05000390/LER-2012-001, Regarding Failure to Meet Technical Specifications Due to Issues Associated with Vital Battery Surveillance Program

Regarding Failure to Meet Technical Specifications Due to Issues Associated with Vital Battery Surveillance Program

ML12076A180
Person / Time
Site:	Watts Bar
Issue date:	03/16/2012
From:	Grissette D Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
LER 12-001-00
Download: ML12076A180 (15)

LER-2012-001, Regarding Failure to Meet Technical Specifications Due to Issues Associated with Vital Battery Surveillance Program

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3902012001R00 - NRC Website

text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 March 16.2012 10 cFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390 Subject: Licensee Event Report 390/2012-001n Failure to Meet Technical Specifications due to lssues Associated with Vital Battery Surveillance Program This submittal provides Licensee Event Report (LER) 390/2012-001. This LER documents an incident where the requirements of several Technical Specifications were not met due to issues associated with the vital battery surveillance program. The condition is reported as an LER in accordance with 10CFR50.73(a)(2XlXB) and 10 CFR 50.73(a)(2)(vii).

There are no regulatory commitments in this letter. Please direct any questions concerning this matterto Donna Guinn, WBN Site Licensing Manager, at(423) 365-1 589.

Respectfully, D. E. Grissette Site Vlce President Watts Bar Nuclear Plant Enclosure cc: See Page 2

U.S. Nuclear Regulatory Commission Page 2 March 16, 2012 Enclosure cc (Enclosure):

NRC Regional Administrator - Region ll NRC Senior Resident Inspector - Watts Bar Nuclear Plant

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

LTGENSEE EVENT REPORT (LER)

APPROVED BY OMB NO. 3150-0104 EXPIRES 10t31t2013 Estimated burden per resporce to comply with this mandatory colledion request:

80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons leamed are incorponated into the licensing pmcess and fed back to industry. Send comments rcgarding burden estimate to FOIA/Privacy Section (T-5 F53), U.S. Nuclear Regulatory Commission, Washlngton, DC 2055t 0001, or by intemet e-mail to infocolleds.resourca@nrc.gov, and to the Desk Ofiicer, Ofiice of Information and Regulatory Affairs, NEOB-10202, (315G0104), Ofiice of Management and Budget, Washington, DC 20503. lf a means usecl to impose an information collec'tion does not dlsplay a cunently valid OMB control number, the NRC may not conduc{ or sponsor, and a person is not required to respond to, the i nformation colledion.

I. FACILIW NAME Watts Bar Nuclear Plant Unit 1

2. DOGKET NUMBER 05000390 1of13

3. PAGE

4. TITLE Failure to Meet Technical Specifications due to lssues Associated with Vital Batterv Surveillance Proqram

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTHI DAY I YEAR YEAR l'=-i,lTJ$rl ftEoY MONTHI DAY YEAR FAUILI I Y NAME N/A UUUKtsI NUMtstsK N/A 02 13 l 2011 2012 - 001 - 00 03 16 2012 FACILITY NAME N/A DOGKET NUMBER N/A

9. OPERATING MODE 1

11. THIS REPORT IS SUBMITTED PURSUANT TO THE fl 20.2201(b)

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10. POWER LEVEL 100 I2. LICENSEE CONTAGT FOR THIS LER FACILITY NAME Stan Day, Licensing Engineer TELEPHONE NUMBER (lnclude Arca Code)

(423) 751-7221CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX

CAUSE

SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX D

EJ BTRY c173 N

14. SUPPLEMENTAL REPORT EXPECTED YES (ffyee oomplete 15. ffiPECTED SUBMISS/ON DATE) x n

NO

15. EXPECTED SUBMISSION DATE MONTH DAY YEAR ABSTRACT (linffr b ta00 sfl6t, 1..., tpp.oxlnlrly 15 &tgb-lpaad Wflfrn M.t)

On 0U17f2O12, TVA deErmined that Mtal BatEry lV (VB4) was inoperable between 02113111 and 12l03li2011.

This was based on an independent analyais of Fst data from the performance of Surveillance RequiEment (SR) 3.8.4.14 for VB4 conducEd on 0211012011 that indicated the actual batEry capacity did not meet the SR 3.8.4.14 accepbnce criterion. On f f212011, VB3 did not meet the SR 3.8.4.14 acceptance cribrion. On 09n4f2012, TvA concluded that VB3 and VB4 may have been inoprable for unknovn periods of time prior b the failed capacity bsb. As a rcsult, there were timeE when VB3 and VB4 were requircd to be operable b comply with Technical Specification (TS) 3.8.4 and TS 3.8.5, and WBN, Unit 1 failed b meet the applicable lequilemenb of TS 3.8.4, TS 3.8.5 and LCO 3.0.4. Also, VB3 and VB4 may have been inopelable concunently; thus, the requiEments of LCO 3.0.3 may not have been met.

During the time periods discussed above, VB3 and VB4 werc capable of performing their safuty function.

Preliminarily, TVA determined that a manufacturing deficiency was the direct cause of the unexpec-ted degradation of VB3 and VB4. The causes were inadequacies in the oversight of the battery surveillance prcgram, and issues with the baftery capacity test procedure. Conctive actions include changes to the battery test program, proceduE revisions, and training of plant personnel.

NRC FORM 366 (10-2010)

IIRC FORN 38GA U.3. I{UCLEAR REGULATORY CO[XIssIOl{

(ro-2olo)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET FACILITY NAME (1I DOCKET (2}

LER NUMBER (6)

PAGE (3I Watts Bar Nuclear Plant Unit 1 05000390 YEAR I SEQUENTTAL I REVTSTON I

ttUMeeR I htUMeen 2ot13 2012 001 00

NARRATIVE

I.

PLANT CONDITIONS

On fin1al'll (the date Vihi Baftery lll (VB3) failed the capacity bst conducted in accodance with Surveillance Requirement (SR) 3.8.4.14), Unit I was operating in Mode 1 at 100% power.

On OU17AO12 (the date of discovery of the Vihl Battery lV (VB4) inoperability), Unit 1 was oprating in Mode 1 at 100% power.

Forthe time period between 0211312011 and 12lO3l'!2O11, the bllouring table establishes when VB4 was requircd to be operable b comply with Technical Specifications 3.8.4 and 3.8.5, the associated Mode or specified condition of operation, and applicable Rated Thermal Porer (RTP).

Tablo I - Plant Conditlon. A.soclalod wlth VB lV InoporNblllty Time Period (Date and Time)

Mode or Gondition RrP (%l Applicable Technical Specification 0211312011 at 1821 through 0410412011 at0741 1,2, 3, 4 100 - 000 3.8.4 - VB4 required to be operable Condition Prohibited by TS Existed 0410412011 at 0741 through 0411612011 at 0925 5and6 000 3.8.5 - VB4 required to be operable Condition Prohibited by TS Existed 0411612011 at 0925 through 0412912011 at2124 No Mode 000 VB4 not required to be operable No Condition Prohibited by TS Existed regarding VB4 0412912011 at2124 through 0511312011 at 0558 5and6 000 3.8.5 - VB4 required to be operable Condition Prohibited by TS Existed 0511312011 at 0558 through 0612712011 at 1647 1,2, 3, and 4 100 - 000 3.8.4 - VB4 required to be operable Condition Prohibited by TS Existed 0612712011 at 1647 through 0710912011 at 0501 1

Various VB4 removed from service - VB5 aligned to Vital Battery Board lV No Condition Prohibited by TS Existed regarding VB4 0710912011 at 0501 through 1210312011 at 0408 1,2, and 3

100 - 000 3.8.4 - VB4 required to be operable Condition Prohibited by TS Existed

t.Note: VB4 was not required to be operable for the time periods of: 1) 0411612011 at 0925 through 0412912011 at2124 when the plantwas in the "No Mode" condition, and 2)0612712011 at1647 through 071098A11 at 0501 when VB4 was removed from service and Vital Battery V (VB5) was aligned to Vital Battery Board lV.

DESCRIPTION OF EVENT

A.

Event VB3 Description of Event On 1 112112011, a battery capacity test was completed for VB3 [Energy Industry ldentification System (EllS) Code ELI in accordance with SR 3.8.4.14. A battery capacity of approximately 70o/o was recorded, which did not meet the acceptance criterion of > 80% for SR 3.8.4.14.

At the time of discovery, VB3 was removed from service, and was not being credited to meet TS 3.8.4. VBS was aligned to Vital Battery Board lll.

NUREG-1022 provides the following guidance regarding discrepancies identified during surveillance tests: "...discrepancies found in technical specifications surveillance tests should be assumed to occur at the time of the test unless there is firm evidence, based on a review of relevant information (e.9., the equipment history and the cause of failure) to indicate that the discrepancy occurred earlier."

For VB3, the previous capacity test conducted in accordance with SR 3.8.4.14 on 10/31/2005 established a battery capacity of 109.857o. A review of maintenance history and the equipment failure analysis did not identify a specific event or action that occurred between 1013112005 (previous successful capacity test for VB3) and 1 112112011 (failed capacity test for VB3) that rendered VB3 inoperable when aligned to a Vital Baftery Board.

Despite the lack of firm evidence, on 03/1412012, TVA conservatively concluded that VB3 may have been inoperable at some point in time prior to 1112112011. However, TVA cannot identify when this inoperability occurred. Thus, for an undefined period of time that VB3 was credited as one of the channels of vital DC to comply with the requirements of LCO 3.8.4 or LCO 3.8.5, a condition prohibited by Technical Specifications may have existed.

During the time periods discussed above, VB3 was capable of performing its safety function (See Section V of this LER for detailed information).

VB4 Description of Event On 1 113012011, Problem Evaluation Report (PER) 468950 was initiated to determine the cause of the unexpected degradation of VB3 and VB4.

On 0211012011, a battery capacity test was completed for VB4 [EllS Code EL] in accordance with SR 3.8.4.14. A battery capacity oI82.5o/o was recorded. The battery was considered operable, because the battery capacity exceeded the acceptance criterion of > 80% for SR 3.8.4.14.

il.

ll. Table3-VB4Events Date Time VB4 Events 09t23t2005 VB4 completed capacity test in accordance with SR 3.8.4.14. Recorded battery capacity was 108.75o/o. Acceptance criterion is > 8oo/o.

08/11/2009 VB4 successfully completed service test in accordance with SR 3.8.4.13.

02t08t2011 1035 VB4 removed from service. VBS aligned to Vital Battery Board lV at 1039.

02t10t2011 VB4 completed capacity test SR 3.8.4.14, Recorded battery capacity was 82.5%.

Acceptance criterion is 2 80%.

02t13t2011 1821 VB4 returned to service. VB5 placed in standby alignment.

04t16t2011 0925 No Mode (Core offloaded in spent fuel pool during refueling outage).

04t29t2011 2124 Mode 6 entered (lnitial entry into a Mode of Applicability for TS 3.8.5).

45n3/2011 0558 Mode 4 entered (lnitial entry into a Mode of Applicability for TS 3.8.4).

06t27 t2011 1647 VB4 removed from service. VB5 aligned to Vital Battery Board lV.

06t27 t2011 VB4 failed battery service test in accordance with SR 3.8.4.13.

07rc6i2011 Replaced the eight weakest cells in VB4 and re-tested VB4 in accordance with SR 3.8.4.13. VB4 met service test acceptance criterion (> 105 Vdc) with a terminal voltage of 105.4 Vdc.

07t09t2011 0501 VB4 returned to service. VBS placed in standby alignment.

11t30t2011 PER 468950 was initiated to determine the cause for the unexpected degradation of VB3 and VB4 capacity.

12t03t2011 0408 VB4 removed from service. VB5 aligned to Vital Battery Board lV at 0409.

12t07 t2011 Service test performed on VB4 with the eight new cells that had been installed on 07106111 utilizing a single unit load profile as described in Section V of this LER.

VB4 met the acceptance criterion (> 105 Vdc).

01t06t2012 Service test performed on VB4 with the eight weak cells that had been removed on 07/06/11 utilizing a single unit load profile as described in Section V of this LER. VB4 met the acceptance criterion (> 105 Vdc).

01t15t2012 Replaced VB4 with new battery. VB4 tested in accordance with service test SR 3.8.4.13. VB4 met the acceptance criterion (> 105 Vdc) with a terminal voltage of 112.1Vdc. Factory capacity test performed by C&D Technologies was credited for meeting the acceptance criterion for SR 3.8.4.14.

01t15t2012 01 16 VB4 returned to service. VBS placed in standby alignment.

01t1712012 Independent engineering analysis of the completed surveillance package for VB4 indicated that the actual battery capacity calculated on 02/1012011 was 79.87o/o.

This is less than the SR 3.8.4.14 acceptance criterion of > 80%. This event was entered into the Corrective Action Program as PER 492211.

3t14t2012 TVA conservatively concluded that VB4 may have been inoperable for an unknown time period prior to 0211012011

ilt.TVA determined that the root causes for the degraded battery capacity issue were:

1) The organization's Risk Assessment System was less than adequate to assess the operability of the station's vital batteries and failed to identify the degraded capacity of VB3 and VB4; and 2l The organization did not promptly identity, fully analyze and resolve in a timely manner unexpected safety significant trend and test data concerning vital battery operability.

Cause of Conditions Prohibited by Technical Specifications Associated with VB4 Inoperability VB4 was inoperable during the time periods identified in Sections I and ll of this LER due to unidentified errors in the baftery capacity calculations that were completed on 02/1012011. The errors were discovered as part of an independent engineering analysis of the completed surveillance package for VB4 completed on 01/1712012. The independent engineering analysis indicated that the actual battery capacity was 79.87%. This is less than the SR 3.8.4.14 acceptiance criterion of > 80%

of manufacturer rating.

There were several problems with both the test equipment and procedure that caused VB4 recorded capacity (82.5To) to be in error. The errors were due to inaccurate calculation of the time interval that battery cell No. 54 was jumpered out of the circuit during the four hour capacity discharge test and rounding errors where times were not calculated to the nearest second. These errors resulted in greater recorded amp-hour capacity than what actually existed. Battery Cell No. 54 was jumpered out due to low cell voltage.

ANALYSIS OF THE EVENT

VB3 and VB4 Unexpected Degraded Capacitv WBN's oversight of the vital battery surveillance program was less than adequate. WBN's Risk Assessment System with respect to the vital batteries consists of implementation of the surveillance program. Additional elements that are used to monitor and assess the condition of the vital battery program are the System Health Report, the Operational Experience program, and the Margin Management program.

WBN's organizational response to the VB4 events in February and June was less than adequate. Site management failed to recognize or understand the potential significance of vital battery degradation. The organizational response to the 0211012011 VB4 capacity test failure was less than adequate to ensure VB4 would not fail the 0612712011 service test in accordance with SR 3.8.4.13. The organizational response to the 0612712011 VB4 service test failure was inadequate to ensure VB3 would not fail the 1112112011 capacity test in accordance with SR 3.8.4.14.

tv.

tv.Preliminarily, TVA determined that the direct cause of the unexpected degradation of VB3 and VB4 to a state in which it could not meet the acceptance criterion was a manufacturing deficiency associated with the forming of the positive plates for VB3 and VB4 cells (paste curing process or paste formulation). This determination is based on the initial results of the destructive failure analysis.

Additional evaluation by the battery manufacturer, C&D Technologies, is ongoing to confirm the failure mechanism that caused the unexpected decrease in the capacity of VB3 and VB4.

VB4 Conditions Prohibited bv Technical Specifications The computer system used for battery testing is obsolete. New test equipment was available, but training and test procedures to allow the use of new equipment had not been completed. Use of the obsolete test equipment and procedure deficiency led to inaccurate test results. Specifically, the test procedures did not specify that the time required to jumper out a defective cell(s) must be subtracted from the total discharge time when calculating battery capacity. In addition, WBN non-conservatively rounded test data during the VB4 capacity test.

The original determination of operability for VB4 was based on the original capacity test results for VB4. lf the test procedure had determined VB4's capacity correctly, VB4 would not have been returned to service until the issue was resolved. Errors in the testing practices as described above caused TVA to not recognize that VB4 was outside the TS acceptance criterion of SR 3.8.4.14.

ASSESSMENT OF SAFETY CONSEQUENCES

lntroduction The vital 125V DC power system is a Class 1E system composed of four redundant channels (Channels I and lll are associated with Train A and Channels ll and lV are associated with Train B).

Each channel consists of a lead-acid-calcium battery, battery charger, distribution board, and the required cabling, instrumentation and protective features. These four channels provide control power to the Class 1E 6.9 kV shutdown boards, 480V motor control centers, inverters and emergency DC lighting systems.

Each vital battery has adequate storage capacity to carry the required load continuously for at least 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> in the event of a loss of all AC power (station blackout) without an accident or for 30 minutes with an accident considering a single failure. Each battery board can also be aligned to the fifth vital battery system. The fifth 125V DC Vital Battery System can serve as a replacementforany one of the four 125V DC vital bafteries during testing, maintenance, and outages with no loss of system reliability under any mode of operation.

The vital bafteries preventative maintenance program has been maintained in accordance with manufactureds recommendations. In addition to the capacity and service tests, battery voltage is checked daily and the battery pilot cell temperature is checked weekly. Individual cell voltages and specific gravity checks are performed quarterly, and the battery circuit connection resistances are checked annually.

V.

V. Surveillance testing is performed for all vital batteries in accordance with SR 3.8.4.13 and SR 3.8.4.14.

r The test conducted in accordance with SR 3.8.4.13 is called the service test in this LER. lt is a timed 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> discharge test that uses a load profile based on WBN's design basis event's equipment load requirements for safe shutdown. The result is the battery's voltage reading at the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> mark which is compared to the SR 3.8.4.13 acceptance criterion of > 105 Vdc.

r The test conducted in accordance with SR 3.8.4.14 is called the capacity test in this LER. lt is a timed discharge at a constant load rate and is terminated when the overall cell voltage reaches 105 Vdc. The results are given as a capacity percentage value with respect to the designed capacity of the battery. The SR 3.8.4.14 acceptance criterion is > 80%.

VB3 Discussion On 1211912011, a service test was performed on the VB3 that was replaced on 1210212012. This service test was a battery discharge test using a single unit load profile, which consists of Unit 1 loads, common loads, and loads transferred from Unit 2 to Unit 1. VB3 met the acceptance criterion

(> 105 Vdc) with a terminal voltage of 1 15.1 Vdc. This test demonstrated that VB3 had sutficient stored energy to meet design bases accident load demands for the time frame between 0212512011 when the last service testwas performed and 1112112011 when VB3 was removed from service for replacement.

This test demonstrated VB3 was capable of performing its safety function for the worst case scenario which is the four-hour station blackout.

VB4 Discussion As indicated in Section ll.C of this LER, VB4 met the acceptance criterion of SR 3.8.4.13 on 0710612011 with a margin of 0.4 Vdc. This service test used a two unit load profile. Atwo unit load profile is conservative, because it assumes not only Unit 1 loads and common loads but also Unit 2 loads. Unit 2 is currently under construction, and all of its loads have not been transferred to VB4.

On 1210712011, a service test was performed on VB4 with the eight new cells that had been installed on 07/0612011. This service test was a battery discharge test using a single unit load profile, which consists of Unit 1 loads, common loads, and loads transferred from Unit 2 to Unit 1. VB4 met the acceptance criterion (> 105 Vdc) with a terminal voltage of 1 14.9 Vdc. This test demonstrated that VB4 had sutficient stored energy to meet design bases accident load demands for the time frame between 071091201 1 and 1210312011.

On 01/0612012, a service test using a single unit load profile was performed on VB4 using the eight weak cells that had been removed on 07/0612011. VB4 met the acceptance criterion (> 105 Vdc) with a terminal voltage of 11 1.9 Vdc. This test demonstrated that VB4 had sufficient stored energy to meet design bases accident load demands for the time frame between 0211312011 and 0612712011.

These tests demonstrated VB4 was capable of performing its safety function for the worst case scenario which is the four-hour station blackout.

Vll. E.

Loss of Normal Heat Removal Consideration vilt.

None

COMMITMENTS

None