05000249/LER-2008-002, From Dresden, Unit 3 Regarding Unit 3 Primary Containment Isolation Valve Declared Inoperable
| ML090060879 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/23/2008 |
| From: | Wozniak D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVPLTR # 08-0066 LER 08-002-00 | |
| Download: ML090060879 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2492008002R00 - NRC Website | |
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Exelon Generation Company, LLC Dresden Nuclear Power Station 6500 North Dresden Road Morris, IL 60450-9765 www.exeloncorp.com Nuclear 10 CFR 50.73 SVPLTR # 08-0066 December 23, 2008 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 3 Renewed Facility Operating License No. DPR-25 NRC Docket No. 50-249
Subject:
Licensee Event Report 249/2008-002-00, "Unit 3 Primary Containment Isolation Valve Declared Inoperable" Enclosed is Licensee Event Report 249/2008-002-00, "Unit 3 Primary Containment Isolation Valve Declared Inoperable" for Dresden Nuclear Power Station, Unit 3. This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications." There are no regulatory commitments contained in this submittal.
Should you have any questions concerning this report, please contact Mr. Stephen Taylor, Regulatory Assurance Manager, at (815) 416-2800.
Respectfully, David B. Wozniak Site Vice President Dresden Nuclear Power Station Enclosure cc:
Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - Dresden Nuclear Power Station L~~fz
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the infnrmitinn rnllp.r.tin-n1
- 3. PAGE Dresden Nuclear Power Station, Unit 3 05000249
- 4. TITLE Unit 3 Primary Containment Isolation Valve Declared Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE J
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NON MONTH DAY YEAR N/A N/A IFACILITY NAME DOCKET NUMBER 10 29 2008 2008 002 -
00 12 23 2008 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1 20.2201(b)
El 20.2203(a)(3)(i)
[3 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
C3 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
[I 20.2203(a)(4)
[I 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
__ 20.2203(a)(2)(i)
[I 50.36(c)(1)(i)(A)
Cl 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[3 50.36(c)(2)
[3 50.73(a)(2)(v)(A)
El 73.71(a)(4) 085 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[E 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
[E 50.73(a)(2)(v)(D)
Specify in Abstract below or in C.
Cause of Event
The cause of the event was an intermittent high resistance electrical connection at the MCC for control power to PCIV 3-3702. The cause of the intermittent high resistance electrical connection is indeterminate. The most probable cause is that the electrical connection was marginal at installation and over time, surrounding equipment vibration caused the connection to be intermittent.
Additionally, the cause of not entering TS 3.6.1.3 on October 29, 2008 was a lack of proper procedure guidance that led operations personnel to assume the problem was a faulty light socket.
Troubleshooting was not immediately pursued, as there have been no previous failures of this type, flickering light indicating the valve was inoperable.
The RBCCW system is a closed loop system that in part, cools primary containment critical heat loads. PCIV 3-3702 is one of two isolation valves in the RBCCW supply line to the containment. The second valve is a check valve.
PCIV 3-3702 is a motor operated valve that is normally open during plant operation. The electrical power to the valve motor operator and its associated OPEN indication light is supplied through one electrical bucket in the MCC. The investigation on November 1, 2008, found intermittent voltage to PCIV 3-3702 that was eliminated when a test jumper was placed across the terminal points of the MCC bucket. The MCC bucket was removed to verify the tightness of all screw terminal points and none were found loose. The MCC bucket's terminal spring clips were tightened. The MCC bucket was reinstalled and successfully returned control power to the valve and the indicating light was illuminated.
The MCC bucket referenced above was installed on November 14, 2006, during a refuel outage and successfully passed maintenance testing. PCIV 3-3702 was last successfully cycled on January 17, 2008 during a maintenance outage. A review of Unit 3 operation logs did not find any reference to flickering lights on PCIV 3-307 prior to October 29, 2008.
An extent of condition review was performed on a sampling of similar motor operator valves and no abnormalities were identified.
The procedures used by operations personnel on October 29, 2008, lacks specific guidance to alert users that a failed or flickering indication light associated with a motor operated valve may indicate problems that could effect valve operation and that valve operability must be verified. An extent of condition review of operation procedures identified that revisions to enhance guidance must be made to procedures DGP 03-02, "Normal Control Room Inspection," DOP 0040-01, "Station Motor Operated Valve Operations," DOP 0040-04, "Control Panel Light Bulb and LED Replacement," DOP 6700-20, "480V Circuit Breaker Trip" and DOS 0040-12, "Penetration Flow Path PCIV Position Channel Check and Control Room PCIV Position Verification," to address this event.
D.
Safety Analysis
The safety significance of the event is minimal. The RBCCW system is a closed loop system that provides a boundary to prevent a radioactive release to the environment during normal plant operation. PCIV 3-3702 is one of two isolation valves in the RBCCW supply line to the containment.
The second valve is a check valve that was operable and capable of isolating the supply line if required. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.
E.
Corrective Actions
PcIV 3-3702 was restored to operable status.
Procedure DES 7300-05, "Maintenance and Surveillance of E.Q. and Safety Related 480 Volt MCC,"
was revised to include a step after installation of a MCC to perform a visual inspection of the electrical mating connections and to verify electrical continuity of the mating connection.
A training request was initiated to re-enforce with operations personnel the potential operability issues when valve /light indications are not functioning properly.
Operations revised procedures DGP 03-02, DOP 0040-01, DOP 0040-04, DOP 6700-20 and DOS 0040-12, to add guidance to alert users that a failed or flickering indication light associated with a motor operated valve may indicate problems that could effect valve operation and that valve operability must be verified.
F.
Previous Occurrences
A review of DNPS Licensee Event Reports (LERs) for the last three years did not identify any LERs associated with an intermittent electrical connection causing the inoperability of a TS component.
G.
Component Failure Data
N/APRINTED ON RECYCLEO PAPERPRINTED ON RECYCLED PAPER