IR 05000457/2023011
| ML24022A100 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 01/25/2024 |
| From: | Jason Kozal NRC/RGN-III/DORS/RPB3 |
| To: | Rhoades D Constellation Energy Generation |
| References | |
| EA-24-003 IR 2023011 | |
| Download: ML24022A100 (1) | |
Text
SUBJECT:
BRAIDWOOD STATION - 2B AUXILIARY FEEDWATER PUMP DIESEL FUEL OIL DILUTION REPORT 05000457/2023011 AND PRELIMINARY GREATER THAN GREEN FINDING AND APPARENT VIOLATION
Dear David Rhoades:
On January 17, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Braidwood Station and discussed the results of this inspection with Gregory Gugle, Site Vice President, and other members of your staff. The results of this inspection are documented in the enclosed report.
The enclosed report documents a finding preliminarily determined to be of Greater-than-Green significance, a finding of greater than very low safety significance resulting in the need for further evaluation to determine significance and therefore the need for additional NRC action, with an associated apparent violation of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix B, Criterion XVI, Corrective Actions. This finding is being considered for escalated enforcement action in accordance with the NRC Enforcement Policy, which can be found at https://www.nrc.gov/about-nrc/regulatory/enforcement/enforce-pol.htm.
Specifically, we determined Braidwood Station failed to identify and correct a condition adverse to quality from June 1, 2023, to September 23, 2023, after receiving lubricating oil sample results for the 2B auxiliary feedwater (AF) pumps diesel engine, which showed the viscosity levels in the alert range provided in licensee procedure MA-AA-716-230-1001, Oil Analysis Interpretation Guideline. As a result, the 2B AF pumps diesel engine lubricating oil continued to degrade due to fuel oil dilution until September 22, 2023, when the licensee declared the 2B AF pump inoperable after receiving additional diesel engine lubricating oil sample results which showed viscosity and fuel oil percentage levels in the fault range specified in MA-AA-716-230-1001. This condition resulted in the 2B AF pump being inoperable and non-functional for approximately 127 days. We assessed the significance of the finding using the significance determination process (SDP) and readily available information. Because we have not made a final determination, no notice of violation is being issued at this time. Please be aware that further NRC review may prompt us to modify the number and characterization of the apparent violations. The final resolution of this issue will be conveyed in separate correspondence.
January 24, 2024 In accordance with NRC Inspection Manual Chapter 0609, we intend to complete our evaluation using the best available information and issue our final significance determination and enforcement decision, in writing, within 90 days from the date of this letter. The NRCs SDP is designed to encourage an open dialogue between your staff and the NRC; however, neither the dialogue nor the written information you provide should affect the timeliness of our final determination.
Before we make a final decision, you may choose to communicate your position on the facts and assumptions used to arrive at the finding and assess its significance by either (1) attending and presenting at a regulatory conference or (2) submitting your position in writing. Regardless of your choice, information regarding the ability of the 2B AF pumps diesel engine to operate would improve the fidelity of our significance characterization. If you request a Regulatory Conference, it should be held within 40 days of the receipt of this letter. Please provide information you would like us to consider at least 10 days prior to any scheduled conference.
The focus of a regulatory conference is to discuss the significance of the finding and not necessarily the root cause(s) or corrective action(s) associated with the finding. If a Regulatory Conference is held, it will be open for public observation. Of note, we would like any information or perspectives you can provide in the following areas:
Information that describes how the test diesel conditions compare to the in-plant 2B AF pump diesel engine and the impact of any differences.
- Information regarding the applicability of similar operating experience (e.g., Surry LER 84-027-00).
If you choose to submit a written response, it should reference the inspection report number and enforcement action number associated with this letter in the subject line. To the extent possible, your written response should not include any personal privacy or proprietary information so that it can be made available to the public without redaction. In addition, your written response should be sent to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region III; the Director, Office of Enforcement; and the NRC Resident Inspector at Braidwood Station, within 40 days of the date of this letter. If an adequate response is not received within the time specified or an extension of time has not been granted by the NRC, the NRC will proceed with its enforcement decision or schedule a Regulatory Conference. If you choose not to request a regulatory conference or to submit a written response, you will not be allowed to appeal the NRCs final significance determination.
Please contact Karla K. Stoedter at 630-829-9731, and in writing, within 10 days from the issue date of this letter to notify the NRC of your intentions. If we have not heard from you within 10 days, we will continue with our significance determination and enforcement decision. 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, Jason W. Kozal, Director Division of Operation Reactor Safety Docket No. 05000457 License No. NPF-77
Enclosure:
As stated
Inspection Report
Docket Number:
05000457
License Number:
Report Number:
Enterprise Identifier:
I-2023-011-0039
Licensee:
Constellation Energy Generation, LLC
Facility:
Braidwood Station
Location:
Braceville, IL
Inspection Dates:
October 30, 2023 to January 17, 2024
Inspectors:
K. Barclay, Senior Reactor Inspector
C. Bickett, Senior Reactor Analyst
D. Kimble, Senior Resident Inspector
Approved By:
Jason W. Kozal, Director
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an inspection of the 2B Auxiliary Feedwater Pump Diesel Fuel Oil Dilution event at Braidwood Station, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
Contamination of Auxiliary Feedwater (AF) Pump Diesel Engine Lubricating Oil Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Preliminary Greater than Green AV 05000457/2023011-01 Open EA-24-003
[H.11] -
Challenge the Unknown 71153 A self-revealed finding with a preliminary greater than very low safety significance (i.e., Preliminary Greater than Green) and an associated apparent violation (AV) of 10 CFR 50, Appendix B, Criterion XVI, Corrective Actions, were identified for the licensees failure to assure that conditions adverse to quality are promptly identified and corrected.
Specifically, no action was taken to identify and correct a deficiency associated with the 2B AF pumps diesel engine after the licensee received the results from a May 19, 2023, lubricating oil sample on June 1, 2023, and these results showed viscosity levels in the alert range. These facts were later revealed on September 21, 2023, when the next regularly scheduled periodic oil sample results for the 2B AF pumps diesel engine were received by the licensee from their oil analysis vendor and showed lubricating oil viscosity values and the value for fuel oil contamination within the lubricating oil to be beyond acceptable fault limits.
Additional Tracking Items
None.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
OTHER ACTIVITIES - BASELINE
71153 - Follow Up of Events and Notices of Enforcement Discretion Event Follow up (IP Section 03.01)
The inspectors reviewed and evaluated licensee performance and the safety significance associated with the following event:
- (1) The identification of fuel oil contamination in the 2B Auxiliary Feedwater (AF) Pump diesel engine oil system, as documented in Issue Report (IR) 4703982, during the weeks ending November 4, 2023, through January 17, 2024. This sample constitutes the completion of a partial inspection sample previously documented in NRC Integrated Inspection Report 05000456/2023004 and 05000457/2023004.
INSPECTION RESULTS
Contamination of Auxiliary Feedwater (AF) Pump Diesel Engine Lubricating Oil Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Preliminary Greater than Green AV 05000457/2023011-01 Open EA-24-003
[H.11] -
Challenge the Unknown 71153 A self-revealed finding with a preliminary greater than very low safety significance (i.e., Preliminary Greater than Green) and an associated apparent violation (AV) of 10 CFR 50, Appendix B, Criterion XVI, Corrective Actions, were identified for the licensees failure to assure that conditions adverse to quality are promptly identified and corrected.
Specifically, no action was taken to identify and correct a deficiency associated with the 2B AF pumps diesel engine after the licensee received the results from a May 19, 2023, lubricating oil sample on June 1, 2023, and these results showed viscosity levels in the alert range. These facts were later revealed on September 21, 2023, when the next regularly scheduled periodic oil sample results for the 2B AF pumps diesel engine were received by the licensee from their oil analysis vendor and showed lubricating oil viscosity values and the value for fuel oil contamination within the lubricating oil to be beyond acceptable fault limits.
Description:
During Braidwood Unit 2 Refueling Outage A2R23, which took place from April 24, 2023, through May 13, 2023, the 2B AF pump underwent a substantial preventative maintenance work window that included the replacement of all sixteen
- (16) fuel injectors on the pumps diesel engine (prime mover). The fuel lines associated with all 16 fuel injectors were also replaced with new lines. While the engine design has connections that support pressure testing the fuel system following fuel line replacement, pressure testing was neither required by the licensees maintenance instructions/procedures nor performed prior to return of the 2B AF pump to service.
Following the completion of Braidwood Unit 2 Refueling Outage A2R23, the 2B AF pump was run on May 19, 2023, for its normal quarterly surveillance in accordance with the stations Inservice Testing (IST) Program. Oil sampling for analysis was performed as a normal part of this surveillance routine. On June 1, 2023, the station received the results of the 2B AF pumps diesel engine lubricating oil analysis from their offsite vendor. The oil sample results indicated a viscosity of 12.6 centistokes (cSt) at 100 degC and 114.6 cSt at 40 degC. Licensee procedure MA-AA-716-230-1001, Oil Analysis Interpretation Guideline, 49 for diesel engines like the 2B AF pump using Mobil Delvac 1640 lubricating oil, placed both of these viscosity parameters outside of acceptable limits and within the Alert Range. In addition, the fuel content parameter indicating the percentage of fuel oil contamination measured within the lubricating oil was listed as N/R (Not Recorded) on the report. In spite of these anomalies, the licensees review of the oil analysis results failed to generate any additional actions or reviews. No corrective action program (CAP) issue report (IR) was written to document the irregular results nor were any follow-up actions performed.
On September 1, 2023, the next quarterly IST surveillance on the 2B AF pump was conducted. Again, oil sampling for analysis was performed as a normal part of this surveillance routine. On September 21, 2023, the station received the results of the 2B AF pumps diesel engine lubricating oil analysis from their offsite vendor. Viscosities of 5.7 cSt at 100 degC and 53.4 cSt at 40 degC were reported by the oil analysis vendor. In addition, a fuel concentration of 17.0 percent was indicated as present within the lubricating oil. All of these values were well outside of the fault range for the respective parameters. Per the licensees MA-AA-716-230-1001 procedure, any oil analysis parameter in the fault range would indicate an immediate need to protect the component from damage or possible failure with continued operation.
Following receipt of the vendors oil analysis results on September 21, 2023, a confirmatory sample was immediately taken from the 2B AF pumps diesel engine and sent off for analysis with an expedited priority. On September 22, 2023, the station received the results of this confirmatory oil sample from their vendor. Viscosities of 8.3 cSt at 100 degC and 52.4 cSt at 40 degC were reported, along with a fuel concentration of 18.2 percent indicated within the lubricating oil. At this point, with the results of the confirmatory oil sample also well outside of the fault range for all of these parameters, the licensee immediately declared the 2B AF pump inoperable and entered an emergent repair work window to drain the 2B AF pumps lubricating oil from the diesel engine, check the fuel system for leakage, perform necessary repairs, and refill the diesel engine crank case with new oil. On September 23, 2023, the licensee returned the 2B AF pump to service after changing the lubricating oil and repairing leaking fuel line connections on two fuel injectors.
Corrective Actions: As part of the corrective actions for this issue, the licensee replaced the engines lubricating oil and repaired fuel leaks on the 5L return line at the fuel injector connection point and at both ends of the 2R return line (injector connection and fuel rail connection points). The 2B AF pump was returned to service on September 23, 2023, following completion of post-maintenance testing activities. A formal root cause evaluation was chartered by station management on October 5, 2023.
Corrective Action References: IR 4703982; Degraded Oil in 2B Diesel-Driven Auxiliary Feedwater (2AF01PB) Engine Crank Case; 09/21/2023
Performance Assessment:
Performance Deficiency: The licensees failure to identify and correct conditions adverse to quality, such as nonconformances and deficiencies, in accordance with 10 CFR 50, Appendix B, Criterion XVI was a performance deficiency. Specifically, the licensee failed to identify and correct a condition adverse to quality from June 1, 2023, to September 23, 2023, when they received the results for a 2B AF pump diesel engine lubricating oil sample which showed the viscosity levels in the alert range provided in licensee procedure MA-AA-716-230-1001, Oil Analysis Interpretation Guideline. As a result, the 2B AF pumps diesel engine lubricating oil continued to degrade due to fuel oil dilution until September 22, 2023, when the licensee declared the 2B AF pump inoperable due to receiving lubricating oil sample results for the diesel engine which showed viscosity and fuel oil percentage levels in the fault range specified in MA-AA-716-230-1001.
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, the inspectors concluded that licensees failure to have taken any actions in response to the anomalies contained within the May 19, 2023, lubricating oil sample results for the 2B AF pumps diesel engine represented a significant missed opportunity that resulted in adverse impact to the 2B AF pumps availability and reliability. The inspectors also compared the finding with the examples listed in IMC 0612, Power Reactor Inspection Reports, Appendix E, Examples of Minor Issues. Example 4.f was found to be similar in that a missed opportunity to have properly identified and/or corrected a condition adverse to quality resulted in an adverse impact to the availability, reliability, and/or capability of a mitigating system.
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 subsequently concluded that because the finding could not be easily screened to be of very low safety significance, a detailed risk evaluation was required. The time from the May 19, 2023, lubricating oil sample that indicated that fuel oil was leaking into the 2B AF pumps diesel engine lubricating oil to the point where the licensee completed their corrective actions on September 23, 2023, led the inspectors to answer yes to Mitigating Systems Screening Question A.3, Does the degraded condition represent a loss of the PRA function of one train of a multi-train technical specification (TS) system for greater than its TS allowed outage time?
The senior reactor analysts (SRAs) estimated the total increase in core damage frequency (CDF) related to the 2B AF pumps diesel engine fuel oil dilution to be Preliminary Greater than Green, a finding with greater than very low safety significance. Based on an initial best-estimate assumption that high levels of fuel oil dilution in the lube oil system would fail the function of the 2B AF pump, the SRAs determined the CDF associated with this performance deficiency to be approximately 1.4E-5/year.
The NRC recognizes that there may be some uncertainty associated with the primary assumptions relied upon in this risk analysis and the impact of any of these potential uncertainties would be to lower the calculated CDF. However, based on best available known information at the time of the exit meeting, the NRC has characterized the significance of this performance deficiency as Preliminary Greater than Green. The NRC was aware of ongoing efforts by Constellation to further refine some of the key assumptions used in support of the risk analysis. Consistent with the normal process for finalizing the significance of an inspection finding, the NRC plans to consider any additional relevant information that may be provided by Constellation in support of the final risk assessment.
Influential Assumptions 2B AF Pump Performance with Fuel Oil Dilution The 2B AF pump demonstrated 1.88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br /> of successful runtime on September 1, 2023, which is when Constellation drew the lube oil sample that was later determined to be in the fault range for both viscosity and fuel oil percentage (approximately 17 percent fuel oil dilution). The SRAs determined there are significant uncertainties associated with how the 2B AF pump would perform as fuel oil dilution in the lube oil system continued to increase as the pump ran throughout its 24-hour mission time. The vendors maximum specification for dilution is 2.5 percent. Additionally, there is limited literature available discussing diesel engine performance with high levels of fuel oil dilution in the lube oil system. Therefore, the SRAs assumed that fuel oil dilution greater than 17 percent would fail the function of the 2B AF pump.
Medium Head FLEX Pump Steam Generator Feed Strategy In their evaluation of risk, Constellation credited the medium head FLEX pumps as a source of feedwater to the steam generators during loss of secondary heat sink events. Normally, for a loss of feedwater at full power, operators would have insufficient time to establish feed flow from the medium head FLEX pump to steam generator prior to core damage. However, based on thermohydraulic calculations conducted for their analysis, Constellation determined that 1.88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br /> of demonstrated 2B AF pump runtime would provide a reduction in decay heat such that upon a loss of secondary heat sink, operators would have sufficient time to deploy one medium head FLEX pump to feed the steam generators from the refueling water storage tank. Constellation created a new human error probability calculation which established an operator action failure probability of 6.3E-2 for this strategy. Additionally, if the first medium head FLEX pump ran successfully for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, Constellation also credited deployment of and feed from the second medium head FLEX pump in their analysis.
Braidwoods implementing procedure in this case is 2BwFR-H.1, Loss of Secondary Heat Sink. The key actions in this procedure included bleed and feed, restoration of AF, crosstie of AF from Unit 1, and restoration of main feedwater or condensate booster flow. If these actions were not successful, 2BwFR-H.1 directed operators to implement 10 CFR 50.54(x)and align the medium head FLEX pump per 2BwFSG-3, Alternate Low Pressure Feedwater. Procedure 2BwFSG-3 then directed operators to 2BwFSG-5, Attachment C, Aligning Medium Head FLEX Pump. The SRAs determined that 2BwFSG-5 did not provide explicit direction to align the medium head FLEX pump suction directly to the refueling water storage tank. Operators were directed to align either the low head or high head FLEX pump in conjunction with the medium head FLEX pump. The SRAs also reviewed operator training and noted that training aligned with the procedures. As such, during an event, operators would have to modify multiple procedure steps to feed the steam generators from the refueling water storage tanks via the medium head FLEX pump.
The SRAs walked down portions of the medium head FLEX pump lineup to determine the feasibility of the action. Based on interviews with station personnel, the SRAs determined that Constellation had not physically deployed the FLEX refueling water storage tank suction piping based on concerns with security barriers and ventilation boundaries. All validations associated with this action were completed via simulated walkthroughs. Based on review of the procedure and discussions with plant staff, the SRAs concluded that deployment of the suction piping may be challenging for operators given the weight of the piping (approximately 360 pounds) and the planned routing path.
Constellation provided this strategy to an operating shift crew for review. The SRAs reviewed the associated documentation and noted that operators were concerned with using the refueling water storage tank due to the potential spread of contamination to the environment via the steam generator power-operated relief valves. Additionally, the operators determined that other methods were available but not proceduralized (e.g., use of fire water which would be substantially quicker than aligning suction to the refueling water storage tank). Operators also recognized that the station would have implemented 10 CFR 50.54(x) at this point, which would allow them to implement non-proceduralized actions to protect the health and safety of the public.
Based on the above, the SRAs determined that crediting steam generator feed from the refueling water storage tank via the medium head FLEX pumps was not appropriate for this detailed risk evaluation. The Risk Assessment of Operational Events (RASP) Handbook, Volume 1, Revision 2.02, Section 6.3, discusses the treatment of recovery actions. Of note, recovery actions should not be credited where certain considerations are not met, including adequate procedures and/or training. Station procedures do not provide explicit direction to align the medium head FLEX pump suction directly to the refueling water storage tank - operators would have to modify multiple procedure steps to accomplish this lineup. Additionally, based on input from the operating crew, the SRAs concluded that implementation of 10 CFR 50.54(x) provides a level of unpredictability in operator response such that crediting operator actions that are not explicitly proceduralized would not be appropriate.
SPAR Model Changes The SRAs evaluated the finding using Systems Analysis Programs for Hands-On Evaluation (SAPHIRE) version 8.2.9, and a test and limited use (TLU) version of the Braidwood SPAR model created by Idaho National Laboratories (TLU3). This TLU3 model included revision to the Braidwood SPAR model of record (version 8.82) to more closely reflected the as-built, as-operated plant. SPAR model changes included the following:
- Crosstie of AFW from the opposite unit for non-dual unit initiators was credited in the SPAR model. This action is covered by station procedures.
- Crosstie of DC buses was credited in the SPAR model and the DC power fault trees were updated to include both the batteries and battery chargers. DC power crosstie is covered by station procedures.
- The ability to crosstie AF with the diesel-driven AF pumps was removed from the model. Per station drawings and procedures, only the motor-driven AF pumps are available to perform this function.
- Modeling of essential service water system support for the diesel-driven AF pump was updated to reflect the plant configuration.
- The SRAs applied credit for FLEX for station blackout scenarios including the FLEX unreliability parameters documented in PWROG-18042-NP, FLEX Equipment Data Collection and Analysis, Revision 1. Use of FLEX in this application did not have a significant impact on this evaluation.
Exposure Time Though fuel dilution occurred while the diesel engine was in standby, the rate of dilution was significantly higher while the engine was running. Therefore, the SRAs used the methodology described in the Risk Assessment of Operational Events (RASP) Handbook, Volume 1, Revision 2.02, Section 2.5, Exposure Time for Component Run Failures, to determine the exposure time. The SRAs determined the exposure time to be 127 days, starting on May 19, 2023, when Constellation drew the oil sample on the 2B AF pumps engine during the normal quarterly surveillance which demonstrated parameters outside of acceptable limits, and ending on September 23, 2023, when Constellation completed repairs to the fuel return lines, replaced the engine oil, and returned the pump to service.
Contributions from Internal Events Using the Events and Conditions Assessment (ECA) module of SAPHIRE, as well as the model modifications discussed above, the SRAs estimated the risk contribution from internal events for an exposure period of 127 days to be 4.2E-6/year. The SRAs did not provide credit for feeding the steam generators from the refueling water storage tank via the medium head FLEX pumps. The dominant core damage sequence for internal events was a dual loss of essential service water initiating event with failure of AF, main feedwater, and failure to recover essential service water.
Contributions from External Events Seismic, High Wind Events, and Tornadoes Using the ECA module of SAPHIRE, the SRAs estimated the risk contribution from seismic, high winds, and tornado events to be 9.5E-7/year. The SRAs did not provide credit for feeding the steam generators from the refueling water storage tank via the medium head FLEX pumps.
Fire The Braidwood SPAR model does not evaluate fire risk. As such, the SRAs reviewed Constellations fire risk results for this issue. Constellation calculated the CDF due to fire to be approximately 9.2E-6/year. This number does not include credit for feeding the steam generators from the refueling water storage tank via the medium head FLEX pumps. The dominant fire sequences involve a fire in a main control board with failure of operators to recognize the loss of secondary heat removal.
Total Estimate of CDF from Internal and External Events Input Value Internal Events 4.2E-6/year Fire Events 9.2E-6/year Seismic, High Wind Events, and Tornadoes 9.5E-7/year Total 1.4E-5/year Sensitivity Evaluations Sensitivity 1: Medium Head FLEX Pump Feed to Steam Generators The SRAs conducted a sensitivity analysis to determine the impact of the medium head FLEX pump strategy on the risk associated with this issue. For this sensitivity, the SRAs set the human error probability for this operator action to 6.3E-2, as proposed by Constellation. The SRAs determined that the results were strongly sensitive to consideration of operator actions to align the medium head FLEX pump to feed the steam generators from the refueling water storage tank during a loss of secondary heat sink scenario. However, the SRAs do not consider this strategy achievable.
Sensitivity 2: 2B AFW Pump Performance with Fuel Oil Dilution The SRAs were aware that Constellation planned to conduct testing on a similar diesel to further refine the assumptions used in the determination of the risk of this issue. Given that the final test report was not available for review prior to completion of this preliminary risk evaluation, the SRAs did not consider this testing in the best-estimate determination of risk.
However, the SRAs conducted a sensitivity analysis by setting the late run component for the 2B AFW fail-to-run basic event to 0.5 instead of TRUE, with a late mission time of 22.12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This effectively credits a probability the 2B AFW pump diesel could run instead of completely failing the diesel. A probability of 0.5 is an increase from the nominal late failure to run probability of 6.96E-2. The SRAs determined that the results were strongly sensitive to this adjustment.
Best Estimate Sensitivity 1 (HEP: 6.3E-2)
Sensitivity 2 (late: 0.5)
Internal Events 4.2E-6/year 1.6E-6/year 1.9E-6/year Seismic, High Wind Events, and Tornadoes 9.5E-7/year 5.0E-7/year 6.5E-7/year Fire Events 9.2E-6/year 4.5E-6/year 4.8E-6/year Total 1.4E-5/year 6.6E-6/year 7.4E-6/year Contributions from Large Early Release Frequency (LERF)
The SRAs evaluated LERF using the SPAR model and determined that the impact to LERF is bounded by the increase in CDF.
Constellations Evaluation Constellation modeled this failure in two separate intervals over a total exposure time of 127 days. The first interval was the exposure period in which the 2B AF pump was shown to run for 1.88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br />, which was from May 19, 2023, to September 1, 2023 (105 days). Based on thermohydraulic calculations conducted for their analysis, Constellation determined that 1.88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br /> of demonstrated runtime would provide enough of a reduction in decay heat such that operators would have sufficient time to deploy one medium head FLEX pump to feed the steam generators from the refueling water storage tank. Constellation created a new human error probability calculation which established an operator action failure probability of 6.3E-2 for this strategy. Additionally, if the first medium head FLEX pump ran successfully for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, Constellation also credited deployment of and feed from the second medium head FLEX pump in their analysis. The second interval is the remainder of the exposure period (22 days) and does not credit any 2B AF pump runtime. As such, the medium head FLEX pump steam generator feed strategy described above is not credited for this interval, as there would not be enough time to deploy the strategy. Constellation also completed other refinements of their model during performance of their evaluation, however, crediting the medium head FLEX pump for steam generator feed provided the most significant reduction in risk for their evaluation.
Cross-Cutting Aspect: H.11 - Challenge the Unknown: Individuals stop when faced with uncertain conditions. Risks are evaluated and managed before proceeding. Specifically, this finding involved licensee individual(s) responsible for reviewing oil analysis results deciding to accept unusual and anomalous test results, rather than stopping and alerting other applicable parties and/or station management to the condition before proceeding on.
Enforcement:
Violation: Title 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Actions, requires, in part, that measures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances are promptly identified and corrected.
Contrary to the above, from June 1, 2023, to September 23, 2023, the licensee failed to establish measures to assure that conditions adverse to quality are promptly identified and corrected. Specifically, the licensee failed to identify and correct a deficiency associated with the 2B AF pumps diesel engine after they received the results from a May 19, 2023, lubricating oil sample on June 1, 2023, indicating viscosity levels in the alert range.
Enforcement Action: This violation is being treated as an apparent violation pending a final significance (enforcement) determination.
EXIT MEETINGS AND DEBRIEFS
The inspectors confirmed that proprietary information was controlled to protect from public disclosure.
- On January 17, 2024, the inspectors presented the 2B Auxiliary Feedwater Pump Diesel Fuel Oil Dilution results to Gregory Gugle, Site Vice President, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
238259
1AF01PB Crankcase Oil Analysis Degrading Trend
04/10/2019
4703982
Degraded Oil in 2AF01PB Crank Case
09/21/2023
4704473
2AF01PB Return Line Leaking
09/23/2023
4704480
2AF01PB - 2R Fuel Return Line Leaking
09/23/2023
4706623
Review of 2B AF Pump Oil Results
10/02/2023
4708247
Review of 2B AF Pump Oil Results
10/09/2023
4708461
2B AF Main Bearing Degraded
10/10/2023
4708525
2B AF Pump 3L Fuel Injector Leaking
10/10/2023
4708613
Inspect / Repair Fuel Leak Visual Identified an Abnormality
10/10/2023
Corrective Action
Documents
4708713
2B Aux Feed Removed Fuel Injector on #3 Left
10/11/2023
Corrective Action
Documents
Resulting from
Inspection
4706606
NRC ID: Information in 2B AF Vendor Manual and Oil
Sample
10/02/2023
Drawings
AF-1
Auxiliary Feed System
Engineering
Changes
1AF01PB Crankcase Oil Fuel Dilution Content Evaluation
000
2B AF RC Two Week Update
10/26/2023
Constellation Braidwood Station 20 - Oil Braceville, IL-
2AF01PM-CC-2AF01PM-CC-2AF01PB-K-PMPA-01PB-E15-
K-202310040026-Normal
10/10/2023
Constellation Braidwood Station 20 - Oil-Braceville_IL-
2AF01PB-CC-2AF01PB-K-PMPA-01PB/E15-K-
2310180028
10/18/2023
Oil Sample Post-PMT Run
09/23/2023
Oil Sample New Barrel
09/22/2023
Miscellaneous
- BV Transmittal Letter
04/06/2023
- BV Cover Letter CEG
2/21/2023-
2/23/2023
and
03/28/2023-
03/29/2023
Report BV
2/21/2023-
2/23/2023
and
03/28/2023-
03/29/2023
Nuclear Procurement Issues Corporation Audit Checklist
Bureau Vistas
Chapter 26 I1-AF-XL-01 PPT
006
09/25/2023
RMTS Report: 2AF01PB 2B AF Diesel Bearing Inspection
10/11/2023
10/11/2023
2B AF Initial Case Signed
10/12/2023
FXPr0 FLEX Procedures
Receipt 282055; Receipt Cat ID 1390618-1; PO 1389979;
04/19/2023
3.7.5
Auxiliary Feedwater (AF) System
10/13/2023
3.7.6
Condensate Storage Tank (CST)
10/14/2023
4101-0031-
OTHR-001
Braidwood 2B AFW Diesel Engine Test Plan
56899
2/19/2023
B 3.75
Auxiliary Feedwater (AF) System
10/13/2023
B/B-UFSAR
010 CH 10 Steam and Power Conversion Sys
BB-PRA-005.04
Byron and Braidwood Probabilistic Risk Analysis; Auxiliary
Feedwater System Notebook (AF)
Chapter 26 I1-AF-
XL-01
PWR Initial License Training Systems
006
D446-0~1
Vendor Service Manual; Detroit Diesel Series 149 Engine
09/28/2023
2/19/2023
FR H.1
AF Crosstie Utilization
09/26/2023
Miscellaneous
No. 17
Present 1AF01PB Oil Issue to PHC MMD to Document the
Cause of the Fuel Oil Leak following 1AF01PB Repair
10/13/2019
No. 19
Perform Rework Investigation per MA-AA-716-017
05/29/2019
LER 2023-001-00
Unit 1 Train B Auxiliary Feedwater Pump was Inoperable due
to Degraded Oil in the Crank Case
11//17/2023
NUPIC No: 4918
Fuel Oil and Lube Oil, Refrigerant Analysis
04/05/2023
PI-SP-14-32
Braidwood LORT Fukushima Flex
0a
PORC: 23-017-2
1/2BwFR H.1 - Response to Loss of Secondary Heat Sink
09/28/2023
BB-PRA-004
Human Reliability Analysis Notebook
Revision 15
BwOP AF-7
Auxiliary Feedwater Pump B (Diesel) Startup on Recirc
BwOP AF-7T1
Diesel Driven Auxiliary Feedwater Pump Operating Log
Paragon Model Capability
Risk Management Support of RICT
001
Calculation of RMAT and RICT for Risk Informed Completion
Time Program
ER-BW-600-2001
Braidwood RICT System Guidelines
Predictive Maintenance Program
MM-AA-716-230-
1001
Oil Analysis Interpretation Guideline
MM-AA-716-230-
1004
Lubricant Sampling Guideline
Risk Informed Completion Time
RICT Record
10/11/2023
2BwFR-H.1
Response to Loss of Secondary Heat Sink
Revision 304
Alternate Low Pressure Feedwater, Unit 2
Revision 2
Initial Assessment and FLEX Equipment Staging, Unit 2
Revision 5
Procedures
BW-SDP-006
2B AF Pump Fuel Oil Leak SDP FLEX HEP Sensitivities
Revision 0
01865780 01
MM 2AF01PB-K - Perform 18 Year Inspection
05/06/2023
05042459 01
MM Change Oil in 2AF01PB Crank Case
09/23/2023
230646
LR-MM 2AF01PB Perform 18 Month Inspection
05/10/2023
05346058 01
LR-OP 2B AF Pump Diesel Lube Oil Sample
05/22/2023
05350643 01
OP-Unit 2 Diesel Driven Aux Feedwater Pump ASME
Qrtly Sur
05/20/2023
05357055 01
OP U-2 Diesel Driven AF PP Monthly Run
05/20/2023
Work Orders
05371917 01
OP U-2 Diesel Driven AF PP Monthly Run
06/08/2023
05373348
LR-OP 2B AF Pump Diesel Lube Oil Sample
09/01/2023
05378877 01
OP U-2 Diesel Driven AF PP Monthly Run
07/14/2023
05379233 01
OP-Unit 2 Diesel Driven Aux Feedwater Pump ASME Qrtly
Sur
09/01/2023
05385077
OP U-2 Diesel Driven AF PP Monthly Run
08/10/2023
05391794 01
OP U-2 Diesel Driven AF PP Monthly Run
09/01/2023
05401827 01
LR-2B AF Pump Monthly Surveillance Run
10/14/2023
05402459 02
OP: PMT 2AF01PB Perform Functional and Verify No Leaks
09/23/2023
05402459 03
MM 2AF01PB Repair Suspected Fuel Leak
09/23/2023
05402459 09
MM 2AF01PB - Inspect Main Crank Shaft Bearings
10/16/2023
05402459 10
OP: PMT 2AF01PB Perform ASME and Verify No Leaks
10/14/2023
05402459 13
MM - 2AF01PB - Inspect / Repair Fuel Leak
10/24/2023
05402459 18
OP - Perform 2AF01PB Engine Break-In following
Maintenance
10/14/2023