ML23186A127
| ML23186A127 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/06/2023 |
| From: | Raymond Mckinley, Blake Welling Division of Operating Reactors |
| To: | Rhoades D Constellation Energy Generation, Constellation Nuclear |
| References | |
| EA-23-035 IR 2022004 | |
| Download: ML23186A127 (1) | |
See also: IR 05000277/2022004
Text
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION I
475 ALLENDALE ROAD, STE 102
KING OF PRUSSIA, PA 19406-1415
July 6, 2023
David P. Rhoades
Senior Vice President
Constellation Energy Generation, LLC
President and Chief Nuclear Officer (CNO)
Constellation Nuclear
4300 Winfield Road
Warrenville, IL 60555
SUBJECT:
RESPONSE TO DISPUTED NON-CITED VIOLATION DOCUMENTED IN
PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3, INSPECTION
REPORT 05000277/2022004 AND 05000278/2022004
Dear David Rhoades:
On March 6, 2023, Constellation Energy Generation (CEG) provided a written response
(ML23065A158)1 to U.S. Nuclear Regulatory Commission (NRC) Inspection Report 05000277,
05000278/2022004 (ML23033A333) issued on February 2, 2023, for an inspection completed at
Peach Bottom Atomic Power Station, Units 2 and 3. In the letter, CEG disputed the
characterization of non-cited violation (NCV) 05000277,05000278/2022004-01, as Green (very
low safety significance) which was documented in the inspection report.
The NRC conducted a detailed review of your response and the applicable NRC policies and
inspection guidance. This review was performed by NRC staff members who possess relevant
regulatory knowledge and who did not participate in the subject inspection.
After consideration of the bases provided by CEG, the NRC concluded that this non-cited
violation was appropriately dispositioned as more-than-minor and of very low safety significance
(Green).
1 Designation refers to an Agencywide Documents Access and Management System (ADAMS) accession number.
Documents referenced in this letter are publicly-available using the accession number in ADAMS at
https://adams.nrc.gov/wba/ For problems with ADAMS, please contact the NRCs Public Document Room (PDR) reference
staff at 1-800-397-4209, 301-415-4737, or by e-mail to pdr.resource@nrc.gov.
D. Rhoades
2
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,
for Blake D. Welling, Director
Division of Operating Reactor Safety
Docket Nos. 50-277 and 50-278
License Nos. DPR-44 and DPR-56
Enclosure:
NRC Staff Assessment of Disputed
NCV 05000277,05000278/2022004-01
cc w/encl: Distribution via ListServ
Raymond R.
McKinley
Digitally signed by Raymond R.
McKinley
Date: 2023.07.06 08:13:33
-04'00'
x
SUNSI Review
x
Non-Sensitive
Sensitive
x
Publicly Available
Non-Publicly Available
OFFICE RI/EAGL
RI/DORS
RI/DORS
RI/RC
RI/DORS
NAME
CCrisden
KMangan
MGray
RSusko
BWelling
DATE
6/12/23
6/12/23
6/12/23
6/12/23
6/12/23
OFFICE HQ/OE
HQ/NRR
RI/DORS
NAME
DJones
RFelts
BWelling
DATE
6/20/23
6/20/23
6/28/23
Enclosure
NRC STAFF ASSESSMENT OF DISPUTED NCV 05000277,05000278/2022004-01, FAILURE
TO IMPLEMENT AN EFFECTIVE MAINTENANCE STRATEGY FOR UNIT 2 AND UNIT 3
RESIDUAL HEAT REMOVAL SYSTEM AGASTAT RELAYS
The U.S. Nuclear Regulatory Commission (NRC) staff reviewed the information provided in
Constellation Energy Generations (CEG) letter (ML23065A158) dated March 6, 2023, to
determine whether non-cited violation (NCV) 05000277,05000278/2022004-01 was
appropriately characterized as more-than-minor. This review was performed by NRC staff who
possess relevant regulatory knowledge and who did not participate in the inspection that
resulted in issuance of this NCV. In performing this assessment, the NRC reviewers relied upon
the documents listed in the reference section of this enclosure and consulted with other NRC
staff members.
A. BACKGROUND
On February 2, 2023, the NRC issued Inspection Report 05000277, 05000278/2022004
(ML23033A333) for baseline inspections completed at Peach Bottom Atomic Power Station
(PBAPS), Units 2 and 3. The inspection report documented a Green finding and associated
non-cited violation (NCV) of Technical Specification (TS) 5.4.1.a, "Procedures," and Regulatory
Guide (RG) 1.33. Specifically, CEG failed to establish an effective maintenance strategy for
Agastat control relays in the safety-related residual heat removal (RHR) systems at Peach Bottom
Unit 2 and Peach Bottom Unit 3.
In their letter dated March 6, 2023, CEG contested the characterization of the finding as more-
than-minor stating that:
Constellation Energy Generation, LLC (CEG) is respectfully contesting the significance
of the Green finding and associated non-cited violation (NCV) documented in the
referenced U.S. Nuclear Regulatory Commission (NRC) Inspection Report for Peach
Bottom Atomic Power Station (PBAPS), Units 2 and 3.
The referenced inspection report documents a Green finding and associated NCV of
Technical Specification (TS) 5.4.1.a, "Procedures," and Regulatory Guide (RG) 1.33,
Quality Assurance Program Requirements (Operation), for CEG's failure to establish
an effective maintenance strategy for Agastat control relays in the safety-related
Residual Heat Removal (RHR) system at both PBAPS, Units 2 and 3. RG 1.33,
Appendix A, November 1972,Section I, requires in part, that preventive maintenance
schedules should be developed to specify inspection of replacement parts that have a
specified lifetime. The NRC noted that the vendor specified lifetime for the Agastat relays
is 25,000 operations or 10 years from the date of manufacture, whichever occurs first,
which was exceeded for a Unit 2 RHR control relay that failed in October 2017 and was
over 37 years old.
The NRC determined that not establishing a preventive maintenance schedule, or
effective maintenance strategy for the PBAPS, Units 2 and 3, RHR system Agastat
control relays in accordance with TS 5.4.1.a, and as implemented in station procedure
ER-AA-200, Preventive Maintenance Program, was a performance deficiency that was
reasonably within CEG's ability to foresee and correct. The inspectors determined that
the performance deficiency was more than minor because if left uncorrected, it would
have the potential to lead to a more significant safety concern.
2
CEGs position is that the more than minor significance is unwarranted and should be
reconsidered based on the supporting information/justification provided in the
Attachment to this letter.
B. RESTATEMENT OF PERFORMANCE DEFICIENCY EVALUATION FOR NCV
05000277/278/2022004-01
The NRC inspection report describes the performance deficiency (PD) and the screening criteria
used as the basis for considering the PD as of more-than-minor safety significance:
Performance Deficiency: The inspectors determined that not establishing a preventive
maintenance schedule, or effective maintenance strategy for Unit 2 and Unit 3 RHR
system Agastat control relays in accordance with TS 5.4.1.a, and as implemented in
station procedure ER-AA-200, was a performance deficiency that was reasonably within
Constellation's ability to foresee and correct.
Screening: The inspectors determined the performance deficiency was more than minor
because if left uncorrected, it would have the potential to lead to a more significant
safety concern. Specifically, Agastat relay failures in the RHR system have the potential
to render a single ECCS instrumentation channel, or single train of the RHR system
inoperable per TS, between quarterly surveillance tests. This performance deficiency is
similar to Example 13.a in NRC IMC 0612, Appendix E, "Examples of Minor Issues,"
dated January 1, 2021.
The NRC inspection report further documents the safety significance resulting from the finding,
evaluated in accordance with NRC Inspection Manual Chapter (IMC) 0609:
Significance: The inspectors assessed the significance of the finding using IMC 0609,
Appendix A, The Significance Determination Process (SDP) for Findings At-Power.
The inspectors utilized IMC 0609, Appendix A, Exhibit 2, Mitigating System Screening
Questions, and answered No to Question 1: If the finding is a deficiency affecting the
design or qualification of a mitigating SSC, does the SSC maintain its operability, or PRA
functionality?. The inspectors answered No to Question 2: Does the degraded
condition represent a loss of the PRA function of a single train TS system for greater
than its TS allowed outage time?. The inspectors answered Yes to Question 3: Does
the degraded condition represent a loss of PRA function of one train of a multi-train TS
system for greater than its TS allowed outage time?
Detailed Risk Assessment: Specifically, TSs related to the RHR system had a 7-day
allowed outage time (AOT) in 2017, when the failure of the Agastat relay for 2A RHR
pump occurred. The last time operability of the A train of the RHR system was
confirmed, was during performance of ST-O-010-301-2, 92 days before the October 5,
2017, surveillance. Therefore, past operability during this 92-day period was unknown
and undetermined, which is greater than the TS AOT of 7 days. Therefore, in
accordance with IMC 0609, Appendix A, a detailed risk evaluation (DRE) was
performed. The Senior Reactor Analyst (SRA) used the Systems Analysis Programs for
Hands-On Evaluation (SAPHIRE), Revision 8.2.6, Peach Bottom Standardized Plant
Analysis Risk Model, version 8.80 to perform the DRE. The basic event, RHR-MOV-CC-
F016A, MINFLOW Valve 10-16A Fails to Open, was set to TRUE. This was performed to
invoke a limited common cause failure potential for the evaluation of the performance
3
deficiency. Other RHR motor operated valve failure probabilities were increased by an
order of magnitude to account for increased failure probability though current
surveillance tests were satisfactory. The SRA did not include recovery for proper
identification and repositioning of the valve(s) by operators. This is considered a
bounding analysis for Unit 2 and would represent the potential risk to Unit 3, separately.
No failures were identified on Unit 3. A 92-day exposure time was used to bound the
degraded condition and performance deficiency. The increase in core damage frequency
(CDF) for the conditional increased failure to open was calculated to be 9E-8/year for the
internal risk contribution. The dominant core damage sequence consisted of a
postulated loss of 4kV E12 bus, containment failure with loss of all injection, failure to
recover the power conversion system, and common failure of the RHR min flow lines.
IMC 0609, Appendix A, SDP For Findings At-Power, does not require a detailed
evaluation of external risk contribution for internal event CDF increases below a 1E-7/yr
threshold. Additionally, the impact on large early release frequency would not change
this risk determination. This issue was determined to be of very low safety significance
(Green) for the calculated increase in CDF/yr due to the degraded condition.
C. LICENSEE POSITION
In their March 6, 2023, letter, CEG contested the more-than minor assessment of the PD
stating:
CEG has reviewed the information from the inspection report as described above and
has elected to not contest the assigned Performance Deficiency, but offers the following
information for further NRC review and consideration in contesting the significance of
this Green NCV. It is the position of CEG that the maintenance strategy developed for
the subject relays is appropriate, meets the requirements of Regulatory Guide 1.33, and
does not require changes in response to this failure. Therefore, it is not reasonable to
conclude that if left uncorrected, the performance deficiency would have the potential to
lead to a more significant safety concern. Similar to the minor Example 13.a from
IMC 0612 Appendix E, the engineering evaluation of this maintenance strategy shows
that a replacement PM is not required over the remaining term of the operating license.
In addition, this situation can be compared to Example 3.l. In this example, the licensee
failed to incorporate industry data in implementation of activities that would provide
assurance that equipment would meet its design basis function. The example can be
screened as minor if the licensee could show that the data population was sufficiently
large to represent the performance of the equipment, such that no changes to the testing
and maintenance programs were necessary. For the Peach Bottom relay failure, as
discussed in detail below, the reviews of site and industry data have demonstrated that
the current maintenance strategy is supported by expected failure modes and failure
rates and provide reasonable assurance of meeting the specified safety function.
D. NRC STAFF REVIEW
The NRC staff reviewed CEGs position regarding the inspectors more-than-minor conclusion
and applicable NRC inspection guidance. The NRC staff reviewed guidance in IMC 0611,
Power Reactor Inspection Reports, IMC 0612, Issue Screening, and IMC 0612, Appendix E,
Examples of Minor Issues.
4
NRC Process for Screening Inspection Issues
NRC IMC 0612 and its appendices provide NRC inspectors guidance to screen inspection
issues. Once the inspectors identify that a PD exists, the PD is screened to determine whether it
is of more-than-minor safety significance in accordance with IMC 0612. IMC 0612,
Section 05.01 lists three screening questions that inspectors use to determine whether a PD is
more-than-minor. This section also provides specific guidance on the use of each of these
questions and directs inspectors to use the examples in IMC 0612, Appendix E, Examples of
Minor Issues, to inform the minor/more-than-minor determination.
IMC 0612, Section 0612-05 states, in part:
The minor/more-than-minor determination requires inspectors to apply reasonable
judgment to assess if the performance deficiency has created the potential of more-than-
minor safety or security consequences. In making this determination, inspectors should
consider the circumstances, the likelihood of adversely affecting the cornerstone
objectives, and the effect on applicable cornerstone objectives affecting safety and
security. Other factors such as maintaining defense in depth, engineered safety margins,
and the prevention of too much reliance on human operators for rapid critical decisions
should also be considered in this assessment. Equipment inoperability is not a
prerequisite for the performance deficiency to be more-than-minor.
It should also be understood that with all judgment-calls, some variability will exist
whenever different inspectors have to apply judgment to unique and site-specific
circumstances to determine if a performance deficiency is more-than-minor. To ensure
that the Reactor Oversight Process is risk-informed, significant effort should not be
expended on making minor or more-than-minor determinations. Inspectors should risk
inform their level of effort commensurate with the potential safety significance of the
performance deficiency. Ultimately, the inspection report signature authority makes the
final determination based on their interpretation of the guidance within the IMC.
As noted in Section B of the Enclosure, the more-than-minor screening question used by
inspectors for this issue was If left uncorrected, would the performance deficiency have the
potential to lead to a more significant safety concern? The inspectors also used IMC 0612,
Appendix E, Example 13.a to inform their decision.
NRC Review of CEGs Written Response
Based on the scope of the contestation discussed in CEGs letter, the reviewers focused on the
basis for the more-than-minor conclusion and arguments presented in CEGs letter that the PD
should be deemed minor. The reviewers did not reconsider the described PD or associated
violation. Additionally, the reviewers did not evaluate whether the corrective actions described in
the CEG letter were adequate.
The NRC inspection report and CEGs contestation letter both focused on the application of
IMC 0612, Appendix E, Example 13.a, as the basis for considering the PD to be more-than-
minor and minor, respectively. Because Example 13.a addresses service life issues and is
directly related to the subject PD, the reviewers agreed the use of this example is appropriate
5
for informing the inspectors more-than-minor response to the NRC IMC 0612, Issue
Screening question, If left uncorrected, would the performance deficiency have the potential to
lead to a more significant safety concern?
Example 13.a states:
In 2005, the licensee assessed (as required by regulatory requirements or self-imposed
standards) a Vendor Bulletin which stated the period of time that a Molded-Case Circuit
Breakers (MCCBs) can be installed without refurbishment or replacement is 20 years for
mild environment applications. Vendor Bulletin stated that this time interval could be
extended through preventive maintenance, testing, and aging analysis based on
operational usage (number of demands or cycles) and actual plant conditions. The
licensees engineering evaluation of the Bulletin concluded that based on the
environmental conditions and usage of the affected MCCBs, the MCCBs should either
be refurbished or replaced before exceeding 20 years of service. The licensee planned
to revise their MCCB preventive maintenance procedures by 2008 to require
refurbishment or replacement of all MCCBs in safety-related systems prior to exceeding
20 years of service.
During this inspection (2016), the preventive maintenance procedures had not been
updated thus the affected MCCBs remained in service for 26 to 28 years, well beyond
their 20 year refurbishment or replacement interval. To date, no MCCBs failures have
occurred at the licensees site.
The PD: The licensee failed to translate MCCB refurbishment/replacement schedules
into maintenance instructions contrary to regulatory requirements or self-imposed
standards.
Minor if: If left uncorrected, it is not reasonable to conclude the PD would have the
potential to lead to a more significant safety concern. Specifically,
the licensee re-evaluated existing preventive maintenance procedures and
determined the intent of the Vendor Bulletin was met,
-or-
the licensee re-analyzed the existing engineering evaluation (or performed a new
one after NRC identification of the issue) and determined the newly calculated
time period extended beyond the expiration of the operating license. In
performing the new engineering evaluation, the conditions in MTM below did not
apply.
MTM if: If left uncorrected, the PD has the potential to lead to a more significant safety
concern. Specifically, absent NRCs intervention, the licenses failure to establish and
perform appropriate preventative maintenance refurbishments or replacements can lead
to in-service component deterioration and resultant failures of MCCBs to perform their
safety-related functions.
-or-
The PD 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
6
prevent undesirable consequences. Specifically, exceeding the previously analyzed time
period for replacement or refurbishment caused reasonable doubt on the continual ability
of the MCCBs to perform their safety-related functions. In re- analyzing the existing
engineering evaluation (or in performing a new one after NRC identification of the issue),
the licensee (a) used a different approach because the original approach resulted in
unfavorable margin; or (b) revised assumptions solely to obtain favorable results; or (c)
revised other calculations in order to establish operability or functionality; or (d)
determined the remaining margin falls outside the licensees design process acceptance
criteria. Unfavorable margin means that had the correct values been used originally, the
licensees design process would not have accepted the modification.
CEG asserted that this issue was minor because an engineering evaluation of the current
maintenance strategy shows that a replacement preventive maintenance activity is not required
over the remaining term of the Peach Bottom operating license. CEG concluded that in the mild
applications with ambient temperatures of 80°F, such as the Peach Bottom application for this
relay, the qualified life of this relay is 209 years. Therefore, CEG asserted that it can reasonably
be expected that an Agastat TR relay installed in a normally deenergized, mild service
condition, non-critical application will not require replacement over Peach Bottoms currently
licensed lifetime.
The reviewers found that the CEG response addressed the first part of IMC 0612, Appendix E,
Example 13.a which states that the issue is minor if the licensee re-analyzed the existing
engineering evaluation (or performed a new one after NRC identification of the issue) and
determined the newly calculated time period extended beyond the expiration of the operating
license. However, the reviewers determined that CEG did not address the guidance in the
example which states, In performing the new engineering evaluation, the conditions in more-
than-minor below did not apply.
These conditions are as follows:
Paragraph 1 - If left uncorrected, the performance deficiency has the potential to lead to
a more significant safety concern. Specifically, absent NRCs intervention, the licenses
failure to establish and perform appropriate preventative maintenance refurbishments or
replacements can lead to in-service component deterioration and resultant failures of
[SSCs] to perform their safety-related functions.
-or-
Paragraph 2 - The performance deficiency 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,
exceeding the previously analyzed time period for replacement or refurbishment caused
reasonable doubt on the continual ability of the [SSC] to perform their safety-related
functions. In re-analyzing the existing engineering evaluation (or in performing a new
one after NRC identification of the issue), the licensee:
(a) used a different approach because the original approach resulted in unfavorable
margin; or
(b) revised assumptions solely to obtain favorable results; or
(c) revised other calculations in order to establish operability or functionality; or
7
(d) determined the remaining margin falls outside the licensees design process
acceptance criteria. Unfavorable margin means that had the correct values been
used originally, the licensees design process would not have accepted the
modification.
With regards to Paragraph 1 above, IMC 0612, Section 05.01.b.3 provides additional clarifying
guidance. Specifically, this section states, The potential to lead to a more significant safety
concern speaks to the realistic potential that the condition introduced by the performance
deficiency would eventually progress to the point of adversely affecting a cornerstone objective
if left uncorrected. Based on the information available, including CEGs response, the reviewers
determined that this more-than-minor condition remains applicable to the PD.
The NRC inspection report states that there are 38 similar relays installed in the Peach Bottom
Unit 2 RHR system and 38 relays in the Unit 3 RHR system with no preventive maintenance
schedule of replacement frequency identified. The NRC inspection report further states that
CEG did not perform a failure analysis of failed relay 2-10A-K084A. The reviewers considered
that for this unexpected failure, CEG did not ascertain why it occurred and what process should
have prevented it. The reviewers concluded that this performance, if left uncorrected, also has
the realistic potential to progress to the point of resulting in unavailability and unreliability of the
RHR system.
With regards to Paragraph 2, the reviewers noted that CEGs response did not address the four
evaluation points in the more-than-minor assessment. However, the reviewers noted that the
CEG contestation letter states, based on evaluations performed by CEG, the life of the relay
was extended to greater than the licensing period of the plant. The evaluation appears to be
based on an environmental qualification report from another site and was performed in
response to inspector questions. CEG stated:
In response to inspector concerns regarding the maintenance question, additional
research was conducted to confirm that the strategy is reasonable for non-critical relays.
This research produced varying expected lifespans for control relays, with significant
influence from the installed service condition and normal state of the relay. Although
Peach Bottom does not use this relay in Environmentally Qualified (EQ) applications,
other sites have analyzed Agastat TR relays for this application. Components required
by 10CFR50.49 for environmental qualification (EQ) must be specifically tested for each
of their service conditions to include duty cycle. The extensive testing that is performed
to environmentally qualify a component results in a lifetime bound by the most limiting
factor based on the test conditions. This testing and analysis produces a Qualified Life
that is specific to the installed service conditions. An EQ analysis was performed for
Quad Cities Station (EQ-80Q), which found that in a more severe application with
ambient temperatures of 120F, the relay has a Qualified Life of 24.6 years. In mild
applications with ambient temperatures of 80F, such as the Peach Bottom application,
the Qualified Life of this relay is 209 years. Therefore, it can reasonably be expected that
an Agastat TR relay installed in a normally deenergized, mild service condition, non-
critical application will not require replacement over Peach Bottoms currently licensed
lifetime.
The reviewers confirmed that the evaluation created by CEG was not performed prior to the
inspection that resulted in the subject NCV. As a result, the reviewers concluded that
Example 13.a, Paragraph 2 part (a), and most likely (b) and (c) should be answered yes. By
8
answering in the affirmative, the reviewers concluded that NRC screening guidance to the
inspectors was properly implemented to reach a conclusion that the PD was more-than-minor.
Finally, the reviewers noted that Example 13.a assumes there were no equipment failures to
date, however, this is not the case for the Peach Bottom installed Agastat relays. CEGs
response letter stated that the failure of time delay relay 2-10A-K084A resulted in an entry into
TS Limiting Condition of Operation (LCO) 3.3.5.1 for inoperable control logic associated with
DPIS-2-10-121A (2A RHR pump differential pressure indicating switch) and was a maintenance
rule functional failure. The reviewers found that an inoperable control logic adversely affects the
mitigating cornerstone objective of maintaining the availability, reliability, and capability of
systems that respond to initiating events, and therefore would cause this issue to be more-than-
minor.
Additional Considerations
In completing this review, which focused on the implementation of the NRCs more-than-minor
process and the inspection conclusions, NRC reviewers noted the following additional avenues
of inquiry may be germane to NCV 05000277,05000278/2022004-01.
CEG did not perform a failure analysis on the 2-10A-K084A relay in 2017 and, thus, did
not ascertain whether the relay failure was due to a random failure, age-related
degradation, or other factors. The reviewers considered that this missing information
impacts CEGs basis for establishing effective preventive maintenance strategies and
replacement programs for the 2-10A-K084A relay, for both the program prior to issuance
of the associated NCV and the program going forward.
The reviewers noted that the 2-10A-K084A relay and other relays of the same model in
the Peach Bottom Unit 2 and Unit 3 RHR systems were classified by CEG as non-critical
components. The reviewers ascertained that CEGs Performance Centered Maintenance
(PCM) template therefore recommends no periodic replacement or preventive
maintenance for these relays. The reviewers considered that no periodic replacement or
preventive maintenance appeared to indicate that CEG considered these relays to be
effectively classified as run-to-failure.
NUMARC 93-01i, Industry Guidelines for Monitoring the Effectiveness of Maintenance
at Nuclear Power Plants, provides guidance to licensees that may be used to implement
the requirements of 10 CFR 50.65 (Maintenance Rule). This guidance states repeatedly
that structures, systems, and components within the scope of the Maintenance Rule can
be allowed to run-to-failure provided they have little or no contribution to system safety
function. The reviewers noted that in the Peach Bottom 50.69 categorization process,
CEG classified valve MO-2-10-016A and associated relay 2-10A-K084A as high safety
significant (RISC-1) to support the RHR pump minimum flow function. This function is
classified by CEG as a high safety significant function. The other Unit 2 and Unit 3 RHR
pumps and associated relays are similarly classified. Though the reviewers questioned
CEGs implementation of maintenance rule guidance and associated commitments (e.g.,
treatment of these relays as run-to-failure) given that CEG categorized these relays as
RISC-1, the reviewers did not consider this to be within the scope of review of CEGs
contestation letter.
9
The reviewers did not evaluate the adequacy of the underlying technical basis cited by
CEG to make their conclusion that relay 2-10A-K084A has an established service life of
209 years. However, the reviewers did note that CEGs conclusion was limited to
theoretical analysis and extrapolation, since there is no operating experience to support
that a 209-year service life is realistic. Such a preventative maintenance strategy for a
class of relays used extensively in emergency safety features (ESF) would warrant
further review both for system performance and for probabilistic risk model equipment
reliability assumptions.
E. CONCLUSION
After consideration of the bases provided by CEG, the NRC staff concluded that this NCV was
appropriately dispositioned as more-than-minor and of very low safety significance (Green).
F. REFERENCES
IMC 0612, Issue Screening, dated 12/12/2019
IMC 0612, Appendix B, Issue Screening Directions, dated 08/08/2022
IMC 0612, Appendix E, Examples of Minor Issues, dated 12/10/2020
NUMARC 93-01, Industry Guideline for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants, Revision 4A
Regulatory Guide 1.160, Monitoring the Effectiveness of Maintenance at Nuclear Power
Plants, Revision 4
PB-5069-10-10A-003, 10 CFR 50.69 SCD - Residual Heat Removal System - Peach Bottom
Units 2 & 3, Revision 1
i The NRC endorsed this guidance in Regulatory Guide 1.160, Monitoring the Effectiveness of Maintenance at Nuclear Power
Plants.