05000247/LER-2010-002, For Indian Point 2, Regarding Technical Specification Prohibited Condition Caused by Two Main Steam Safety Valves Outside As-Found Lift Setpoint Test Acceptance Criteria
| ML101310228 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 04/30/2010 |
| From: | Joseph E Pollock Entergy Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-10-035 LER 10-002-00 | |
| Download: ML101310228 (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 |
| 2472010002R00 - NRC Website | |
text
-Entergy Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, N.Y. 10511-0249 Tel (914) 734-6700 J. E. Pollock Site Vice President NL-10-035 April 30, 2010 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555-0001
SUBJECT:
Licensee Event Report # 2010-002-00, "Technical Specification Prohibited Condition Caused by Two Main Steam Safety Valves Outside As-Found Lift Setpoint Test Acceptance Criteria" 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) 2010-002-00. The attached LER identifies an event where there was a Technical Specification prohibited condition for two inoperable Main Steam Safety Valves, 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-IP2-2010-01181.
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) 734-6710.
Sincerely, JEP/cbr cc:
Mr. Samuel J Collins, Regional Administrator, NRC Region I NRC Resident Inspector's Office, Indian Point 3 Mr. Paul Eddy, New York State Public Service Commission LEREvents@lNPO.org
Abstract
On March 9, 2010, during surveillance testing, main steam safety valves (MSSV)
MS-45C and MS-48C failed their As-Found lift set point test.
Per the test, these valves must lift at +/-
3% of their required setting.
Valve MS-45C lifted at 1108.6 psig, 12.6 psig outside its acceptance range of 1034 to 1096 psig.
Valve MS-48C lifted at 1147.4 psig, 4.4 psig outside its acceptance range of 1077 to 1143 psig.
All other MSSVs tested passed their test criteria and left within +/-
1% per test procedure.
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 In-service Testing Program.
Operability of the MSSVs is defined as the ability to open within the set point tolerances.
As these two valves were found outside their limit they were inoperable.
The most likely cause of MS-45C outside its acceptance range was set point drift.
The most likely cause of MS-48C outside its acceptance range was valve spring skew.
The valves are subject to material property changes due to temperature, pressure and vibration which can affect set point accuracy and repeatability.
Valve spring skew causes the spindle and internals to not remain perpendicular to the centerline of the valve producing frictional forces affecting the set point.
Corrective actions included performing maintenance on both valves, adjusting as required, re-testing and left within the +/-
1% As-Left set point criteria.
The MSSV maintenance procedure will be revised to provide more specific guidance on increasing valve guide bearing 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)
This condition does not meet the reporting criteria of 10CFR50.73(a) (2) (v) (The licensee shall report any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: A)
Shutdown the reactor and maintain it in a safe condition, B) remove residual heat, C) control the release of radioactive material, or D) Mitigate the consequences of an accident).
An evaluation of the condition determined it would not have prevented accident mitigation capability and the MSSVs overpressure function would have been adequate.
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 safety relief valve failures as a result of testing and none were identified for unit 2.
Unit 3 had a similar occurrence on March 10, 2009, which was reported in LER-2009-002.
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 signi-ficant potential safety impact of the condition under reasonable and credible alternate conditions.
Had an accident or transient occurred during the condition of the two out of tolerance MSSVs, the condition would not have affected accident mitigation capability and the MSSVs overpressure function would have been adequate.
Although the safety valves lifted at 1108.6 psig and 1147.4 psig which is above their accepted lift set point, the piping code per ANSI/ASME B31 for these pipes has a maximum design pressure of 1170.5 psig.
The design basis of the MSSVs is to limit the secondary system pressure to less than or equal to 110% of design pressure when passing 100% of design steam flow.
The combined MSSVs are sufficient to relieve approximately 108% of design steam flow.
Each MS line has an atmospheric dump valve (ADV) capable of releasing steam to the atmosphere.
The ADVs have the capability to relieve approximately 10% of total steam flow.
The combined pressure relief capability of the MSSVs and ADVs is approximately 118% of rated steam flow.
An Engineering evaluation concluded adequate pressure relief was available with 2 of the 20 MSSVs lifting at a higher pressure setpoint than specified.