05000335/LER-2010-007, For St. Lucie, Unit 1, Regarding Latent Failure of Steam Driven AFW Pump Led to Operation Prohibited by TSs

For St. Lucie, Unit 1, Regarding Latent Failure of Steam Driven AFW Pump Led to Operation Prohibited by TSs

ML102430167
Person / Time
Site:	Saint Lucie
Issue date:	08/24/2010
From:	Richard Anderson Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2010-190 LER 10-007-00
Download: ML102430167 (6)

LER-2010-007, For St. Lucie, Unit 1, Regarding Latent Failure of Steam Driven AFW Pump Led to Operation Prohibited by TSs

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3352010007R00 - NRC Website

text

0 IFPL Florida Power & Light Company, 6501 S. Ocean Drive, Jensen Beach, FL 34957 August 24, 2010 L-2010-190 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Re:

St. Lucie Unit I Docket No. 50-335 Reportable Event: 2010-007 Date of Event: June 25, 2010 Latent Failure of Steam Driven AFW Pump Led to Operation Prohibited by TSs The attached Licensee Event Report 2010-007 is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Respectfully, Richard L. Anderson Site Vice President St. Lucie Plant RLA/KWF Attachment an FPL Group company

.1?,.>:

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/201(

(9-20071 Estimated burden per response to comply with this mandatory collection request: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records and FOIA/Privacy Service Branch (T-5 LICENSEE EVENT REPORT (LER)

F52), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-1 0202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

13. PAGE St. Lucie Unit 1 05000335 1 OF 5

4. TITLE Latent Failure of Steam Driven AFW Pump Led to Operation Prohibited by TSs

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER SEQUENTIAL REV MONTH DAY YEAR M N H D Y Y A YE R

NUMBER NO.

_____________I________________________

[ACILITY NAME DOCKET NUMBER 06 25 2010 2 010 -

0 07 0 0 08 24 2010

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check a// that apply)

[1 20.2201 (b)

[I 2D.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 3 El 20.2201(d)

El 20.2203(a)(3)(ii)

El 5D.73(a)(2)(ii)(A)

[I 50.73(a)(2)(viii)(A)

[I 20.22D3(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

___________El 20.22D3(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL [I 20.2203(a)(2)(ii)

El 5D.36(c)(1)(ii)(A)

El 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

El 2D.22D3(a)(2)(iii)

El 50.36(c)(2)

El 50.73(a)(2)(v)(A)

E] 73.71(a)(4) 0%l[

20.22D3(a)(2)(iv)

El 50.46(a)(3)(ii)

El50.73(a)(2)(v)(B)

El 73.71(a)(5) 0%El 2D.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

El50.73(a)(2)(v)(C)

El OTHER El 20.2203(a)(2)(vi)

X 50.73(a)(2)(i)(B)

El 50.73(a)(2)(v)(D)

Specify in Abstract below

___________________or in procedures will be revised to include precautions, notes, and steps related to the verification of proper governor valve as-found and as-left position and condition.

Analysis of the Event

The St. Lucie Unit 1 Technical Specifications (TS) require that the 1C steam driven AFW pump pass TS surveillance requirement (SR) 4.7.1.2.c within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of reaching Mode 3 and prior to entering Mode 2.

This testing verifies that the AFW pump developed head at the flow test point meets inservice test (IST) requirements and is performed with local operators stationed at the pump to monitor the condition of the pump during the surveillance.

During the spring 2010 SL1-23 refueling outage St.

Lucie Unit 1 entered Mode 3 from Mode 4 on May 29, 2010, at 1456 hours0.0169 days <br />0.404 hours <br />0.00241 weeks <br />5.54008e-4 months <br />, and this surveillance requirement was successfully met on May 30, 2010, at 0412 hours0.00477 days <br />0.114 hours <br />6.812169e-4 weeks <br />1.56766e-4 months <br />.

Between May 30,

2010, and June 25, 2010, the last time the 1C AFW pump was started and run was on June 1, 2010, at 1924 hours0.0223 days <br />0.534 hours <br />0.00318 weeks <br />7.32082e-4 months <br />, when the IC AFW pump was started to satisfy TS SR 4.7.1.2.b.2 (the 18-month AFW pump auto-start verification test).

Note that with the iC AFW pump in standby, the governor valve is open.

The governor would have to be actively modulating the AFW pump turbine speed for debris to enter the governor assembly and cause binding.

FPL concludes that the extended operation of the ADVs allowed the ADV silencer debris to settle on the 1C AFW pump governor assembly.

On June 25, 2010, during the failed surveillance, this debris entered and bound the governor assembly when the governor attempted to modulate the speed of the turbine during the 1C AFW pump start.

This is consistent with the observed pump performance during the failed surveillance..

This condition is reportable in accordance with 10 CFR 50.73(a) (2) (i) (B) because it resulted in the operation of the facility in a manner prohibited by TSs for the following reasons:

" TS 3/4.7.1.2 only allows one inoperable AFW pump for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

This latent failure existed for a time greater than the allowed outage time.

• The lB emergency diesel generator (EDG) was declared out of service (OOS) on June 17, 2010.

If the condition of the steam driven 1C AFW pump had been known at the time, TS 3.8.1.1 ACTION b-would have required that the motor driven lB AFW pump be declared OOS within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of discovery, placing the unit in TS 3.0.3 for two inoperable AFW pumps.

Although the Unit 2 steam driven 2C AFW pump turbine governor has the same design as Unit 1 1C AFW pump and is susceptible to the same condition, the LER investigation did not identify comparable issues with the Unit 2 ADVs and 2C AFW pump.

Analysis of Safety Significance The AFW system is provided with two motor driven AFW pumps and one steam driven AFW pump.

The AFW System is designed to provide feedwater for the removal of sensible and decay heat from the reactor coolant system.

The system can cool the reactor coolant system to 325F for normal plant cooldowns or during events where the main condensate pumps or the main feedwater pumps are inoperative due to pump failures or due to a loss of normal electric power..

The AFW system can achieve this design requirement with one operable motor driven AFW pump and one intact steam generator. For this event, only the 1C AFW (steam driven) pump was inoperable.

Although the lB AFW pump would have been considered TS

inoperable per TS 3.8.1.1 ACTION b four hours after the lB EDG was declared OOS on June 17, 2010, the lB AFW pump remained available for use with offsite power.

The AFW system is able to meet design requirements with only one motor driven AFW pump, bounding the condition evaluated in this LER.

In addition, the FPL probabilistic risk assessment (PRA) group reviewed the risk associated with the inoperable 1C AFW pump in conjunction with the EDG outage windows and concluded that the risk was "small" as discussed below.

The evaluation concluded that the integrated risk for the plant configuration as described is a "small" risk in accordance with RG-I.174.

Core damage probability (CDP) is lower than 1.0E-06 and large early release probability (LERP) is lower than 1.OE-07.

As Unit 1 was in Mode 3, it should be noted component failure rates and human failure probability should be at lower values than those of Mode 1. However, no credit was considered as the risk evaluation assumed failure of structures,

systems, and components (SSCs) and human failure probabilities at the same level as those of Mode 1 (full power level).

If such credit were to be considered, the risk would be considered "very small."

The integrated (cumulative) risk impact for the plant configuration during the entire time (starting June 1, 2010, until June 25, 2010) is estimated to have a conditional core damage probability (CCDP) of 2.06E-07 and conditional large early release probability (CLERP) of 3.47E-08.

These values are below the threshold required by RG-I.174 for the risk to be considered "small" (i.e.,

CDP below 1.OE-6 and LERP below 1.0E-07).

Based on the above, this condition had minimal impact on the health and safety of the public.

Corrective Actions

The corrective actions below are being managed by the Corrective Action Program.

Any changes to the actions below will be processed in accordance with the St. Lucie Commitment Management Program.

1. The 1C AFW pump governor assembly was disassembled, cleaned, lubricated, reassembled, and the AFW pump was returned to service.

2.

The main steam system engineer designated work orders (WOs) 29025873 and 29025874 as Yellow WOs for the replacement of the ADV silencers for Unit 1.

3.

The St. Lucie Unit 1 ADVs are scheduled for replacement during the next refueling outage, SL1-24.

4.

A temporary enclosure was built around the 1C AFW pump to enhance housekeeping in the area until the ADVs are replaced.

This enclosure will be subject to shiftly operator walkdowns and weekly SCE walkdowns.

5.

The AFW system engineer will revise the system monitoring plan to include inspection of the turbine driven AFW pump governor and trip throttle valve condition following operation of ADVs until such time that repairs are completed.

6.

The AFW System Engineer will revise the steam driven AFW pump surveillance procedures for St. Lucie Units 1 and 2 to include precautions, notes and steps to address as-found and and-left governor valve position/condition.

Similar Events

A search of the corrective action program database identified no similar events in the last three years.

Failed Components 1C AFW pump governor assembly Manufacturer: Woodward Governor Model Number:

PG-PL PSL-modified