05000255/LER-2011-004-01, For Palisades, Regarding Turbine-Driven Auxiliary Feedwater Pump Inoperable in Excess of Technical Specification Requirements Due to Unexpected Trip
| ML12031A237 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 01/31/2012 |
| From: | Vitale A Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PNP 2012-001 LER 11-004-01 | |
| Download: ML12031A237 (6) | |
| 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)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(viii) 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), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 2552011004R01 - NRC Website | |
text
- =:=-Enlergy PNP 2012-001 January 31, 2012 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.
Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel 269 764 2000 Anthony J. Vitale Site Vice President
SUBJECT:
Licensee Event Report 2011-004-01, Turbine-Driven Auxiliary Feedwater Pump Inoperable in Excess of Technical Specification Requirements Due to Unexpected Trip
REFERENCES:
Dear Sir or Madam:
Palisades Nuclear Plant Docket 50-255 License No. DPR-20 10 CFR 50.73 Supplemental Licensee Event Report (LER) 2011-004-01 is enclosed. The event was originally reported on July 8, 2011. At that time, additional causal evaluations were ongoing. The enclosed supplemental LER includes the results of the additional evaluations and subsequent corrective actions.
Summary of Commitments This letter contains no new commitments. This letter completes a commitment to provide a supplemental LER as described in the LER submittal of July 8, 2011, and the commitment revision letter submitted December 9, 2011.
The completed commitment is as follows:
ENO will provide a supplement to LER 2011-004 containing the results of the additional causal evaluation and potential new corrective actions by January 31, 2012.
Document Control Desk PNP 2012-001 Page 2 Sincerely, Attachment: Licensee Event Report 2011-004-01 CC Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC
NRC FORM 366 APPROVED BY OMB NO. 3150-0104 EXPIRES 10/31/2013 U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 13. PAG~
PALISADES NUCLEAR PLANT 05000255 of 4
- 4. TITLE:
Turbine-Driven Auxiliary Feedwater Pump Inoperable in Excess of Technical Specification Requirements Due to Unexpected Trip
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05 10 2011 2011 -
004 -
01 01 31 2012
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 0 20.2201 (b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) 1 0
20.2201 (d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) 0 20.2203(a)(1 )
0 20.2203(a)(4) 0 50.73(a)(2)(ii)(S) 0 50.73(a)(2)(viii)(S) 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)
- 10. POWER LEVEL 0
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) 0 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71 (a)(4) 99 0
20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(S) 0 73.71 (a)(5) 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER 0
20.2203(a)(2)(vi)
[8J 50.73(a)(2)(i)(S) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME I
TELEPHONE NUMBER (Include Area Code)
Terry Davis (269) 764-2117 CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX D
BA TRB E220 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED I MONTH I DAY YEAR SUBMISSION I
I 0
YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
[8J NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines On May 10, 2011, during routine auxiliary feedwater (AFW) pump Technical Specification (TS) testing, the turbine-driven AFW pump, P-SB, tripped due to the unexpected actuation of the mechanical overspeed trip linkage. Examinations revealed that the knife-edge of the trip resetting lever had disengaged from the hand I
trip lever latch area allowing the trip valve assembly to isolate steam flow to the turbine-driver.
The initial causal evaluation determined supplemental contract employees had inappropriately applied grease to knife-edge area on the mechanical overspeed trip linkage during maintenance activities performed in the October 2010 refueling outage. Therefore, P-SB and its corresponding AFW train were considered inoperable for a period of time longer than the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed by TS 3.7.5.A.
Based on the information available at that time, greasing of the knife-edge area on the mechanical overspeed trip linkage was considered to be the sole cause of the P-SB trip. Subsequent discussions with the turbine vendor revealed other possible causes for the trip. In addition, an independent analysis determined that the greasing alone, would not account for the overspeed trip of the pump turbine. As a result, additional investigations were completed. The outcome of the investigations did not identify any single physical cause for the pump trip. However, several other potential causes were identified. All the identified potential causes for the overspeed trip were addressed to ensure overspeed trip reliability.
Planned corrective actions include a revision to the applicable maintenance procedure to incorporate vendor recommendations, process enhancements in the identification of critical maintenance activities and ensuring appropriate oversight of supplemental workers performing critical maintenance activities.
NRC FORM 366 (10-2010) (10*2010)
- 1. FACILITY NAME PALISADES NUCLEAR PLANT
PLANT CONDITIONS
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKET
- 6. LER NUMBER SEQUENTIAL REVISION YEAR NUMBER NUMBER 05000255 2011 004 01
- 3. PAGE 2
OF 4
On May 10, 2011, at the time the turbine-driven auxiliary feedwater (AFW) pump (P-8B) tripped, the plant was operating at approximately 99% power.
EVENT DESCRIPTION
The Palisades AFW system [BA] supplies water to the secondary side of the steam generators for reactor decay heat removal when normal feedwater sources are unavailable. The system consists of two electric motor-driven pumps, P-8A and P-8C, and one turbine-driven [TRB] pump [P], P-8B. Anyone of the three pumps can supply 100% of the required feedwater flow to both steam generators.
Between October 6 and 22, 2010, during the 1 R21 refueling outage, several maintenance activities were performed on the turbine-driver, and the associated mechanical overspeed trip linkage, on P-8B. On October 28,2010, P-8B was returned to operable status following satisfactory completion of Technical Specifications (TS) surveillance test, RO-145, "Comprehensive Pump Test." The pump was required to be operable when the reactor was made critical on October 29, 2010, following the 1 R21 refueling outage.
I P-8B operated satisfactorily again on February 15, 2011, for the required periodic TS surveillance test, 00-21, "Inservice Test."
On May 1 0, 2011, during TS surveillance test, RO-97, "AFW Automatic Initiation Test," P-8B, tripped due to the unexpected actuation of the mechanical overspeed trip linkage allowing the trip valve assembly to isolate steam flow to the turbine-driver. An examination revealed that the knife-edge of the trip resetting lever had disengaged from the hand trip lever latch area allowing the trip valve assembly to isolate steam flow to the turbine-driver.
A past operability evaluation identified there was one instance between October 29, 2010, and May 10, 2011, when the contact point between the hand trip lever and the resetting lever was disturbed. On February 14, 2011, in accordance with TS surveillance test, 00-21, the resetting lever was manually lowered then raised, causing the trip valve assembly to travel from the open to closed to open position (see figure below). This manipulation is performed to verify freedom of movement of the trip valve assembly. A 00-21 post-test check was performed that ensured proper alignment, i.e., no gap, between the resetting lever and the hand trip lever. No physical manipulations are performed as a part of this post-test alignment check. The alignment check was also performed on May 10, 2011, prior to pump operation for TS I
surveillance test, RO-97. No discrepancies were identified. u.s. NUCLEAR REGULATORY COMMISSION (10*201 0)
- 1. FACILITY NAME PALISADES NUCLEAR PLANT
CAUSE OF THE EVENT
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKET YEAR 05000255 2011
- 6. LER NUMBER I
SEQUENTIAL I REVISION NUMBER NUMBER 004
- - 01
- 3. PAGE 3 OF 4 The initial causal evaluation determined supplemental contract employees had inappropriately applied grease to knife-edge area on the mechanical overspeed trip linkage during maintenance activities performed in the October 2010 refueling outage. Based on the information available at that time, the greasing of the knife-edge on the mechanical overspeed trip linkage was considered to be the sole cause of the P-8B trip.
Subsequent discussions with the turbine vendor revealed other possible causes for the trip could have existed. Greasing of the knife-edge area may not have been the only cause. To address the actual impact of the greased knife-edge condition, Entergy Nuclear Operations, Inc. (ENO) contracted an independent engineering firm to perform a force analysis on the overspeed trip mechanism components.
The preliminary force analysis results showed that the greasing of the knife-edge area on the mechanical overspeed trip linkage alone would not have caused the trip.
Based on this information, it was determined that a P-8B maintenance outage was needed to investigate other possible causes, identified by the turbine vendor, by gathering supporting/refuting evidence for a failure mode analysis (FMA) and to obtain field data critical for completion of a formal force analysis.
P-8B was removed from service on October 25, 2011 for inspection. Data collected during the maintenance outage was used to complete the FMA and formal force analysis. The FMA was used as input for a root cause evaluation.
The root cause evaluation did not identify any single physical cause for the pump trip. Several potential physical causes were identified. The evaluation concluded that preparation for, and execution of, the P-8B turbine overhaul during October 2010 refueling outage did not maintain the turbine and turbine governor in a manner that ensured overspeed trip reliability.
The conclusion of the independent engineering firm's formal force analysis remained the same. Greasing of the knife-edge area on the mechanical overspeed trip linkage alone, could not have caused the overspeed trip.
CORRECTIVE ACTIONS TAKEN On May 11, 2011, the grease was removed from the mechanical overspeed trip linkage, the mechanical overspeed trip linkage was reset, and TS surveillance test, RO-97, was completed satisfactorily. On May 12,2011, after satisfactory completion of TS surveillance test, 00-21, P-88 was returned to operable status. During the October 2011 maintenance outage, all the identified potential physical causes for the I overspeed trip were addressed to ensure overspeed trip reliability.
CORRECTIVE ACTIONS TO BE TAKEN Planned corrective actions include a revision to the applicable maintenance procedure to incorporate vendor recommendations, process enhancements in the identification of critical maintenance activities and ensuring appropriate oversight of supplemental workers performing critical maintenance activities. (10-201 0)
- 1. FACILITY NAME PALISADES NUCLEAR PLANT u.s. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKET
- 6. LER NUMBER I
SEQUENTIAL I REVISION YEAR NUMBER NUMBER 05000255 2011 004
- - 01
- 3. PAGE 4 OF 4
ASSESSMENT OF SAFETY CONSEQUENCES
The event is considered to be of low safety significance based on the availability of AFW from at least one alternate AFW pump. AFW flow remained available via operable AFW pumps P-8A and P-8C, except for two brief periods << one hour each); once on April 28, 2011, when P-8C was inoperable due to being in manual control for testing and once on May 10, 2011, when P-8A was inoperable due to being in manual control for testing. In either of those instances, if needed, operators would have been directed by procedure to recover steam generator level, and could have readily started P-8A or P-8C from the control room. In addition, the ability to manually reset the mechanical overspeed trip linkage on P-8B is proceduralized and considered a simple task that can be executed in a relatively short period of time.
PREVIOUS SIMILAR EVENTS
None