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LER-2018-002, Inoperable 250V Shutdown Board Battery Charger Results in Condition Prohibited by Technical Specifications
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded; 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition; 10 CFR 50.73(a)(2)(iv)(A), System Actuation; 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)(v), Loss of Safety Function; 10 CFR 50.73(a)(2)(i)
	2962018002R00 - NRC Website
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Inoperable 250V Shutdown Board Battery Charger Results in Condition Prohibited by Technical Specifications
	ML18120A191
Person / Time
Site:	Browns Ferry ; (DPR-068)
Issue date:	04/30/2018
From:	Hughes D; Tennessee Valley Authority
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	LER 2018-002-00
	Download: ML18120A191 (9)
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Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 April 30, 2018 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001

Subject:

Browns Ferry Nuclear Plant, Unit 3 Renewed Facility Operating License No. DPR-68 NRC Docket No. 50-296 Licensee Event Report 50-296/2018-002-00 10 CFR 50.73 The enclosed Licensee Event Report provides details of the inoperability of the 250V Shutdown Board Battery Charger resulting in a condition prohibited by Technical Specifications. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations 50. 73(a)(2)(i)(B).

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Nuclear Site Licensing Manag, t (256) 729-2636.

D. L. Hughes Site Vice President Enclosure: Licensee Event Report 50-296/2018-002 Inoperable 250V Shutdown Board Battery Charger Results in Condition Prohibited by Technical Specifications cc (w/ Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant

ENCLOSURE Browns Ferry Nuclear Plant Unit 3 Licensee Event Report 50-296/2018-002-00 Inoperable 250V Shutdown Board Battery Charger Results in Condition Prohibited by Technical Specifications See Enclosed

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (02-2018)

Estimared, the NRG may rot conduct or sponsor, and a person is rot required 1D respond 1D, the information collection.

3.Page Browns Ferrv Nuclear Plant Unit 3 05000296 1 OF 7

4. Title Inoperable 250V Shutdown Board Battery Charger Results in Condition Prohibited by Technical Specifications

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved I

Sequential I Rev Facility Name Docket Number Month Day Year Year Month Day Year N/A N/A Number No.

02 28 2018 2018

- 002

- 00 04 30 2018 Facility Name Docket Number Nill Nill

9. Operating Mode

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)

D 20.2201 (b)

D 20.2203(a)(3)(i)

D 50.73(a)(2)(ii)(A)

D 50. 73( a )(2)(viii)(A) 5 D 20.2201 (d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50. 73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 5o.73(a)(2)(iii)

D 50. 73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D 50.73(a)(2)(iv)(A)

D 50. 73(a)(2)(x)

10. Power Level D 20.2203(a)(2)(ii)

D 50.36(c)(1)(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11(a)(4)

D 20.2203(a)(2)(iii)

D 5o.36(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11(a)(5)

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

D 50.73(a)(2)(v)(C)

D 13.77(a)(1) 000 D 20.2203(a)(2)(v)

D 50. 73(a)(2)(i)(A)

D 50.73(a)(2)(v)(D)

D 13.77(a)(2)(i)

D 20.2203(a)(2)(vi)

~ 50. 73(a)(2)(i)(B)

D 50. 73(a)(2)(vii)

D 73.77(a)(2)(ii)

D 50.73(a)(2)(i)(C)

D OTHER Specify in Abstract below or in 2018 -

002 B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event There were no structures, systems, or components (SSCs) whose inoperability contributed to this event.

C. Dates and approximate times of occurrences

Date & Approximate Times Event April 3, 2014 During performance of Surveillance 3-SR-3.8.4.4 (SB-3EB), 250V SDBD 3EB Battery Charger was unable to provide more than 40A.

December 22, 2017, 0404 CST During performance of Surveillance 3-SR-3.8.4.4 (SB-3EB), 250V SDBD 3EB Battery Charger was unable to provide more than 42A, and the Battery Charger Spare was placed in service.

00 January 30, 2018, 0242 CST Operations personnel declared the 250V 3EB Battery inoperable for load testing of the 3EB SDBD Battery Charger.

February 2, 2018, 0921 CST The 250V SDBD 3EB Battery was declared Operable after replacement of a firing card in the 250V SDBD 3EB Battery Charger.

D. Manufacturer and model number of each component that failed during the event

The failed component during this event was the 250V SDBD 3EB Battery Charger. The model number for the 250V SDBD 3EB Battery Charger is ARR260K50 manufactured by C&D Technologies.

E. Other systems or secondary functions affected

The Apparent Cause Evaluation determined that the extent of condition is limited to the subcomponents of the 250V DC SDBD Battery Chargers installed at BFN on Units 1, 2, and 3. Other than the 250V DC SDBD Battery Charger, no other systems or secondary functions were affected.

F. Method of discovery of each component or system failure or procedural error

On December 22, 2017, during the performance of Surveillance 3-SR-3.8.4.4 (SB-3EB),

the 250V SDBD 3EB Battery Charger was unable to the meet TS Surveillance Requirement to supply the minimum current of 50A at greater than or equal to 210 V DC.

2018 -

002 00 G. Failure mode, mechanism, and effect of each failed component This event was the result of a failed solid state capacitor on the B phase firing card in the 250V SDBD 3EB Battery Charger. Failure of the solid state capacitor was caused by age degradation due to continued operation of the 250V SDBD 3EB Battery past its 20 year life expectancy of the 250V SDBD 3EB Battery Charger. The 250V SDBD 3EB Battery Charger is approximately 26 years old, with no history of this type of failure. Failure of the solid state capacitor prevented the Battery Charger's ability to provide the TS required minimum current of SOA at greater than or equal to 210V DC. As a result of this condition, the 250V SDBD 3EB Battery Charger was functional but inoperable from April 3, 2014, to December 22, 2017.

H. Operator actions

At the time of discovery, no Operator actions were required or performed for this condition.

I.

Automatically and manually initiated safety system responses

No safety system responses resulted from this event.

Ill.

Cause of the Event

A. Cause of each component or system failure or personnel error The direct cause of this event was failure of the solid state capacitor on the B phase firing card in the 250V SDBD 3EB Battery Charger.

The apparent cause of this event was no Preventive Maintenance (PM) strategy exists to replace or refurbish subcomponents of the SDBD Battery Chargers that are vulnerable to age degradation failures.

B. Cause(s) and circumstances for each human performance related root cause

The apparent cause evaluation determined that a lack of precise and rigorous communication between Operations and Engineering personnel in regards to the operability determination of the 3EB Battery Charger in 2014 was a contributing cause.

This resulted in the WO that was created in 2014 to validate the condition of the 3EB Battery Charger being placed in the WO process without adequate tracking.

IV.

Analysis of the Event

One 250V DC SDBD subsystem supplies control power for 4.16 kilovolt (kV) SDBD 3EB. The DC SDBD subsystem consists of a battery together with the associated charger, circuitry, switches, 2018 -

002 00 indicators, and alarms. The SDBD DC subsystem can receive power from its own battery, battery charger, or from the spare charger. Each battery charger has sufficient capacity to restore the battery from the design minimum charge to its fully charged state within twelve hours while supplying normal steady state loads.

For this event, the 250V SDBD 3EB Battery Charger was able to provide 40A on April 3, 2014, and 42A on December 22, 2017. According to BFN design calculations, a battery charger capacity of 27.92A is required to function. The POE determined that a 40A charger can recharge the batteries in 0.392 hours0.00454 days 0.109 hours 6.481481e-4 weeks 1.49156e-4 months , and a 50A charger can recharge the batteries in 0.287 hours0.00332 days 0.0797 hours 4.74537e-4 weeks 1.092035e-4 months . While the charger did not meet the TS Surveillance Requirement to supply the minimum current of 50A at greater than or equal to 21 OV DC, the charger was capable of fully charging the battery in less than 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months . Therefore, the SDBD subsystem was considered functional but inoperable from April 3, 2014, to December 22, 2017.

The DC electrical power systems are required to be OPERABLE in MODES 1, 2, 3, 4, and 5, and during movement of irradiated fuel assemblies in the secondary containment. The following TS LCOs are applicable to this event.

BFN, Unit 3, TS LCO 3.8.4 requires the 3EB Shutdown Board DC electrical power subsystem to be operable.

BFN, Unit 3, TS LCO 3.8. 7 requires the Shutdown Board Distribution Panel 3EB to be operable.

BFN, Unit 3, TS LCO 3.8.5 requires if one or more DC electrical power subsystem is inoperable, it is required to be restored to Operability immediately.

BFN, Unit 3, TS LCO 3.8.8 requires if one or more AC or DC electrical power subsystem is inoperable, it is required to be restored to Operability immediately.

On February 22, 2016, at approximately 0212 CST, Operations personnel entered Mode 5 for refueling, and on March 19, 2016, at approximately 1552 Central Daylight Time (CDT),

Operations personnel entered Mode 4 for refueling. During this time, Unit 3 was also in violation of TS LCO 3.8.5 and 3.8.8.

Additionally, since equipment required for a Mode change was inoperable, BFN, Unit 3, was in violation of TS 3.0.4 on March 26, 2016, during startup from a planned refueling outage.

V.

Assessment of Safety Consequences

A qualitative Probabilistic Risk Assessment (PRA) was performed to evaluate the failure of the 250V SDBD 3EB Battery Charger to meet the TS minimum current of 50A during performance of Surveillance 3-SR-3.8.4.4 (SB-3EB). The 250V SDBD 3EB Battery Charger would have performed its design safety function because the 250V SDBD 3EB Battery Charger was 2018 -

002 00 delivering above the minimum amperage to be considered functional. Therefore, there was no risk impact from this condition.

Based on the above discussion, TVA has concluded that, during the time period that the 250V SDBD 3EB Battery Charger was inoperable, there was no significant risk to the health and safety of the public or plant personnel for this event.

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The SDBD DC subsystem can receive power from its own battery, battery charger, or from the spare charger. The spare charger was a viable alternative to the 250V SDBD 3EB Battery Charger.

B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident During the time the reactor was shutdown, all affected systems remained functional to perform their required safety functions.

C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service This event resulted in inoperability of the 250V SDBD 3EB Battery Charger for a time longer than allowed by TS, from the last time the 250V SDBD 3EB Battery Charger was unable to meet the TS Surveillance Requirement on April 3, 2014, until the time the 250V 3EB SDBD Battery was aligned to the spare charger and the 3EB SDBD DC electrical power subsystem and 3EB SDBD distribution panel was declared Operable on December 22, 2017.

VI.

Corrective Actions

Corrective Actions (CAs) are being managed in TVA's corrective action program under Condition Report (CR) 1383682.

A. Immediate Corrective Actions

The firing card was replaced in the 250V SDBD 3EB Battery Charger.

- -- "' vmB:... v. 3 1au-v IU4 t:Jll'lt<t::;: u~*~ ll LULU Estima1ed, the NRC may not conduct or sponsor, and a person is not reqlired to respond to, the infonnation conection.

YEAR 2018 -

3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.

00 B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future The corrective action to reduce the probability of similar events occurring in the future will be to create a PM strategy to replace or refurbish subcomponents of the SDBD Battery Chargers that are vulnerable to similar age degradation failures.

VII.

Previous Similar Events at the Same Site

There were no previous similar events at the same site over the last five years.

VIII.

Additional Information

None.

IX.

Commitments

None.

I.

Plant Operating Conditions Before the Event

At the time of discovery on February 28, 2018, Browns Ferry Nuclear Plant (BFN), Unit 3 was in Mode 5 at 0 percent power, due to the Unit 3 Cycle 18 Refueling Outage.

II.

Description of Event

A. Event Summary 2018 -