05000286/LER-2009-009, Regarding Loss of Single Train Neutron Flux Detector N-38 Required for Plant Shutdown Remote from the Control Room Due to a Power Supply Failure
| ML093490996 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  (DPR-064) |
| Issue date: | 12/10/2009 |
| From: | Joseph E Pollock Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-09-1588 LER 09-009-00 | |
| Download: ML093490996 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2862009009R00 - NRC Website | |
text
~En tergy 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-09-158 December 10, 2009 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555-0001
SUBJECT:
Licensee Event Report # 2009-009-00, "Loss of Single Train Neutron Flux Detector N-38 Required for Plant Shutdown Remote From the Control Room Due to a Power Supply Failure" 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) 2009-009-00. The attached LER identifies an event where the Technical Specification 3.3.4 Remote Shutdown safety function for neutron flux was inoperable due to a failed power supply for neutron source range detector N-38 thereby not available for remote shutdown from the control room, which is reportable as a safety system functional failure under 10 CFR 50.73(a)(2)(v). This condition was recorded in the Entergy Corrective Action Program as Condition Report CR-IP3-2009-04123.
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 f~
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@inpo.org
Abstract
On October 14,
- 2009, the power supply for neutron flux detector N-38 was determined to be unable to provide reliable power to the detector.
The detector was declared inoperable and Technical Specification (TS) 3.3.4 (Remote Shutdown) Condition A was entered. The neutron flux detector (source range) N-38 is a function specified in TS Basis Table 3.3.4-1 Function 1, Reactivity Control (and credited in Technical Requirements Manual (TRM) 3.3.D, Appendix R Alternate Safe Shutdown Monitoring).
The inoperable N-38 failed to meet the specified safety function of TS 3.3.4.
The apparent cause was a lack of a recurring preventive maintenance (PM) action to replace the power supplies because N-38 is not included in the Indian Point Energy Center (IPEC)
Power Supply PM Program nor the IPEC Capacitor Replacement Program.
Entergy procedure EN-DC-153, "Preventive Maintenance Component Classification,"
classified N-38 as a non-critical component.
Corrective actions included replacement of the failed power supply with the operable power supply from redundant neutron flux detector N-39 which is not credited in TS 3.3.4.
A new PM was initiated to periodically replace the power supplies of N-38 and N-39.
A review will be performed of all non-critical components with power supplies to ensure the appropriate PMs are provided to replace or refurbish the equipment per EN-DC-153.
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)
Past Similar Events A review was performed of the past three years of Licensee Event Reports (LERs) for events that involved inoperable remote shutdown functions.
LER-2008-002 reported on April 18, 2008, a safety system functional failure due to the loss of single train 31 pressurizer heater as a result of a failed power supply transformer.
The 31 pressurizer heater was credited in TS 3.3.4 for plant shutdown remote from the CR.
The unit 3 event was a different cause as that event was due to transformer insulation breakdown.
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 shutdown outside the CR.
Detector N-38 provides no actuation function only indication.
Nuclear Instrumentation System (NIS) source range neutron flux detectors provide high flux level reactor trip and alarms signals to the reactor control and protection systems.
The power range neutron flux low bounds uncontrolled control rod assembly withdrawal from subcritical.
In addition, with the reactor in hot shutdown conditions, boration is not required immediately after shutdown.
The core Xenon transient does not decay to equilibrium level until at least nine hours after shutdown and a further period would elapse before the reactivity margin provided by the full-length control rods had been canceled.
This delay would provide time for implementing emergency measures.
In accordance with NUREG-0800, Section 7.4, shutdown remote from the CR is not an event analyzed in the USFAR for accident analysis (Chapter 14).
Specific scenarios are not specified on which the adequacy of shutdown capability remote from the CR is evaluated.
A recognized type of event that could force the evacuation of the CR and the need to shut down remote from the CR is smoke from a fire.
Fire damage limits as they impact safe shutdown do not require consideration of an additional random single failure in the capability to safely shut down.
Therefore, application of single failure to remote shutdown is applicable only to other events that could cause the CR to become uninhabitable.
These events would not result in consequential damage or unavailability of systems required for safe shutdown.