IR 05000352/2022004
| ML23041A388 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/13/2023 |
| From: | Jon Greives NRC/RGN-I/DORS |
| To: | Rhoades D Constellation Energy Generation, Constellation Nuclear |
| References | |
| IR 2022004 | |
| Download: ML23041A388 (1) | |
Text
February 13, 2023
SUBJECT:
LIMERICK GENERATING STATION, UNITS 1 AND 2 - INTEGRATED INSPECTION REPORT 05000352/2022004 AND 05000353/2022004
Dear David Rhoades:
On December 31, 2022, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Limerick Generating Station, Units 1 and 2. On February 10, 2023, the NRC inspectors discussed the results of this inspection with Michael Gillin, Site Vice President, and other members of your staff. The results of this inspection are documented in the enclosed report.
Three findings of very low safety significance (Green) are documented in this report. One of these findings 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 I; the Director, Office of Enforcement; and the NRC Resident Inspector at Limerick Generating Station, Units 1 and 2.
If you disagree with a cross-cutting aspect assignment or a finding not associated with a regulatory requirement in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region I; and the NRC Resident Inspector at Limerick Generating Station, Units 1 and 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, Jonathan E. Greives, Chief Projects Branch 4 Division of Operating Reactor Safety
Docket Nos. 05000352 and 05000353 License Nos. NPF-39 and NPF-85
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000352 and 05000353
License Numbers:
Report Numbers:
05000352/2022004 and 05000353/2022004
Enterprise Identifier: I-2022-004-0035
Licensee:
Constellation Energy Generation, LLC
Facility:
Limerick Generating Station, Units 1 and 2
Location:
Sanatoga, PA 19464
Inspection Dates:
October 1, 2022 to December 31, 2022
Inspectors:
A. Ziedonis, Senior Resident Inspector
L. Grimes, Resident Inspector
M. Henrion, Health Physicist
B. Edwards, Health Physicist
Approved By:
Jonathan E. Greives, Chief
Projects Branch 4
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees
performance by conducting an integrated inspection at Limerick Generating Station, Units 1
and 2, 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 use engineering controls in accordance with Radiation Work Permit (RWP)
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Occupational
Radiation Safety
Green
NCV 05000352,05000353/2022004-01
Open/Closed
[H.8] -
Procedure
Adherence
A finding of very low safety significance (Green) and associated non-cited violation (NCV) of
Title 10 of the Code of Federal Regulations (10 CFR) 20.1701, Use of process or other
engineering controls, was self-revealed on April 9, 2022, when Constellation workers failed to
use, to the extent practical, process or other engineering controls (e.g., containment,
decontamination, or ventilation) to control the concentration of radioactive material in air meet
the requirements of 10 CFR 20.1701. Specifically, on April 9, 2022, during a refuel outage at
Limerick Generating Station, Constellation failed to use process or other engineering controls
(e.g., high-efficiency particulate air (HEPA) ventilation unit and maintain the work in a wetted
condition) prior to engaging in aggressive work activities on the main steam isolation valve
(MSIV) in the Unit 1 drywell. This resulted in airborne radioactivity in the immediate work area
and one worker received an unplanned exposure of 49 millirem committed effective dose
equivalent.
Inadequate maintenance procedure results in electrohydraulic (EHC) fluid leak from main
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Mitigating
Systems
Green
FIN 05000352,05000353/2022004-02
Open/Closed
None (NPP)
71152A
The inspectors determined there was a Green, self-revealing finding because maintenance
procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring
Can, Revision 0, did not include adequate steps to effectively reassemble BPV number 1
(BPV-1) actuator following the performance of preventive maintenance activities, which
resulted in an EHC fluid leak on May 14, 2022, and adversely impacted the reliability of the
Inadequate performance monitoring and margin management associated with MSIV local leak
rate testing (LLRT)
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Green
FIN 05000352,05000353/2022004-03
Open/Closed
[H.6] - Design
Margins
71152A
The inspectors identified a Green finding against procedure ER-AA-2003, System
Performance Monitoring and Analysis, Revision 8, because Constellation did not perform
adequate performance monitoring and analysis of MSIV LLRT results to ensure that
degrading trends were identified prior to challenging required limits during the operating cycle.
Additional Tracking Items
Type
Issue Number
Title
Report Section
Status
05000352,05000353/
2022004-04
Failure to follow
maintenance procedure
results in emergency diesel
generator (EDG) jacket
water (JW) leak
71152A
Open
PLANT STATUS
Unit 1 began the inspection period at rated thermal power (RTP). On November 26, 2022, the
unit was down-powered to approximately 75 percent thermal power for a control rod sequence
exchange. The unit was returned to full power on November 27, 2022, and remained at or near
RTP for the remainder of the inspection period.
Unit 2 began the inspection period at RTP. On November 19, 2022, the unit was down-powered
to approximately 75 percent thermal power for a control rod sequence exchange. The unit was
returned to full power on November 20, 2022, and remained at or near RTP for the remainder of
the inspection period.
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 performed activities described in IMC 2515,
Appendix D, Plant Status, observed risk significant activities, and completed on-site portions of
IPs. 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.
REACTOR SAFETY
71111.01 - Adverse Weather Protection
Seasonal Extreme Weather Sample (IP Section 03.01) (1 Sample)
(1)
The inspectors evaluated readiness for seasonal extreme weather conditions prior to
the onset of seasonal cold temperatures for the following systems during the week of
December 12, 2022:
- Unit 1 and 2 hardened vent remote operation control system batteries
Unit 1 and 2 residual heat removal (RHR) systems
Unit 1 and 2 control rod hydraulic control units and scram discharge volumes
Impending Severe Weather Sample (IP Section 03.02) (1 Sample)
(1)
The inspectors evaluated the adequacy of the overall preparations to protect risk-
significant systems from impending severe weather associated with a winter weather
advisory during the week of December 12, 2022
71111.04 - Equipment Alignment
Partial Walkdown Sample (IP Section 03.01) (3 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following
systems/trains:
(1)
Unit 1 'A' drywell chiller following 'B' chiller trip on October 11, 2022
(2)
Unit common off-site power alignment during period of elevated voltage on the 20
regulating transformer on October 20, 2022
(3)
Unit 2 safeguard battery divisions 1, 2, and 4, during troubleshooting of Division 3 on
December 13, 2022
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (5 Samples)
The inspectors evaluated the implementation of the fire protection program by conducting a
walkdown and performing a review to verify program compliance, equipment functionality,
material condition, and operational readiness of the following fire areas:
(1)
Unit common fire area 25, auxiliary equipment room 542 with area fire panel non-
functional due to heat detection trouble on October 28, 2022
(2)
Unit 2 fire area 16, D24 emergency 4KV switchgear room on November 10, 2022
(3)
Unit common FLEX diesel generator storage building on November 15, 2022
(4)
Unit 2 fire area 64, reactor enclosure cooling water heat exchanger area rooms 284
and 286 on December 9, 2022
(5)
Unit 1 fire area 31, 'B' and 'D' RHR heat exchanger and pump room, rooms 103 and
204 on December 16, 2022
71111.07A - Heat Exchanger/Sink Performance
Annual Review (IP Section 03.01) (1 Sample)
The inspectors evaluated readiness and performance of:
(1)
Unit common, RT-1-011-391-0, main control room chiller heat transfer performance
calculation test on December 15, 2022
71111.11A - Licensed Operator Requalification Program and Licensed Operator Performance
Requalification Examination Results (IP Section 03.03) (1 Sample)
(1)
The inspectors reviewed and evaluated the licensed operator annual requalification
results for the annual operating exams completed on November 17, 2022.
71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance
Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (1 Sample)
(1)
The inspectors observed and evaluated licensed operator performance in the control
room during a Unit 2 planned power reduction for a rod pattern adjustment on
November 19 and 20, 2022; and during near-rated rod notching on Unit 2 on
December 11, 2022
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
(1)
The inspectors observed and evaluated licensed operator requalification training
scenarios in the simulator on November 8, 2022
71111.12 - Maintenance Effectiveness
Maintenance Effectiveness (IP Section 03.01) (3 Samples)
The inspectors evaluated the effectiveness of maintenance to ensure the following
structures, systems, and components remain capable of performing their intended function:
(1)
Unit 2 'B' primary containment instrument gas subsystem on November 10, 2022
(2)
Unit 1 EDG D12 following speed switch failure on December 20 and 21, 2022
(3)
Unit 2 EDG D22 following output breaker trip on reverse power trip during the week
December 19, 2022
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (5 Samples)
The inspectors evaluated the accuracy and completeness of risk assessments for the
following planned and emergent work activities to ensure configuration changes and
appropriate work controls were addressed:
(1)
Unit 1 implementation of risk informed completion time with the average power range
monitor (APRM) voter number 1 inoperable on October 14, 2022
(2)
Unit 1 high-pressure coolant injection (HPCI) emergent work on October 14, 15,
and 16
(3)
Unit 2 EDG D22 emergent work following surveillance test (ST) failure on October 15
and 16, 2022
(4)
Unit 2 EDG D21 emergent work following ST failure on November 3, 2022
(5)
Unit 1 risk assessment during planned testing with select nuclear steam supply
shutoff system valves inoperable on December 19, 2022
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (6 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the
following operability determinations and functionality assessments:
(1)
Unit 1 APRM ST results evaluation on October 14, 2022
(2)
Unit 2 EDG D22 following ST failure on October 14, 17, and 18, 2022
(3)
Unit 1 'A' adjustable speed drive functionality with the runback feature placed in
bypass on October 31, 2022
(4)
Unit 1 EDG D12 after unexpected 'EDG running' alarms received in main control
room November 1 and 2, 2022
(5)
Unit 2 EDG D22 following receipt of motor control center shunt trip coil undervoltage
alarm during the week of November 14, 2022
(6)
Unit 1 'L' safety relief valve following step increase in tailpipe temperature on
November 28 and 29, 2022
71111.18 - Plant Modifications
Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (1 Sample)
The inspectors evaluated the following temporary or permanent modifications:
(1)
Unit common third off-site source transfer switch on October 3 and 4, 2022
71111.19 - Post-Maintenance Testing
Post-Maintenance Test Sample (IP Section 03.01) (7 Samples)
The inspectors evaluated the following post-maintenance testing activities to verify system
operability and/or functionality:
(1)
Unit common 101 safeguard transformer load tap changer following transformer
replacement on October 4, 5, and 6, 2022
(2)
Unit 2 EDG D21 following speed switch replacement on November 4, 2022
(3)
Unit 2 reactor core isolation cooling following planned maintenance on November 16,
2022
(4)
Unit common 'A' emergency service water system following motor replacement on
November 22, 2022
(5)
Unit 1 'A' RHR following planned maintenance on November 30, 2022
(6)
Unit common 'A' RHR service water pump following planned maintenance on
December 14 and 15, 2022
(7)
Unit 2 'B' core spray system unit cooler following corrective maintenance on
December 22, 2022
71111.22 - Surveillance Testing
The inspectors evaluated the following surveillance testing activities to verify system operability
and/or functionality:
Surveillance Tests (other) (IP Section 03.01) (2 Samples)
(1)
ST-6-092-312-2, Unit 2 D22 diesel generator slow start operability test run, with
additional instrumentation, on November 7, 2022
(2)
ST-6-055-230-2, Unit 2 HPCI pump, valve, and flow test on December 21, 2022
Reactor Coolant System (RCS) Leakage Detection Testing (IP Section 03.01) (1 Sample)
(1)
ST-6-107-590-2, Unit 2 daily surveillance log with elevated RCS unidentified leakage
on December 16, 2022
71114.06 - Drill Evaluation
Drill/Training Evolution Observation (IP Section 03.02) (1 Sample)
The inspectors evaluated:
(1)
An emergency preparedness training evolution on November 17, 2022
RADIATION SAFETY
71124.03 - In-Plant Airborne Radioactivity Control and Mitigation
Permanent Ventilation Systems (IP Section 03.01) (1 Sample)
The inspectors evaluated the configuration of the following permanently installed ventilation
systems:
(1)
Unit common spent fuel pool ventilation system
Temporary Ventilation Systems (IP Section 03.02) (1 Sample)
The inspectors evaluated the configuration of the following temporary ventilation system:
(1)
Walked down HEPA vacuum and unit storage locations and reviewed inventory
procedures
Use of Respiratory Protection Devices (IP Section 03.03) (1 Sample)
(1)
The inspectors evaluated the licensees use of respiratory protection devices
Self-Contained Breathing Apparatus for Emergency Use (IP Section 03.04) (1 Sample)
(1)
The inspectors evaluated the licensees use and maintenance of self-contained
breathing apparatuses
71124.04 - Occupational Dose Assessment
Source Term Characterization (IP Section 03.01) (1 Sample)
(1)
The inspectors evaluated licensee performance as it pertains to radioactive source
term characterization
External Dosimetry (IP Section 03.02) (1 Sample)
(1)
The inspectors evaluated how the licensee processes, stores, and uses external
dosimetry
Internal Dosimetry (IP Section 03.03) (2 Samples)
The inspectors evaluated the following internal dose assessments:
(1)
Reviewed Accuscan of worker with internal contamination
(2)
Reviewed Fastscan of worker with internal contamination
Special Dosimetric Situations (IP Section 03.04) (2 Samples)
The inspectors evaluated the following special dosimetric situations:
(1)
Reviewed evaluation of a declared pregnant worker
(2)
Reviewed procedure for special increased exposures
71124.07 - Radiological Environmental Monitoring Program
Environmental Monitoring Equipment and Sampling (IP Section 03.01) (1 Sample)
(1)
The inspectors evaluated environmental monitoring equipment and observed
collection of environmental samples
Radiological Environmental Monitoring Program (IP Section 03.02) (1 Sample)
(1)
The inspectors evaluated the implementation of the licensees radiological
environmental monitoring program
GPI Implementation (IP Section 03.03) (1 Sample)
(1)
The inspectors evaluated the licensees implementation of the Groundwater
Protection Initiative program to identify incomplete or discontinued program elements
OTHER ACTIVITIES - BASELINE
71151 - Performance Indicator Verification
The inspectors verified licensee performance indicators submittals listed below:
MS10: Cooling Water Support Systems (IP Section 02.09) (2 Samples)
(1)
Unit 1 for the period of October 1, 2021, through September 30, 2022
(2)
Unit 2 for the period of October 1, 2021, through September 30, 2022
BI01: RCS Specific Activity Sample (IP Section 02.10) (2 Samples)
(1)
Unit 1 for the period of October 1, 2021, through September 30, 2022
(2)
Unit 2 for the period of October 1, 2021, through September 30, 2022
BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)
(1)
Unit 1 for the period of October 1, 2021, through September 30, 2022
(2)
Unit 2 for the period of October 1, 2021, through September 30, 2022
OR01: Occupational Exposure Control Effectiveness Sample (IP Section 02.15) (1 Sample)
(1)
December 2021 through October 2022
PR01: Radiological Effluent Technical Specifications (TSs)/Offsite Dose Calculation Manual
Radiological Effluent Occurrences (RETS/ODCM) Radiological Effluent Occurrences Sample
(IP Section 02.16) (1 Sample)
(1)
December 2021 through October 2022
71152A - Annual Follow-up Problem Identification and Resolution
Annual Follow-up of Selected Issues (Section 03.03) (3 Samples)
The inspectors reviewed the licensees implementation of its corrective action program
(CAP) related to the following issues:
(1)
Potential adverse trends associated with MSIV LLRT on November 17, 18, 21,
and 30, 2022
(2)
Evaluation and corrective actions associated with Unit 1 BPV #1 EHC fluid leakage,
and associated work group evaluation (WGE) 4499745 on November 21 and
December 12, 2022
(3)
Evaluation and corrective actions associated with Unit 2 EDG D21 jacket water
leakage, and associated WGE 4514473 on December 9, 12, and 21, 2022
71152S - Semiannual Trend Problem Identification and Resolution
Semiannual Trend Review (Section 03.02) (1 Sample)
(1)
The inspectors reviewed Constellations CAP for potential adverse trends that might
be indicative of a more significant safety issue. The inspectors determined that
Constellation was appropriately identifying, evaluating, and resolving adverse trends.
INSPECTION RESULTS
Failure to use engineering controls in accordance with RWP
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Occupational
Radiation Safety
Green
NCV 05000352,05000353/2022004-01
Open/Closed
[H.8] -
Procedure
Adherence
A finding of very low safety significance (Green) and associated NCV of 10 CFR 20.1701,
Use of process or other engineering controls, was self-revealed on April 9, 2022, when
Constellation workers failed to use, to the extent practical, process or other engineering
controls (e.g., containment, decontamination, or ventilation) to control the concentration of
radioactive material in air meet the requirements on of 10 CFR 20.1701. Specifically, on
April 9, 2022, during a refuel outage at Limerick Generating Station, Constellation failed to
use process or other engineering controls (e.g., HEPA ventilation unit and maintain the work
in a wetted condition) prior to engaging in aggressive work activities on the MSIV in the Unit 1
drywell. This resulted in airborne radioactivity in the immediate work area and one worker
received an unplanned exposure of 49 millirem committed effective dose equivalent.
Description: On April 9, 2022, two workers entered the Unit 1 drywell under RWP (LG-0-22-
00509) to complete machining work of MSIV valves 'B' and 'D'. The individuals alarmed the
personnel contamination monitor (PM-12) at the radiologically controlled area (RCA) exit.
One worker was machining in the drywell on the B MSIV. The other individual was setting up
on the D MSIV nearby. The individual machining on the B MSIV had assumed the work
after receiving turnover from the previous crew who had set the machine in the valve. The B
MSIV did not have the required HEPA ventilation, and the valve seat was not properly
maintained wet during the evolution as required by the RWP and the as low as reasonably
achievable (ALARA) plan. The worker at the B MSIV also reported hearing a loud banging
noise above where they were working and that the pipe and valve vibrated with the banging.
The vibrations were determined to be from power tool ratcheting to loosen the main steam
relief valve (MSRV) bolts on the same line nearby. This vibration is thought to have
contributed to an airborne event in the work area from the valve. The lack of proper HEPA
ventilation and maintaining the work wet caused one worker to receive 49 millirem (mrem)
committed effective dose equivalent (internal dose).
The licensee evaluated the event and found that contributing factors which led to these
degraded conditions were as follows:
- The workers did not understand ALARA plan requirements and were not aware of the
requirements due to only being discussed verbally well in advance of the work.
The ALARA brief was not discussed by radiation protection (RP) staff and the workers
during the radiological conditions briefing provided before the workers entered to
perform the work on the MSIVs. Workers stated that the briefing was focused on the
dose rates in the area and did not include the contamination control aspects of the
ALARA plan. In addition, the ALARA plan was not reviewed in detail as the RP
technician thought the initial ALARA brief was adequate.
Various roles and responsibilities were not made clear at the initial ALARA brief, as
RP staff assumed that the workers would set up the HEPA and the workers thought
that a HEPA vacuum in the valve was adequate.
RP did not provide adequate oversite of the work area. The RP brief should have
identified the need for the workers to contact RP to verify the engineering controls
(HEPA placement and wetting of surfaces) were adequate prior to aggressive
work. This did not occur due to the key ALARA plan requirements not being reviewed
during subsequent briefs.
Corrective Actions:
- Performed a training performance analysis
Define which jobs will require oversight/observations to ensure RP/ALARA plan
compliance and invite corporate oversight to those activities
Identify critical jobs using the RP manpower sheet for on-line and schedule review for
outages and assign the responsible oversight Supervisor/Manager
Benchmark industry leader for education of outage supplemental workforce on basic
RP fundamentals including engineering controls and site operating experience
Implement actions from the benchmark
Review and validate the use of engineering controls
Corrective Action References: Issue Report (IR) 04491897
Performance Assessment:
Performance Deficiency: The improper use of engineering controls (HEPA unit and
maintaining work wet) was reasonably within Constellations ability to foresee and correct and
should have been prevented and therefore was a performance deficiency.
Screening: The inspectors determined the performance deficiency was more than minor
because it was associated with the Program and Process attribute of the Occupational
Radiation Safety cornerstone and adversely affected the cornerstone objective to ensure the
adequate protection of the worker health and safety from exposure to radiation from
radioactive material during routine civilian nuclear reactor operation. In addition, it is similar to
example 6.h of IMC 0612, Appendix E. Specifically, the worker failed to use a HEPA and
keep work wet during the duration of the valve work per the RWP ALARA Plan, which
resulted in an unplanned exposure of 49 mrem committed effective dose equivalent (internal
dose).
Significance: The inspectors assessed the significance of the finding using IMC 0609,
Appendix C, Occupational Radiation Safety Significance Determination Process (SDP). The
finding was of very low safety significance (Green) because: 1) it was not ALARA finding, 2)
there was no overexposure, 3) there was no substantial potential for an overexposure, and 4)
the ability to assess dose was not compromised.
Cross-Cutting Aspect: H.8 - Procedure Adherence: Individuals follow processes, procedures,
and work instructions. The inspectors determined that this finding had a cross-cutting aspect
in the area of Human Performance, Procedure Adherence, because the individuals failed to
follow verbal and written work instructions.
Enforcement:
Violation: Title 10 of the CFR 20.1701, Use of process or other engineering controls, states
that, The licensee shall use, to the extent practical, process or other engineering controls
(e.g., containment, decontamination, or ventilation) to control the concentration of radioactive
material in air." Contrary to the above, on April 9, 2022, Constellation failed to use process or
other engineering controls (e.g., HEPA ventilation unit and maintain the work in a wetted
condition), in violation of 10 CFR 20.1701; resulting in airborne radioactivity and unplanned
dose of 49 mrem committed effective dose equivalent to one worker.
Enforcement Action: This violation is being treated as a NCV, consistent with Section 2.3.2 of
the Enforcement Policy.
Inadequate maintenance procedure results in EHC fluid leak from main turbine BPV
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Mitigating
Systems
Green
FIN 05000352,05000353/2022004-02
Open/Closed
None (NPP)
71152A
The inspectors determined there was a Green, self-revealing finding because maintenance
procedure MA-LG-763-473, Disassemble and Assemble Main Steam BPV Actuator/Spring
Can, Revision 0, did not include adequate steps to effectively reassemble BPV number 1
(BPV-1) actuator following the performance of preventive maintenance activities, which
resulted in an EHC fluid leak on May 14, 2022, and adversely impacted the reliability of the
Description: The main turbine steam bypass system is designed to control steam pressure
when reactor steam generation exceeds turbine requirements during unit startup, sudden
load reduction, and cooldown. It allows excess steam flow from the reactor to the condenser
without going through the turbine. The system is comprised of nine valves that have a total
bypass capacity of approximately 25 percent of the nuclear steam supply system rated steam
flow. The main turbine bypass system is designed to limit the peak pressure in the main
steam lines and maintain reactor pressure within acceptable limits during events that cause
rapid pressurization such that the safety limit minimum critical power ration is not exceeded.
Each of the nine BPVs consist of a dual-acting actuator that uses EHC fluid flow both over
and under an actuator piston to allow for precise control in both the open and close direction
of the valve. EHC fluid is directed to the top and bottom of the actuator piston using an
electronic servo. When a BPV is closed, the servo directs EHC fluid to the top of the actuator
piston at full EHC system pressure (approximately 1600 pounder per square inch) to maintain
the valve closed, with some residual amount of fluid maintained at the bottom of the piston to
support a fast opening function. For the BPV to open, the servo repositions to increase the
volume of fluid at the bottom of the actuator piston.
On May 14, 2022, during Unit 1 shutdown for a planned maintenance outage, operators
received a low-level alarm for the EHC fluid reservoir. Operators entered the abnormal
operating procedure for response to EHC leaks, and dispatched operators into the plant in an
attempt to identify the leak location. After approximately 24 minutes, operators in the main
control room decided to secure the in-service EHC pump, based on the leak location not
being identified, and the fact that Unit 1 had entered OPCON 4 (Cold Shutdown)
approximately 8 minutes prior to receipt of the alarm with shutdown cooling already placed in-
service following closure of the final BPV (BPV-1) during the plant cooldown. Trending of
plant data for EHC level estimated the leak was approximately 6.5 gallons per minute (gpm).
Subsequent operator entry into the main condenser bay identified the leak location was from
BPV-1. Upon disassembly of the BPV-1 for repairs, it was identified that there was a loose
mounting bolt and deteriorated o-ring from one of four bolts that secure the actuator assembly
to the servo mounting plate, which is referred to as the tombstone. The tombstone is
designed with internal fluid ports that direct EHC fluid flow from the servo to the actuator. The
loose mounting bolt was therefore determined to have allowed pressurized EHC fluid to leak
from the mating surface between the tombstone and the actuator following closure of BPV-1,
which is the last BPV to close during unit cooldown.
Constellation performed a WGE under IR 4499745, and determined that the loose mounting
bolt was most likely caused by an o-ring extruding through a clearance gap between the
tombstone and actuator, as a result of inadequate procedural guidance that omitted any steps
to check for clearance gaps to ensure for proper alignment between mating surfaces.
Specifically, Limerick procedure MA-LG-763-473, Disassemble and Assemble Main Steam
BPV Actuator/Spring Can, was used during the previous reassembly of the BPV-1 actuator
and tombstone following the completion of preventive maintenance activities in 2012, under
work order (WO) R1130130. Procedure step 4.6.17 specified a torque value of 95 foot-
pounds, applied over 3 torque passes, but did not include a step to check clearance gaps to
ensure proper alignment between mating surfaces.
The inspectors reviewed WGE 4499745, as well as the completed WO R1130130 from 2012,
and verified that step 4.6.17 of MA-LG-763-473 was signed off as completed with the
specified torque value of 95 foot-pounds. The inspectors also reviewed procedure MA-LG-
763-473, Revision 0, and noted that it was issued in 2012, just prior to performance of WO
R1130130. The inspectors subsequently reviewed Constellation procedure MA-AA-736-600,
Torquing and Tightening of Bolted Connections, Revision 14, issued in 2022, and noted that
Section 4.2, Connection Reassembly, included steps to remove all clearance gaps during
application of torque passes, and contained clearance gap criteria for misaligned joints. The
inspectors subsequently reviewed the equivalent Limerick maintenance procedure in effect in
2012, MA-LG-716-1017, Control of Bolting / Torquing / Tensioning, Revision 0 (issued in
2010), and noted that section 7.2.5 covered torque sequencing and contained steps to
ensure uniform surface alignment, including steps to ensure uniform gap checks for
misaligned flanges. Based on this procedure review, the inspectors determined that it was
reasonably within Limericks ability to foresee and correct the inadequate instructions for BPV
reassembly contained in maintenance procedure MA-LG-763-473 that was issued in 2012,
and the inspectors therefore determined that uneven clearance gaps between the tombstone
and actuator should have been prevented to ensure reliable BPV operation.
Corrective Actions: Constellation replaced the failed BPV-1 actuator and verified all four of
the tombstone-to-actuator mounting bolts were adequately torqued to the required values and
performed an extent of condition torque check on all the remaining BPV accessible bolts to
verify as-found values of 95 foot-pounds. Constellation assigned WGE action 4499745-14 to
add a step to procedure MA-LG-763-473 to ensure that clearance values were less than
0.0015 inches between the tombstone and the actuator. WGE action 4499745-15 was
created to scope torque checks of all remaining BPV bolts into the next refueling outages for
Unit 1 (1R20) and Unit 2 (2R17), and action 4499745-16 was created to evaluate creating a
new preventive maintenance task to perform torque checks, in between actuator inspection
preventive maintenance activities, if additional bolts are found loose under action 4499745-
15.
Corrective Action References: IRs 4499745, 4499944, 4499968, 4537024
Performance Assessment:
Performance Deficiency: The inspectors determined that Constellations inadequate
maintenance procedure instructions for BPV reassembly was reasonably within
Constellations ability to foresee and correct, and should have been prevented, and therefore
constituted a performance deficiency. Specifically, procedure MA-LG-763-473, Disassemble
and Assemble Main Steam BPV Actuator/Spring Can, Revision 0, did not contain adequate
instructions to ensure the BPV actuator and tombstone mounting surfaces were properly
aligned with consistent clearance gaps to prevent o-ring extrusion and EHC fluid leakage.
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, failure to ensure properly assembly of the BPV-1
actuator resulted in a significant EHC fluid leak from the valve and challenged reliable
operation of the main turbine bypass system.
Significance: The inspectors assessed the significance of the finding using IMC 0609
Appendix A, The SDP for Findings At-Power. This finding was screened to Green using the
Mitigating Systems screening questions because it did not involve a design deficiency, did not
represent the loss of a train of TS equipment for longer than its allowed outage time, and did
not represent loss of a probabilistic risk analysis system or function.
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. Specifically, the BPV-1 maintenance utilizing the deficient preventive
maintenance procedure was performed in 2012, and no maintenance was performed on the
actuator and tombstone of any other BPVs on either unit in the last three years using the
deficient preventive maintenance procedure.
Enforcement: Inspectors did not identify a violation of regulatory requirements associated
with this finding.
Inadequate performance monitoring and margin management associated with MSIV LLRT
Cornerstone
Significance
Cross-Cutting
Aspect
Report
Section
Green
FIN 05000352,05000353/2022004-03
Open/Closed
[H.6] - Design
Margins
71152A
The inspectors identified a Green finding against procedure ER-AA-2003, System
Performance Monitoring and Analysis, Revision 8, because Constellation did not perform
adequate performance monitoring and analysis of MSIV LLRT results to ensure that
degrading trends were identified prior to challenging required limits during the operating
cycle.
Description: The inspectors performed a historical review of MSIV as-found LLRT data on
Unit 1, and noted in refueling outage 1R18 (spring of 2020) three of the eight MSIVs
exceeded the TS limit of 100 standard cubic foot per hour (scfh): specifically, outboard valves
28B, 28C and 28D. TS 3.6.1.2 requires each MSIV leak rate to be less than or equal to 100
scfh, and the total leak rate through all four main steam lines to be less than or equal to 200
scfh, in operational conditions 1, 2 and 3. Constellation determined the 200 scfh total as-
found limit through all four main steam lines was not exceeded, because the leakage values
through the A main steam line, as well as the B, C, and D inboard MSIVs, were all
sufficiently low enough to ensure the total leakage was less than 200 scfh, when considering
the performance of the redundant inboard valve in each line. Two of the MSIVs (28C and
28D) were repaired in 1R18 to restore leakage below the 100 scfh single MSIV limit. For the
third MSIV (28D), an emergency license amendment was approved (ML20098C922) to allow
for a one-time TS change from 100 scfh to 105 scfh, due to challenges related to the COVID-
19 public health emergency.
The inspectors reviewed the LLRT performance data for the 28C and 28D MSIVs and noted
progressively increasing trends from 1R15 through 1R18. As a result, inspectors determined
that further review was warranted to understand whether appropriate MSIV LLRT
performance monitoring and margin management was being performed to ensure leak rates
were maintained below required limits during plant operation.
The inspectors reviewed MSIV maintenance history, and noted MSIVs did not have regularly
scheduled in-body preventive maintenance activities to proactively limit valve seat leakage,
and further noted that no in-body maintenance was performed on the 28C or 28D during the
time period from 1R15 until 1R18, when as-found results exceeded TS limits. The inspectors
noted that MSIVs at Limerick were exempt from 10 CFR Part 50, Appendix J, Primary
Containment Leakage Testing, and were therefore not subject to overall allowable
containment leakage limits required under Appendix J. The inspectors reviewed design
analysis LM-0646, Re-analysis of loss of coolant accident (LOCA) Using Alternate Source
Terms, Revision 6, and noted the TS 3.6.1.2 total MSIV leakage limit of 200 scfh was used
as an analytical input to validate the radiological consequences of a LOCA remained below
regulatory limits. The inspectors subsequently reviewed ST-4-LLR-001-1, The Local Leak
Rate (LLR) Program an Accountability Test, Revision 18, and ST-4-LLR-03/4/5/61-001,
Main Steam Line A/B/C/D LLR STs, Revisions 16, 15, 15, and 16, respectively, and noted
the acceptance criteria were established at the TS 3.6.1.2 limits. The inspectors noted that
there was no established margin between the LLRT ST limits, the LM-0646 analysis of
record, and the TS 3.6.1.2 limits.
The inspectors reviewed Constellation procedure ER-AA-2003, System Performance
Monitoring and Analysis, Revision 8, and noted that performance monitoring plans were
required for Tier 1 systems, which included the main steam system. Step 4.1.5 requires
establishment of alert levels and action levels. An alert level is described as a parameter level
that when exceeded is indicative of equipment degradation and requires IR initiation. An
action level is described as the threshold where action is required to prevent a consequential
event, though consequential events are undefined. Attachment 2 further describes monitoring
alert level considerations, and states that monitoring bands and frequencies should be
sufficient to identify degrading trends before design, operating, or licensing requirements are
challenged. In addition, Attachment 1 lists items to consider for trending, and refers to ER-
AA-2007, Management of Design and Operating Margins, Revision 8, which discusses how
to identify and control design and analytical margins. The inspectors reviewed the main
steam performance monitoring plan, and noted MSIV LLR STs were included in the plan, but
the alert and action levels were each established at the TS limits. The inspectors further
noted the MSIV LLR STs did not establish any administrative limits. The inspectors therefore
concluded that Constellation did not adequately perform step 4.1.5 of ER-AA-2003 to conduct
performance monitoring of MSIV LLRT data, because alert levels were not established to
indicate equipment degradation, and IRs were not initiated until TS limits were exceeded.
Corrective Actions: Constellation performed industry benchmarking and captured the
performance deficiency under IR 4553559, to evaluate the issue and develop appropriate
corrective actions. There were no violations of regulatory requirements that warranted
immediate corrective action, because both C and D outboard MSIVs had been repaired in
1R18 and there were no existing MSIVs with adverse trends.
Corrective Action References: IRs 4553559, 4331517, 4331518, 4331519
Performance Assessment:
Performance Deficiency: The inspectors determined that Constellations inadequate
performance monitoring and analysis in accordance with station procedures was reasonably
within Constellations ability to foresee and correct, should have been prevented, and was
therefore determined to be a performance deficiency.
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, the inspectors determined that if no additional actions were taken to
monitor MSIV leakage performance, then TS and analytical limits could be exceeded during
the operating cycle.
Significance: The inspectors assessed the significance of the finding using IMC 0609,
Appendix A, The SDP for Findings At-Power. The inspectors utilized IMC 0609, Appendix A,
Exhibit 3, Barrier Integrity Screening Questions, to determine this finding was of very low
safety significance (Green) because it did not represent an actual open pathway in the
reactor containment barrier, and did not involve a failure of the any one of the following: the
containment isolation system, containment pressure control equipment, containment heat
removal components, or severe accident mitigation features.
Cross-Cutting Aspect: H.6 - Design Margins: The organization operates and maintains
equipment within design margins. Margins are carefully guarded and changed only through a
systematic and rigorous process. Special attention is placed on maintaining fission product
barriers, defense-in-depth, and safety-related equipment. Specifically, Constellation did not
perform adequate performance monitoring of MSIV LLRT results to guard and maintain
design margins to the allowable limits and did not place special attention on maintaining
containment barrier margins below analyzed limits.
Enforcement: Inspectors did not identify a violation of regulatory requirements associated
with this finding.
Unresolved Item
(Open)
Failure to follow maintenance procedure results in EDG JW
leak
URI 05000352,05000353/2022004-04
71152A
Description: On August 2, 2022, during a monthly ST of D21 EDG at full load, equipment
operators discovered a JW leak from a threaded fitting connection on a 0.25-inch diameter
tubing instrument root valve connection to the five-inch JW piping header. At approximately
30 minutes into the loaded run, operators measure leakage at 0.37 ounces per minute. Just
prior to completion of the two-hour loaded run, operators measure leakage at 0.78 ounces
per minute. Operators subsequently declared D21 EDG inoperable, because leakage was
measured above the pre-determined operability limit of 0.5 ounces per minute, as calculated
in Technical Evaluation (TE) 202873-01. The inspectors noted the 0.5 ounce per minute limit
supported successful operation of the EDG over the seven-day mission time required for TS
operability, without credit for inventory make-up to the closed-loop JW sub-system. The
inspectors further noted that Updated Final Safety Analysis Report section 9.5.5.2.1, stated
that normal maintenance of system components will ensure that leakage rates will be kept
below the amount requiring tank makeup within a seven-day period. Operators determined
that D21 EDG remained available, because leakage was not expected to exceed the 24-hour
probabilistic risk assessment mission time limit of 3.5 ounces per minute, based on no visible
cracks observed in the fitting connection, and no evidence that there was a risk of complete
fitting failure. In addition, the downstream (JW outlet) side of the instrument root valve was
noted to consist of a second, leak-tight, threaded connection to a pressure switch and small
diameter hard pipe tubing, such that complete unthreading of the upstream (JW inlet)
threaded connection to the JW header was determined by Constellation to be very unlikely.
On August 3, 2022, Constellation performed corrective maintenance repairs that consisted of
tagging out D21 EDG, draining the JW system, disassembling the two fittings on either side of
the instrument root valve, replacing a reducer coupling at the threaded connection between
the instrument root valve and JW header, re-installing the threaded fittings on either side of
the instrument root valve one at a time, and performing an unloaded EDG run with no JW
leakage observed from the re-assembled threaded connections.
Following corrective maintenance, Constellation performed WGE 4514473-12, to determine
the cause of the leaking fitting that resulted in D21 EDG inoperability. Constellation
determined that the cause was attributed to inadequately tightening the instrument root valve
fitting connection to the JW header during D21 EDG planned maintenance that was
completed on June 18, 2022. The WGE further stated that the instrument root valve fitting
was re-assembled under maintenance procedure M-020-002, Fairbanks Morse Opposed
Piston Diesel Generator Major Examination and General Maintenance. In addition, while no
leakage was noted during multiple post-maintenance test runs that were conducted on
June 17 and 18, Constellation noted that IR 4508586 was generated on June 30, during
equipment operator rounds with D21 EDG in a standby condition, which documented minor
weepage at the instrument root valve threaded connection to the JW piping header. The
inspectors noted that no observations of leakage were documented during the July 5, 2022,
monthly ST. As part of the WGE, Constellation sent the reducer coupling, which was removed
during the August 3 corrective maintenance, off-site for a failure analysis. No presence of
cracks, galling, or cross-threading were noted in the reducer coupling.
The inspectors reviewed the WGE, and discussed the D21 EDG JW leak with maintenance
technicians, operators, and engineers. The inspectors agreed with Constellations causal
determination in the WGE. In addition, the inspectors noted that after the D21 EDG
instrument root valve fitting connection was not properly tightened during planned
maintenance that completed on June 18, minor leakage from the fitting was subsequently
discovered on June 30 that progressively degraded to 0.78 ounces per minute on August 2,
after accruing approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> of run time during post-maintenance test runs and
ST. Based on this information, the inspectors questioned Constellation as to whether the D21
EDG was inoperable for greater than the allowed outage time of 30 days, and whether it
therefore constituted a violation of TS Limiting Condition for Operation 3.8.1. At the close of
the inspection period, Constellation was re-evaluating the assumptions and inherent margin
in TE 202873-01, with respect to the allowable JW leakage over the 7-day mission time, in
response to the inspectors question.
Planned Closure Actions: The inspectors will review Constellation's re-evaluation of TE
202873-01 to understand the allowable JW leak rate in support of the 7-day mission time of
the D21 EDG, and whether the D21 EDG was inoperable from June 18 to August 2, 2021.
Licensee Actions: At the close of the inspection period, Constellation was re-evaluating the
assumptions and inherent margin in TE 202873-01, with respect to the allowable JW leakage
over the 7-day mission time, in response to the inspectors question.
Corrective Action References: IRs 4514473 and 4508586, and TE 202873
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On February 10, 2023, the inspectors presented the integrated inspection results to
Michael Gillin, Site Vice President, and other members of the licensee staff.
On December 15, 2022, the inspectors presented the IP 71124.03 and IP 71124.04
inspection results to Mike Gillin, Site Vice President, and other members of the licensee
staff.
On November 10, 2022, the inspectors presented the IP 71124.07, Radiological
Environmental Monitoring Program, inspection results to Matt Bonanno, Plant Manager,
and other members of the licensee staff.