05000247/LER-2012-005, For Indian Point Unit 2, Regarding Technical Specification Prohibited Condition Caused by a Main Steam Safety Valve Outside Its As-Found Lift Setpoint Test Acceptance Criteria Due to Spring Skew/Spindle Wear
| ML12165A247 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 05/24/2012 |
| From: | Ventosa J Entergy Corp, Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-12-073 LER 12-005-00 | |
| Download: ML12165A247 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2472012005R00 - NRC Website | |
text
.Entergy Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, N.Y. 10511-0249 Tel (914) 254-6700 John A. Ventosa Site Vice President NL-12-073 May 24, 2012 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555-0001
SUBJECT:
Licensee Event Report # 2012-005-00, "Technical Specification Prohibited Condition Caused by a Main Steam Safety Valve Outside Its As-Found Lift Setpoint Test Acceptance Criteria Due to Spring Skew/Spindle Wear" Indian Point Unit No. 2 Docket No. 50-247 DPR-26
Dear Sir or Madam:
Pursuant to 10 CFR 50.73(a)(1), Entergy Nuclear Operations Inc. (ENO) hereby provides Licensee Event Report (LER) 2012-005-00. The attached LER identifies an event where there was a Technical Specification prohibited condition for an inoperable Main Steam Safety Valve, which is reportable under 10 CFR 50.73(a)(2)(i)(B). This condition was recorded in the Entergy Corrective Action Program as Condition Report CR-IP2-2012-0131 1.
There are no new commitments identified in this letter. Should you have any questions regarding this submittal, please contact Mr. Robert Walpole, Manager, Licensing at (914) 254-6710.
Sincerely, JAV/cbr 774 j-,
/ re* ja.,
cc:
Mr. William Dean, Regional Administrator, NRC Region I NRC Resident Inspector's Office, Indian Point 2 Mrs. Bridget Frymire, New York State Public Service Commission LEREvents@INPO.org
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Abstract
On March 2, 2012, during the performance of surveillance procedure 3-PT-RO06A, main steam safety valve (MSSV)
MS-46D failed its As-Found lift set point pressure test.
In accordance with the test, these valves must lift at +/-
3% of their required setting.
Valve MS-46D lifted at 1136.9 psig, 24.9 psig outside its acceptance range of 1048 to 1112 psig.
The other 9 MSSVs tested passed their As-Found test criteria.
Technical Specification (TS) 3.7.1,"Main Steam Safety Valves," requires the MSSVs to be operable in accordance with TS Table 3.7.1-1 and Table 3.7.1-2.
TS Surveillance Requirement (SR) 3.7.1.1 requires each MSSV be verified to lift per Table 3.7.1-2 in accordance with the Inservice Testing Program.
Operability of the MSSVs includes the ability to open within the setpoint tolerances.
As valve MS-46D was found outside its limit it failed As-Found testing and was declared inoperable.
Valve MS-46D was adjusted and returned to operable.
Subsequent disassembly and evaluation identified the cause.
The direct cause of MSSV MS-46D failing its pressure test was lifting outside its acceptable range (greater than 3% of its nominal set point).
The apparent cause was internal friction caused by spring skew and spindle wear.
Corrective actions included valve disassembly/inspection and repair, valve adjustment to the operability set-pressure band, and re-testing.
A modification approved in 2011 will install bronze wear sleeves along the inner diameter of the spindle contact points (adjusting bolt inner diameter, upper and lower spring washer inner diameter).
The event had no-effect on public health and safety.
(if more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
An apparent cause evaluation per CR-IP2-2012-01311 concluded the condition resulted in inoperability of the valve.
An evaluation of the accident analysis was performed to determine the impact of one MSSV with a higher opening set point.
The analysis concluded the condition would not result in loss of safety function.
Therefore, this condition is not reportable under 10CFR50.73(a) (2) (v) as a safety system functional failure.
Past Similar Events A review was performed of Licensee Event Reports (LERs) for the past three years for any events reporting TS prohibited conditions due to multiple test valve failures.
LER-2010-002 reported two MSSV's failures, one of which was due to valve spring skew and the other was set point drift.
The inner diameter of both valves' guide bearings were increased to reduce the potential for spring skew.
The work history of the valve reported in LER-2010-002 was determined to have had its guide bearing inner diameters increased to the vendor recommended maximum.
A corrective action (CAs) for one valve (MS-48C) reported in LER-2010-002 was to polish out a mark on the spindle where it had been coming in contact with the guide bearing.
The valve spindle was not replaced.
After reviewing the collective issues from the past events, the frequency of the PM for the MSSVs was increased from 8 to 6 years.
This event was not prevented by the change in PM frequency as the PM frequency change implementation was still outstanding for this valve.
Safety Significance
This event had no effect on the health and safety of the public. There were no actual safety consequences for the event because there were no accidents or transients requiring the MSSVs.
There was no significant potential safety impact of the condition under reasonable and credible alternate conditions.
Had an accident or transient occurred during the condition of the out of tolerance MSSV, the condition would not have significantly affected accident mitigation capability and the MSSVs overpressure function would have been adequate.
The design basis of the MSSVs is to limit the secondary system pressure to 110% of design pressure when passing 100% of design steam flow.
The combined MSSVs are sufficient to relieve 108% of design steam flow.
Each MS line has an ADV capable of releasing steam to the atmosphere.
The ADVs have the capability to relieve approximately 10% of total steam.
The combined pressure relief capability of the MSSVs and ADVs is approximately 118% of rated steam flow and adequate pressure relief was available with 19 of 20 MSSVs and 4 ADVs as a result of 1 of the 20 MSSVs being out of tolerance.
The limiting UFSAR Chapter 14 transients which do not credit the ADVs and which are impacted by the higher MSSV set point, were evaluated and it was concluded that the acceptance criteria for the transients would have been met with the one out of tolerance MSSV.
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