBER NO.

4 OF 2010 005 01 Post-trip indications showed that the A EDG tripped on reverse power. A reverse power scenario occurs if the diesel engine is no longer supplying sufficient power (torque) to the generator. If insufficient power is generated by the diesel engine, the generator will act as a motor and drive the diesel engine.

A one-hour run of the B EDG was completed to meet the common-cause determination requirement ofTS Required Action B.3.2.

4.

ASSESSMENT OF SAFETY CONSEQUENCES

This event resulted in the loss of the safety function of the A EDG to provide emergency 4160-V AC power to the NB01 bus in the event of a loss of offsite power (LOOP). This event was evaluated with the Callaway PRA model. The evaluation determined the conditional core damage probability (CCDP) of this event was less than 1E-6; therefore, this event was of very low risk significance. Use of the PRA model to evaluate the event provides for a comprehensive, quantitative assessment of the potential safety consequences and implications of the event, including consideration of alternative conditions beyond those analyzed in the FSAR.

It was determined that the A EDG was inoperable between May 11,2007 and April 4, 2010.

(See section 5 below.) Review of plant documents indicates that the B EDG was taken out-of-service during the time frames listed below (while it was unknown that the A EDG was inoperable)_ During these timeframes both EDGs were inoperable.

6. LER NUMBER I

SEQUENTIAL I NUMBER 005 REV NO.

01

3. PAGE 5

OF

5.

REPORTING REQUIREMENTS

This LER is submitted pursuant to 10CFRSO.73(a)(2)(i)(B) to report a condition prohibited by the Technical Specifications and 10CFRSO.73(a)(2)(v) as an event or condition that could have prevented fulfillment of a safety function.

10CFRSO.73(a)(2)(i)(B): The A EDG failed at approximately 16.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> into its 24-hour TS surveillance run. TS SR 3.8.1.14 requires verifying that "each DG operates at a power factor less than or equal to 0.9 and greater than or equal 0.8 and operates for greater than or equal to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />... " Since this was not met, the condition constituted a failure to meet the TS Limiting Condition for Operation (LCO).

TS 3.8.l requires both EDGs to be operable during plant operation (i.e., Modes 1,2, 3, and 4).

With one EDG inoperable during plant operation, Condition B in the ACTIONS section of TS 3.8.1 applies, and per associated Required Action B.4, the inoperable EDG must be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. If the Completion Time of72 hours cannot be met, Condition G must be entered, wherein Required Action G.1 requires commencement of a controlled plant shutdown such that the plant is required to be in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND in Mode S within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

After the test failure, and once the cause of the failure and the means to restore the EDG were identified, Callaway Plant determined that the EDG would not be restored to operable status within the time frame allowed by the TS. Callaway Plant requested and NRC granted enforcement discretion. This is documented in AmerenUE ULNRC-OS693 and in the NRC's approval letter for Notice of Enforcement Discretion (NOED) 10-4-001. The A EDG was declared operable on April 4, 2010 at 1220. The plant was not required to be shut down because the EDG was repaired and declared operable within the timeframe allowed by the NOED.

Results from the cause investigation indicate that the EDG was not able to meet its 24-hour surveillance time prior to the failure on March 30, 2010. Based on evaluation of the failure mechanism that caused the A EDG to become inoperable, it is estimated that the last time the EDG would have been able to meet the 24-hour surveillance test was on February 3,2010.

That timeframe exceeds the 72-hour allowed out-of-service time permitted by TS 3.8.1 per Required Action B.4.

Beyond the above, an evaluation was performed to determine when the A EDG became incapable of meeting its 7-day mission time (which is also considered to be an operability requirement). Based on the failure mechanism identified for the EDG (as described in section 6), and as determined by extrapolation of the wear rate associated with the failure mechanism (as related to the number of operating hours accumulated by the EDG), it was determined that the EDG became incapable of meeting its 7-day mission in May 2007. (Specifically, it was during the performance of a 24-hour run on May 11, 2007 that the accumulated hours of operation exceeded the threshold established as the point when the EDG became incapable of

6. LER NUMBER I

SEQUENTIAL I NUMBER 005 REV NO.

01

3. PAGE 6

OF meeting its 7-day mission time). On this basis the EDG was determined to be inoperable from May 11,2007 to April 4, 2010 (when it was restored to operable status following the March 30, 2010 test failure).

10CFR50.73(a)(2)(v): As discussed above, the A EDG was determined to be inoperable between May 11,2007 and April 4, 2010. Review of plant documents indicates that the B EDG was taken out-of-service during the timeframes listed above in the Assessment of Safety Consequences section (as it was not known that the A EDG was inoperable during those times).

During these time frames both EDGs were inoperable such that the EDG safety function(s) could not be fulfilled.

During a design basis accident, the EDGs are designed and intended to supply power to the ECCS systems and residual heat removal (RHR) pumps and valves, as well as the component cooling water systems and essential service water systems. As such, the EDGs support safety functions A, B, and D of 10CFR50.73(a)(2)(v). Those safety functions are:

(A) Shut down the reactor and maintain it in a safe shutdown condition, (B) Remove residual heat, (D) Mitigate the consequences of an accident.

6.

CAUSE OF THE EVENT

The cause of the A EDG shutdown was due to a failure of the governor to maintain the fuel rack open during operation. The governor operates as a hydraulic actuator. Hydraulic pressure within the governor was lost when the splined coupling on the drive shaft failed.

Troubleshooting, disassembly and inspection of the governor drive assembly revealed an improperly cut gasket which blocked the oil port to the gear case. Operation without forced oil lubrication to the governor drive gear case resulted in increased wear of the vertical shaft bearing. The bearing wear resulted in the radial movement of the vertical gear shaft in the gear case which caused wear on the teeth on the spline sleeve and mating male spline on the governor drive shaft. The worn teeth on the spline resulted in the governor failing to rotate with engine speed and subsequent diesel shutdown on March 30,2010. The damaged parts were replaced and a post-maintenance test was conducted to restore the EDG to an operable condition.

The root cause for this event was determined to be inattention to detail by craft during fabrication and installation of the EDG governor gear drive assembly gasket which resulted in the failure of the governor drive due to blockage of the lubrication supply port. This fabrication and installation of the gasket occurred eleven years prior to the EDG failure event.

In addition, a contributing cause was determined to be the failure to implement industry recommended preventive maintenance practices which if implemented may have identified the lack of forced oil flow in the governor drive or the degrading governor spline and degraded

1. FACILITY NAME

2. DOCKET YEAR Callaway Plant Unit 1 05000483 2010 governor drive components prior to the failure event.

6. LER NUMBER I

SEQUENTIAL I NUMBER 005 REV NO.

01

3. PAGE 7

OF As an extent of condition review, oil flow to the B EDG governor drive assembly was verified on April 6, 2010. Additionally, the B EDG governor was removed and inspected on April 23, 2010. The spline on the shaft was found to be in like new condition with no evidence of wear.

7.

CORRECTIVE ACTIONS

The Corrective Action to Prevent Recurrence is to revise the standard work instructions for the governor drive assembly for the emergency diesel engines to verify the governor drive assembly gasket has an oil supply port and that it is appropriately aligned to the oil port in the governor drive case during installation. In addition, an independent verification for this configuration was added to the standard work instructions. The revision of the standard work instructions has been implemented.

Corrective actions to ensure proper material stocking levels and to more effectively implement vendor maintenance recommendations for the EDGs and other risk-significant equipment were implemented.

8.

PREVIOUS SIMILAR EVENTS

The EDG failure event causal factor was: Governor Drive Assembly Gasket did not have the oil supply port. None of the internal operating experience reviewed had events originating in this Causal Factor. 7