05000247/LER-2011-003, Regarding Technical Specification (TS) Violation for Entry Into TS 3.0.3 for 3 Inoperable Fan Cooler Unit Trains and Failure to Correct within 1 Hour and Actions Taken for Plant Shutdown
| ML11348A195 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 12/01/2011 |
| From: | Joseph E Pollock Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-11-125 LER 11-003-00 | |
| Download: ML11348A195 (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 |
| 2472011003R00 - 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-1 1-125 December 1, 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 (TS)
Violation for Entry into TS 3.0.3 for 3 Inoperable Fan Cooler Unit Trains and Failure to Correct Condition within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and Actions Taken for Plant Shutdown" 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) 2011-003-00. The attached LER identifies an event where there was a Technical Specification (TS) violation for entry into TS 3.0.3 for three inoperable Fan Cooler Unit trains and failure to correct condition within one hour and actions initiated to shutdown the plant, 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-IP2-2011-04894.
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 2 Mr. Paul Eddy, New York State Public Service Commission LEREvents@inpo.org
Abstract
On October 3, 2011, during performance of the quarterly surveillance test of the Containment Fan Cooler Unit (FCU) cooling water flow, all five FCUs failed to meet minimum flow requirements with the essential service water (SW) header (1/2/3 header) supplied by the 22 and 23 SW pumps.
Operations entered Technical Specification (TS) 3.0.3 per TS 3.6.6.F for 3 trains of FCUs inoperable.
In accordance with TS 3.0.3 operations initiated actions to place the plant in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />.
Operations initiated turbine load reduction by approximately 5 MW and swap of the essential SW supply to the 4/5/6 header.
Upon completion of the essential header swap, operations re-performed the quarterly surveillance test on the 4/5/6 header with satisfactory results.
Based on successful completion of the test, Operations exited the TS 3.0.3 action statement and commenced power ascension to 100% power.
The direct cause was excessive accumulation of silt in the SW Bay that resulted in degraded inlet flow to the SW pumps.
The root cause was ineffective barriers established to monitor and remove silt accumulations that would affect SW pump Net Positive Suction Head (NPSH) margin failed to include predictive elements that account for changing environmental conditions.
Corrective actions included sonar mapping and de-silting of the SW Bay.
The sonar mapping frequency will be increased and the SW System Monitoring Plan will be revised to include alert and action levels for silt buildup.
A comprehensive silt monitoring and mitigation plan will be developed to include predictive trending and monitoring methods.
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)
There was no safety system functional failure reportable under 10CFR50.73(a) (2) (v).
Monitored SW header pressure was within normal range until September 29, 2011, when there was a drop in pressure that alarmed in the control room.
Operations rotated pumps and the pressure returned to normal but subsequently degraded until tested on October 3, 2011.
Engineering judgment concluded there was a non-linear buildup of silt that resulted in reduced SW pressure and flow.
The minimum required safeguards components were available to perform the function during the time the 5 FCUs were declared inoperable as both containment spray pumps (CSPs) were available.
Considering the CSPs as a subsystem of the Containment Heat Removal System then both CSPs can be credited because in accordance with reporting guidance in NUREG-1022, an additional random single failure need not be assumed in that system during the
- condition.
A review of SW header pressure determined that the 1/2/3 SW header pressure had been within normal range until September 29, 2011, when the Control Room received a low SW pressure alarm at 20.02 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
A graph of SW header pressure showed a significant dip in pressure that started earlier in the day.
The indicated pressure drop exceeded the low indicated pressure associated later with inadequate SW FCU flow from the scheduled functional test (2-PT-Q016) of the FCUs on October 3, 2011.
TS 3.6.6 has a Surveillance Requirement (SR) 3.6.6.3 that requires each FCU cooling water flow rate to be equal or greater than 1600 gpm.
The alarm for low SW pressure on September 29,
- 2011, is indicative that the TS SR was not likely met and required entry into the appropriate TS condition.
Because there was a failure to enter the applicable TS condition for the low header pressure condition, this was a TS prohibited condition reportable under 10CFR50.73(a) (2) (i) (B).
Past Similar Events A review was performed of the past three years of Licensee Event Reports (LERs) for events that involved a TS prohibited condition (e.g., TS 3.0.3 violation) due to a SW flow inadequacy.
No LERs were identified.
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 requiring the CSS or FCUs.
During the declared inoperability of the three trains of FCUs (October 3, 2011 at 3:45 hours through 5:32 hours), both CSPs were available.
The Containment Spray System and Containment Fan Cooler System are Engineered Safety Feature (ESF) systems are designed to ensure that the heat removal capability required during the post accident period can be attained. The CSS and the Containment FCU System provide redundant methods to limit and maintain post accident conditions to less than the containment design values (5 FCUs/3 FCUs & 1 CSP/2 CSPs).
The configuration with one CS train and two FCU trains is the configuration available following the loss of any safeguards power train (e.g., diesel failure).
Accident analysis assumptions regarding containment air cooling and iodine removal are met by one CS train and any two FCU trains (i.e., at least three FCUs).
The Containment FCU System consisting of five 20 percent capacity FCUs and the CSS consisting of two 50% trains are divided into trains based on the safeguards power train which supports them.
During the period of the declared inoperable FCU trains, there was minimum safeguards capability available.
A Westinghouse calculation demonstrates that adequate heat removal can be provided at lower river water temperatures. The required TS surveillance SW flow rate through the FCUs is based on a LOCA at worst case river water temperature (95 degrees F) however, during this event the river water temperature was significantly lower than 95 degrees F, being measured at approximately 65 degrees F.
The as-found test values of SW flow exceed the calculation value indicating acceptable cooling for a postulated DBA during the event.