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| | number = ML18138A137 | | | number = ML18138A137 |
| | issue date = 05/22/2018 | | | issue date = 05/22/2018 |
| | title = Calvert Cliffs Nuclear Plants, Units 1 and 2 - Request for Additional Information Regarding Risk Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) | | | title = Plants, Units 1 and 2 - Request for Additional Information Regarding Risk Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) |
| | author name = Marshall M L | | | author name = Marshall M |
| | author affiliation = NRC/NRR/DORL/LPLI | | | author affiliation = NRC/NRR/DORL/LPLI |
| | addressee name = Hanson B C | | | addressee name = Hanson B |
| | addressee affiliation = Exelon Generation Co, LLC, Exelon Nuclear | | | addressee affiliation = Exelon Generation Co, LLC, Exelon Nuclear |
| | docket = 05000317, 05000318 | | | docket = 05000317, 05000318 |
| | license number = DPR-053, DPR-069 | | | license number = DPR-053, DPR-069 |
| | contact person = Marshall M L, NRR/DORL/LPLI, 415-2871 | | | contact person = Marshall M, NRR/DORL/LPLI, 415-2871 |
| | case reference number = CAC MF7415, CAC MF7416, EPID L-2016-LLA-0001 | | | case reference number = CAC MF7415, CAC MF7416, EPID L-2016-LLA-0001 |
| | document type = Letter, Request for Additional Information (RAI) | | | document type = Letter, Request for Additional Information (RAI) |
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| =Text= | | =Text= |
| {{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MAy 22, 2018 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 | | {{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MAy 22, 2018 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 |
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| ==SUBJECT:== | | ==SUBJECT:== |
| CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2-REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES (CAC NOS. MF7415 AND MF7416; EPID L-2016-LLA-0001) | | CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2- REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES (CAC NOS. MF7415 AND MF7416; EPID L-2016-LLA-0001) |
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| ==Dear Mr. Hanson:== | | ==Dear Mr. Hanson:== |
| By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML 17094A591 ), January 11, 2018 (ADAMS Accession No. ML 18011A665), and January 18, 2018 (ADAMS Accession No. ML 18018B340), Exelon Generation Company, LLC submitted a license amendment request proposing to modify the Calvert Cliffs Nuclear Power Plant, Units 1 and 2, Technical Specification requirements to permit the use of risk-informed completion times. The U.S. Nuclear Regulatory Commission staff is reviewing the submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information. The request for additional information was discussed with your staff on May 16, 2018, and it was agreed that your response would be provided within 30 days from the date of this letter. If you have any questions regarding this matter, please contact me at (301) 415-2871 or Michael.Marshall@nrc.gov. Docket Nos. 50-317 and 50-318 | | |
| | By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML17094A591 ), January 11, 2018 (ADAMS Accession No. ML18011A665), and January 18, 2018 (ADAMS Accession No. ML18018B340), Exelon Generation Company, LLC submitted a license amendment request proposing to modify the Calvert Cliffs Nuclear Power Plant, Units 1 and 2, Technical Specification requirements to permit the use of risk-informed completion times. |
| | The U.S. Nuclear Regulatory Commission staff is reviewing the submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information. The request for additional information was discussed with your staff on May 16, 2018, and it was agreed that your response would be provided within 30 days from the date of this letter. |
| | If you have any questions regarding this matter, please contact me at (301) 415-2871 or Michael.Marshall@nrc.gov. |
| | Sincerely, Michael L. Marshall, Jr., Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-317 and 50-318 |
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| ==Enclosure:== | | ==Enclosure:== |
| Request for Additional Information cc: Listserv Sincerely, Michael L. Marshall, Jr., Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES EXELON GENERATION COMPANY, LLC CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-317 AND 50-318 By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML 17094A591 ), January 11, 2018 (ADAMS Accession No. ML 18011A665), and January 18, 2018 (ADAMS Accession No. ML 180188340), Exelon Generation Company, LLC (the licensee) submitted a license amendment request (LAR) proposing to modify the Calvert Cliffs Nuclear Power Plant (Calvert Cliffs), Units 1 and 2, Technical Specification (TS} requirements to permit the use of risk-informed completion times. The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review of the LAR. The request for additional information (RAI) listed below is not a complete listing of the additional information needed to complete the NRC staff's review. Additional RAls (i.e., numbers 1 through 19) were provided by separate correspondences dated November 13, 2017 (ADAMS Accession No. ML 17304A941) and December 21, 2017 (ADAMS Accession No. ML 17346A909). Section 36(c)(2) of Title 10 of Code of Federal Regulation requires in part that limiting conditions of operations be included in TSs and that licensees shall follow any remedial action permitted by the TS until the condition can be met. The TSs for Calvert Cliffs, Units 1 and 2, contain limiting conditions of operations that prescribe completion times for remedial actions. The licensee has proposed using its probabilistic risk assessment (PRA) to determine risk-informed completion times that may be used in lieu of the prescribed completion times. Regulatory Guide (RG) 1.174, Revision 2, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed 51 Decisions on Plant-Specific Changes to the Licensing Basis," May 2011 (ADAMS Accession No. ML 100910006) describes an acceptable risk-informed approach for assessing the nature and impact of proposed permanent licensing basis changes by considering engineering issues and applying risk insights. This RG also provides risk acceptance guidelines for evaluating the results of such evaluations. Revision 1 of RG 1.177, "An Approach for Plant-Specific, Informed Decision-making: Technical Specifications," May 2011 (ADAMS Accession No. ML 100910008) describes an acceptable risk-informed approach specifically for assessing proposed TS changes. To ensure that any remedial actions are completed in a timely manner, consistent with RG 1.17 4 and RG 1.177, the PRA models used in the calculation of the informed completion times need to be based on the as-built, as-operated and maintained plant, and reflect operating experience at the plant. 20. Enclosure 4 of the letter dated February 25, 2016, states that a total seismic core damage frequency (CDF) contribution of 1.1 E-6/year and a seismic large early release frequency (LERF) contribution of 1.1 E-7/year will be added to the configuration specific delta CDF and Enclosure delta LERF from the internal events and fire initiating event contributions to estimate the risk-informed completion time. The LAR states that these seismic estimates are based on the re-evaluated seismic hazard for Calvert Cliffs performed in response to the Near-Term Task Force 2.1 (ADAMS Accession No. ML 14099A196) and an estimated plant level high confidence of low probability of failure (HCLPF) of 0.27 the acceleration due to Earth's gravity (g) peak ground acceleration (PGA) as used in the 2003 LAR entitled "Extension of Diesel Generator Required Action Completion Time" (ADAMS Accession No. ML031360410). a. The staff notes that the Calvert Cliffs Expedited Seismic Evaluation Process Report (ESEP), submitted to the NRC on December 17, 2014 (ADAMS Accession No. ML 14365A138), indicates that certain components, such as safety injection tanks, motor control centers, electrical buses, and main control room panels, would fail in a seismic event through interaction with nearby block walls, and those components were assigned a lower HCLPF of 0.175 g due to the block wall lower capacity. This lower HCLPF could increase the seismic CDF and LERF estimates provided in the LAR. Justify the plant level HCLPF of 0.27 g PGA, given the noted block walls failures at 0.175 g indicated in the ESEP, or provide, with justification, updated seismic CDF and LERF estimates. b. The 2003 LAR for extension of emergency diesel generator (EOG) completion times shows differences in estimated seismic CDF and LERF between Unit 1 and Unit 2. According to the NRC Technical Evaluation Report for the Individual Plant Examination for External Events, because the EDGs dedicated to Unit 2 are more dependent on service water cooling, which has a low fragility, the CDF value is higher for Unit 2 than for Unit 1. Explain and justify how the seismic CDF and LERF estimates apply to both units. To estimate the seismic LERF, the LAR assumes a 0.1 conditional large early release probability (CLERP) for seismic events, based on the internal events LERF to CDF ratio. The staff notes that a seismic event could lead to seismic-specific failures of structures, systems, and components, resulting in additional LERF sequences that are not in the internal events probabilistic risk assessment (PRA) model or potentially converting LERF sequences in the internal events PRA model to seismic LERF sequences. The LAR does not provide sufficient justification for the selected CLERP being able to capture or bound such considerations. c. Justify the assumed value of 0.1 for CLERP. In the justification, explain why the containment is not expected to fail and other containment failure or bypass scenarios are not expected to be impacted by seismic events and therefore, would not noticeably affect the assumed 0.1 CLERP. 21. In RAI 10 (see letter dated November 13, 2017), the staff asked the licensee to explain how common cause failures (CCFs) are included in the PRA model and how the treatment of CCF either meets the guidance in RG 1.177 or meets the intent of this guidance when quantifying a risk-informed completion time (RICT) for preventative maintenance for components from a CCF group of three or more components. The response to the RAI states "common cause failures are modeled as separate basic events, with common cause combinations in the fault tree as different basic events." The licensee further stated that the "common cause grouping is not dynamically changed when a component is removed from service for preventative maintenance" and that this is appropriate because "the component, though not out of service for a reason subject to common cause failure, remains a participant in the common cause events for the remainder of the component operation." It is unclear how the out of service component "remains a participant in the common cause events for the remainder of the component operation" and; therefore, it is unclear how the intent of RG 1.177 is met. Explain clearly how CCFs are modeled in the Calvert Cliffs PRA and justify why adjusting the common cause grouping is not necessary for preventative maintenance. In the explanation, include examples of fault trees for a CCF group of three components and the associated numerical results. 22. In RAI 11.a (see letter dated November 13, 2017), the staff requested the licensee to confirm and describe how the treatment of CCF in the case of emergent failures either meets the guidance in RG 1.177 or meets the intent of this guidance when quantifying a RICT. In response to RAI 11.a the licensee stated that risk management actions will be implemented. However in the response to RAI 11.b the licensee added the option to "numerically account for the increased possibility of CCF in the RICT calculation" to the text for the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18, without further justification on how it meets the intent of the guidance in RG 1.177 requested in RAI 11.a. a. Explain how the task to "numerically account for the increased possibility of CCF in the RICT calculation" will be performed for emergent failures. b. Justify how the treatment of CCF meets the intent of the guidance in RG 1.177. 23. In RAI 14 (see letter dated November 13, 2017), the staff requested explanation on how the containment spray and the containment cooling systems are modeled, and how a RICT based on CDF and LERF can be quantitatively determined for these systems. In response to RAI 14 the licensee stated that both systems are explicitly modeled in the PRA and that the PRA modeling "includes system components, such as pumps, valves and heat exchangers, and system dependencies, such as electrical and cooling water systems." The licensee further explained that the PRA success criteria is one of the two headers for the containment spray system, and two out of four air coolers for the containment air recirculation and cooling system. The licensee stated that these systems "can be numerally quantified for impact on CDF and LERF," however the licensee did not explain how these systems impact core damage or large early release. Since the containment spray and containment cooling systems are generally related to the long-term release sequences (not large early release), it is not immediately clear to the NRC staff the impact that these systems have on the core damage and large early release in the licensee's PRA model. Further, the iodine removal function of the containment spray system is not usually captured in the PRA. Explain and justify how these systems impact CDF and LERF. 24. Section 36( c )( 5) of 10 CFR Part 50 requires, in part, that TSs contain administrative controls related to procedures and reporting necessary to assure operation of the facility in a safe manner. The licensee is proposing that a new program called Risk-Informed Completion Time Program be added to TS Section 5, "Administrative Controls" that describes the controls on the calculated risk-informed completion time that may be used in lieu of the prescribed completion time. Appropriate controls are needed to ensure that any changes to the PRA models used in the calculation of the risk-informed completion time be based on methods approved by the NRC, and be based on the as-built, as-operated and maintained plant, and reflect the operating experience at the plant, consistent with the guidance in RG 1.17 4, Revision 2. In RAI 15 (see letter dated November 13, 2017), the staff provided wording for a proposed license condition, consistent with the license condition included in NRG-approved Amendment Nos. 188 and 171 for the pilot risk-informed completion time LAR (ADAMS Accession No. ML 15127A669). In response, the licensee proposed the following text to be added to the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18: a. A RICT must be calculated using the PRA and non-PRA methods approved by the NRC, including internal events, internal floods, and fire PRA. Changes to these PRA and non-PRA methods require prior NRG approval. The PRA maintenance and upgrade process will validate that changes to the PRA models used in the RICT program follow the guidance in Appendix 1-A of ASMEIANS RA-Sa-2009, "Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications." b. A report shall be submitted following each PRA upgrade and associated peer review, and prior to using the upgraded PRA to calculate a RICT The report shall describe the scope of the upgrade. The license condition approved for the pilot contains both "methods" and "approaches." The proposed TS 5.5.18 text does not appear to be consistent with the approved precedent. Propose TS 5.5.18 text consistent with the approved precedent or the draft TSTF-505, Revision 2 (ADAMS Accession No. ML 17290A003), or provide detailed technical justification for your proposal. This justification should describe, with examples, what constitutes a PRA and non-PRA methods and approaches that if changed, would require prior NRC approval.
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| ML 18138A137 OFFICE DORL/LPL 1 /PM DORL/LPL 1 /LA DRA/APLA/BC NAME MMarshall !Betts SRosenberg DATE 5/18/18 05/18/18 5/18/18}}
| | Request for Additional Information cc: Listserv |
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| | REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES EXELON GENERATION COMPANY, LLC CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-317 AND 50-318 By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML17094A591 ), January 11, 2018 (ADAMS Accession No. ML18011A665), and January 18, 2018 (ADAMS Accession No. ML180188340), Exelon Generation Company, LLC (the licensee) submitted a license amendment request (LAR) proposing to modify the Calvert Cliffs Nuclear Power Plant (Calvert Cliffs), Units 1 and 2, Technical Specification (TS} requirements to permit the use of risk-informed completion times. |
| | The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review of the LAR. The request for additional information (RAI) listed below is not a complete listing of the additional information needed to complete the NRC staff's review. Additional RAls (i.e., numbers 1 through 19) were provided by separate correspondences dated November 13, 2017 (ADAMS Accession No. ML17304A941) and December 21, 2017 (ADAMS Accession No. ML17346A909). |
| | Section 36(c)(2) of Title 10 of Code of Federal Regulation requires in part that limiting conditions of operations be included in TSs and that licensees shall follow any remedial action permitted by the TS until the condition can be met. The TSs for Calvert Cliffs, Units 1 and 2, contain limiting conditions of operations that prescribe completion times for remedial actions. The licensee has proposed using its probabilistic risk assessment (PRA) to determine risk-informed completion times that may be used in lieu of the prescribed completion times. Regulatory Guide (RG) 1.174, Revision 2, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed 51 Decisions on Plant-Specific Changes to the Licensing Basis," May 2011 (ADAMS Accession No. ML100910006) describes an acceptable risk-informed approach for assessing the nature and impact of proposed permanent licensing basis changes by considering engineering issues and applying risk insights. This RG also provides risk acceptance guidelines for evaluating the results of such evaluations. Revision 1 of RG 1.177, "An Approach for Plant-Specific, Risk-Informed Decision-making: Technical Specifications," May 2011 (ADAMS Accession No. ML100910008) describes an acceptable risk-informed approach specifically for assessing proposed TS changes. To ensure that any remedial actions are completed in a timely manner, consistent with RG 1.174 and RG 1.177, the PRA models used in the calculation of the risk-informed completion times need to be based on the as-built, as-operated and maintained plant, and reflect operating experience at the plant. |
| | : 20. Enclosure 4 of the letter dated February 25, 2016, states that a total seismic core damage frequency (CDF) contribution of 1.1 E-6/year and a seismic large early release frequency (LERF) contribution of 1.1 E-7/year will be added to the configuration specific delta CDF and Enclosure |
| | |
| | delta LERF from the internal events and fire initiating event contributions to estimate the risk-informed completion time. The LAR states that these seismic estimates are based on the re-evaluated seismic hazard for Calvert Cliffs performed in response to the Near-Term Task Force 2.1 (ADAMS Accession No. ML14099A196) and an estimated plant level high confidence of low probability of failure (HCLPF) of 0.27 the acceleration due to Earth's gravity (g) peak ground acceleration (PGA) as used in the 2003 LAR entitled "Extension of Diesel Generator Required Action Completion Time" (ADAMS Accession No. ML031360410). |
| | : a. The staff notes that the Calvert Cliffs Expedited Seismic Evaluation Process Report (ESEP), submitted to the NRC on December 17, 2014 (ADAMS Accession No. ML14365A138), indicates that certain components, such as safety injection tanks, motor control centers, electrical buses, and main control room panels, would fail in a seismic event through interaction with nearby block walls, and those components were assigned a lower HCLPF of 0.175 g due to the block wall lower capacity. This lower HCLPF could increase the seismic CDF and LERF estimates provided in the LAR. |
| | Justify the plant level HCLPF of 0.27 g PGA, given the noted block walls failures at 0.175 g indicated in the ESEP, or provide, with justification, updated seismic CDF and LERF estimates. |
| | : b. The 2003 LAR for extension of emergency diesel generator (EOG) completion times shows differences in estimated seismic CDF and LERF between Unit 1 and Unit 2. |
| | According to the NRC Technical Evaluation Report for the Individual Plant Examination for External Events, because the EDGs dedicated to Unit 2 are more dependent on service water cooling, which has a low fragility, the CDF value is higher for Unit 2 than for Unit 1. |
| | Explain and justify how the seismic CDF and LERF estimates apply to both units. |
| | To estimate the seismic LERF, the LAR assumes a 0.1 conditional large early release probability (CLERP) for seismic events, based on the internal events LERF to CDF ratio. The staff notes that a seismic event could lead to seismic-specific failures of structures, systems, and components, resulting in additional LERF sequences that are not in the internal events probabilistic risk assessment (PRA) model or potentially converting non-LERF sequences in the internal events PRA model to seismic LERF sequences. The LAR does not provide sufficient justification for the selected CLERP being able to capture or bound such considerations. |
| | : c. Justify the assumed value of 0.1 for CLERP. In the justification, explain why the containment is not expected to fail and other containment failure or bypass scenarios are not expected to be impacted by seismic events and therefore, would not noticeably affect the assumed 0.1 CLERP. |
| | : 21. In RAI 10 (see letter dated November 13, 2017), the staff asked the licensee to explain how common cause failures (CCFs) are included in the PRA model and how the treatment of CCF either meets the guidance in RG 1.177 or meets the intent of this guidance when |
| | |
| | quantifying a risk-informed completion time (RICT) for preventative maintenance for components from a CCF group of three or more components. The response to the RAI states "common cause failures are modeled as separate basic events, with common cause combinations in the fault tree as different basic events." The licensee further stated that the "common cause grouping is not dynamically changed when a component is removed from service for preventative maintenance" and that this is appropriate because "the component, though not out of service for a reason subject to common cause failure, remains a participant in the common cause events for the remainder of the component operation." It is unclear how the out of service component "remains a participant in the common cause events for the remainder of the component operation" and; therefore, it is unclear how the intent of RG 1.177 is met. |
| | Explain clearly how CCFs are modeled in the Calvert Cliffs PRA and justify why adjusting the common cause grouping is not necessary for preventative maintenance. In the explanation, include examples of fault trees for a CCF group of three components and the associated numerical results. |
| | : 22. In RAI 11.a (see letter dated November 13, 2017), the staff requested the licensee to confirm and describe how the treatment of CCF in the case of emergent failures either meets the guidance in RG 1.177 or meets the intent of this guidance when quantifying a RICT. In response to RAI 11.a the licensee stated that risk management actions will be implemented. However in the response to RAI 11.b the licensee added the option to "numerically account for the increased possibility of CCF in the RICT calculation" to the text for the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18, without further justification on how it meets the intent of the guidance in RG 1.177 requested in RAI 11.a. |
| | : a. Explain how the task to "numerically account for the increased possibility of CCF in the RICT calculation" will be performed for emergent failures. |
| | : b. Justify how the treatment of CCF meets the intent of the guidance in RG 1.177. |
| | : 23. In RAI 14 (see letter dated November 13, 2017), the staff requested explanation on how the containment spray and the containment cooling systems are modeled, and how a RICT based on CDF and LERF can be quantitatively determined for these systems. In response to RAI 14 the licensee stated that both systems are explicitly modeled in the PRA and that the PRA modeling "includes system components, such as pumps, valves and heat exchangers, and system dependencies, such as electrical and cooling water systems." The licensee further explained that the PRA success criteria is one of the two headers for the containment spray system, and two out of four air coolers for the containment air recirculation and cooling system. The licensee stated that these systems "can be numerally quantified for impact on CDF and LERF," however the licensee did not explain how these systems impact core damage or large early release. Since the containment spray and containment cooling systems are generally related to the long-term release sequences (not large early release), it is not immediately clear to the NRC staff the impact that these systems have on the core damage and large early release in the licensee's PRA model. |
| | Further, the iodine removal function of the containment spray system is not usually captured in the PRA. |
| | Explain and justify how these systems impact CDF and LERF. |
| | : 24. Section 36( c )( 5) of 10 CFR Part 50 requires, in part, that TSs contain administrative controls related to procedures and reporting necessary to assure operation of the facility in a safe manner. The licensee is proposing that a new program called Risk-Informed Completion Time Program be added to TS Section 5, "Administrative Controls" that describes the controls on the calculated risk-informed completion time that may be used in lieu of the prescribed completion time. Appropriate controls are needed to ensure that any changes to the PRA models used in the calculation of the risk-informed completion time be based on methods approved by the NRC, and be based on the as-built, as-operated and maintained plant, and reflect the operating experience at the plant, consistent with the guidance in RG 1.174, Revision 2. |
| | In RAI 15 (see letter dated November 13, 2017), the staff provided wording for a proposed license condition, consistent with the license condition included in NRG-approved Amendment Nos. 188 and 171 for the pilot risk-informed completion time LAR (ADAMS Accession No. ML15127A669). In response, the licensee proposed the following text to be added to the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18: |
| | : a. A RICT must be calculated using the PRA and non-PRA methods approved by the NRC, including internal events, internal floods, and fire PRA. Changes to these PRA and non-PRA methods require prior NRG approval. The PRA maintenance and upgrade process will validate that changes to the PRA models used in the RICT program follow the guidance in Appendix 1-A of ASMEIANS RA-Sa-2009, "Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications." |
| | : b. A report shall be submitted following each PRA upgrade and associated peer review, and prior to using the upgraded PRA to calculate a RICT The report shall describe the scope of the upgrade. |
| | The license condition approved for the pilot contains both "methods" and "approaches." The proposed TS 5.5.18 text does not appear to be consistent with the approved precedent. |
| | Propose TS 5.5.18 text consistent with the approved precedent or the draft TSTF-505, Revision 2 (ADAMS Accession No. ML17290A003), or provide detailed technical justification for your proposal. This justification should describe, with examples, what constitutes a PRA and non-PRA methods and approaches that if changed, would require prior NRC approval. |
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| | ML18138A137 OFFICE DORL/LPL 1/PM DORL/LPL 1/LA DRA/APLA/BC DORL/LPL 1/BC DORL/LPL 1/PM NAME MMarshall !Betts SRosenberg JDanna MMarshall DATE 5/18/18 05/18/18 5/18/18 5/21/18 5/22/18}} |
Letter Sequence RAI |
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MONTHYEARML16326A2682016-11-21021 November 2016 2016/11/21 E-mail from R.Guzman to E.Villar - Acceptance Review Determination - Control Room Emergency Ventilation System LAR Project stage: Acceptance Review ML17304A0202017-10-31031 October 2017 Licensing Basis Charge for Evaluating the Need for Tornado Generated Missile Barriers - Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 (TAC Nos. M90621 and M90622) Project stage: Other ML17304A9412017-11-13013 November 2017 Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) Project stage: RAI ML17346A9092017-12-21021 December 2017 Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) Project stage: RAI ML18011A6652018-01-11011 January 2018 Response to Request for Additional Information License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk-Informed Extended Completion Times. Project stage: Response to RAI ML18018B3402018-01-18018 January 2018 Response to Request for Additional Information License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk-Informed Extended Completion Times. Project stage: Response to RAI ML18128A3842018-05-0808 May 2018 Plants, Units 1 and 2 - Draft Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) Project stage: Draft RAI ML18138A1372018-05-22022 May 2018 Plants, Units 1 and 2 - Request for Additional Information Regarding Risk Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) Project stage: RAI ML18143A3102018-05-24024 May 2018 Plants, Units 1 and 2 - Audit Plan in Support of the Review of the License Amendment Request to Allow the Use of Risk-Informed Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-001) Project stage: Other ML18172A1452018-06-21021 June 2018 Response to Request for Additional Information License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk-Informed ... Project stage: Response to RAI ML18239A2602018-08-27027 August 2018 Supplement to Response to Request for Additional Information License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 1, Provide Risk .. Project stage: Supplement ML18270A1302018-10-30030 October 2018 Issuance of Amendment Nos. 326 and 304 to Add Risk-Informed Completion Time Program Project stage: Approval ML18318A0142018-11-30030 November 2018 Correction to Amendment Nos. 326 and 304 Add Risk-Informed Completion Time Program Project stage: Other 2018-10-30
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Category:Letter
MONTHYEARIR 05000317/20230042024-02-0101 February 2024 Integrated Inspection Report 05000317/2023004 and 05000318/2023004 ML24029A0102024-01-29029 January 2024 Request for Information and Notification of Conduct of IP 71111.21.N.04, Age-Related Degradation, Reference Inspection Report 05000317/2024010 and 05000318/2024010 ML24003A8872024-01-19019 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0033 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) 05000318/LER-2023-004, Submittal of LER 2023-004-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Submittal of Automatic Reactor Trip from Reactor Protection System Actuation Due to Loss of Unit Service Transformer2024-01-16016 January 2024 Submittal of LER 2023-004-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Submittal of Automatic Reactor Trip from Reactor Protection System Actuation Due to Loss of Unit Service Transformer ML24011A0732024-01-11011 January 2024 Proposed Alternative to the Requirements for Repair/Replacement of Saltwater (SW) System Buried Piping 05000318/LER-2023-002, Forward LER 2023-002-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Automatic Reactor Trip from Reactor Protection System Actuation Due to Loss of Unit Service Transformer2024-01-0808 January 2024 Forward LER 2023-002-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Automatic Reactor Trip from Reactor Protection System Actuation Due to Loss of Unit Service Transformer 05000318/LER-2023-003, Forward LER 2023-003-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Manual Actuation of Auxiliary Feedwater System Due to 22 Steam Generator Feedwater Pump Trip2024-01-0808 January 2024 Forward LER 2023-003-00 for Calvert Cliffs Nuclear Power Plant, Unit 2, Manual Actuation of Auxiliary Feedwater System Due to 22 Steam Generator Feedwater Pump Trip ML24005A0222024-01-0505 January 2024 Revised Steam Generator Tube Inspection Reports ML23304A0642024-01-0202 January 2024 Issuance of Amendment No. 349 to Modify the Long-Term Coupon Surveillance Program RS-23-125, Request for Exemption from 10 CFR 2.109(b)2023-12-0707 December 2023 Request for Exemption from 10 CFR 2.109(b) ML23331A2992023-11-27027 November 2023 Submittal of Condition Prohibited by Technical Specifications Due to Failure to Sample Diesel Generator Fuel Oil Storage Tank IR 05000317/20230102023-11-20020 November 2023 Biennial Problem Identification and Resolution Inspection Report 05000317/2023010 and 05000318/2023010 ML23318A4722023-11-14014 November 2023 Supplement to License Amendment Request to Adopt TSTF-59-A ML23317A1032023-11-10010 November 2023 Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information ML23317A1192023-11-10010 November 2023 Constellation Energy Generation, LLC - 2023 Annual Report - Guarantees of Payment of Deferred Premiums ML23310A0442023-11-0707 November 2023 Project Manager Assignment IR 05000317/20230402023-11-0202 November 2023 95001 Supplemental Inspection Report 05000317/2023040 and Follow-Up Assessment Letter IR 05000317/20230032023-11-0101 November 2023 Integrated Inspection Report 05000317/2023003 and 05000318/2023003 IR 05000317/20230902023-10-26026 October 2023 Final Significance Determination of a White Finding with Assessment Follow-Up and Notice of Violation; Inspection Report 05000317/2023090 ML23289A1202023-10-16016 October 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation RS-23-097, Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans2023-10-12012 October 2023 Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans RS-23-108, Proposed Alternative for Examinations of Examination Categories B-B, B-D, and C-A Steam Generator Pressure Retaining Welds and Full Penetration Welded Nozzles2023-10-11011 October 2023 Proposed Alternative for Examinations of Examination Categories B-B, B-D, and C-A Steam Generator Pressure Retaining Welds and Full Penetration Welded Nozzles RS-23-105, Proposed Alternative for Examinations of Examination Category C-B Steam Generator Nozzle-to-Shell Welds and Nozzle Inside Radius Sections2023-10-10010 October 2023 Proposed Alternative for Examinations of Examination Category C-B Steam Generator Nozzle-to-Shell Welds and Nozzle Inside Radius Sections ML23279A1202023-10-0606 October 2023 Response to NRC Inspection Report and Preliminary White Finding IR 05000317/20230502023-09-29029 September 2023 Special Inspection Report 05000317/2023050 and Preliminary White Finding and Apparent Violation ML23272A1032023-09-29029 September 2023 Condition Prohibited by Technical Specifications Due to Inoperable Nuclear Instrumentation at Very Low Power IR 05000317/20234012023-09-18018 September 2023 Cyber Security Inspection Report 05000317/2023401 and 05000318/2023401 ML23254A0012023-09-0505 September 2023 Registration of Use of Casks to Store Spent Fuel IR 05000317/20230052023-08-31031 August 2023 Updated Inspection Plan for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Report 05000317/2023005 and 05000318/2023005) ML23158A1952023-08-30030 August 2023 R. E. Ginna - Issuance of Amendments to Adopt TSTF-273-A, Revision 2, Safety Function Determination Program Clarifications ML23241A8412023-08-29029 August 2023 Response to Request for Additional Information - Proposed Alternative to the Requirements for Repair/Replacement of Saltwater (SW) System Buried Piping ML23240A3872023-08-28028 August 2023 Senior Reactor and Reactor Operator Initial License Examinations ML23151A3472023-08-21021 August 2023 Issuance of Amendments to Adopt TSTF-295-A, Modify Note 2 to Actions of PAM Table to Allow Separate Condition Entry for Each Penetration ML23219A1662023-08-16016 August 2023 Request for Additional Information Regarding Proposed Alternative to the Requirements for Repair/Replacement of Saltwater (SW) System Buried Piping (EPID: L-2023-LLR-0006) - Non-proprietary ML23228A1002023-08-15015 August 2023 Notification of Readiness for NRC 95001 Inspection ML23188A0402023-08-0808 August 2023 Issuance of Amendment Nos. 346 and 324 Adoption of TSTF-577, Revised Frequencies for Steam Generator Tube Inspections, Revision 1 ML23214A1572023-08-0707 August 2023 Correction to the Renewed Facility Operating License Page 3 in Amendment No 345 IR 05000317/20230022023-08-0303 August 2023 Integrated Inspection Report 05000317/2023002 ML23188A0512023-07-13013 July 2023 Correction to the Renewed Facility Operating License Pages in Amendment Nos. 336 and 314 ML23186A0372023-07-13013 July 2023 Correction to the Renewed Facility Operating License Pages in Amendment Nos. 340 and 318 IR 05000317/20233012023-07-12012 July 2023 Initial Operator Licensing Examination Report 05000317/2023301 and 05000318/2023301 IR 05000317/20230122023-07-10010 July 2023 Commercial Grade Dedication Report 05000317/2023012 and 05000318/2023012 ML23180A2362023-06-29029 June 2023 Correction of Errors on Technical Specification Pages RS-23-083, Withdrawal - Proposed Alternatives Related to the Steam Generators2023-06-27027 June 2023 Withdrawal - Proposed Alternatives Related to the Steam Generators ML23156A6752023-06-20020 June 2023 Request for Withholding Information from Public Disclosure for Proposed Alternative to the Requirements for Repair/Replacement of Saltwater System Buried Piping 2024-02-01
[Table view] Category:Request for Additional Information (RAI)
MONTHYEARML24012A0492024-01-11011 January 2024 Request for Additional Information Regarding Final Response to Generic Letter 2004-02 ML23219A1662023-08-16016 August 2023 Request for Additional Information Regarding Proposed Alternative to the Requirements for Repair/Replacement of Saltwater (SW) System Buried Piping (EPID: L-2023-LLR-0006) - Non-proprietary ML23160A0222023-06-0606 June 2023 NRR E-mail Capture - Calvert Cliffs - Long Term Coupon Surveillance Program RAI ML23156A0102023-06-0404 June 2023 NRR E-mail Capture - Calvert Cliffs - RAI License Amendment Request for Emergency Desiel Generator ML22179A2112022-06-28028 June 2022 Notification of Conduct of a Fire Protection Team Inspection ML22129A0132022-05-0606 May 2022 NRR E-mail Capture - Draft RAIs for Requests for Alternatives I4R-17, I4R-23, ISI-05-018, I6R-10 ML22271A0772022-05-0606 May 2022 NRR E-mail Capture - Final RAIs 9.1.2021 Constellation Relief Request ML22091A0852022-04-0101 April 2022 NRR E-mail Capture - Braidwood and Byron - Final RAI Regarding Proposed Alternative for Various Pressurizer Welds (EPID L-2021-LLR-0035 and 0036) ML22091A2392022-04-0101 April 2022 NRR E-mail Capture - Calvert Cliffs - Formal RAI for Proposed Alternative for Examinations of Certain Pressurizer Welds ML22041B5362022-02-10010 February 2022 NRR E-mail Capture - Constellation Energy Generation, LLC - Request for Additional Information Regarding Fleet License Amendment Request to Adopt TSTF-541 ML21287A0322021-10-13013 October 2021 Request for Additional Information Re Proposed Alternative for Pressurizer Circumferential and Longitudinal Shell-to-Head Welds and Nozzle-to-Vessel Welds ML21287A0932021-10-0505 October 2021 Request for Additional Information: Calvert Cliffs 1 & 2 LAR to Revise Spent Fuel Pool Cooling - Shutdown Cooling Systems Licensing Basis (EPID L-2021-LLA-0112) (Email) ML21256A1902021-09-10010 September 2021 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding License Transfer Application ML21187A2232021-07-29029 July 2021 Temporary Instruction 2515/194 Inspection Documentation Request ML21180A1562021-06-28028 June 2021 Request for Additional Information Regarding License Amendment Request Concerning Containment Sump ML21144A2132021-05-24024 May 2021 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding License Transfer Application ML21130A0382021-05-21021 May 2021 Memo to File - Draft Request for Additional Information Relief Request CISI-03-01 Concerning Containment Unbonded Post-Tensioning System Inservice Inspection Requirements ML21117A0342021-05-0505 May 2021 Request for Additional Information Regarding Proposed Alternative to Use ASME Code Case N-893 ML21062A0652021-03-0101 March 2021 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding Proposed Fleet Alternative to Documentation Requirements for Pressure Retaining Bolting ML21053A3142021-02-22022 February 2021 Information Request for a Triennial Baseline Design Bases Assurance Inspection (Team); Inspection Report 05000317/2021010 and 05000318/2021010 ML21049A2572021-02-18018 February 2021 Request for Additional Information Byron/Dresden Proposed Changes to Site Emergency Plans to Support Post-Shutdown and Permanently Defueled Conditions (EPID-2020-LLA-0240 & EPID-2020-LLA-0237) ML21029A3302021-01-29029 January 2021 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding Fleet Alternative Request to Use ASME Code Case N-885 ML20275A0032020-09-30030 September 2020 Request for Additional Information Regarding Alternative Request Re Inservice Inspection Impracticality (L-2020-LLR-0089) ML20167A2532020-06-15015 June 2020 Second Request for Additional Information Regarding License Amendment Request Concerning Emergency Diesel Generator Surveillance Requirements for Frequency and Voltage Tolerances ML20157A0782020-06-0505 June 2020 Request for Additional Information Regarding License Amendment Request Concerning Emergency Diesel Generator Surveillance Requirements for Frequency and Voltage Tolerances ML20153A7042020-06-0101 June 2020 NRR E-mail Capture - Preliminary RAI for Fleet Request to Use Alternative OMN-26 ML20135H0132020-05-14014 May 2020 IP 71111.17T (50.59) List of Documents Request ML20083F5892020-03-21021 March 2020 Request for Additional Information Regarding License Amendment Request Concerning Reactor Coolant Pump Flywheel Inspection Program ML19275H1362019-10-0202 October 2019 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding Request to Use ASME Code Case N-879 ML19261B2202019-09-18018 September 2019 Request for Additional Information Regarding Final Response to Generic Letter 2004-02 ML19179A0612019-07-19019 July 2019 Three Mile Point 1 - Supplemental Information Needed to Proposed Alternative to Use ASME Code Case N-879 ML19155A1612019-06-11011 June 2019 Changes to Draft Request for Additional Information Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Systems, Structures and Components ML19155A1272019-06-0404 June 2019 Request for Additional Information Regarding Request to Adopt 10 CFR 50.69 Risk Informed Categorization and Treatment of Systems, Structures, and Components ML19070A0192019-03-11011 March 2019 Request for Additional Information Regarding Exemption Request from 10CFR50.46(A)(1) to Support Resolution of GSI-191 ML19025A1202019-01-24024 January 2019 NRR E-mail Capture - Calvert Cliffs, Fitzpatrick, and Nine Mile Point - Request for Additional Information Regarding License Amendment Request to Revise Emergency Response Organization Staffing ML18347A3972018-12-13013 December 2018 Request for Additional Information Regarding Relocation of Emergency Operation Facility ML18138A1372018-05-22022 May 2018 Plants, Units 1 and 2 - Request for Additional Information Regarding Risk Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) ML18128A3842018-05-0808 May 2018 Plants, Units 1 and 2 - Draft Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) ML18102A2372018-04-12012 April 2018 NRR E-mail Capture - Calvert Cliffs, Ginna, and Nine Mile Point - Request for Additional Information Regarding License Amendment Request to Revise Emergency Action Level Schemes (EPID-L-2017-LLA-0237) ML18067A1482018-03-0808 March 2018 Enclosurequest for Additional Information (Letter to P. R. Simpson Request for Additional Information Regarding Exelon Generating Company, Llc'S Decommissioning Funding Plan Update for Independent Spent Fuel Storage Installation) ML17345A0912018-01-19019 January 2018 Plants, Units 1 and 2 - Request for Additional Information Regarding Alternative Request SI-RR-01, Rev. 0 (CAC Nos. MG0068 and MG0069; EPID L-2017-LLR-0078) ML17346A9092017-12-21021 December 2017 Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) ML17331B1342017-12-12012 December 2017 2, and R.E. Ginna Nuclear Power Plant - Request for Additional Information - Regarding ML17304A9412017-11-13013 November 2017 Request for Additional Information Regarding Risk-Informed Technical Specification Completion Times (CAC Nos. MF7415 and MF7416; EPID L-2016-LLA-0001) ML17285B1962017-10-27027 October 2017 Request for Additional Information Regarding Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools. ML17075A0152017-03-16016 March 2017 E-mail from R. Guzman to E. Villar - Calvert Cliffs Unit Nos. 1 and 2 - Request for Additional Information License Amendment Request - Control Room Emergency Ventilation System ML17062A4912017-03-0303 March 2017 NRR E-mail Capture - Exelon Generation Company, LLC - Request for Additional Information Regarding Fleet Alternative to RPV Threads in Flange Examination (CAC Nos. MF8712-MF8729) ML16222A1252016-08-0909 August 2016 Request for Additional Information - Relief Request No. RR-ISI-04-11, 2016/08/08 E-mail from R.Guzman to T.Loomis ML15299A2792015-11-0303 November 2015 Request for Additional Information Regarding Relief Request for Dissimilar Metal Butt Welds ML15230A0322015-08-13013 August 2015 Request for Additional Information Regarding the National Association Standard 805 License Amendment Request Fire Protection 2024-01-11
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MAy 22, 2018 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2- REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES (CAC NOS. MF7415 AND MF7416; EPID L-2016-LLA-0001)
Dear Mr. Hanson:
By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML17094A591 ), January 11, 2018 (ADAMS Accession No. ML18011A665), and January 18, 2018 (ADAMS Accession No. ML18018B340), Exelon Generation Company, LLC submitted a license amendment request proposing to modify the Calvert Cliffs Nuclear Power Plant, Units 1 and 2, Technical Specification requirements to permit the use of risk-informed completion times.
The U.S. Nuclear Regulatory Commission staff is reviewing the submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information. The request for additional information was discussed with your staff on May 16, 2018, and it was agreed that your response would be provided within 30 days from the date of this letter.
If you have any questions regarding this matter, please contact me at (301) 415-2871 or Michael.Marshall@nrc.gov.
Sincerely, Michael L. Marshall, Jr., Senior Project Manager Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-317 and 50-318
Enclosure:
Request for Additional Information cc: Listserv
REQUEST FOR ADDITIONAL INFORMATION REGARDING RISK-INFORMED TECHNICAL SPECIFICATION COMPLETION TIMES EXELON GENERATION COMPANY, LLC CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-317 AND 50-318 By letter dated February 25, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16060A223), as supplemented by letters dated April 3, 2017 (ADAMS Accession No. ML17094A591 ), January 11, 2018 (ADAMS Accession No. ML18011A665), and January 18, 2018 (ADAMS Accession No. ML180188340), Exelon Generation Company, LLC (the licensee) submitted a license amendment request (LAR) proposing to modify the Calvert Cliffs Nuclear Power Plant (Calvert Cliffs), Units 1 and 2, Technical Specification (TS} requirements to permit the use of risk-informed completion times.
The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review of the LAR. The request for additional information (RAI) listed below is not a complete listing of the additional information needed to complete the NRC staff's review. Additional RAls (i.e., numbers 1 through 19) were provided by separate correspondences dated November 13, 2017 (ADAMS Accession No. ML17304A941) and December 21, 2017 (ADAMS Accession No. ML17346A909).
Section 36(c)(2) of Title 10 of Code of Federal Regulation requires in part that limiting conditions of operations be included in TSs and that licensees shall follow any remedial action permitted by the TS until the condition can be met. The TSs for Calvert Cliffs, Units 1 and 2, contain limiting conditions of operations that prescribe completion times for remedial actions. The licensee has proposed using its probabilistic risk assessment (PRA) to determine risk-informed completion times that may be used in lieu of the prescribed completion times. Regulatory Guide (RG) 1.174, Revision 2, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed 51 Decisions on Plant-Specific Changes to the Licensing Basis," May 2011 (ADAMS Accession No. ML100910006) describes an acceptable risk-informed approach for assessing the nature and impact of proposed permanent licensing basis changes by considering engineering issues and applying risk insights. This RG also provides risk acceptance guidelines for evaluating the results of such evaluations. Revision 1 of RG 1.177, "An Approach for Plant-Specific, Risk-Informed Decision-making: Technical Specifications," May 2011 (ADAMS Accession No. ML100910008) describes an acceptable risk-informed approach specifically for assessing proposed TS changes. To ensure that any remedial actions are completed in a timely manner, consistent with RG 1.174 and RG 1.177, the PRA models used in the calculation of the risk-informed completion times need to be based on the as-built, as-operated and maintained plant, and reflect operating experience at the plant.
- 20. Enclosure 4 of the letter dated February 25, 2016, states that a total seismic core damage frequency (CDF) contribution of 1.1 E-6/year and a seismic large early release frequency (LERF) contribution of 1.1 E-7/year will be added to the configuration specific delta CDF and Enclosure
delta LERF from the internal events and fire initiating event contributions to estimate the risk-informed completion time. The LAR states that these seismic estimates are based on the re-evaluated seismic hazard for Calvert Cliffs performed in response to the Near-Term Task Force 2.1 (ADAMS Accession No. ML14099A196) and an estimated plant level high confidence of low probability of failure (HCLPF) of 0.27 the acceleration due to Earth's gravity (g) peak ground acceleration (PGA) as used in the 2003 LAR entitled "Extension of Diesel Generator Required Action Completion Time" (ADAMS Accession No. ML031360410).
- a. The staff notes that the Calvert Cliffs Expedited Seismic Evaluation Process Report (ESEP), submitted to the NRC on December 17, 2014 (ADAMS Accession No. ML14365A138), indicates that certain components, such as safety injection tanks, motor control centers, electrical buses, and main control room panels, would fail in a seismic event through interaction with nearby block walls, and those components were assigned a lower HCLPF of 0.175 g due to the block wall lower capacity. This lower HCLPF could increase the seismic CDF and LERF estimates provided in the LAR.
Justify the plant level HCLPF of 0.27 g PGA, given the noted block walls failures at 0.175 g indicated in the ESEP, or provide, with justification, updated seismic CDF and LERF estimates.
- b. The 2003 LAR for extension of emergency diesel generator (EOG) completion times shows differences in estimated seismic CDF and LERF between Unit 1 and Unit 2.
According to the NRC Technical Evaluation Report for the Individual Plant Examination for External Events, because the EDGs dedicated to Unit 2 are more dependent on service water cooling, which has a low fragility, the CDF value is higher for Unit 2 than for Unit 1.
Explain and justify how the seismic CDF and LERF estimates apply to both units.
To estimate the seismic LERF, the LAR assumes a 0.1 conditional large early release probability (CLERP) for seismic events, based on the internal events LERF to CDF ratio. The staff notes that a seismic event could lead to seismic-specific failures of structures, systems, and components, resulting in additional LERF sequences that are not in the internal events probabilistic risk assessment (PRA) model or potentially converting non-LERF sequences in the internal events PRA model to seismic LERF sequences. The LAR does not provide sufficient justification for the selected CLERP being able to capture or bound such considerations.
- c. Justify the assumed value of 0.1 for CLERP. In the justification, explain why the containment is not expected to fail and other containment failure or bypass scenarios are not expected to be impacted by seismic events and therefore, would not noticeably affect the assumed 0.1 CLERP.
- 21. In RAI 10 (see letter dated November 13, 2017), the staff asked the licensee to explain how common cause failures (CCFs) are included in the PRA model and how the treatment of CCF either meets the guidance in RG 1.177 or meets the intent of this guidance when
quantifying a risk-informed completion time (RICT) for preventative maintenance for components from a CCF group of three or more components. The response to the RAI states "common cause failures are modeled as separate basic events, with common cause combinations in the fault tree as different basic events." The licensee further stated that the "common cause grouping is not dynamically changed when a component is removed from service for preventative maintenance" and that this is appropriate because "the component, though not out of service for a reason subject to common cause failure, remains a participant in the common cause events for the remainder of the component operation." It is unclear how the out of service component "remains a participant in the common cause events for the remainder of the component operation" and; therefore, it is unclear how the intent of RG 1.177 is met.
Explain clearly how CCFs are modeled in the Calvert Cliffs PRA and justify why adjusting the common cause grouping is not necessary for preventative maintenance. In the explanation, include examples of fault trees for a CCF group of three components and the associated numerical results.
- 22. In RAI 11.a (see letter dated November 13, 2017), the staff requested the licensee to confirm and describe how the treatment of CCF in the case of emergent failures either meets the guidance in RG 1.177 or meets the intent of this guidance when quantifying a RICT. In response to RAI 11.a the licensee stated that risk management actions will be implemented. However in the response to RAI 11.b the licensee added the option to "numerically account for the increased possibility of CCF in the RICT calculation" to the text for the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18, without further justification on how it meets the intent of the guidance in RG 1.177 requested in RAI 11.a.
- a. Explain how the task to "numerically account for the increased possibility of CCF in the RICT calculation" will be performed for emergent failures.
- b. Justify how the treatment of CCF meets the intent of the guidance in RG 1.177.
- 23. In RAI 14 (see letter dated November 13, 2017), the staff requested explanation on how the containment spray and the containment cooling systems are modeled, and how a RICT based on CDF and LERF can be quantitatively determined for these systems. In response to RAI 14 the licensee stated that both systems are explicitly modeled in the PRA and that the PRA modeling "includes system components, such as pumps, valves and heat exchangers, and system dependencies, such as electrical and cooling water systems." The licensee further explained that the PRA success criteria is one of the two headers for the containment spray system, and two out of four air coolers for the containment air recirculation and cooling system. The licensee stated that these systems "can be numerally quantified for impact on CDF and LERF," however the licensee did not explain how these systems impact core damage or large early release. Since the containment spray and containment cooling systems are generally related to the long-term release sequences (not large early release), it is not immediately clear to the NRC staff the impact that these systems have on the core damage and large early release in the licensee's PRA model.
Further, the iodine removal function of the containment spray system is not usually captured in the PRA.
Explain and justify how these systems impact CDF and LERF.
- 24. Section 36( c )( 5) of 10 CFR Part 50 requires, in part, that TSs contain administrative controls related to procedures and reporting necessary to assure operation of the facility in a safe manner. The licensee is proposing that a new program called Risk-Informed Completion Time Program be added to TS Section 5, "Administrative Controls" that describes the controls on the calculated risk-informed completion time that may be used in lieu of the prescribed completion time. Appropriate controls are needed to ensure that any changes to the PRA models used in the calculation of the risk-informed completion time be based on methods approved by the NRC, and be based on the as-built, as-operated and maintained plant, and reflect the operating experience at the plant, consistent with the guidance in RG 1.174, Revision 2.
In RAI 15 (see letter dated November 13, 2017), the staff provided wording for a proposed license condition, consistent with the license condition included in NRG-approved Amendment Nos. 188 and 171 for the pilot risk-informed completion time LAR (ADAMS Accession No. ML15127A669). In response, the licensee proposed the following text to be added to the Calvert Cliffs, Units 1 and 2, TS Administrative Section 5.5.18:
- a. A RICT must be calculated using the PRA and non-PRA methods approved by the NRC, including internal events, internal floods, and fire PRA. Changes to these PRA and non-PRA methods require prior NRG approval. The PRA maintenance and upgrade process will validate that changes to the PRA models used in the RICT program follow the guidance in Appendix 1-A of ASMEIANS RA-Sa-2009, "Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications."
- b. A report shall be submitted following each PRA upgrade and associated peer review, and prior to using the upgraded PRA to calculate a RICT The report shall describe the scope of the upgrade.
The license condition approved for the pilot contains both "methods" and "approaches." The proposed TS 5.5.18 text does not appear to be consistent with the approved precedent.
Propose TS 5.5.18 text consistent with the approved precedent or the draft TSTF-505, Revision 2 (ADAMS Accession No. ML17290A003), or provide detailed technical justification for your proposal. This justification should describe, with examples, what constitutes a PRA and non-PRA methods and approaches that if changed, would require prior NRC approval.
ML18138A137 OFFICE DORL/LPL 1/PM DORL/LPL 1/LA DRA/APLA/BC DORL/LPL 1/BC DORL/LPL 1/PM NAME MMarshall !Betts SRosenberg JDanna MMarshall DATE 5/18/18 05/18/18 5/18/18 5/21/18 5/22/18