05000499/LER-2015-001, Regarding Technical Specification Action Statement Time Exceeded Due to Turbine-Driven Auxiliary Feedwater Pump Test Failure Not Recognized
| ML15133A323 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/05/2015 |
| From: | Gerry Powell South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-15003252 LER 15-001-00 | |
| Download: ML15133A323 (7) | |
| 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)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4992015001R00 - NRC Website | |
text
Nuclear Operating Company South Teas Prect Electric Generatl'n Station P.O Box 289 Wadsworth Tes 77483 May 5, 2015 NOC-AE-1 5003252 10 CFR 50.73 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Unit 2 Docket No. STN 50-499 Licensee Event Report 2015-001-00 Technical Specification Action Statement Time Exceeded Due to Turbine-Driven Auxiliary Feedwater Pump Test Failure Not Recognized Pursuant to 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(v)(B), STP Nuclear Operating Company (STPNOC) hereby submits the attached South Texas Project (STP) Unit 2 Licensee Event Report (LER) 2015-001-00. STPNOC is also reporting a condition that could have prevented the fulfillment of the safety function of systems to remove residual heat.
The event did not have an adverse effect on the health and safety of the public.
There are no commitments in this letter.
If there are any questions, please contact Drew Richards at (361) 972-7666 or me at (361) 972-7566.
G. T. Powell Site Vice President amr
Attachment:
Unit 2 LER 2015-001-00 STI: 34116054
NOC-AE-1 5003252 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, TX 76011-4511 Lisa M. Regner Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (08H04) 11555 Rockville Pike Rockville, MD 20852 NRC Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 MorQan, Lewis & Bockius LLP Steve Frantz, Esquire U.S. Nuclear Regulatory Commission Lisa M. Regner NRG South Texas LP John Ragan Chris O'Hara Jim von Suskil CPS Enerav Kevin Polio Cris Eugster L. D. Blaylock Crain Caton & James, P.C.
Peter Nemeth City of Austin Cheryl Mele John Wester Texas Dept. of State Health Services Richard A. Ratliff Robert Free
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 0113112017 (02-2014)
(02-2014)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE South Texas Unit 2 05000499 1 OF 5
- 4. TITLE Technical Specification Action Statement Time Exceeded Due to Turbine-Driven Auxiliary Feedwater Pump Test Failure Not Recognized
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YA SEUNIL REV MONTH DAY YERN/A N/A NUMBER NO.
FACILITY NAME DOCKET NUMBER 03 04 2015 2015 -
001
- - 00 05 05 2015 N/A N/A 9._OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[E 20.2201(b)
[1 20.2203(a)(3)(i)
LI 50.73(a)(2)(i)(C)
[]
50.73(a)(2)(vii)
M 1 20.2201(d)
[] 20.2203(a)(3)(ii)
El 50.73(a)(2)(jj)(A)
El 50.73(a)(2)(viii)(A)
Mode 1 El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
__ 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 El 20.2203(a)(2)(ii)
El 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)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[
50.73(a)(2)(v)(B)
El 73.71(a)(5) 100%
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER L_ j 20.2203(a)(2)(vi)
Z 50.73(a)(2)(i)(B)
E 50.73(a)(2)(v)(D)
Specfy in Abstract below or in
Description of reportable event
A. Reportable event classification
This event is reportable under §50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications and §50.73(a)(2)(v)(B) as an event that could have prevented the fulfillment of the safety function of systems that are needed to remove residual heat.
B. Plant operating conditions prior to event
On March 4, 2015 Unit 2 was operating in Mode 1 at 100% power.
C. Status of structures, systems, and components (SSCs) that were inoperable at the start of the event and that contributed to the event There were no SSCs that were inoperable at the start of the event that contributed to the event.
D. Narrative summary of the event
On March 4, 2015 at 1417 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.391685e-4 months <br />, a scheduled surveillance test was performed on the Unit 2 turbine-driven auxiliary feedwater (AFW) pump 24. AFW pump 24 was declared inoperable for the surveillance at 1507 hours0.0174 days <br />0.419 hours <br />0.00249 weeks <br />5.734135e-4 months <br />. During the test, the as-found pump discharge pressure was recorded by the STP Nuclear Operating Company (STPNOC) licensed Reactor Operator (RO) as 1430 pounds per square inch gauge (psig). The recorded pressure was below the surveillance acceptance criteria of greater than or equal to 1519 psig. The pump was declared operable again at 1608 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.11844e-4 months <br />. At 1646 hours0.0191 days <br />0.457 hours <br />0.00272 weeks <br />6.26303e-4 months <br />, the RO logged the surveillance as completed satisfactorily and forwarded the surveillance to the Unit Supervisor (US) for review. The US, who is a STPNOC licensed Senior Reactor Operator (SRO), performed his review prior to the end of shift at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> and indicated on the surveillance package cover sheet that the test data was within acceptance criteria.
On March 11, 2015 the Operations Surveillance Coordinator, who is a STPNOC licensed SRO, performed a subsequent review of the March 4, 2015 AFW pump 24 surveillance and discovered that the acceptance criteria for the as-found discharge pressure had not been met.
The Unit 2 Shift Manager was contacted and at 1631 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.205955e-4 months <br /> AFW pump 24 was declared inoperable. A follow-up surveillance was performed at 1957 hours0.0227 days <br />0.544 hours <br />0.00324 weeks <br />7.446385e-4 months <br /> and the as-found discharge pressure was 1747 psig. Although this value is within the acceptance criteria, it was higher than expected. A prompt operability determination (POD) concluded that even though the March 11, 2015 surveillance acceptance criteria was met, the results indicated a degrading trend and there was no reasonable assurance that the acceptance-criteria would be met during subsequent surveillance testing. The POD was accepted by the Unit 2 Shift Manager on March 12, 2015 resulting in AFW pump 24 being declared inoperable beginning on March 4, 2015 at 1417 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.391685e-4 months <br />.
The AFW pump 24 governor and servo actuator were replaced on March 12, 2015. Following a satisfactory surveillance test, AFW pump 24 was declared operable on March 14, 2015 at 0315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br />. The total duration of AFW pump 24 being inoperable was approximately 229 hours0.00265 days <br />0.0636 hours <br />3.786376e-4 weeks <br />8.71345e-5 months <br /> which exceeds the Technical Specification Allowed Outage Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />; additionally, the Configuration Risk Management Program was not applied. This condition is reportable under §50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
A review of equipment availability during the period of AFW pump 24 inoperability was conducted. On March 9, 2015 at 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />, one of the Unit 2 motor-driven auxiliary feedwater pumps (AFW pump 21) was declared inoperable for planned maintenance and was returned to operable status on March 9, 2015 at 1634 hours0.0189 days <br />0.454 hours <br />0.0027 weeks <br />6.21737e-4 months <br /> (duration of approximately 13.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />). Although plant Technical Specifications allow two auxiliary feedwater pumps to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, this period of inoperability occurred after AFW pump 24 had exceeded its Allowed Outage Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This condition is also reportable under
§50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
The STP Updated Final Safety Analysis Report (UFSAR) Chapter 15 analysis for the Condition II loss of normal feedwater event assumes that operator action is performed within fifteen minutes after a reactor trip to start a third AFW pump to deliver flow to a third steam generator. During the AFW pump 21 maintenance on March 9, 2015 the pump motor's breaker was racked out from 0348 hours0.00403 days <br />0.0967 hours <br />5.753968e-4 weeks <br />1.32414e-4 months <br /> until 1006 hours0.0116 days <br />0.279 hours <br />0.00166 weeks <br />3.82783e-4 months <br />. During this period of time, the two remaining operable AFW trains would not have been capable of mitigating a loss of normal feedwater flow event as analyzed in UFSAR Chapter 15. This condition is reportable pursuant to §50.73(a)(2)(v)(B) as a condition that could have prevented the fulfillment of the safety function of systems to remove residual heat.
Prior to being declared inoperable on March 4, 2015, AFW pump 24 was previously demonstrated operable via surveillance testing on February 5, 2015.
E. Method of discovery
The AFW pump 24 surveillance acceptance criteria not being met was discovered during a post-surveillance review by the Operations Surveillance Coordinator. The condition that could have prevented the fulfillment of the safety function of systems to remove residual heat was discovered during a review of equipment availability during the period of AFW pump 24 inoperability. Note that for this event, the discovery date is different than the event date because the inoperable component was discovered on March 11, 2015 a week after the surveillance test was performed. Therefore, the event date is March 4, 2015 and the discovery date is March 11, 2015.
I1. Component failures
A. Failure mode, mechanism, and effects of failed component
The AFW pump 24 failure mode was the inability to reliably maintain adequate pump discharge pressure. Degradation of the AFW pump 24 governor was the failure mechanism leading to the inoperable condition. The effect of the degraded component was inoperability of AFW Pump 24; no other dependent systems or components were rendered inoperable or degraded. During the period of inoperability, there were three redundant motor-driven AFW pumps operable and available except for a 13.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period on March 9, 2015 when only two
redundant motor-driven AFW pumps were operable and available. During these time periods, no event occurred that would have required an AFW actuation.
B. Cause of component failure
Preliminary investigation by an offsite vendor identified that the AFW pump 24 governor was degraded. A combination of as-found compensation needle valve position being too low and blemishes found on the pilot valve plunger likely contributed to the variability in governor speed response.
C. Systems or secondary functions that were affected by failure of components with multiple functions As stated in the narrative summary above, during the 13.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> that two AFW pumps were inoperable, the UFSAR described operator action to start a third AFW pump would not have been able to be performed following a loss of normal feedwater event.
D. Failed component information (Energy Industry Identification System (EIIS) designators provided in {brackets})
Auxiliary feedwater system {BA}
Turbine-drive auxiliary feedwater pump: {P}
Manufacturer: Suizer Bingham Pumps, Inc.
Model: 4X6X9C-MSD Turbine-driven auxiliary feedwater pump governor: {65}
Manufacturer: Woodward Governor Company Model: PGA Ill. Analysis of the event A. Safety system responses that occurred There were no safety systems that responded during this event.
B. Duration of safety system inoperability
AFW pump 24 was declared inoperable for 228 hours0.00264 days <br />0.0633 hours <br />3.769841e-4 weeks <br />8.6754e-5 months <br /> and 58 minutes.
C. Safety consequences and implications
AFW pump 24 was demonstrated operable per surveillance testing on February 5, 2015 and was declared inoperable on March 11, 2015. Since the AFW pump 24 failure could have occurred at any time between February 5, 2015 and March 4, 2015, the actual failure duration cannot be conclusively determined. The STP Probabilistic Risk Assessment (PRA) was used to estimate the Incremental Core Damage Probability (ICDP) and Incremental Large Early Release Probability (ILERP) associated with this AFW pump 24 condition. The ICDP and ILERP were determined to be less than 1 E-06 and 1 E-07 respectively, indicating a very small increase in safety risk.
An actual demand for AFW did not occur during the period of inoperability; therefore, there was no adverse effect on the health and safety of the public.
IV. Cause of the event
On March 4, 2015, AFW pump 24 was not recognized as inoperable due to human error. The two Control Room operators involved used ineffective verification practices of surveillance acceptance criteria. There were no other extenuating circumstances (e.g., time or situational pressures) surrounding the failure to recognize that the acceptance criteria was not met.
V. Corrective actions
The RO and SRO involved in the event were coached and counseled and remediated by Operations Management. A lessons learned bulletin was issued to all operations crew for dissemination and review.
After AFW pump 24 was declared inoperable, corrective maintenance was performed to replace the turbine governor and servo actuator. Post-maintenance surveillance testing restored AFW pump 24 to operable status.
VI. Previous similar events
There are no previous STP LERs with a cause similar to failing to recognize that surveillance acceptance criteria were not met.