05000250/LER-2013-009, Regarding Loose Breaker Control Power Fuse Holder Caused 3B Jcw Pump to Be Inoperable Longer than AOT
| ML14008A196 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 11/27/2013 |
| From: | Kiley M Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2013-326 LER 13-009-00 | |
| Download: ML14008A196 (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)(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 |
| 2502013009R00 - NRC Website | |
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L-2013-326 10 CFR § 50.73 November 27, 2013 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555-0001 Re:
Turkey Point Unit 3 Docket No. 50-250 Reportable Event: 2013-009-00 Loose Breaker Control Power Fuse Holder Caused 3B ICW Pump to be Inoperable Longer than Allowed Outage Time The attached Licensee Event Report 05000250/2013-009-00 is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the Technical Specifications.
If there are any questions, please call Mr. Robert J. Tomonto at 305-246-7327.
Very truly yours, Michael Kiley Vice President Turkey Point Nuclear Plant Attachment cc:
Regional Administrator, USNRC, Region II Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant Florida Power & Light Company 9760 SW 344t' St., Florida City, FL 33035
w NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
I. FACILITY NAME
- 2. DOCKET NUMBER I3.
PAGE Turkey Point Unit 3 05000250I 1 of 4
- 4. TITLE Loose Breaker Control Power Fuse Holder Caused 3B ICW Pump to be Inoperable Longer than AOT
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE 8 8. OTHER FACILITIES INVOLVED J
FACILITY NAME DOCKET NUJMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR CI NUMBER NO. I I
FACILITY NAME DOCKET NUMBER 9
28 2013 2013 -
009 00 11 27 2013
- 9. OPERATING MODE II. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
E] 20.2201(b)
El 20,2203(a)(3)(i)
EJ 50.73(a)(2)(i)(C)
El 50,73(a)(2)(vii) 1 El 20.2201(d)
El 20.2203(a)(3)(ii)
Dl 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A) 0 20.2203(a)(I)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
[: 50.36(c)(1)(i)(A)
Dl 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
E] 50.73(a)(2)(iv)(A)
E] 50.73(a)(2)(x)
"l 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
El 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)0 El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 100 [1 20.2203(a)(2)(v)
[] 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER
[] 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Three ICW pumps are provided for each unit. One, two, or three pumps are operated as required to support normal plant operating conditions. However, only one pump is required following a maximum hypothetical accident. The A and B pumps are powered by 4160 volt buses which can be powered by each train's associated Emergency Diesel Generator (EDG). The C pump is powered by a swing 4160 volt safety related bus which can be powered, through aligning the bus manually, by either the train A or train B EDG associated with the same unit. This pump is interlocked such that it is started on a LOOP or safety injection signal, if the supply breaker for the A or B pump associated with the A or B 4160 volt bus to which it is aligned is open and racked out.
Analysis The fuse holder assembly consists of two pieces, the fuse holder and the base. The fuse holder is removable.
The two fuses (one on the positive side of the power supply and one on the negative side of the power supply) are mounted in the holder, with four long stabs that extend into the base to complete the electrical circuits.
The base is mounted to the cubicle, and consists of four short clips, that mate to its corresponding stab. The stabs fit on the inside of the clips on the base. The tension of the clips against the stabs (as well as the complementary curve of both pieces) keeps the fuse holder connected to the base. If all four clips are making good electrical contact with their respective stabs, the fuse holder will be tight in the base and difficult to remove.
There are two types of UC fuse holder assemblies in the GE Magne-Blast 4160 volt breakers. The fuse holder in the 3B ICW pump breaker has been in service for at least 20 years and is likely original plant equipment. Some in-service 4160 volt breaker cubicles have been refitted with a newer fuse holder assembly.
The new fuse holder assembly stabs and clips hold more tightly because they have not been subject to as many cycles of removal, reinstallation, and adjustment.
During the cause evaluation, it was discovered that it is possible to insert the fuse holder stabs on the outside of the clips (i.e. between the copper clips and the plastic casing) by approaching the base at a slight angle.
Based on walkdowns of the cubicles, the fuse holder assembly is approximately 5 to 6 feet off the ground.
With the location of the fuse holder assembly, approaching the fuse holder base at an angle is conceivable. In this installation alignment, the fuse holder stabs are making contact with the copper clips and the white light would be on. As part of preventive maintenance to ensure proper engagement, the copper clips are squeezed slightly, which increases the possibility of widening the gap between the copper clips and the plastic.
Prior to the loss of control power on September 28, 2013, the UC fuses were installed in the 3B ICW pump breaker on September 4, 2013. No other fuse holder manipulations were noted to have occurred between September 4, 2013 and September 28, 2013 and the breaker was cycled closed and open approximately six times. It is judged that during this period the UC fuse holder gradually worked loose due to improper installation and breaker operation vibration to the point where contact between the fuse holder stabs with the base clips was lost. Therefore, the 3B ICW pump breaker would not have been able to open on a LOOP and close for EDG loading from the last pump start on September 24, 2013.
5IO0
Reportability
TS Limiting Condition for Operation (LCO) 3.7.3.a requires three ICW pumps to be operable in Modes 1-4.
If one ICW pump is inoperable, then the AOT is 14 days if both remaining pumps are powered by independent sources. If the remaining two ICW pumps are not powered from independent sources, then the AOT is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. During the approximate 4 day period September 24, 2013 to early September 29, 2013, with the 3B ICW pump inoperable, the 3A pump was powered via the A 4160 volt bus and the 3C ICW pump was not powered via the B 4160 volt bus because the 3B ICW pump breaker was not open and racked out.
Therefore, the 3A and 3C ICW pumps were not independently powered, and so the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> AOT applied. As a result, the TS LCO, AOT and shutdown Actions were not met and a condition prohibited by the TS existed, reportable in accordance with 10 CFR 50.73(a)(2)(i)(B).
ANALYSIS OF SAFETY SIGNIFICANCE During the approximate 4 day period the 3B ICW pump was inoperable, the 3A and 3C ICW pumps were available to perform the heat removal safety function of the ICW system. The 3B and 3C ICW pumps were aligned to the 3B 4160V safety bus and the capability existed to power the 3C ICW pump should the need have arisen. In addition, it was possible to recover the functionality of the 3B ICW pump by restoring the UC fuse holder in the fuse base. Only one ICW pump in operation is needed to remove design basis heat loads.
Therefore, the ICW system remained functional with redundant capability to perform the safety function and so the safety significance is considered to be low.
CORRECTIVE ACTIONS
Corrective actions are in accordance with condition report 1907650 and include the following:
- 1. UC fuses of adjacent similar breakers were checked following breaker operation.
- 2. Baseline UC fuse engagement measurements have been taken for 4160 volt breakers.
- 3. Establish UC fuse holding force inspection acceptance criteria for 4160 volt breakers, perform inspections, and replace fuse holder assemblies as required.
- 4. Revise 4160 volt breaker operating procedure to provide guidance for ensuring UC fuse holders are tight after installation and perform verification.
ADDITIONAL INFORMATION
EIIS Codes are shown in the format [IEEE system identifier, component function identifier, second component function identifier (if appropriate)].
FAILED COMPONENTS IDENTIFIED: None
PREVIOUS SIMILAR EVENTS
None