05000286/LER-2013-002, Regarding Safety System Functional Failure and Common Cause Inoperability of the Emergency Core Cooling System Due to Violation of Containment Sump Debris Barrier Integrity
| ML13141A255 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 04/29/2013 |
| From: | Ventosa J Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-13-056 LER 13-002-00 | |
| Download: ML13141A255 (6) | |
| 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 10 CFR 50.73(a)(2) |
| 2862013002R00 - 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-13-056 April 29, 2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, D.C. 20555-0001
SUBJECT:
Licensee Event Report # 2013-002-00, "Safety System Functional Failure and Common Cause Inoperability of the Emergency Core Cooling System Due to Violation of Containment Sump Debris Barrier Integrity" 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) 2013-002-00. The attached LER identifies an event where there was a Safety System Functional Failure and a common cause inoperability of the Emergency Core Cooling System while in Hot Shutdown due to violation of the design basis for Containment sump debris barrier, which is reportable under 10 CFR 50.73(a)(2)(v) and 10CFR50.73(a)(2)((vii). This condition was recorded in the Entergy Corrective Action Program as Condition Report CR-1P3-2013-00975.
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, cc:
Mr. William Dean, Regional Administrator, NRC Region I NRC Resident Inspector's Office, Indian Point 3 Ms. Bridget Frymire, New York State Public Service Commission LEREvents@inpo.org 7zjz~~
~A~L
Abstract
On March 4, 2013, during shutdown for a refueling outage, Radiation Protection (RP) personnel entered the reactor containment building to install plastic RP fencing for the Reactor Coolant Drain Tank (RCDT).
After receiving clearance at Mode 4 to enter the Inner Crane Wall (ICW) to install fencing around the RCDT and post it as a Locked High Radiation Area (LHRA).
The RP work crew assumed they could enter the ICW area through any sump barrier gate for the Emergency Core Cooling System (ECCS).
The RP work crew chose to use a single gate access point due to its proximity to the RCDT.
Subsequently, a RP Technician identified that personnel had not entered the area using the double access gate and had brought in plastic fencing which was inappropriate material for the sump area.
The opening of the single sump barrier gate violated ECCS operability basis which requires the sump barrier system to be operable in Modes 1-4.
The apparent causes were an inadequate pre-job brief and inadequate procedure for Containment Entry and Egress (OAP-007, 0-RP-RWP-405) due to poor change management.
The pre-job brief failed to cover the requirement to use the dual sump barrier gate access point when in Modes 1-4, nor did it address the type of fencing allowed.
The brief did not specify that only steel RP fencing could be used for the RCDT.
Corrective actions included bolting closed the single gate, removal of the plastic fencing in Mode 5, and briefing RP personnel on the event, lessons learned and management expectations.
Procedure OAP-007 will be revised to include the required use of the sump barrier dual access gate in applicable attachments, and RP procedure 0-RP-RWP-405 will be revised to address Mode applicability for use of the sump barrier dual gate and approved RCDT fencing material.
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 (If more space is required, use additional copies of NRC Form 366A) (17)
The condition was not reportable as a TS prohibited condition.
TS 3.5.3 Condition B (Required ECCS Recirculation subsystem inoperable) required action is to restore required ECCS recirculation subsystem to operable status in one hour or be in Mode 5 within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The ECCS sump flow barrier single gate was unbolted at 04:15 hours on March 4, 2013, and plastic RP fencing carried into the area for installation around the RCDT.
The improper condition was identified and immediate action taken to bolt the single gate after approximately 30 minutes while in Mode 4.
The plastic RP fence was replaced when the plant reached Mode 5 at approximately 08:52 hours.
The period of inoperability for the two conditions was approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> thirty seven minutes which is within the TS allowed completion time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to Mode 5.
Past Similar Events A review was performed of the past three years of Licensee Event Reports (LERs) for events that involved SSFFs and/or common cause inoperability of an Engineered Safety Feature System.
The review identified LER-2012-001 which reported a common cause inoperability of both trains of Auxiliary Feedwater Pumps on October 11, 2011, due to the inability to control AFW regulating valves after isolation of nitrogen backup to pneumatic actuators.
The condition could result in pump trip due to high flow from fail open on loss of instrument air without local operator action.
The apparent cause of not recognizing the need to station an operator locally to operate the AFW regulating valves prior to isolating the nitrogen supply was inadequate procedural guidance and licensing basis documents.
This event has a similar aspect as part of the cause was inadequate document quality.
Procedure OAP-007, checklist for RP personnel for containment entry does not address use of only the dual gate access point.
Procedure 0-RP-RWP-405 precautions and limitations, and the pre-job brief criteria does not address use of only the dual access gate nor does it specify that only steel fencing can be used for the RCDT fencing prior to Cold shutdown.
- However, corrective actions for LER-2012-001 would not have prevented this event as the issues associated with LER-2012-001 are unrelated to the issue identified in this LER.
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.
The analysis performed in response to GL-2004-02 included debris transport analysis conservatisms for transport of debris to both the IR sump and the Containment sump in excess of quantities that would be generated.
Establishing normal RHR cooling to the RCS has RCS temperature below 350 degrees F and pressure less than 400 psig.
In Mode 4 the reactor is not critical and reactivity is stable.
In Mode 4 there is significantly less energy in the RCS to generate debris. At the time the actual RCS pressure was approximately 490 psig.
An evaluation of a LOCA during Mode 3 and 4 operation was performed by Westinghouse (WCAP-12476) that showed a direct reduction in break probability for Mode 4 and a relative risk as the ratio of the frequency of core damage in either Mode 3 or 4 to Mode 1. This resulted in a mean relative risk probability of 1/6.5 for Mode 4 assuming the running RHR pump could not be restarted when compared to the risk for large break LOCAs in Mode 1. The evaluation concluded that Mode 4 LOCAs are not a significant contributor to shutdown risk.
During this event the entire flow barrier was not disabled because only one debris barrier gate was unbolted and only for the time to allow personnel to enter the ICW.
Therefore most debris would have been intercepted by the flow barrier system.
Also, the barrier gate swings into the crane wall so that DBA flow and forces would tend to close the gate when pressure is applied (e.g.,
DBA debris loads) therefore limit flow barrier bypass and sump debris loading.
The plastic fencing was not considered a significant contributor to inoperability of both ECCS sumps.
It is reasonable to conclude the fencing would have been caught on structures or components either on the way to the reactor sump or in the sump and not travel to one or both ECCS sumps.