IR 05000414/2024092
| ML24320A111 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 11/20/2024 |
| From: | Robert Williams NRC/RGN-II/DORS/PB1 |
| To: | Flippin N Duke Energy Carolinas |
| References | |
| EA?24?084 IR 2024092 | |
| Download: ML24320A111 (1) | |
Text
SUBJECT:
CATAWBA NUCLEAR STATION - NRC INSPECTION REPORT 05000414/2024092
Dear Nicole Flippin:
On August 7, 2024, the U.S. Nuclear Regulatory Commission (NRC) issued Inspection Report 05000413/2024002 and 05000414/2024002 (ADAMS Accession No. ML24215A302). The report documented an apparent violation (AV) for which the NRC had not yet reached a preliminary significance determination. Based on subsequent review, the NRC has completed the final disposition regarding this apparent violation. On November 14, 2024, the NRC discussed the results of the evaluation with you and other members of your staff. The results are documented in the enclosed report.
One finding of very low safety significance (Green) is documented in this report. This finding involved a violation of NRC requirements. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violation or the significance or severity of the violation documented in this inspection report, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region II; the Director, Office of Enforcement; and the NRC Resident Inspector at Catawba Nuclear Station.
For administrative purposes, this letter is issued as NRC Inspection Report 05000414/2024092.
Accordingly, the AV documented in NRC Inspection Report Inspection Report 05000413/2024002 and 05000414/2024002 is now designated as NCV 05000414/2024002-02.
November 20, 2024 This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely, Robert E. Williams, Jr., Chief Projects Branch 1 Division of Operating Reactor Safety Docket No. 05000414 License No. NPF-52
Enclosure:
As stated
Inspection Report
Docket Number:
05000414
License Number:
Report Number:
Enterprise Identifier:
I2024-092-0000
Licensee:
Duke Energy Carolinas, LLC
Facility:
Catawba Nuclear Station
Location:
York, South Carolina
Inspection Dates:
September 22, 2024 to November 1, 2024
Inspectors:
D. Rivard, Senior Resident Inspector
S. Sandal, Senior Reactor Analyst
A. Wang, Resident Inspector
Approved By:
Robert E. Williams, Jr., Chief
Projects Branch 1
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees
performance by conducting a NRC inspection at Catawba Nuclear Station, in accordance with
the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for
overseeing the safe operation of commercial nuclear power reactors. Refer to
https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
Failure to Implement Replacement Preventive Maintenance Strategies for Emergency Diesel
Generator Run Relays
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Mitigating
Systems
Green
NCV 05000414/202400202
Closed
EA24-084
None (NPP)
A self-revealed Green finding and associated non-cited violation (NCV) of technical specification (TS) 5.4, Procedures, was identified for the licensees failure to implement
licensee procedures for preventive maintenance in accordance with Regulatory Guide
(RG) 1.33, Revision 2, Appendix A, February 1978. Specifically, the licensee failed to develop
replacement preventive maintenance strategies for relay R1A in the emergency diesel
generator (EDG) start control circuitry, in accordance with licensee procedure
ADEGALL1202, Preventive Maintenance and Surveillance Testing Administration.
Additional Tracking Items
None.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in
effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with
their attached revision histories are located on the public website at http://www.nrc.gov/reading-
rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared
complete when the IP requirements most appropriate to the inspection activity were met
consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection
Program - Operations Phase. The inspectors reviewed selected procedures and records,
observed activities, and interviewed personnel to assess licensee performance and compliance
with Commission rules and regulations, license conditions, site procedures, and standards.
INSPECTION RESULTS
Failure to Implement Replacement Preventive Maintenance Strategies for Emergency Diesel
Generator Run Relays
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Mitigating
Systems
Green
NCV 05000413,05000414/2024002-02
Closed
EA24-048
None (NPP)
A self-revealed Green finding and associated NCV of TS 5.4, Procedures, was identified for
the licensees failure to implement licensee procedures for preventive maintenance in
accordance with RG 1.33, Revision 2, Appendix A, February 1978. Specifically, the licensee
failed to develop replacement preventive maintenance strategies for relay R1A in the EDG
start control circuitry, in accordance with licensee procedure ADEGALL-1202, Preventive
Maintenance and Surveillance Testing Administration.
Description: On March 5, 2024, the licensee declared the 2A EDG inoperable and entered TS
limiting condition for operation 3.8.1.B, because the 2A EDG failed to flash the generator field
during a surveillance test. The surveillance test was conducted in accordance with licensee
procedure PT/2/A/4350/002 A, Diesel Generator 2A Operability Test, Enclosure 13.1, D/G
2A Operation from D/G Room. The licensee used procedure PT/2/A/4200/009 A, Auxiliary
Safeguards Test Cabinet Periodic Test, Enclosure 13.19, Safety Injection (K-608) -
Train A, to generate the start signal. The cause of the failure of 2A EDG was attributed to the
R1A relay in the start control circuit. Analysis showed that a set of normally open contacts of
relay R1A exhibited high and unstable resistance at times with the relay latched. Relay R1A
is a normally deenergized D26 series Cutler-Hammer relay, and it allows an emergency
shutdown reset to the voltage regulator with the relay latched. Without the reset, voltage will
not be developed on startup and the EDG cannot perform its function. Relay R1A for the 2A
EDG was installed at initial construction and had approximately 38 years of service life at the
time of failure.
DPC-1381.05-00-0018, Cutler-Hammer Relay Qualified Life Analysis dated April 1997,
evaluates the estimated life of the relay based on the ambient temperature conditions as well
as the percent of time the relay is energized. Higher temperatures and higher utilization of the
relay correlate to a lower estimated lifespan of the relay. The normally deenergized R1A
relay is infrequently energized during EDG surveillance testing. The estimated lifespan can
vary from 17.24 years assuming constant ambient temperatures of 120°F and a 20 percent
duty cycle to as long as 339.7 years assuming constant ambient temperatures of 80°F and a
five percent duty cycle. The licensee calculated a service life of 77 years based on an
ambient temperature of 100°F and a duty cycle of 10 percent.
WCAP-15977-NP, Reliability Assessment of Cutler-Hammer D26MR802A Relays Used as
SSPS [Solid State Protection System] Slave Relays, dated June 2003, is a Westinghouse
reliability assessment of normally deenergized D26 series Cutler-Hammer relays.
WCAP15977-NP discusses that given appropriate conditions including cleanliness,
temperature, and humidity, normally deenergized D26 series Cutler-Hammer relays can be
expected to last at least for a plants 40-year life span, and that factors such as high
temperatures and high relative humidity can contribute to the accelerated failure mechanism
of high resistance on relay contacts via pitting, corrosion, or contamination. Although the EDG
room that the relay is located in has a ventilation system to control ambient temperature, the
humidity of the room is not controlled and varies based on outside air that is drawn into the
room.
In 2015, Calculation CNC -1301.00-00-0009, Emergency Diesel Generator Controls Failure
Modes and Effects Analysis, (FMEA) was prepared to support the maintenance strategy for
the EDG control system components including relays. Replacement preventive maintenance
was recommended if failure of the component resulted in the EDG not being able to perform
its function and failure of the component was not detected immediately. The licensee
identified a failure mode for relay R1A that would make the EDG inoperable and would not be
detected immediately (i.e., until the next monthly EDG surveillance). However, relay R1A was
incorrectly classified as having failure modes that were detectable immediately upon failure in
Calculation CNC -1301.00-00-0009. Therefore, the licensee did not consider relay R1A for
replacement as prescribed by the preventive maintenance strategy in procedure
ADEGALL1202, Preventive Maintenance and Surveillance Testing Administration,
Revision 13. Procedure ADEG-ALL-1202 states, ER [equipment reliability] Classification 1,
Critical, equipment has the highest reliability goal of no failures that result in unacceptable
consequences for nuclear safety or generation. The R1A relay is classified as ER
Classification 1.
Corrective Actions: The licensee established a one-time replacement preventive maintenance
strategy and replaced the R1A relay in the 2A EDG. Corrective actions were also initiated to
replace the R1A relay in the remaining EDGs.
Corrective Action References: Nuclear Condition Report 02507690
Performance Assessment:
Performance Deficiency: The licensees failure to develop preventive maintenance strategies
for the replacement of the R1A relay in the EDG start control circuitry in accordance with
licensee procedure ADEG-ALL1202 is a performance deficiency.
Screening: The inspectors determined the performance deficiency was more than minor
because it was associated with the Equipment Performance attribute of the Mitigating
Systems cornerstone and adversely affected the cornerstone objective to ensure the
availability, reliability, and capability of systems that respond to initiating events to prevent
undesirable consequences. Specifically, a failure mode was identified for the R1A relay that
rendered the 2A EDG inoperable and could remain undetected at the time of failure.
Significance: The inspectors assessed the significance of the finding using IMC 0609
Appendix AProperty "Inspection Manual Chapter" (as page type) with input value "NRC Inspection Manual 0609</br></br>Appendix A" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process., The Significance Determination Process (SDP) for Findings At-Power. The
inspectors screened the significance of the finding using Exhibit 2 of IMC 0609 Appendix A
for the Mitigating Systems cornerstone and determined that a detailed risk evaluation was
required because the condition involved the loss of the probabilistic risk assessment (PRA)
function of one train of a multi-train TS system for greater than its TS allowed outage time. A
detailed risk evaluation was performed by a regional Senior Reactor Analyst using Systems
Analysis Program for Hands-On Integrated Reliability Evaluations (SAPHIRE),
Version 8.2.11, and Catawba Standardized Plant Analysis Risk (SPAR) model, Version 8.83.
A conditional analysis was performed for Unit 2 using an exposure period of 12 days. No
additional credit was provided in the analysis for post-failure repair of equipment impacted by
the performance deficiency. Because the internal events estimated core damage frequency
(CDF) was greater than 1E07, the analysis also considered additional risk contributions from
SPAR model external events sequences as well as fire and internal flooding risk insights from
the licensees PRA model. The dominant SPAR model sequences involved weather-related
Loss of Offsite Power (LOOP) initiating events. The LOOP was followed by random
failure/unavailability of the B train component cooling water pumps, accompanied by failure
of the turbine-driven auxiliary feedwater pump to run, resulting in failure of the auxiliary
feedwater and feed and bleed functions, leading to core damage. The overall risk of the
finding was mitigated by the relatively short exposure period of the degraded condition. The
analysis determined that the estimated increase in CDF and large early release frequency
(LERF) was less than 1E06/year for delta-CDF and less than 1E07/year for delta-LERF,
representing a finding of very low safety significance (Green) for Unit 2.
Cross-Cutting Aspect: Not Present Performance. No cross-cutting aspect was assigned to
this finding because the inspectors determined the finding did not reflect present licensee
performance.
Enforcement:
Violation: TS 5.4, Procedures, states in part, written procedures shall be established,
implemented, and maintained covering applicable procedures recommended in RG 1.33,
Revision 2, Appendix A, February 1978. Section 9b of RG 1.33, requires in part that, the
preventive maintenance schedules should be developed to specify replacement of such items
that have a specific lifetime. Licensee procedure ADEG-ALL-1202, Preventive Maintenance
and Surveillance Testing Administration, Revision 13, Section 5.2.3 2, requires in part, the
development of maintenance strategies with the goal of no failures that result in unacceptable
consequences to nuclear safety or generation.
Contrary to the above, since 2015, the licensee failed to develop preventive maintenance
strategies for the replacement of items with a specific lifetime. Specifically, the licensee did
not develop replacement preventive maintenance strategies (i.e., replacement schedule) in
accordance with procedure ADEG-ALL1202 for EDG control circuit relay R1A.
Consequently, relay R1A remained installed past the licensee-determined replacement
frequency and experienced an undetectable failure that rendered the 2A EDG inoperable.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with
Section 2.3.2 of the Enforcement Policy.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
On November 14, 2024, the inspectors presented the NRC inspection results to
Nicole Flippin, Site Vice President, and other members of the licensee staff.