05000247/LER-2015-004, Regarding Safety System Functional Failure Due to an Inoperable Containment Caused by a Flawed Elbow on the 21 Fan Cooler Unit Service Water Motor Cooling Return Pipe
| ML16057A178 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 02/18/2016 |
| From: | Coyle L Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 15-004-00 | |
| Download: ML16057A178 (7) | |
| 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 |
| 2472015004R00 - NRC Website | |
text
En tergy Lnawrnc Poin nryl Cete 450e Bieroaidwaynt Lawrence Coyle Site Vice President NL-1 6-0;12 February 18, 2016 U.S. Nuclear Regulatory Commission Document Control Desk 11545 Rockville Pike, TWFN-2 F1 Rockville, MD 20852-2738
SUBJECT:
Licensee Event Report # 2015-004-00, "Safety System Functional Failure Due to an Inoperable Containment Caused by a Flawed Elbow on the 21 Fan Cooler Unit Service Water Motor Cooling Return Pipe" 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) 2014-004-00. The attached LER identifies an event where there was a safety system functional failure due to an inoperable Containment as a result of a Containment Fan Cooler Unit motor cooler service water return pipe flaw. This condition is reportable under 10 CFR 50.73(a)(2)(v). This condition was recorded in the Entergy Corrective Action Program as Condition Report CR-IP2-2015-5755.
NL-16-012 Page 2 of 2 There are no new commitments identified in this letter. Should you have any questions regarding this submittal, please contact Mr. Robert Walpole, Manager, Regulatory Assurance at (914) 254-6710.
Sincerely, LC/cbr Attachment: LER-201 5-004 cc:
Mr. Daniel H. Dorman, Regional Administrator, NRC Region I NRC Resident Inspector's Office Ms. Bridget Frymire, New York State Public Service Commission
Abstract
On December 20,
- 2015, operator investigations identified service water (SW) leakage in containment and on December 22, 2015 discovered a through wall leak on a socket welded elbow for the 21 Fan Cooler Unit (FCU) motor cooler SW 2 inch copper-nickel return line.
The leak was located in a pipe fitting that is within the ASME Section XI Code ISI Class 3 boundary and estimated to be. approximately*l gpm.
Since the pipe flaw was through wall and was located within the ASME Section XI boundary, it exceeded the flaw allowable limits provided per IWD-3000.
Engineering determined that since the through wall flaw was located on a socket welded fitting, the ASME Code Case N-513-3 did not apply.
The 21 FCU was declared inoperable and Technical Specification (TS) 3.6.6 (Containment Spray and Containment FCU System),
entered for one FCU train inoperable and TS 3.6S.1 Condition A entered for containment inoperable.
The 21 FCU SW return line was isolated.
The pipe is part of a closed loop system inside containment and is required to meet containment integrity.
Since a containment leakage evaluation was not performed, the pipe flaw-was conservatively assumed to result in post-accident containment out leakage in excess of the 10CFR50, Appendix J limits resulting in violation 6f the containment integrity requirements and therefore is a safety system functional failure.
The direct cause was flow assisted erosion-corrosion.
The apparent cause was high SW flow conditions that caused high localized velocities and flow separation at the sharp interior edge of the socket welded fitting.
Corrective actions included replacement of the affected fitting.
The faulted fitting was sent out to a vendor for metallurgical failure analysis.
The procedure for FCU SW flow balanced will be revised to reduce the SW flow in FCU motor coolers.
.The event had no significant effect on public health and safety.
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The containment consists of the concrete reactor building, its steel liner, and the penetrations through the structure.
The containment building is designed to contain radioactive material that might be released from the reactor following a design basis accident (DBA)
The containment building steel liner and its penetrations establish the leakage limiting boundary of the containment.
Maintaining the containment operable limits the leakage of fission product radioactivity from the containment to the environment.
The DBA analysis assumes that the containment is operable such that, for the DBAs involving release of fission product radioactivity, release to the environment is controlled by the rate of containment leakage.
The containment was designed with an allowable leakage rate of 0.1 percent of containment air weight per day.
Containment isolation valves form a part of the containment pressure boundary.
Two barriers in series are provided for each penetration so that no single credible failure or malfunction of an active component can result in a loss of isolation or leakage that exceeds limits assumed in the safety analysis.
One of these barriers may be a closed system such as the SW piping for the FCUs.
The only time containment integrity can be effected is post accident when the FCUs safety function is being performed and SW pressure for the FCU cooling piping and coils fall below peak accident pressure.
SW effluent is monitored by radiation monitors R-46 and R-53 prior to discharge.
If radiation is detected, each FCU heat exchanger can be individually sampled to determine the leaking unit.
The SW for the 21 FCU and 21 FCU fan motor cooler can be isolated to prevent radioactive effluent releases.
During the time the FCTJ SW piping was degraded there was no leakage out of containment.