05000423/LER-2010-004, For Millstone Power Station, Regarding Inoperable Turbine Driven Auxiliary Feedwater Pump Due to Degraded Relief Valve
| ML103070124 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/19/2010 |
| From: | Jordan A Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 10-585, FOIA/PA-2011-0115 LER 10-004-00 | |
| Download: ML103070124 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(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 |
| 4232010004R00 - NRC Website | |
text
79kDominion-Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 OCT 1 9 2010 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
MPS Lic/LES Docket No.
License No.10-585 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 3 LICENSEE-EVENT REPORT 2010-004-00 INOPERABLE TURBINE DRIVEN AUXILIARY FEEDWATER PUMP DUE TO DEGRADED RELIEF VALVE This letter forwards Licensee Event Report (LER) 2010-004-00 documenting a condition discovered at Millstone Power Station Unit 3, on August 21, 2010. This LER is being submitted pursuant to 10 CFR 50.73 (a)(2)(i)(B) as a condition prohibited by Technical Specifications.
If you have any questions or require additional information, please contact Mr.
William D. Bartron at (860) 444-4301.
Sincerely, in Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None
Serial No.10-585 Docket No. 50-423 Licensee'Event Report 2010-004-00 Page 2 of 2 cc:
U.S. Nuclear Regulatory-Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 C. J. Sanders Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville.Pike Mail Stop 08B3 Rockville, MD 20852:2738 NRC Senior Resident Inspector Millstone Power'Station
'Serial No.10-585 Docket No. 50-423
,Licensee-Event Report 2010-004-00 ATTACHMENT LICENSEE EVENT REPORT 2010-004-00 INOPERABLE TURBINE DRIVEN AUXILIARY FEEDWATER PUMP DUE TO DEGRADED RELIEF VALVE MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may not conduct or sponsor, digits/characters for each block) and a person is not required to respond to, the information collection.
- 3. PAGE Millstone Power Station - Unit 3 05000423 1 OF3
- 4. TITLE Inoperable Turbine Driven Auxiliary Feedwater Pump Due to Degraded Relief Valve
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER SEQUENTIAL REV MNH DY YA 50 MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 08 21 2010 2010-004-00 10 19 2010 05000
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR Check all that apply) 20.2201 (b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. POWER LEVEL 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71 (a)(5) 100 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi)
X 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below or in
- 1.
Event Description
On August 21, 2010, while operating in MODE 1 at 100 percent power, Millstone Power Station Unit 3's (MPS3)
Turbine Driven Auxiliary Feedwater (TDAFW) [BA] [P] pump was declared inoperable due to leakage past its associated discharge relief valve's [V] seat. This condition was identified while performing Operations Surveillance Procedure SP 3622.3-001. Using a Controlotron, measured recirculation flow for this pump was 115 gallons per minute (gpm), as compared with a maximum allowed value of 105.6 gpm. The flow measured at this point is the sum of minimum recirculation flow plus any flow through the discharge relief valve. Exceeding the allowable flow is indicative of relief valve seat leakage.
Further investigation revealed that this condition existed on June 30, 2010. On June 30, 2010, surveillance testing of the TDAFW pump was performed per SP 3622.3-001. Recirculation flow was 107 gpm. Operations Surveillance Procedure SP 3622.3-001 did not specify a high flow limit. Operations personnel did not recognize that the recirculation flow exceeded the upper limit value of 105.6 gpm specified in the quarterly pump in-service test procedure, EN31121-019. Excessive recirculation flow of 115 gpm was identified on August 20,.2010 at 1423, during another performance of this Operations surveillance procedure. As soon as Operations became aware that flow exceeded the acceptance criteria in EN31121-019, the TDAFW pump was declared inoperable.
The extended period of inoperability of the TDAFW pump exceeded the allowed outage time in Technical Specification 3.7.1.2.c of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and constitutes a condition prohibited by the MPS3's Technical Specifications.
Therefore this condition is being reported pursuant to 10 CFR 50.73(a)(2)(i)(B).
- 2.
Cause
The cause of the inoperability of the TDAFW pump was a failed relief valve. The relief valve failure was a consequence of minimal margin between the setpoint of TDAFW Pump Discharge Relief Valve 3FWA*RV45 and Auxiliary Feedwater system pressure while on recirculation flow.
A contributing cause was the Operations surveillance procedure lacked adequate detail on flow limits. SP-3622.1-003 did not contain reference band values for high recirculation flow that were included in quarterly in-service testing (IST).procedure EN31121-019.
- 3.
Assessment of Safety Consequences
An engineering evaluation has been performed to determine whether the degraded relief valve would have diverted sufficient TDAFW flow to challenge the system's ability to perform its safety function. This evaluation concluded that there was substantial margin available for the required AFW flow to the steam generators during an accident. If the amount of flow passed through the relief valve's seat had risen to 90 gpm, the TDAFW pump would have successfully performed its safety function. With 90 gpm flow assumed through the relief valve's seat, the evaluation showed that delivered AFW flow to the two steam generators would have decreased by a maximum of 2.6%, as compared with a minimum available design margin of 6.7%.
This conclusion is based upon the fact that increased diverted flow seen during the TDAFW Pump Operational Readiness Test was due to a partial relief valve lift and subsequent chatter, and not valve leak-by. Since this surveillance is done with the pump operating at minimum flow, discharge pressure (and, therefore, relief valve leakage) was much higher (1740 psig) than it would be if the pump had been called upon to perform its safety function (1530 psig). Actual valve leakage was determined to be less than 1/2 gpm at 1665 psig during a bench test. With the relief valve failed full open, the pump would still be able to provide adequate flow less than an hour into the event. Therefore it is concluded that the TDAFW Pump would be fully capable of providing the required design flow.
I NR, F-UXM 366A (9-2UU7)
- 4.
Corrective Action
As interim corrective actions, leaking relief valve 3FWS*RV45 was repaired on August 16, 2010, and a standing order was issued to Operations personnel to ensure that all applicable acceptance criteria for in-service testing of safety related equipment are reviewed prior to declaring the equipment operable.
As corrective action to prevent recurrence of this condition, design changes are being evaluated to modify the system configuration.
Other corrective actions taken to address the failure to recognize the inoperability of the TDAFW pump are:
Operating Surveillance Procedure SP 3622.3-001 has been revised to definitively specify an upper limit for TDAFW pump recirculation flow, and, A review of other Operations Surveillance Procedures has been completed to verify that appropriate acceptance criteria that are already specified in quarterly in-service test procedures are consistently included and clearly specified in the Operations Surveillance Procedures.
Additional corrective actions are being taken in accordance with the station's corrective action program.
- 5.
Previous Occurrences
No previous similar events/conditions were identified.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
INRG F-ORM~ 366A (9-2007)