05000327/LER-2011-002, Regarding Feedwater Regulator Valve Inoperable
| ML11117A270 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/22/2011 |
| From: | Skaggs M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-002-00 | |
| Download: ML11117A270 (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)(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 |
| 3272011002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Soddy Daisy, Tennessee 37384-2000 April 22, 2011
.10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Unit 1 Facility Operating License No. DPR-77 NRC Docket Nos. 50-327
Subject:
License Event Report 327/2011-002, "Feedwater Regulator Valve Inoperable" The enclosed licensee event report provides details concerning the failure of the loop 3 feedwater regulator valve and exceeding the technical specifications allowed outage time for correction of the issue. This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B), as any operation or condition that was prohibited by technical specifications.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact G. M. Cook, Sequoyah Site Licensing Manager, at (423) 843-7170.
Respectfully, Michael D Skaggs Site Vice President Sequoyah Nuclear Plant
Enclosure:
Licensee Event Report - Feedwater Regulator Valve Inoperable cc:
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant
U.S. Nuclear Regulatory Commission Page 2 April 22, 2011 GMC:JWP:SKD Enclosure bcc (Enclosure):
NRC Project Manager - Sequoyah Nuclear Plant Institute of Nuclear Power Operations G. Arent P. M. Billingsley S. M. Connors G. M. Cook R. M. Cook D. A. Day R. E. Detwiler G. D. Franceschi D. E. Jernigan R. M. Krich K. Langdon C. P. Dieckmann Jr.
NSRB Support P. D. Swafford E. J. Vigluicci C. T. Ware J. D. Williams WBN Site Licensing Files EDMS I:license/lers/201 1/LER 1-2011-002.doc
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/20 (10-2010)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the digis/carater foreac blck)information collection.
- 3. PAGE Sequoyah Nuclear Plant Unit 1 05000327 1 OF5
- 4. TITLE:
Feedwater Regulator Valve Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKETNUMBER NUMBER NO.
FACILITY NAME DOCKET NUMBER 02 15 2010 2011 -
002 00 04 22 2011
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1
[
20.2201(b)
Z 20.2203(a)(3)(i)
E 50.73(a)(2)(i)(C)
[
50.73(a)(2)(vii)
Z 20.2201(d)
[
20.2203(a)(3)(ii)
[
50.73(a)(2)(ii)(A)
Z 50.73(a)(2)(viii)(A)
[] 20.2203(a)(1)
El 20.2203(a)(4)
[-I 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i)
Ej 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iii)
[1 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL L1 20.2203(a)(2)(ii)
LI 50.36(c)(1)(ii)(A)
L] 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x) 100 El 20.2203(a)(2)(iii)
Z 50.36(c)(2)
El 50.73(a)(2)(v)(A)
LI 73.71(a)(4)
Ej 20.2203(a)(2)(iv)
[
50.46(a)(3)(ii)
[1 50.73(a)(2)(v)(B)
LI 73.71(a)(5)
Li 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
EL 50.73(a)(2)(v)(C)
LI OTHER S20.2203(a)(2)(vi)
[50.73(a)(2)(i)(B)
[1 50.73(a)(2)(v)(D)
Specify in Abstract below or in Date
Description
November 15, 2010 After placing a main feedwater pump in service, SG at 2218 EST Number 3 level increased with the MFRV and MFRV bypass valves closed. Leak identification indicated that the Loop 3 MFRV was leaking. TS Limiting Condition for Operation (LCO) 3.7.1.6. Action b was entered.
November 16, 2010 The Loop 3 MFRV was isolated to comply with TS at 0233 EST LCO 3.7.1.6. Action b.
November 16, 2010 TS LCO 3.0.6 was entered for opening the isolation valve at 1915 EST to Loop 3 for verification of the associated MFRV operability.
November 16, 2010 The Loop 3 MFRV was declared operable and TS at 2049 EST LCOs 3.0.6 and LCO 3.7.1.6. were exited February 21, 2011 The cause evaluation concluded the maintenance activity performed during the Unit 1 Cycle 17 outage resulted in the inoperability of the MFRV.
D.
Other Systems or Secondary Functions Affected
No other systems or secondary functions were affected by this event.
E.
Method of Discovery
Control room personnel identified an uncontrolled increase in steam generator Number 3 level from main control room indicators.
F.
Operator Actions
The operators identified an uncontrolled rise in SG Number 3 resulting from a leaking MFRV. The Operators entered TS LCO 3.7.1.6 Action b. and manually isolated the Loop 3 MFRV. There was no abnormal increase in SG Number 3 identified with the Loop 3 MFRV isolated.
G.
Safety System Responses:
No safety systems were actuated during this event.
Ill. CAUSE OF THE EVENT A.
Immediate Cause:
The immediate cause of the Loop 3 MFRV leaking was an anti-rotation device on the valve stem was not properly secured.
B.
Root Cause:
The root cause was identified as an inadequate preventative maintenance procedure. The preventative maintenance procedure did not verify that there was no stem rotation during reassembly of the valve following maintenance on the valve.
Additionally, the post maintenance test was not sufficient to identify the capability of the valve to perform its isolation function.
IV.
ANALYSIS OF THE EVENT
The condition of the Loop 3 MFRV not being capable of performing its isolation function and exceeding LCO 3.7.1.6 Action b allowed outage time is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by TS.
Isolation of the main feedwater (MFW) system is provided when required to mitigate the consequences of a steam line break, feedwater line break, excessive feedwater flow, and loss of normal feedwater (and station blackout) accident. Redundant isolation capability is provided on each feedwater line consisting of the feedwater isolation valve (MFIV) and the MFRV and its associated bypass valve. The safety function of these valves is fulfilled when the valve is closed or isolated by a closed manual isolation valve.
Therefore, the feedwater isolation function would have been performed by the operable redundant feedwater isolation valve. Additionally, the main feedwater pump would trip on a feedwater isolation signal, thereby effectively isolating feedwater flow from the condensate system.
V.
ASSESSMENT OF SAFETY CONSEQUENCES
Based on the above "Analysis of The Event," this event did not adversely affect the health and safety of plant personnel or the general public.
VI.
CORRECTIVE ACTIONS
A.
Immediate Corrective Actions
The immediate corrective action was to identify and isolated the leaking valve. The valve was repaired and returned to operable status.
B.
Corrective Actions to Prevent Recurrence:
Corrective actions will be implemented to revise the preventative maintenance procedure on the MFRV and bypass MFRV to verify stem connector/anti-rotation device is secure and visually verify there is no rotation of the actuator or valve stem during valve reassembly following maintenance activities. Additionally, the post maintenance test is to be revised to ensure the capability of the valve to perform its isolation function.
VII.
ADDITIONAL INFORMATION
A.
Failed Components:
The failed component was a Fisher, Model Number 667ENA flow control valve.
B. Previous LERs on Similar Events:
A review of previous reportable events for the past three years identified one previous similar event associated with failure of a MFRV. LER 50-327/2009-005-00 dated July 6, 2009 was associated with a failure of a MFRV. The failure of the MFRV was the result of a diaphragm failure. The diaphragm failure was attributed to an improper clamping force of the diaphragm to the actuator stem. The insufficient clamping force allowed stress concentrations at the diaphragm hole, which caused a tear and failure of the diaphragm.
The root cause of the MFRV failure was determined to be that the governing vendor manual control procedure did not require checking for updates to non-safety related vendor manuals. The corrective actions could not have prevented this event.
C.
Additional Information
None.
D.
Safety System Functional Failure:
This event did not result in a safety system functional failure in accordance with 10 CFR 50.73(a)(2)(v).
E.
Unplanned Scram with Complications:
This event did not result in an unplanned scram with complications.
VIII.
COMMITMENTS
None.