IR 05000317/2024040

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95001 Supplemental Inspection Report 05000317/2024040 and Follow-Up Assessment Letter
ML24101A261
Person / Time
Site: Calvert Cliffs Constellation icon.png
Issue date: 04/11/2024
From: Brice Bickett
NRC Region 1
To: Rhoades D
Constellation Energy Generation, Constellation Nuclear
References
IR 2024040
Download: ML24101A261 (1)


Text

April 11, 2024

SUBJECT:

CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT 1 - 95001 SUPPLEMENTAL INSPECTION REPORT 05000317/2024040 AND FOLLOW-UP ASSESSMENT LETTER

Dear David Rhoades:

On March 21, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed a supplemental inspection using Inspection Procedure 95001, "Supplemental Inspection Response to Action Matrix Column 2 (Regulatory Response) Inputs, and discussed the results of this inspection and the implementation of your corrective actions with Patrick Navin, Site Vice President, and other members of your staff.

The NRC performed this inspection to review your stations actions in response to a White finding in the Mitigating Systems cornerstone which was documented and finalized in NRC Inspection Report 05000317/2023090. On February 9, 2024, you informed the NRC that your station was ready for the supplemental inspection.

The NRC determined that your staffs evaluation identified the cause of the White finding.

Specifically, the root cause analysis for the White finding identified two root causes. The first root cause determined that engineering personnel did not successfully identify fuel injector preventive and predictive maintenance strategies for the Société Alsacienne De Constructions Mecaniques De Mulhouse (SACM) diesel generators, which includes the 1A emergency diesel generator. The second root cause identified that system engineers and engineering managers did not exercise adequate technical human performance behaviors and technical conscience principles when developing the preventive maintenance strategy for the SACM diesel generators. Corrective actions to preclude repetition (CAPR) are discussed in detail in the enclosed inspection report.

Overall, the NRC determined that Constellations problem identification, causal analyses, and corrective actions sufficiently addressed the performance issues that led to the White finding.

All inspection objectives, as described in Inspection Procedure 95001, were met, and this inspection is, therefore, closed. With the closure of this White finding, and as a result of our continuous review of plant performance, the NRC has updated its assessment of Calvert Cliffs Unit 1. This assessment supplements, but does not supersede, the end-of-cycle letter issued on March 1, 2024. Based on successful completion of the supplemental inspection, and issuance of this inspection report, Calvert Cliffs Unit 1 has transitioned to the licensee response column of the NRC Action Matrix (Column 1) as of the date of the exit and regulatory performance meeting for this inspection on March 21, 2024.

No findings or violations of more than minor significance were identified during this inspection.

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 (10CFR) 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely, Brice A. Bickett, Chief Projects Branch 3 Division of Operating Reactor Safety

Docket No. 05000317 License No. DPR-53

Enclosure:

As stated

Inspection Report

Docket Number:

05000317

License Number:

DPR-53

Report Number:

05000317/2024040

Enterprise Identifier: I-2024-040-0003

Licensee:

Constellation Energy Generation, LLC

Facility:

Calvert Cliffs Nuclear Power Plant, Unit 1

Location:

Lusby, MD

Inspection Dates:

March 18, 2024 to March 21, 2024

Inspectors:

E. Eve, Senior Project Engineer

E. Garcia, Resident Inspector

Approved By:

Brice A. Bickett, Chief

Projects Branch 3

Division of Operating Reactor Safety

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a 95001 supplemental inspection at Calvert Cliffs Nuclear Power Plant, Unit 1, 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

No findings or violations of more than minor significance were identified.

Additional Tracking Items

Type Issue Number Title Report Section Status NOV 05000317/2023050-04 Failure to establish and implement adequate maintenance practices and work instructions regarding maintenance of the 1A EDG contributing to the 1A EDG failure on April 24, 2023 EA-23-097 95001 Closed

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.

OTHER ACTIVITIES

- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL

95001 - Supplemental Inspection Response to Action Matrix Column 2 (Regulatory Response)

Inputs

The inspectors reviewed and selectively challenged aspects of Constellations problem identification, causal analysis, and corrective actions to ensure the causes of the White performance issue were correctly identified and corrective actions were adequate to promptly and effectively address and preclude repetition. The White finding and related Notice of Violation of Calvert Cliffs Unit 1, Technical Specification (TS) 5.4.1, "Procedures," was associated with the failure to establish and implement appropriate procedures and instructions for performing maintenance that can affect the performance of the safety-related 1A emergency diesel generator (EDG). Consequently, on April 24, 2023, the 1A EDG failed while performing a monthly surveillance test due to an imbalanced fueling condition and loss of compression on the EDG requiring the engine to be placed in an emergency shutdown condition. The preliminary White finding and Apparent Violation was documented in NRC Inspection Report 05000317/2023050 (ML23272A027). The final significance determination of the White finding and Notice of Violation was documented in NRC Inspection Report 05000317/2023090 (ML23297A192).

Constellation performed and documented an initial root cause analysis (RCA) in issue report (IR) 04672350 and revised the RCA in IR 04735065. The NRC inspectors' review of the Calvert Cliffs Nuclear Power Plant, Unit 1 White performance issue and the associated assessment are documented below.

Objective 1: Ensure that the root and contributing causes of the White performance issue are understood

Under this objective, the inspectors reviewed the RCA the licensee conducted for the failure to establish and implement appropriate procedures and instructions for performing maintenance that can affect the performance of the 1A EDG as documented in NRC Inspection Reports 05000317/2023050 and 05000317/2023090. The inspectors' review consisted of an evaluation of the following:

  • the licensee's identification of the issue(s),
  • when and how long the issue(s) existed,
  • prior opportunities for identification,
  • documentation of significant plant-specific consequences and compliance concerns,
  • use of systematic methodology to identify causes with a sufficient level of supporting detail,
  • consideration of prior occurrences, and
  • identification of extent of condition and extent of cause.

NRC Assessment: The team concluded that this objective was met.

The inspectors determined the licensee had prior opportunities to identify and address the conditions that led to the White finding, prior to the recent licensee identification. The RCA adequately assessed and addressed prior opportunities to identify the issues. The licensee appropriately understood the risk and compliance aspects of the White finding. The RCA identified two root causes and one contributing cause.

Root Cause 1 (RC1): Engineering personnel did not successfully identify fuel injector preventive and predictive maintenance strategies.

Root Cause 2 (RC2): The system engineers and engineering managers did not exercise adequate technical human performance behaviors and technical conscience principles when developing the preventive maintenance (PM) strategy for the SACM diesel generators.

Contributing

Cause:

Longer term impacts of deposit buildup were not identified nor proactively addressed even though non-nuclear operating experience was available that identified multiple diesel engine injector failures since the introduction of ultra-low sulfur diesel fuel oil. As a result, PM strategies were not revised to account for deposit buildup in the fuel injectors.

a. Identification. The issues resulting in the White finding were identified by the licensee. The licensee's root cause analysis noted that the event became self-revealing on April 24, 2023, during the performance of STP-O-008A, Test of 1A EDG and 11 4KV Bus UV. The EDG had been fully loaded for approximately 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> when an improper combustion event due to deposit buildup inside 1A2 B1 fuel oil injector resulted in an exhaust gas temperature (EGT) high alarm.

b. Exposure Time. The licensee's RCA documented gaps in the PM strategy dating back to the original SACM EDG installation in 1996 and existed until the failure in 2023.

c. Identification Opportunities. The licensee documented that there were multiple opportunities to identify the conditions leading to the White finding. The RCA captured that multiple past internal and third party reviews had recommended enhanced PM strategies and were missed opportunities for identification. Specifically, the licensee identified a missed opportunity in 1997 to address SACM recommended 10-12 year overhaul deviations when other maintenance strategy differences were being considered. In 1999, the station commissioned a third party to analyze PM strategy alternatives, which recommended using engine signature analysis (ESA) to monitor and trend performance. The station decided to not implement ESA based on a belief that the technology was not fully developed or proven to provide meaningful results. In 2016, the SACM PM template was created for the merger with Exelon Corporation, which allowed for the use of EGT trending or ESA to monitor performance. The station continued to use EGT to monitor performance. Additionally, in 2017, a third party review of alternating current reliability at the station recommended the use of ESA to improve the reliability of the EDGs. The licensees RCA identified that the recommendation was captured in the corrective action program but that the action to establish an alternate SACM PM strategy was closed out with no action taken documented.

d. Risk and Compliance. The licensee's RCA documented significant plant-specific consequences and compliance concerns associated with the performance issue. Specifically, the licensee documented that the failure of the 1A EDG due to an over fuel condition caused by intermittent sticking of the fuel oil injector spindle on April 24, 2023, resulted in declaring the 1A EDG inoperable and entry into Unit 1 TS Limiting Condition of Operation (LCO) 3.8.1.B (one EDG inoperable) and U2 TS LCO 3.8.1.E (1A EDG is backup to 11 Control Room Emergency Ventilation System and 11 Control Room Emergency Temperature (CREVS/CRETS)). In addition, the licensee documented the NRC's determination of a White finding and Notice of Violation as documented in NRC Inspection Reports 05000317/2023050 and 05000317/2023090. The NRC's risk evaluation was documented in NRC Inspection Report 05000317/2023050.

e. Methodology. The licensee's RCA evaluated performance issues using a systematic evidence-based approach to identify root and contributing causes. Specifically, the licensee's RCA utilized a diverse set of techniques in conducting the investigation, these included Independent Vendor Analysis, Event and Causal Factor Chart, Barrier Analysis, Organizational Effectiveness Evaluation, and Safety Culture Assessment.

The inspectors reviewed each of the documented method results and determined that the different methods provided a detailed, reliable, and scrutable evaluation. Also, the inspectors determined these analyses were performed with sufficient rigor and depth to identify the root and contributing causes. The inspectors noted that the initial RCA was completed in July 2023, which identified the initial root cause (RC1). Following the issuance of NRC Inspection Reports 05000317/2023050 and 05000317/2023090, which documented the preliminary and final White finding, the licensee revised the RCA and identified a second root cause (RC2).

f. Level of Detail. The inspectors determined that the licensee's RCA was conducted to a level of detail commensurate with the significance and complexity of the White performance issue. Specifically, the licensee's RCA utilized a formal cause evaluation process to identify problems and determine corrective actions. The RCA was performed by a cross-disciplinary team of individuals with various backgrounds and levels of experience, including external subject matter experts in causal analysis. Additionally, the RCA was reviewed by a third party, as required by licensee procedures.

g. Operating Experience. The inspectors determined that the licensee's RCA considered prior occurrences of the performance issue and knowledge of prior operating experience. Specifically, the RCA included searches of industry databases, the licensee's corrective action program, and review of other internal and external operating experience. Additionally, the licensee expanded its review of operating experience to non-nuclear sources, which resulted in the discovery of publications regarding the phenomenon of particle buildup on fuel injectors. The inspectors noted that, as a result of this review, the licensee identified instances that supported the development of RC1 and RC2.

Objective 2: Ensure that the extent of condition and extent of cause of White performance issues are identified

Under this objective, the inspectors assessed the licensee's RCA, associated corrective actions, procedures, and work orders to evaluate the licensee's extent of condition and extent of cause.

NRC Assessment: The team concluded that this objective was met.

Extent of Condition and

Cause.

The inspectors determined that the licensee's RCA identified the extent of condition and the extent of cause of the performance issue. Specifically, the RCA determined that the extent of condition applied to all of the diesel generator engines at Calvert Cliffs, which included the safety-related 1A, 1B, 2A, and 2B engines and the augmented quality station blackout 0C engine. As a result, the licensee developed corrective actions to replace all SACM diesel generator (1A and 0C) fuel injectors and to inspect for deposit buildup on a of minimum of two nozzles from all Fairbank Morse EDGs (1B, 2A, and 2B). For the extent of cause, the inspectors noted that the licensee developed corrective actions to assess the potential for instances of RC1, RC2, and contributing cause to exist within other plant processes, programs, equipment, or human performance.

Objective 3: Ensure that completed corrective actions to address and preclude repetition of White performance issues are timely and effective

Under this objective, the inspectors assessed the appropriateness and timeliness of the licensee's corrective actions.

NRC Assessment: The team concluded that this objective was met. The inspectors noted that there were two completed corrective actions to preclude repetition associated with RC1.

a. Completed Corrective Actions to Preclude Repetition

1) CAPR 04672350-49: Implement a two-year time-directed replacement strategy with new fuel injectors or Wrtsil/SACM refurbished fuel injectors for 1A and 0C diesel generators (RC1).

2) CAPR 04672350-51: Revise PM/PM strategy to utilize ESA as the condition monitoring method used to monitor the performance of the fuel injectors. Perform trending, take appropriate actions and document (RC1).

The inspectors reviewed the applicable work orders and PM strategy documentation to ensure the CAPRs were implemented timely and appropriately.

b. Other Completed Corrective Actions

The licensee identified the following corrective actions to address Root Cause (RC1):

1) Replacement of all 1A EDG fuel injectors (CA 04672350-94)

The inspectors reviewed work order C93913020 to confirm this corrective action was completed in July 2023.

2) Implement a two-year time-directed replacement strategy with new fuel injectors or Wrtsil/SACM refurbished fuel injectors for 0C station blackout diesel generator.

(CA 04672350-56)

The inspectors reviewed the PM strategy to confirm this corrective action was completed in September 2023.

3) Review the current PM strategy against the recommendations from the MPR-4300 report dated May 2017, the corporate PM High Impact Team and non-nuclear fuel injector operating experience and perform a review of the results with the engineering manager and corporate diesel subject matter expert. Resolve the identified gaps once alignment has been obtained from the review authorities.

Provide technical justification for any deviation(s). (CA 04672350-83)

The inspectors reviewed closure documentation to confirm this corrective action was completed in December 2023.

4) Update performance centered maintenance template to require both EGT monitoring and ESA to be performed. Currently the guidance allows for one or the other to be performed. (CA 04672350-53)

The inspectors reviewed the diesel generator performance centered maintenance template and confirmed it was updated in February 2024.

5) Implement training for engineering personnel and engineering managers to establish effective oversight of the PM strategy and fundamental knowledge required to maintain equipment reliability as documented in Performance Analysis PA-230731-001. (CA 04672350-89)

The inspectors reviewed lesson plan N-CC-ENG-PMSTRAT-2023, 2023 Preventive Maintenance Engineering Case Study, and attendance rosters to confirm the training was completed in the fourth quarter of 2023.

6) Update the maintenance strategy database to require the use of ESA and EGT. (CA 04672350-90)

The inspectors noted this CA is associated with CA 04672350-53 and confirmed that the database was updated in February 2024.

7) Review the failure modes causal trees and Wrtsil/SACM report associated with this root cause and ensure that all failure mechanisms that could result in a piston melt have associated PM frequency and scope that align with the significance of its failure mode. Review the technical basis for recommended changes with engineering manager and corporate diesel subject matter expert. Revise the PM strategy to address gaps that are identified. (CA 04672350-59)

The inspectors reviewed the 1A2 engine lube oil leak failure mode causal trees and Wrtsil/SACM report MTRC 23-026 and confirmed the PM strategy was revised in November 2023.

The licensee identified the following corrective actions to address Root Cause (RC2):

1) Conduct training which will include station must know operating experience related to less than adequate technical conscience principle gaps. (CA 04672350-95)

The inspectors reviewed the training materials and attendance rosters to confirm the training was completed in the fourth quarter of 2023.

2) Implement leadership training developed from 04672350-68 that includes lessons learned and gaps in leadership behavior related to the contributing cause that determined that non-corrective action program action tracking was not effectively implemented when addressing previously identified vulnerabilities related to condition monitoring. (CA 04672350-70)

The inspectors reviewed the training materials and attendance rosters to confirm the training was completed in the fourth quarter of 2023.

3) Training Review Committee shall establish an appropriate frequency for training associated with process requirements for establishing or modifying a PM strategy for initial and continuing training that is presented and approved by engineering Training Review Committee. (CA 04735065-02)

The inspectors reviewed closure documentation and confirmed this corrective action was completed in March 2024.

The licensee identified the following corrective action to address the Contributing

Cause:

1) Establish limits for inductively coupled plasma analysis results for new fuel receipt based on the impact to the SACM fuel injector performance. (CA 04672350-63)

The inspectors reviewed closure documentation and confirmed this corrective action was completed in February 2024.

Objective 4: Ensure that pending corrective action plans direct prompt and effective actions to address and preclude repetition of White performance issues

Under this objective, the inspectors assessed the appropriateness and timeliness of the licensee's planned corrective actions.

NRC Assessment: The team concluded that this objective was met. The inspectors noted that there was one planned CAPR associated with RC2. When complete, the NRC plans to inspect and assess the planned corrective action to preclude repetition discussed below.

a. Planned Corrective Actions to Preclude Repetition

1) CAPR 04735065-32: Implement a series of initial and recurring training and behavioral monitoring methods that when combined establishes and reinforces the required standards for effective use and application of technical human performance behaviors and technical conscience principles for all engineering personnel as it relates to preventive maintenance strategy development and modification processes (RC2). This CAPR was developed as a result of Revision 1 of the RCA, which was completed in January 2024. The planned completion date of this CAPR is July 31, 2024. The inspectors determined the planned CAPR identified a corresponding effectiveness review that contained quantitative and qualitative measures of effectiveness.

b. Other Planned Corrective Actions

The licensee identified the following corrective actions to address Root Cause (RC1):

1) Replace 0C station blackout diesel generator fuel injectors with new or Wrtsil/SACM refurbished fuel injectors at the next scheduled maintenance window.

(CA 04672350-52)

The inspectors noted that the 0C station blackout diesel generator fuel injectors are planned to be replaced during a maintenance window in 2024.

The licensee identified the following corrective actions to address Root Cause (RC2):

1) Implement training regarding the process requirements for establishing or modifying a PM strategy to the onsite engineering organization. (CA 04735065-08)

2) Implement proposed changes to Engineering Certification Guide N-AN-ENG-CERT-SM02, Equipment Reliability, per TR-240123-005. [Reference TQ-AA-167 Engineering Training Program, Revision 15, Section 5.6 for Certification Guide Revision Process.] (CA 04735065-09)

3) Engineering branch managers will perform three targeted technical human performance and/or technical conscience principles observations per week on a task that supports PM strategy development or modification. (CA 04735065-18)

The inspectors reviewed the licensee's planned CAPR and corrective actions and determined they were appropriate to address the root causes of the White performance issue and were prioritized commensurate with the significance.

Conclusion

Overall, the inspectors determined that the licensees problem identification, causal analyses, and corrective actions sufficiently addressed the performance issues that led to the White finding. The inspectors determined the corrective actions have been prioritized commensurate with the significance and regulatory compliance, corrective actions taken were prompt and effective, and the Notice of Violation related to the supplemental inspection is sufficiently addressed. All inspection objectives, as described in Inspection Procedure 95001, were met.

Scheduled corrective action items will be inspected as part of the ongoing NRC baseline inspection program. Therefore, this inspection is closed.

INSPECTION RESULTS

No findings were identified.

EXIT MEETINGS AND DEBRIEFS

The inspectors verified no proprietary information was retained or documented in this report.

  • On March 21, 2024, the inspectors conducted an exit and regulatory performance meeting regarding the 95001 supplemental inspection results to Patrick Navin, Site Vice President, and other members of the licensee staff.

DOCUMENTS REVIEWED

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

95001

Corrective Action

Documents

AR 01785507

1A Diesel Generator Tripped While Fully Loaded on 11

4KV Bus

07/28/2007

AR 04040612

Two Recommendations Identified from AC Reliability Visit

08/09/2017

AR 04479267

1A EDG Tripped Due to High Crankcase Pressure

2/19/2022

IR

04672350/04735065

Root Cause Investigation Report, 1A Emergency Diesel

Generator (EDG) Manually Shutdown Due to High Exhaust

Temperature

01/26/2024

Miscellaneous

Calvert Cliffs 1A EDG Failure Investigation 04672350

Roadmap

Revision 0

CCN-70068

Laboratory Inspection of 1A EDG Fuel Injectors

Revision 1

ESR-23-000480

Calvert Cliff 1A2 Piston and Oil Lube Pump Failure,

Observation, and Recommendations on CCNPP

Installations

07/07/2023

Procedures

PI-AA-120

Issue Identification and Screening Process

Revision 13

PI-AA-125

Corrective Action Program (CAP) Procedure

Revision 8

PI-AA-125-1001

Root Cause Analysis Manual

Revision 7

PI-AA-125-1003

Corrective Action Program Evaluation Manual

Revision 7

PI-AA-125-1004

Effectiveness Review Manual

Revision 2

PI-AA-125-1006

Investigation Techniques Manual

Revision 7

PI-AA-126-1001

Self-Assessments

Revision 6

PI-AA-126-1006

Benchmarking Activities

Revision 6