05000286/LER-2011-003, For Indian Point Unit 3, Regarding Technical Specification Required Shutdown and a Safety System Functional Failure for a Leaking Service Water Piper Causing Flooding in the SW Valve Pit Preventing Access for Accident Mitigatio
| ML11123A165 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 04/25/2011 |
| From: | Joseph E Pollock Entergy Corp, Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-11-028 LER 11-003-00 | |
| Download: ML11123A165 (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)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2862011003R00 - NRC Website | |
text
SEntergy 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-1 1-028 April 25, 2011 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555-0001
SUBJECT:
Licensee Event Report # 2011-003-00, "Technical Specification Required Shutdown and a Safety System Functional Failure for a Leaking Service Water Pipe Causing Flooding in the SW Valve Pit Preventing Access for Accident Mitigation" Indian Point Unit No. 3 Docket No. 50-286 DPR-64
Dear Sir or Madam:
Pursuant to 10 CFR 50.73(a)(1), Entergy Nuclear Operations Inc. (ENO) hereby provides Licensee Event Report (LER) 2011-003-00. The attached LER identifies an event where there was the completion of a Technical Specification (TS) required shutdown and a Safety System Functional Failure, which is reportable under 10 CFR 50.73(a)(2)(i)(A) and 10CFR50.73(a)(2)(v) (D). This condition was recorded in the Entergy Corrective Action Program as Condition Report CR-IP3-2011-00680.
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. William Dean, Regional Administrator, NRC Region I NRC Resident Inspector's Office, Indian Point 3 Mr. Paul Eddy, New York State Public Service Commission LEREvents@inpo.org zz~~
Abstract
On February 22, 2011, the Control Room was notified of flooding in the south service water (SW) valve pit.
Subsequent investigation determined there was approximately three feet of water in the south valve pit with leakage in the area of Conventional Essential Header Discharge Isolation Valves SWN-6 and SWN-7.
The leak was estimated to be approximately 150 gpm and not isolable.
Technical Specification (TS) 3.7.9 (Service Water System)
Condition E was entered.
After further evaluation, it was concluded there was a loss of safety function because the condition would prevent the credited method of isolating the SW loads in the event of a Design Basis Accident due to the inaccessibility to the valve pit for valve operation.
As a result of this determination TS 3.7.9 Condition E was no longer applicable and the plant was in a condition not specified in the TS and required a plant shutdown per TS 3.0.3.
The direct cause was a 3/4 inch hole in the 10 inch SW pipe (line 1222) downstream of valve SWN-6.
The root cause was an inadequate installation plan and repair of a flaw identified in 1992.
Interim corrective actions included installation of a modified pipe clamp and UT readings to determine pipe operability.
Corrective action
was replacement of the effected pipe section in spring 2011 refueling outage.
An engineering guideline will be developed providing direction on how SW leak repairs should be performed.
The Generic Letter 89-13 program will be revised to prioritize inspection frequencies of SW pipe welds and include SW lines 1221 and 1222.
Inspections of SW piping in the Unit 2 SW valve pit and the Unit 3 north SW valve pit will be performed.
The event had no significant 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)
Event Analysis
The event is reportable under 10CFR50.73(a) (2) (i) (A).
The licensee shall report the completion of any plant shutdown required by the plant's Technical Specification.
At 12:03 hours, TS 3.7.9 Condition E was entered for SWS piping and valves inoperable for reasons other than Condition A, B, C, or D with no loss of safety function.
After further assessment of the condition, it was concluded at 14:25 hours, that the condition would prevent the credited method of isolating the SW loads in the event of a Design Basis Accident requiring cold leg recirculation due to the inaccessibility to the valve pit for valve operation.
As a result of this determination TS 3.7.9 Condition E was no longer applicable and the plant was in a condition not specified in the TS.
In accordance with TS 3.0.3 when an associated action is not provided, action shall be initiated within one hour to place the unit in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, Mode 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and Mode 5 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.
TS 3.0.3 was entered at 14:25 hours and the shutdown commenced at 15:25 hours.
At 18:38 hours, a manual reactor trip was initiated and the plant entered mode 3 (Hot Shutdown).
Entry into TS 3.0.3 and completion of any plant shutdown required by the TS is reportable under 10CFR50.73(a) (2) (i) (A) and 10CFR50.73(a) (2) (i) (B).
The condition was also a safety system functional failure reportable under 10CFR50.73(a) (2) (v) (D) as the condition would have prevented access to valves in the valve pit used for accident mitigation.
Failure to provide applicable valve manipulations could have resulted in inoperability of a non-essential SW pump required for accident mitigation.
Past Similar Events A review was performed of the past three years of Licensee Event Reports (LERs) for events that involved a TS required shutdown or safety system functional failure.
There were no LERs identified that were similar to this event.
LER-2010-002 reported a manual reactor trip as a result of a SW leak in the exciter.
However, the shutdown was not required by TS and was not a SSFF.
CAs for that event would not have prevented this event as the causes were different.
Safety Significance
This event had no significant 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 during the time of the event.
As an alternative to operating valves SWN-6 and SWN-7, FCV-1111 and FCV-1112 in the SW pit there are other valves that can be operated to isolate the conventional loads and prevent SW pump run out.
In addition, there are three SW pumps on the designated non essential SW header.
Therefore, there are remaining SW pump capabilities as backup to the SW pump designated for use in DBA recovery.
A risk impact was performed of the flooding with an exposure time of 31.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> (discovery on February 22, 2011 at 10:30 hours to operability declared on February 23, 2011, at 17:55 hours).
Assuming operators would have been unable to enter the SW valve pit to operate isolation valves, the Core Damage Frequency (CDF) increased to 2.7E-5 per year which results in an incremental CDF (ICDF) of 1.24E-5 per year.
Considering the event for a 31.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period of unavailability, results in an incremental core damage probability (ICDP) of 4.46E-8.
This impact is not considered significant.