IR 05000298/2017011

NRC Baseline Inspection Report 05000298/2017011 and Preliminary White Finding

ML17223A459
Person / Time
Site:	Cooper
Issue date:	08/14/2017
From:	Troy Pruett NRC/RGN-IV/DRP
To:	Dent J Nebraska Public Power District (NPPD)
Jason Kozal
References
EA-17-057 IR 2017011
Download: ML17223A459 (25)

Text

UNITED STATES ust 14, 2017

SUBJECT:

COOPER NUCLEAR STATION - NRC BASELINE INSPECTION REPORT 05000298/2017011 AND PRELIMINARY WHITE FINDING

Dear Mr. Dent:

On June 15, 2017, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Cooper Nuclear Station. On August 11, 2017, the NRC inspectors discussed the results of this inspection with you and other members of your staff. The results of this inspection are documented in the enclosed report.

The enclosed report documents a finding with two associated apparent violations that the NRC has preliminarily determined to be White with low-to-moderate safety significance. This finding involved two apparent violations of Technical Specification 5.4.1.a for the failure to:

(1) implement inspection instructions to examine the emergency transformer bus insulation for discoloration and repair the associated components, and (2) maintain adequate instructions for performing high potential testing of the emergency transformer bus bars. As a result, indications of corona-related degradation on the emergency transformer bus were not identified and repaired, which resulted in a bus fault, a loss of the emergency transformer, and a loss of the supplemental diesel generator on January 17, 2017. This finding was assessed based on the best available information, using the applicable significance determination process. The final resolution of this finding will be conveyed in separate correspondence.

The finding is associated with two apparent violations and is being considered for escalated enforcement in accordance with the NRC Enforcement Policy, which can be found at http://www.nrc.gov/about-nrc/regulatory/enforcement/enforce-pol.html.

In accordance with NRC Inspection Manual Chapter 0609, Significance Determination Process, we intend to issue our final significance determination and enforcement decision, in writing, within 90 days from the date of this letter. The NRCs significance determination process encourages an open dialogue between your staff and the NRC; however, the dialogue should not impact the timeliness of the staffs final determination. Before we make a final decision on this matter, we are providing you with an opportunity to (1) attend a regulatory conference where you can present to the NRC your perspective on the facts and assumptions the NRC used to arrive at the finding and assess its significance, or (2) submit your position on the finding to the NRC in writing.

If you request a regulatory conference, it should be held within 40 days of your receipt of this letter, and we encourage you to submit supporting documentation at least one week prior to the conference in an effort to make the conference more efficient and effective. The focus of the regulatory conference is to discuss the significance of the finding and not necessarily the root cause(s) or corrective action(s) associated with the finding. If you choose to attend a regulatory conference, it will be open for public observation.

If you decide to submit only a written response, it should be sent to the NRC within 40 days of your receipt of this letter. Written responses should reference the inspection report number and enforcement action number associated with this letter in the subject line. If you choose not to request a regulatory conference or to submit a written response, you relinquish your right to appeal the NRCs final significance determination, in that, by not doing either, you fail to meet the appeal requirements stated in the Prerequisite and Limitation sections of Attachment 2 of NRC Inspection Manual Chapter 0609.

Please contact Jason Kozal at 817-200-1144, and in writing, within 10 days from the issue date of this letter to notify the NRC of your intentions. If we have not heard from you within 10 days, we will continue with our significance determination and enforcement decision. The final resolution of this matter will be conveyed in separate correspondence.

Because the NRC has not made a final determination in this matter, no Notice of Violation is being issued for this inspection finding at this time. In addition, please be advised that the number and characterization of the apparent violations described in the enclosed inspection report may change as a result of further NRC review.

In accordance with 10 CFR 2.390 of the NRCs Rules of Practice and Procedure, a copy of this letter and its enclosure will be made available electronically for public inspection in the NRC Public Document Room and in the NRCs Agencywide Documents Access and Management System (ADAMS), accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html.

Sincerely,

/RA/

Troy W. Pruett, Director Division of Reactor Projects Docket No. 50-298 License No. DPR-46 Enclosure:

Inspection Report 05000298/2017011 w/ Attachments:

1. Supplemental Information 2. Significance Determination

SUNSI Review: ADAMS: Non-Publicly Available Non-Sensitive Keyword:

By:CHY/dll Yes No Publicly Available Sensitive NRC-002 OFFICE RI:DRP/C RI:DRS/EB2 SRI:DRS/EB2 SES:ACES SRA:DRS/PSB2 SPE:DRP/C NAME CHenderson JWatkins SGraves JKramer RDeese CYoung SIGNATURE /RA/ /RA/ /RA/ /RA/ /RA/ /RA/

DATE 8/3/2017 6/28/17 6/28/17 8/3/17 8/2/2017 8/2/2017 OFFICE SRI:DRP/C RC:ORA TL:ACES BC:DRP/C DD:DRA:NRR D:DRS NAME PVoss KFuller MHay JKozal RFelts AVegel SIGNATURE /RA/ /RA/ /RA/ /RA/ /RA/ E /RA/JAC for DATE 8/2/2017 6/28/17 8/2/2017 8/3/2017 8/9/17 8/9/17 OFFICE D:DRP NAME TPruett SIGNATURE /RA/

DATE 8/11/17

U.S. NUCLEAR REGULATORY COMMISSION

REGION IV

Docket: 05000298 License: DPR-46 Report: 05000298/2017011 Licensee: Nebraska Public Power District Facility: Cooper Nuclear Station Location: 72676 648A Ave Brownville, NE Dates: January 17 through June 15, 2017 Inspectors: P. Voss, Senior Resident Inspector C. Henderson, Resident Inspector J. Watkins, Reactor Inspector R. Deese, Senior Reactor Analyst Approved By: Troy W. Pruett, Director Division of Reactor Projects Enclosure

SUMMARY

IR 05000298/2017011; 01/17/2017 - 06/15/2017; Cooper Nuclear Station; Problem

Identification and Resolution.

The inspection activities described in this report were performed between January 17 and June 15, 2017, by the resident inspectors at Cooper Nuclear Station and inspectors from the NRCs Region IV office. One finding of preliminary low-to-moderate safety significance (White)is documented in this report. This finding involved apparent violations of NRC requirements.

The significance of inspection findings is indicated by their color (i.e., Green, greater than Green, White, Yellow, or Red), determined using NRC Inspection Manual Chapter 0609,

Significance Determination Process, dated April 29, 2015. Their cross-cutting aspects are determined using NRC Inspection Manual Chapter 0310, Aspects Within the Cross-Cutting Areas, dated December 4, 2014. Violations of NRC requirements are dispositioned in accordance with the NRC Enforcement Policy. The NRCs program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process, dated July 2016.

Cornerstone: Initiating Events

• AV. The inspectors identified a preliminary low-to-moderate safety significance (White)finding with two NRC-identified apparent violations of Technical Specification 5.4.1.a, for the licensees failure to implement and maintain Maintenance Procedure 7.3.41, Examination and High Pot Testing of Non-Segregated Buses and Associated Equipment, Revision 10, during testing and inspection of the emergency station service transformer 4160 V bus bars.

Specifically, the inspectors identified:

1. A violation of Technical Specification 5.4.1.a, for the failure to implement inspection instructions to examine the emergency transformer bus insulation for discoloration and repair the associated components on March 23, 2015; and 2. A violation of Technical Specification 5.4.1.a, for the failure to maintain adequate instructions for performing high potential testing of the emergency transformer bus bars between March 23, 2015, and April 18, 2017.

As a result, the licensee did not properly assess corona-related degradation on the emergency transformer bus, which resulted in an emergency transformer bus fault and a loss of the emergency transformer and the supplemental diesel generator on January 17, 2017. Corrective actions to restore compliance included replacement of the faulted portions of the emergency transformer bus, extent of condition inspection and cleaning of the remainder of the emergency transformer bus bars, long term corrective actions to replace the emergency transformer bus insulation, and revision of high potential testing procedure instructions. The licensee entered these issues into the corrective action program as Condition Reports CR-CNS-2017-00223 and CR-CNS-2017-02164.

The licensees failure to implement and maintain Maintenance Procedure 7.3.41 to properly assess degradation of the emergency station service transformer bus, in violation of Technical Specification 5.4.1.a, was a performance deficiency. The performance deficiency was determined to be more than minor, and therefore a finding, because it was associated with the equipment performance attribute of the Initiating Events Cornerstone and affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown, as well as power operations.

Specifically, the finding resulted in an emergency transformer bus fault and a loss of the emergency transformer and the supplemental diesel generator. Using NRC Inspection Manual Chapter 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, dated June 19, 2012, the inspectors determined that the finding required a detailed risk evaluation because it involved the partial loss of a support system that contributes to the likelihood of, or causes, an initiating event (loss-of-offsite power), and the finding affected mitigation equipment (supplemental diesel generator).

A senior reactor analyst performed a detailed risk evaluation in accordance with Inspection Manual Chapter 0609, Appendix A, Section 6.0, Detailed Risk Evaluation. The calculated increase in core damage frequency was dominated by station blackout initiators. The NRC preliminarily determined that the increase in core damage frequency for internal and external initiators was 6.3E-6/year, a finding of low-to-moderate risk significance (White).

The performance deficiency had a cross-cutting aspect in the area of problem identification and resolution associated with evaluation, because the licensee failed to thoroughly evaluate emergency transformer electrical bus discoloration and high potential test failures to ensure that resolutions addressed the causes and extent of conditions commensurate with their safety significance [P.2]. (Section 4OA2)

REPORT DETAILS

REACTOR SAFETY

Cornerstones: Initiating Events, Mitigating Systems

1R13 Maintenance Risk Assessments and Emergent Work Control

a. Inspection Scope

On January 23, 2017, the inspectors observed portions of one emergent work activity associated with repair of an emergency station service transformer (ESST) bus fault that had the potential to cause an initiating event and affect the functional capability of mitigating systems.

The inspectors verified that the licensee appropriately developed and followed a work plan for these activities. The inspectors verified that the licensee took precautions to minimize the impact of the work activities on unaffected structures, systems, and components (SSCs).

These activities constituted completion of one emergent work control inspection sample, as defined in Inspection Procedure 71111.13.

b. Findings

No findings were identified.

1R19 Post-Maintenance Testing

a. Inspection Scope

The inspectors reviewed one post-maintenance testing activity that affected risk-significant SSCs. On January 23, 2017, the inspectors reviewed the post-maintenance testing activity following the emergent repairs of the ESST. The inspectors reviewed licensing- and design-basis documents for the SSCs and the maintenance and post-maintenance test procedures. The inspectors observed the performance of the post-maintenance tests to verify that the licensee performed the tests in accordance with approved procedures, satisfied the established acceptance criteria, and restored the operability of the affected SSCs.

These activities constituted completion of one post-maintenance testing inspection sample, as defined in Inspection Procedure 71111.19.

b. Findings

No findings were identified.

OTHER ACTIVITIES

Cornerstones: Initiating Events, Mitigating Systems

4OA2 Problem Identification and Resolution

Annual Follow-up of Selected Issues

a. Inspection Scope

The inspectors selected one issue for an in-depth follow-up. The inspectors assessed the licensees problem identification threshold, cause analyses, extent of condition reviews, and compensatory actions for the January 17, 2017, ESST bus fault. The inspectors verified that the licensee appropriately prioritized the planned corrective actions and that these actions were adequate to correct the condition.

These activities constituted completion of one annual follow-up sample, as defined in Inspection Procedure 71152.

b. Findings

Introduction.

The inspectors identified a finding of preliminary low-to-moderate safety significance (White) with two associated violations of Technical Specification (TS) 5.4.1.a, for the licensees failure to implement and maintain Maintenance Procedure 7.3.41, Examination and High Pot Testing of Non-Segregated Buses and Associated Equipment, Revision 10, during testing and inspection of the ESST 4160 V bus bars. Specifically, the inspectors identified:

1. A violation of TS 5.4.1.a, for the failure to implement inspection instructions to examine the ESST bus insulation for discoloration and repair the associated components on March 23, 2015; and 2. A violation of TS 5.4.1.a, for the failure to maintain adequate instructions for performing high potential testing of the ESST bus bars between March 23, 2015, and April 18, 2017.

As a result, the licensee did not properly assess corona-related degradation on the ESST bus, which resulted in an ESST bus fault and a loss of the ESST and the supplemental diesel generator (SDG) on January 17, 2017.

Description.

On January 17, 2017, the plant experienced a phasetophase fault of the nonsegregated bus on the secondary side of the ESST. When the fault occurred, the control room received several annunciators alerting the operators to the loss of voltage to the ESST. Operations personnel entered Abnormal Procedure 5.3GRID, Degraded Grid Voltage, Revision 46, in response to the event. Shortly thereafter, the control room received a report from the Nebraska Public Power District grid operations center, which notified the station that there was an apparent 3-phase fault on the bus bars between the ESST transformer and the plants safety-related 4160 V buses. Subsequently, the licensee discovered that an area of the nonsegregated ESST bus duct near the turbine building was discolored and at an elevated temperature. The ESST was not loaded, and no ESSTrelated switching activities were occurring at the time of the fault. The Nebraska Public Power District grid operations center analyzed the fault and determined that the circuit protection operated correctly.

Station loads are normally powered by the normal transformer, which is fed by the stations main generator or by the startup station service transformer (SSST) when the plant is not generating power. Because the ESST is normally on standby as one of the stations two offsite power sources required by TS Limiting Condition for Operation 3.8.1, AC Sources - Operating, operations personnel entered TS 3.8.1, Condition A, a 7-day TS action statement, after the fault occurred. In addition, the fault resulted in a loss of the nonsafety-related SDG because the faulted ESST bus bars were common to the SDG. No other equipment was directly impacted by the fault.

The licensee initiated an apparent cause evaluation (ACE) to review the cause of the event. The licensee determined that the direct cause of the fault was due to damage associated with corona, a voltage-related phenomenon that can result in insulation breakdown and generation of a white conductive powder residue. Specifically, the licensee determined that corona present at the interface between the ESST nonsegregated bus bar supports and the bus bars caused degradation of the bus bar insulation, which led to tracking across the ESST bus bar supports and an eventual fault.

The licensee also recognized that humidity and moisture increases corona tracking. The licensee concluded that the apparent cause of the event was that the inspection procedure did not give adequate guidance to support operation of the ESST bus until the next scheduled inspection.

The licensee determined that the procedure guidance in Maintenance Procedure 7.3.41 did not ensure that a thorough inspection of the ESST bus was performed to support the 10-year inspection interval. Specifically, the licensee concluded that the procedural guidance was inadequate, in that, it did not direct removal of the ESST bus bar support insulators to allow for inspection of the insulation under the support or specify inspection for signs of tracking on bus support insulators.

The inspectors reviewed the licensees assessment of the cause of the event.

Specifically, the inspectors reviewed the January 17, 2017, event; walked down the faulted ESST bus bars and related equipment; interviewed plant personnel; and reviewed condition reports and work orders associated with the most recent ESST bus bar inspections. The inspectors noted that the ESST bus bar inspection was a preventative maintenance activity with a 10-year frequency, and that the last time the ESST bus bar inspection was performed was between March 23 and 29, 2015. The licensees ACE noted that corona-related degradation was a slowly developing failure mechanism, and that the degradation would have been present during the 2015 inspection. As a result, the inspectors concluded that during the 2015 ESST inspection, the licensee had failed to identify white corona-related discoloration and insulation damage in the location where the 2017 fault occurred.

The inspectors noted that during the previous 10-year inspection that was completed in 2005, the licensee discovered corona-related degradation on the ESST bus throughout the bus duct and performed an ACE to address the issue. As a result of the 2005 ACE, the licensee added more prescriptive steps to the inspection procedure to require more thorough inspections. The procedure steps that were added were labeled as protected steps, which meant that they were referenced to the 2005 ACE and the associated deficient condition for which they were created. Specifically, Step 5.9 stated, Examine nonsegregated bus insulations for discoloration. IF insulation discoloration is present, THEN clean as necessary. Remove bus bar supports, if necessary, to clean insulation.

The inspectors concluded that the added steps contained adequate direction to allow for identification of corona-related condition degradation, and that the licensees 2017 ACE that was performed in response to the ESST bus fault had not fully identified the cause of the event.

The inspectors challenged licensee personnel on their conclusion that insufficient detail in the inspection instructions was the apparent cause of the inadequate 2015 inspection, as concluded by the 2017 ACE. The NRC did not independently perform a causal analysis for this event. However, the inspectors concluded that the procedure, which was even less detailed during the 2005 inspection, was adequate to allow identification of corona-related degradation.

The inspectors identified that the procedure directed inspection and/or cleaning of all insulations, which should reasonably have included the ESST bus bar insulator supports. The inspectors noted that because tracking across the insulator support bars was a necessary contributor to the fault, maintenance personnel should not have needed to remove the support bars in order to identify the discoloration and tracking across them. As a result, the inspectors questioned the licensee on whether the inadequate 2015 ESST bus inspection was due to weaknesses in the training of the individuals performing the inspection, inadequate corrective actions for bus discoloration when it was identified, an inadequate high potential (hipot) testing process, and/or a failure to utilize internal operating experience from the last ESST bus inspection in 2005 to ensure the workers knew what they were looking for and what to expect to find.

The licensees ACE did not address or discredit these potential causal factors. In addition, the inspectors challenged the licensees 2017 extent of condition review, because it was narrowly scoped and only directed a spot check of the X winding of the SSST bus section immediately below where the ESST fault occurred. The inspectors discussed these concerns with the licensee, and the licensee entered these issues into the corrective action program as Condition Report-CR-CNS-2017-04126.

The inspectors reviewed Maintenance Procedure 7.3.41, the licensees procedure for performing maintenance on the ESST, SSST, and normal transformer buses. The inspectors noted that on March 23, 2015, the licensee changed the method of performing bus testing from megger to hipot testing. The inspectors noted that Step 5.16 of Maintenance Procedure 7.3.41, required, in part, High Pot each bus phase to ground at approximately 14kV for a minimum of 30 seconds.

The inspectors determined that the licensees hipot testing practice was not consistent with industry Institute of Electrical and Electronics Engineers (IEEE) standards. The inspectors determined that IEEE Standard C37.23-2003, IEEE Standard for Metal-Enclosed Bus, was applicable for this condition because the licensee was relying on the adequacy of the hipot test in combination with the visual inspection to verify functionality of the ESST bus bars. This IEEE standard states, in part, that for nonsegregated buses, test voltages shall be applied between each phase (or pole)individually and ground, with the other phases and the enclosure grounded.

The inspectors noted that with the IEEE test configuration, the test would check for both phase-to-phase and phase-to-ground degradation for each phase. However, the inspectors determined the configuration described in the licensees procedure would only test for phase-to-ground degradation. As a result, the hipot testing performed in 2015 and again in 2017 would not have identified the existence of the conditions that led to the January 2017 bus fault. In addition, the inspectors noted that the IEEE standard stated that the test voltage should be increased gradually from zero to reach the required test value and held at that value for 1 minute. Contrary to the IEEE standard, the licensees procedure only required holding the test voltage for 30 seconds.

The inspectors noted that the licensee implemented a permanent change during the 2015 hipot test, which allowed station personnel to test the bus at a voltage of 10kV rather than the 14kV described in the procedure. The inspectors observed that Section 6.4.2 of the IEEE standard allowed test voltages up to 75 percent of the values specified in Tables 1, 2, 3, and 4 of the document. Tables 1, 2, 3, and 4 allowed testing at up to 14.25kV ac (75 percent of 19kV rms (ac)) or 20.25kV dc (75 percent of 27kV (dc)) for the ESST bus in question. The inspectors observed that the decreased 10kV ac test voltage appeared nonconservative. The inspectors concluded that the instructions contained in Procedure 7.3.41 for performance of hipot testing were inadequate.

The inspectors observed that the station had a history of corona-related degradation in the ESST bus duct. As previously discussed, in 2005 the ESST bus inspection revealed corona-related degradation (CR-CNS-2005-03946), which prompted the site to clean and repair the affected locations. In 2011, the site experienced additional corona-related degradation when an ESST work window was extended as a result of discovery of corona damage to the ESST bus insulation (CR-CNS-2011-03839).

During the 2015 inspection, which took place March 23-29, 2015, the licensee identified black discoloration (not corona-related) on all three phases of the horizontal section of the ESST bus duct that ran from the entrance to the noncritical switchgear room to an area near the SSST (CR-CNS-2015-01745). This long horizontal run included the location where the 2017 ESST bus fault eventually occurred. Although the inspection procedure directed workers to clean the insulation if discoloration was found, the licensee instead evaluated that the black discoloration would not impact the function of the ESST bus. As a result, this section of the ESST bus duct was not cleaned, and the licensee relied on an improperly performed hipot test to verify that bus function was not impacted. The licensee concluded that the black discoloration was the result of dust and debris accumulation on the bus bar insulation.

The inspectors noted that contamination in the form of dust, oils, fluids, or other particulate on conductors and insulators would result in increased corona generation and tracking, and that not cleaning it could exacerbate the degradation. In addition, the inspectors noted that the dust could have obscured the evidence of corona tracking and degradation. Finally, the inspectors concluded that if the licensee had cleaned the discoloration identified during the 2015 inspection, as described by their procedure, it would likely have resulted in the removal and replacement of the ESST bus bar supports to facilitate cleaning. Those repair activities could have prevented the ESST bus fault from occurring. At the end of the March 2015 inspection and work window, the ESST bus failed the initial hipot test, indicating that there was a ground somewhere on the bus.

The licensee isolated segments of the ESST bus and identified the ground, but did not revisit the adequacy of the inspection or perform an extent of condition evaluation.

As a result of their review of the ESST bus fault event, the inspectors determined that the most likely contributor to the failure to implement Maintenance Procedure 7.3.41 was the licensees failure to thoroughly evaluate deficiencies identified with the condition of the ESST bus duct during the 2015 inspection. Specifically, the licensee failed to thoroughly evaluate ESST bus discoloration identified during the 2015 inspection, the hipot testing failures that followed the inspection, and the extent of condition of the 2015 testing and inspection deficiencies.

Analysis.

The licensees failure to implement and maintain Maintenance Procedure 7.3.41 to properly assess degradation of the ESST bus, in violation of Technical Specification 5.4.1.a, was a performance deficiency. The performance deficiency was determined to be more than minor, and therefore a finding, because it was associated with the equipment performance attribute of the Initiating Events Cornerstone, and affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown, as well as, power operations. Specifically, the finding resulted in the licensees failure to identify and repair indications of corona-related degradation on the ESST bus, which resulted in an ESST bus fault, and a loss of the ESST and SDG on January 17, 2017.

The inspectors used Inspection Manual Chapter (IMC) 0609, Attachment 4, Initial Characterization of Findings, and determined that the finding could be evaluated using the significance determination process. In accordance with Table 3, SDP Appendix Router, the inspectors determined that the finding should be processed through Appendix A, The Significance Determination Process (SDP) for Findings At-Power, Exhibit 1, Initiating Events Screening Questions, dated July 1, 2012. Using IMC 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, dated June 19, 2012, the inspectors determined that the finding required a detailed risk evaluation because it involved the partial loss of a support system that contributes to the likelihood of, or causes, an initiating event (loss-of-offsite power) and the finding affected mitigation equipment (SDG).

A senior reactor analyst performed a detailed risk evaluation in accordance with IMC 0609, Appendix A, Section 6.0, Detailed Risk Evaluation. The calculated increase in core damage frequency was dominated by station blackout initiators. The NRC preliminarily determined that the increase in core damage frequency for internal and external initiators was 6.3E-6/year, a finding of low-to-moderate risk significance (White).

The results of the detailed risk evaluation are included in Attachment 2 of this report.

The performance deficiency had a cross-cutting aspect in the area of problem identification and resolution, associated with evaluation because the licensee failed to thoroughly evaluate ESST bus discoloration and hipot test failures to ensure that resolutions addressed the causes and extent of conditions commensurate with their safety significance. Specifically, the licensee failed to thoroughly evaluate ESST bus discoloration identified during the 2015 inspection, the hipot testing failures that followed the inspection, and the extent of condition of the 2015 testing and inspection deficiencies [P.2].

Enforcement.

The two apparent violations described below are associated with a preliminary White significance determination process finding.

1. Technical Specification 5.4.1.a requires, in part, that procedures shall be

established, implemented, and maintained covering the applicable procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2. Section 9.a of Appendix A to Regulatory Guide 1.33, Revision 2, requires, Procedures for Performing Maintenance. The licensee established Maintenance Procedure 7.3.41, Examination and High Pot Testing of Non-Segregated Buses and Associated Equipment, Revision 10, to meet the Regulatory Guide 1.33 requirement. Step 5.9 of Procedure 7.3.41 requires maintenance personnel to, Examine nonsegregated bus insulations for discoloration. IF insulation discoloration is present, THEN clean as necessary. Remove bus bar supports, if necessary, to clean insulation.

Contrary to the above, between March 23-29, 2015, maintenance personnel failed to fully examine nonsegregated bus insulations for discoloration; and when insulation discoloration was present, did not clean as necessary. Specifically, during inspection and testing of the ESST nonsegregated bus, the licensee failed to implement inspection instructions to examine the bus insulations for evidence of corona deposits and repair the associated components.

2. Technical Specification 5.4.1.a requires, in part, that procedures shall be

established, implemented, and maintained covering the applicable procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2. Section 9.a of Appendix A to Regulatory Guide 1.33, Revision 2, requires, Procedures for Performing Maintenance. The licensee established Maintenance Procedure 7.3.41, Examination and High Pot Testing of Non-Segregated Buses and Associated Equipment, Revision 10, to meet the Regulatory Guide 1.33 requirement.

Contrary to the above, between March 23, 2015, and April 18, 2017, the licensee failed to maintain adequate written procedures covering the applicable procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2. Specifically, the licensee failed to maintain Procedure 7.3.41 with adequate instructions for performing hipot testing of the ESST bus bars to ensure that the buses were appropriately tested for phase-to-phase degradation in addition to phase-to-ground degradation. In particular, the test instructions did not ensure that test voltages were applied between each phase individually and ground, with the other phases and the enclosure grounded, so that the phase-to-phase degradation that resulted in the ESST bus fault could be identified.

As a result of these apparent violations, the licensee did not properly assess corona-related degradation on the ESST bus, which resulted in a bus fault and a loss of the ESST and SDG on January 17, 2017. Corrective actions to restore compliance included replacement of the faulted portions of the ESST bus, extent of condition inspection and cleaning of the remainder of the ESST bus bars, long-term corrective actions to replace all of the ESST bus insulation, and revision of hipot testing procedure instructions.

The licensee entered these issues into the corrective action program as Condition Reports CR-CNS-2017-00223 and CR-CNS-2017-02164. These apparent violations have preliminarily been determined to be associated with a finding of low-to-moderate safety significance (White), and are being treated as apparent violations (AVs),consistent with the Enforcement Policy, pending a final significance determination.

(AV 05000298/2017011-01, Emergency Transformer Bus Failure due to Inadequate Inspection and Testing Activities)

4OA6 Meetings, Including Exit

Exit Meeting Summary

On August 11, 2017, the inspectors presented the inspection results to Mr. John Dent, Vice President-Nuclear and CNO, and other members of the licensee staff. The licensee acknowledged the issues presented. The licensee confirmed that any proprietary information reviewed by the inspectors had been returned or destroyed.

SUPPLEMENTAL INFORMATION

KEY POINTS OF CONTACT

Licensee Personnel

M. Bakker, System Engineer

T. Barker, Manager, Engineering Program and Components

D. Buman, Director, Nuclear Safety Assurance

B. Chapin, Manager, Maintenance

J. Dent, Vice President, Chief Nuclear Officer

L. Dewhirst, Manager, Corrective Action and Assessment

K. Dia, Director, Engineering

J. Ehlers, Supervisor, System Engineering

T. Forland, Engineer, Licensing

G. Gardner, Engineering Design Manager

D. Goodman, Manager, Operations

K. Higginbotham, Former Vice President, Chief Nuclear Officer

J. Kalamaja, General Manager Plant Operations

J. Reimers, Manager, System Engineering

J. Shaw, Manager, Licensing

LIST OF ITEMS OPENED, CLOSED, AND DISCUSSED

Opened

Emergency Transformer Bus Failure due to Inadequate

05000298/2017011-01 AV Inspection and Testing Activities (Section 4OA2)