05000369/LER-2008-001, Regarding Potential Failure of Containment Isolation Valves (CIV) to Remain Fully Closed and Inoperable Longer than Allowed by Technical Specification 3.6.3
| ML081490323 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 05/19/2008 |
| From: | Brandi Hamilton Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| M-08-01541 LER-08-001-00 | |
| Download: ML081490323 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) |
| 3692008001R00 - NRC Website | |
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1.
.1 P Duke Energy BRUCE H HAMILTON Vice President McGuire Nuclear Station Duke Energy Corporation MG01VP / 12700 Hagers Ferry Road Huntersville, NC 28078 704-875-5333 704-875-4809 fax bhhamilton@duke-energy. com May 19, 2008 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Attention: Document Control Desk
Subject:
McGuire Nuclear Station, Units 1 and 2 Docket No. 50-369, 50-370 Licensee Event Report 369/2008-01, Revision 0 Problem Investigation Process (PIP) M-08-01541 Pursuant to 10 CFR 50.73, Sections (a)(1) and (d), attached is Licensee Event Report (LER) 369/2008-01, Revision 0 concerning the potential failure of McGuire's Unit 1 & 2 Containment Isolation Valves (CIV) 2NC-56B, 1/2KC-320A, 1/2KC-332B, 1/2KC-333A, 1/2RV-79A, 1/2RV-80B, and 1/2RV-101A to remain fully closed under certain conditions.
The report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B), an operation prohibited by Technical Specifications, and 10CFR 50.73 (a)(2)(v)(C), a condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material.
This event has been determined to be of no significance to the health and safety of the public. There are no regulatory commitments contained in this LER.
B. Hamilton Attachment U-L&~
www. duke-energy. com
U.
S.
Nuclear Regulatory Commission May 19, 2008 Page 2 of 2 cc:
L.A. Reyes U. S. Nuclear Regulatory Commission Regional Administrator, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 J. F. Stang, Jr. (Addressee Only)
NRC Project Manager (McGuire)
U. S. Nuclear Regulatory Commission Mail Stop 8-H4A Washington, DC 20555-0001 J. B. Brady Senior Resident Inspector U. S. Nuclear Regulatory Commission McGuire Nuclear Site Beverly 0. Hall, Section Chief Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645
Abstract
On March 20, 2008; Air Operated diaphragm Containment Isolation Valves (CIVs) were declared inoperable when it was discovered inadequate bleed paths during thermal pressurization could cause actuator closing margins to be exceeded. Exceeding actuator closing margins could cause a CIV to open during an event requiring containment isolation.
This condition existed during a mode of applicability specified in the plant's Technical Specifications (TS) and is reportable as an operation or condition which was prohibited by the plant's TS in accordance with 10CFR 50.73(a) (2) (i) (B).
In addition, since the CIV could have opened when required to be closed, this condition could have prevented fulfillment of the safety function and is reported in accordance with 10CFR 50.73 (a) (2),(v) (C).
The Safety Analysis for this event has concluded that this condition was not significant with respect to the health and safety of the public.
Upon discovery, the applicable CIVs were declared inoperable and immediate corrective action was taken to restore CIV operability on the operating unit.
Corrective actions
to restore operability included modifications and procedural alignment changes necessary to restore adequate closing margins. The root cause for this event was a lack of formal expectations or guidelines relative to timely completion of corrective actions having significant regulatory impact.
A previous corrective action to review calculations for air operated diaphragm valves susceptible to the thermal pressurization was not completed in a timely manner and resulted in station operation with inoperable CIVs.
Corrective actions
have been initiated to ensure timely completion of corrective actions having significant regulatory impact.
NRC FORM 366 (7-2001)
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Flow paths through the Unit 1 penetrations are considered in the McGuire Containment Isolation analysis.
Those results are deemed applicable to Unit 2 due to plant symmetry.
For the present analysis, one of the CIVs (2NC-56B) could open due to expansion of the fluid trapped between the containment isolation valves.
If this were to occur, it would relieve pressure and the redundant inboard passive check containment isolation valve would remain closed.
In order for a release of airborne fission products through this pathway to occur, a significant breach in the piping would need to occur after resetting the safety signal.
Thus a release through this pathway is concluded to be probabilistically insignificant..
The remaining valves were screened out as insignificant contributors to LERF (Large Early Release Frequency) on the basis that they connect to closed piping within containment and do not constitute a probabilistically significant pathway for the release of airborne fission products.
Even if redundant CIVs were to open, a significant breach in the piping would need to occur.
Thus a release through these pathways is also concluded to be probabilistically insignificant.
Since the penetrations involve closed piping within containment, they do not constitute a probabilistically significant pathway for the release of airborne fission products.
- - Even if inboard and outboard CIVs were to open, a
significant breach in the piping would need to occur to provide a viable release pathway.
Thus the Conditional Large Early Release Probability (CLERP) associated with this event is evaluated to be < 1E-7.
Given the above, this event is considered to be of no significance with respect to the health and safety of the public.
ADDITIONAL INFORMATION
The Ice Condenser Refrigeration [BC]
(NF) Containment Isolation Valves INF-234A & 2NF-234A had a similar failure in June 2006.
This failure is classified as a Recurring Event (LER 369/2006-01).
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