05000369/LER-2003-001, For McGuire Nuclear Station Unit 1 Regarding Failure of Refueling Water Storage Tank Level Instrumentation During Cold Weather Due to Sensing Line Heat Trace & Insulation Deficiencies
| ML030970588 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 03/24/2003 |
| From: | Jamil D Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 03-001-00 | |
| Download: ML030970588 (11) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3692003001R00 - NRC Website | |
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4 11Duke PW Power.
A D-k, E-0~ C-P-~'y Duke Power McGuire Nuclear Station 12700 Hagers Ferry Road Huntersville, NC 28078-9340 (704) 875-4000 D. Al. Jamil Vice President, McGuire Nuclear Generation Department (704) 875-5333 OFFICE (704) 8754809 FAX March 24, 2003 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555
Subject:
McGuire Nuclear Station, Unit 1 Docket No. 50-369 Licensee Event Report 369/03-01, Revision 0 Pursuant to 10 CFR 50.73, Sections (a)(1) and (d), attached is Licensee Event Report (LER) 369/03-01, Revision 0.
On January 24, 2003, with Unit 1 at 100 percent power, McGuire experienced a failure of the Unit 1 Refueling Water Storage Tank (FWST) level instrumentation designed to initiate automatic swapover of the Emergency Core Cooling System (ECCS) suction from the FWST to the Containment Sump.
During an event requiring ECCS operation, this condition could have prevented fulfillment of this ECCS safety function.
Probabilistic risk assessment has determined this event to be of no significance to the health and safety of the public.
This LER is being submitted as per the requirements of 10 CFR 50.73 (a)(2)(v)(B), 10 CFR 50.73 (a)(2)(v)(D), 10 CFR 50.73 (a)(2)(vii), and 10 CFR 50.73 (a)(2)(i)(B).
There are no regulatory commitments contained in this LER.
Attachment I-
U. S. Nuclear Regulatory Commission March 24, 2003 Page 2 of 2 cc:
Mr. L. A. Reyes U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30323 Mr. R. E. Martin U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D.C.
20555 INPO Records Center 700 Galleria Parkway Atlanta, GA 30339 Mr. S. M. Shaeffer NRC Resident Inspector McGuire Nuclear Station
bxc: Dhiaa M. Jamil (MGO1VP)
Braxton L. Peele (MGO1VP)
Scotty L. Bradshaw (MGOOP)
Thomas P. Harrall Jr. (MGOlVP)
Guynn H. Savage (EC12X)
Gregg B. Swindlehurst (EC08H)
Ken D. Thomas (MG05EE)
Thomas C. Geer (MGOSSE)
Michael S. Kitlan (EC08I)
H. Duncan Brewer (EC08I)
Kay L. Crane (MGOlRC)
Gary D. Gilbert (CN01RC)
L. E. Nicholson (ON03RC)
Lisa Vaughn (ECliX)
Michael T. Cash (ECO50)
(NSRB Support Staff) (EC05N)
INPO Paper Distribution:
Master File (3.3.7)
ELL (ECO50)
RGC File
Abstract
Unit Status:
At the time of the event, Unit 1 and Unit 2 were in Mode 1 (Power Operation) at 100 percent power.
Event Description
On January 24, 2003, Unit 1 experienced a failure of the Refueling Water Storage Tank (FWST) level instrumentation designed to initiate automatic swapover of the Emergency Core Cooling System (ECCS) suction from the FWST to the Containment Sump. While in this condition, automatic swapover of the ECCS suction from the FWST to the Containment Sump would not have occurred during an event requiring ECCS operation.
This condition could have prevented fulfillment of this ECCS safety function.
The level instrumentation failed due to frozen sensing lines.
Annunciators immediately alerted operators who operated heat tracing in manual override such that continuous heat was applied to the sensing lines.
These actions restored the'Unit 1 FWST level instrumentation to operable status. This event was not significant with respect to the health and safety of the public.
Event Cause
Design deficiencies with the sensing lines heat trace system and configuration control deficiency with the sensing lines insulation.
Corrective Action
Redesign of the Unit 1 & 2 FWST level instrumentation heat trace systems.
Revise heat trace system design documentation and ensure conformance. Insulate sensing lines in accordance with design documents.
Revise FWST heat trace related configuration control documents.
NRC FORM 366 (7-2001)
(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 Form3 66A) (17) 1/24/2003 at 0342 1FWLP5000 and 1FWLP5010 were returned to operable status.
Exited TS 3.0.3 prior to any Unit 1 power reduction.
1/24/2003 at 1152 1FWLP5020 was returned to operable status.
Exited TS 3.3.2. 1FWLP5341 returned to service.
Upon reaching the Unit 1 FWST low level setpoint during a LOCA coincident with a SI signal, 1FWLP5000, 1FWLP5010, and lFWLP5020 initiate automatic swapover of ECCS suction from the Unit 1 FWST to the Unit 1 Containment Sump.
This provides protection against a loss of NPSH for the ECCS pumps which helps ensure the ECCS safety function can be performed.
As shown in the above timeline, at least two of these level instrument loops were simultaneously in a failed high condition on January 24, 2003 from 0045 until 0342 hours0.00396 days <br />0.095 hours <br />5.654762e-4 weeks <br />1.30131e-4 months <br />.
With two FWST level instrument loops failed high, Unit 1 was not capable of achieving the 2 out of 3 logic needed to generate an FWST low level signal.
This condition could have prevented fulfillment of the ECCS safety function which is reportable under the requirements of 10 CFR 50.73(a)(2)(v)(B) and 10 CFR 50.73(a)(2)(v)(D).
This event also represented a common-cause inoperability of independent channels reportable as per 10 CFR 50.73(a)(2)(vii).
Finally, during this event, more than one of the safety related Unit 1 FWST level instrument loops were inoperable at the same time.
Since TS 3.3.2 provides no associated required action for this condition, Unit 1 was in a condition prohibited by TS's for which the provisions of TS 3.0.3 were applicable for greater than one hour.
This is reportable under the requirements of 10 CFR 50.73(a)(2)(i)(B).
CAUSAL FACTORS Inspection of sensing lines and heat trace system components associated with 1FWLP5000, lFWLP5010, lFWLP5020, and lFWLP5341 identified the design and configuration control deficiencies listed below:
Design Deficiencies:
- Some thermocouples were mounted in close proximity to the respective heat trace cables.
Thus, when energized, the heat trace cables unduly influenced the thermocouple indication.
Therefore, the temperature measured by the thermocouples was higher than the actual temperature of the associated sensing line.
This caused the heat trace controller to (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 (If more space is required, use additional copies of NRC Form 366A) (17)
ADDITIONAL INFORMATION
A review of the McGuire corrective action database identified the following previous similar occurrences since 1990:
- In 1996, Unit 2 FWST level instrumentation was rendered inoperable during cold weather.
In that case, the FWST level transmitters failed when strip heaters and thermostats in the panels housing the transmitters did not function properly.
The cause was determined to be lack of a formal program to monitor proper operation of the FWST level transmitter panel strip heaters and thermostats. Although similar instrumentation failed during that event, the circumstances, cause, and corrective actions differed from the event described in this report.
- In 2000, one of the Unit 1 FWST level instrument loops failed due to a frozen sensing line.
The cause was determined to be separation of insulation from a small portion of the sensing line.
That event was not attributed to a design deficiency or a failure to insulate in accordance with applicable design documents.
Consequently, the cause and corrective actions differed from the event described in this report.