05000423/LER-2014-003, Regarding Turbine Driven Auxiliary Feedwater Pump Operability Impacted by Incorrect Bearing
| ML14189A071 | |
| Person / Time | |
|---|---|
| Site: | Millstone  (NPF-049) |
| Issue date: | 06/30/2014 |
| From: | Scace S Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 14-330 LER 14-003-00 | |
| Download: ML14189A071 (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 |
| 4232014003R00 - NRC Website | |
text
'jýDominioiif Dominion Nuclear Connecticut, Inc.
Rope Ferry Rd., Waterford, CT 06385 Mailing Address: P.O. Box 128 Waterford, CT 06385 dom.com JUN 3 0 2014 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
MPS Lic/GJC Docket No.
License No.14-330 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2014-003-00 TURBINE DRIVEN AUXILIARY FEEDWATER PUMP OPERABILITY IMPACTED BY INCORRECT BEARING This letter forwards Licensee Event Report (LER) 2014-003-00 documenting a condition at Millstone Power Station Unit 3 on May 1, 2014. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B).
If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.
Sincerely, Stephen E. Scace U
Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None (1*
Serial No.14-330 Docket No. 50-423 Licensee Event Report 2014-003-00 Page 2 of 2 cc:
U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 M. C. Thadani NRC Project Manager Millstone Units 2 and 3 U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 B-1 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No.14-330 Docket No. 50-423 Licensee Event Report 2014-003-00 ATTACHMENT LICENSEE EVENT REPORT 2014-003-00 TURBINE DRIVEN AUXILIARY FEEDWATER PUMP OPERABILITY IMPACTED BY INCORRECT BEARING MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/3112017 (02-2014)
(02"2014 Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections SLICENSEE EVENT REPORT (LER)
Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC sfor each block) 20503. If a means used to impose an information collection does not display a currently valid OMB digits/characters fcontrol number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Millstone Power Station Unit 3 05000423 1 OF 3
- 4. TITLE Turbine Driven Auxiliary Feedwater Pump Operability Impacted by Incorrect Bearing
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONT DA Y YEA YEA SEQUENTIAL REVI MOTI A ER FCLTYNMOKTNME YER NUMBER NO.
MOT A
ER05000 FACILITY NAME DOCKET NUMBER 05 01 2014 2014 -
003 00 06 30 2014 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[E 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
El 20.2201(d)
El 20.2203(a)(3)(ii)
[]
50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
[-
50.73(a)(2)(ii)(B)
E-50.73(a)(2)(viii)(B)
_-E 20.2203(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 [E
20.2203(a)(2)(ii)
[E 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
E] 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 1E 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in
______________________________________________________________________________N_____FoNRCForm66A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (include Area Code)
William D. Bartron, Supervisor Nuclear Station Licensing 1 (860) 444-4301sYSTEM ICOMPONEN MANU-REPORTABLE MANU-REPORTABLE C
FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED 15.DEXPECTED MONTH DAY YEAR SUBMISSION
[]YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
[]NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On May 1, 2014 with Millstone Power Station Unit 3 in operating mode 1 and 100% reactor power, an evaluation determined the installation of an incorrect vendor supplied bearing introduced a non-conforming condition, which over time and under certain variable conditions, resulted in excessive friction affecting the ability of the turbine driven auxiliary feedwater (TDAFW) pump to operate properly and could render it inoperable. Plant Technical Specification 3.7.1.2 Action c, requires, if one auxiliary feedwater pump is inoperable in operating modes 1, 2, and 3, the pump must be returned to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or the plant be placed in at least hot standby within six hours and in hot shutdown within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
An investigation determined the installation of an incorrect bearing in the TDAFW pump steam supply valve control linkage during refueling outage 3R15 (spring of 2013) caused a discrepant condition rendering the TDAFW pump inoperable for periods of time exceeding the limiting conditions for operations action statement for TS 3.7.1.2. The bearing manufacturer issued a 10 CFR 21 report on this issue. (ADAMS accession # ML14079A353).
The incorrect bearing was replaced, the governor and associated linkage were groomed/adjusted, and the TDAFW pump was tested satisfactorily. Additional corrective actions are being taken in accordance with the station's corrective action program.
This condition is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plant's TS.
NRC FORM 366 (02-2014)
1. EVENT DESCRIPTION
On May 1, 2014 with Millstone Power Station Unit 3 (MPS3) in operating mode 1 and 100% reactor power, an evaluation determined the installation of an incorrect vendor supplied bearing introduced a non-conforming condition, which over time and under certain variable conditions, resulted in excessive friction affecting the ability of the turbine driven auxiliary feedwater (TDAFW) pump to operate properly. The root cause evaluation (RCE) noted that the frictional conditions were highly variable and time dependent. Factors such as environmental conditions, wear, corrosion, actual starting position, time between start, and other factors could result in different responses. There were numerous successful tests between 3R1 5 and the TDAFW pump trips in which the installation of the incorrect bearing did not result in an inoperable TDAFW pump. The installation of the incorrect bearing created an intermittent condition (i.e., pump trip events on November 4, 2013, December 18, 2013, and January 23, 2014).
NUREG 1022 Rev. 3 "Event Report Guidelines 10 CFR 50.72 and 50.73" provides guidance on assessing reportability. The NUREG introduces the concept of "firm evidence" in terms of assessing
reportability
It states in part "...it should be assumed that the discrepancy occurred at the time of discovery unless there is firm evidence, based on a review of relevant information such as the equipment history and the cause of the failure, to indicate that the discrepancy existed previously".
For the purposes of reportability, the installation of the incorrect bearing during refueling outage 3R1 5 (spring of 2013) is firm evidence that a discrepant condition existed for periods of time exceeding the limiting conditions for operations (LCO) actions for Technical Specifications (TS) 3.7.1.2.
Plant TS 3.7.1.2 Action c, requires, if one auxiliary feedwater pump is inoperable in operating modes 1, 2, and 3, the pump must be returned to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or the plant must be placed in at least hot standby within six hours and in hot shutdown within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
For the pump trip events, the requirements of TS action statements (TSAS) were met with the exception of January 23, 2014 trip, for which the NRC granted enforcement discretion on January 26, 2014. This was reported in LER MPS3 2014-001-00.
Installation of the incorrect bearing was a non-conforming condition that introduced a degradation mechanism, which over time and under certain conditions could render the TDAFW pump inoperable (i.e., an intermittent failure). This does not alter the conclusion that this condition is reportable, but is considered in the assessment of safety consequences.
This condition is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plant's TS.
2. CAUSE
The RCE determined the direct cause of the TDAFW pump over speed trips was the installation of an incorrect bearing in the turbine control valve linkage. The cause for the incorrect bearing being installed was that the vendor shipped the incorrect bearing with a certificate of conformance and with the same part number as the correct bearing. The bearing manufacturer issued a 10 CFR 21 report on this issue. (ADAMS accession # ML14079A353). This non-conforming bearing caused binding of the TDAFW pump steam supply control valve linkage, due to friction between the bearing and the cam plate.
3. ASSESSMENT OF SAFETY CONSEQUENCES
The direct cause that led to the MPS3 TDAFW pump over speed trip events resulted in a reduction in nuclear safety defense in depth. The auxiliary feedwater system (AFW) consists of three pumps, the TDAFW pump and two motor-driven AFW pumps, which are designed to remove decay heat from the steam generators following a reactor trip. Failure of the TDAFW pump results in loss of one of the redundant sources. The TDAFW pump contributes 1.5% to the total core damage frequency and 7.1%
to the total large early release frequency.
As stated above, the direct cause of the TDAFW pump over speed trips was the installation of the incorrect bearing. The degraded bearing caused binding of the TDAFW pump steam supply control valve linkage due to friction between the bearing and the cam plate. This friction is most impactful nearest the linkage full open position on a pump automatic start. When steam was admitted to the control valve, the steam pressure placed forces on the control valve stem, increasing the friction at the bearing/cam plate interface. Sometimes this friction was sufficient to overcome the output force of the governor, which prevented the control valve from closing, resulting in an over speed trip. When the trip/throttle valve closed on over speed trip, the force on the control valve stem, and the friction at the bearing/cam plate interface, was removed, and the control valve shut which supports the ability to restart the TDAFW pump.
After the November 4, 2013 over speed trip, the TDAFW pump was started and successfully run by manually opening the trip/throttle valve, as required for a maintenance run. No work was performed between the trip and the maintenance run. After the December 18, 2013 over speed trip, the TDAFW pump was started and successfully run from a TS surveillance automatic start signal. No work was performed, except for isolating the 'D' steam supply line. Emergency Operating Procedures (EOPS) provide guidance on starting a tripped TDAFW pump by manually throttling open the steam supply valve. Therefore, it is expected that, if the TDAFW pump had tripped on a demand start on either November 4, 2013 or December 18, 2013, the operators would have successfully restarted the TDAFW pump based on the guidance in the existing EOPs.
After the January 23, 2014 trip, the control valve shut and then, as the TDAFW pump coasted down, the governor opened the control valve, as designed. If the TDAFW pump was then started in manual, the steam supply valve would control steam pressure to the control valve. The initial force on the control valve stem would be less, reducing the resistance at the bearing/cam plate interface and allowing the governor to take control as the speed increased. Therefore, it is expected that, if the TDAFW pump had tripped on a demand start, the operators would have successfully restarted the pump based on the existing guidance in the EOPs.
4. CORRECTIVE ACTION
The incorrect bearing was replaced, the governor and associated linkage was groomed/adjusted and the TDAFW pump was tested satisfactorily. Additional corrective actions are being taken in accordance with the station's corrective action program.
5. PREVIOUS OCCURRENCES
None
- 6. Energy Industry Identification System (EIIS) codes
" Auxiliary feedwater system - BA
" Turbine - TRB
- Pump-P
- Valve - V