ML23101A123
| ML23101A123 | |
| Person / Time | |
|---|---|
| Issue date: | 04/18/2023 |
| From: | Anders Gilbertson Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| Download: ML23101A123 (27) | |
Text
PRA Used to Implement LMP for Non-LWR CP Applications Under 10 CFR Part 50 APRIL 18, 2023
Initialisms and Acronyms ADAMS Agencywide Documents Access and DC design certification NSRST non-safety-related special treatment Management System DG draft regulatory guide NST no special treatment ANS American Nuclear Society DID defense in depth OL operating license AOO abnormal operating occurrence EAB exclusion area boundary PDC principal design criteria ASME American Society of Mechanical Engineers FOAK first-of-a-kind POS plant operating state ARCAP Advanced Reactor Content of Applications FR Federal Register PRA probabilistic risk assessment ARCOP Advanced Reactor Construction Oversite FSAR final safety analysis report PSAR preliminary safety analysis report Process ISG interim staff guidance RFDC required functional design criteria BDBE beyond design-basis event CDC complementary design criteria LBE licensing basis event RG regulatory guide CFR Code of Federal Regulations LMP Licensing Modernization Project RSF required safety function COL combined license LPSD low-power and shutdown SAR safety analysis report CP construction permit NEI Nuclear Energy Institute SE supplemental evaluation DBA design-basis accident NEIMA Nuclear Energy Innovation and Modernization SR safety related Act SRM staff requirements memorandum DBE design-basis event NLWR or non-light-water reactor DBEHL design-basis event hazard level (NEI 18-04) non-LWR SSC structure, system, and component DBHL design-basis hazard level (NEI 21-07) NPUF non-power utilization facility TEDE total effective dose equivalent TICAP Technology-Inclusive Content of Applications PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 2
Overview Purpose
Background
Non-LWR CP applications implementing LMP Discussion of staff views and perspectives Summary Next steps PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 3
Purpose To share the staff perspectives on important information related to a PRA used to support implementation of the Licensing Modernization Project methodology for a non-LWR CP applicant under 10 CFR Part 50 Obtain public feedback on staff perspectives PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 4
Background:
Fitting the Pieces Together Licensing Modernization Project NLWR PRA Acceptability
- NEI 18-04, Rev. 1
- ASME/ANS-RA-S-1.4-2021
- NEI 21-07, Rev. 1 (TICAP)
- DG-1404 (pending)
Consistency with the Underlying Commission Policies Principles of § 50.69 SSC Classification
- Advanced reactor policy statement (2008)
- NEI 00-04, Rev. 0
- Safety goal policy statement (1986)
- Severe accident policy statement (1985)
- Previous approved LARs
- PRA policy statement (1995)
Relevant Regulations and Guidance Related to Part 50 Construction Permits
- § 50.34(a) - PSAR content
- § 50.35 - Issuance of construction permits
- § 50.40 - Common standards
- § 50.50 - Issuance of licensees and construction permits
- Consistency with DNRL-ISG-2022-01 and coordination with related LWR efforts PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 5
Background:
Applications and Guidance Construction Permit Applications Some Non-LWR applicants will be using the two-step licensing process under 10 CFR Part 50.
The last CP application for a power reactor was in 1978 (Watts Bar).
NPUF CP applications have been submitted more recently (e.g., SHINE, Kairos Hermes).
No previous CP applications have been supported by a PRA.
Guidance Development LMP Guidance - NEI 18-04, Rev. 1, Modernization of Technical Requirements for Licensing of Advanced Non-Light Water Reactors: Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development, August 2019.
Staff Endorsement of the LMP Guidance - RG 1.233, Rev. 0, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors, June 2020.
TICAP (Technology-Inclusive Content of Application) - NEI 21-07, Rev. 1, Technology Inclusive Guidance for Non-Light Water Reactors: Safety Analysis Report Content for Applicants Using the NEI 18-04 Methodology, February 2022.
Staff Endorsement of TICAP - DG-1404 (proposed new RG 1.253), Technology Inclusive Content of Application Guidance for Advanced Non-Light Water Reactors, pending.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 6
As-built Design Evolution of the PRA Fuel load PRA Final Design (OL)
Overall Design Maturity PRA at OL application Enterprise Risk PRA leads design Design PRA Capability leads Preliminary Design (CP) PRA PRA at CP Conceptual application Design (CP)
PRA development path and use of Progression Through Licensing Fuel Load risk insights to inform the design preop startup Construction tests tests pre-application CP application pre-application OL application review review review review CP Application CP Issuance OL Application OL Issuance Submittal (50.35) Submittal (50.57)
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 7 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50
Regulations Requirement Comment
§ 50.34(a)(4) - A preliminary analysis and PRA and the LMP process may be used to help evaluation of the design and performance of demonstrate this requirement is met.
structures, systems, and components of the facility with the objective of assessing the risk to public Associated policy statements:
health and safety resulting from operation of the
- Advanced reactor policy statement (2008) facility and including determination of the margins
- Safety goal policy statement (1986) of safety during normal operations and transient
- Severe accident policy statement (1985) conditions anticipated during the life of the facility,
- PRA policy statement (1995) and the adequacy of structures, systems, and components provided for the prevention of accidents and the mitigation of the consequences of accidents.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 8
Regulations Requirement Comment
§ 50.35(a) - When an applicant has not supplied initially all of the Allows use of the LMP process after technical information , the Commission may issue a construction the CP is issued to complete the permit if the Commission finds that (2) such further technical or design.
design information as may be required to complete the safety analysis, and which can reasonably be left for later consideration, May have less-than-full-scope PRA will be supplied in the final safety analysis report and that (4) on for the CP application.
the basis of the foregoing, there is reasonable assurance that, (i) such safety questions will be satisfactorily resolved at or before the latest date stated in the application for completion of construction of the proposed facility, and (ii) taking into consideration the site criteria contained in part 100 of this chapter, the proposed facility can be constructed and operated at the proposed location without undue risk to the health and safety of the public.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 9
Regulations Requirement Comment
§ 50.40 Common standards.
In determining that a construction permit or operating license in this part, or early site permit, combined license, or manufacturing license in part 52 of this chapter will be issued to an applicant, the Commission will be guided by the following considerations:
(a) Except for an early site permit or manufacturing license, the Includes the LMP process and its processes to be performed, the operating procedures, the facility underlying PRA.
and equipment, the use of the facility, and other technical specifications, or the proposals, in regard to any of the foregoing collectively provide reasonable assurance that the applicant will comply with the regulations in this chapter, including the regulations in part 20 of this chapter, and that the health and safety of the public will not be endangered.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 10
Regulations Requirement Comment
§ 50.50 - Upon determination that an Add conditions to the CP to lock-in:
application for a license meets the standards and requirements of the act and regulations, and that
- PDC and design bases notifications, if any, to other agencies or bodies
- LBE selection, SSC classification, and DID have been duly made, the Commission will issue a adequacy evaluation processes license, or if appropriate a construction permit, in
- Plan for finalizing the design and PRA such form and containing such conditions and limitations including technical specifications, as it deems appropriate and necessary.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 11
What is a PRA?
Risk Assessment / Risk Evaluation
- SRM-SECY-98-144 - A risk assessment is a systematic method for addressing the risk triplet as it relates to the performance of a Probabilistic Risk Assessment particular system (which may include a human component) to
- RG 1.247, Section C.1 - A risk assessment approach is understand likely outcomes, sensitivities, areas of importance, considered to be a PRA when it (1) provides a quantitative system interactions and areas of uncertainty. From this assessment assessment of the identified risk in terms of scenarios that the important scenarios can be identified. result in undesired consequences (e.g., releases of
- § 52.47(a)(27) - Provide A description of the design-specific radioactive material, radiological consequences) and their probabilistic risk assessment (PRA) and its results. frequencies and (2) is comprised of specific PRA elements
SRM-SECY-93-087):
- Non-LWR PRA Standard: Probabilistic risk assessment o The Commission approved the use of 1.67 times the design-basis (PRA): a quantitative assessment of the risk associated with SSE for a margin-type assessment of seismic events. plant operation and maintenance that is measured in terms o The Commission approved the use of simplified probabilistic of frequency of occurrence and consequences of event methods, such as but not limited to the Electric Power Research sequences, event sequence families, or release categories Institute (EPRI) Fire-Induced Vulnerability Evaluation (FIVE) [also referred to as a probabilistic safety analysis (PSA)].
methodology, to evaluate fire risk.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 12
TICAP: Location of PRA-Related Information in the SAR 6 - Safety-Related SSC Criteria and 1 - General Plant and Site Description Capabilities and Overview of the Safety Case 5 - Safety Functions, Design Criteria, 6.1 - Design Requirements for 1.1 - Plant Description 3 - Licensing Basis Events and SSC Safety Classification Safety-Related SSCs 1.2 - Site Description 3.1 - Licensing Basis Event 5.1 - Safety Classification of SSCs 6.2 - Reliability and Capability Selection Methodology (5)
Targets for SR SSCs 1.3.1 - Safety Case Methodology (1) 5.2 - Required Safety Functions 3.2 - LBE Summary (6) 6.3 - Special Treatment 1.3.2 - Fundamental Safety Functions 5.3 - Principal Design Criteria Requirements for SR SSCs 3.3 - AOOs 1.3.3 - Defense-in-Depth 5.4 - Safety-Related SSCs 6.4 - Descriptions for SR SSCs 3.4 - DBEs 5.5 - Non-Safety-Related with 3.5 - BDBEs Special Treatments SSCs (8) 7 - NSRST SSC Criteria and Capabilities 2 - Methodologies and Analyses 3.6 - DBAs 5.6 - Principal Design Criteria - 7.1 - Reliability and Capability 2.1.1 - Overview of PRA (2) Complementary Design Criteria Targets for NSRST SSCs 4 - Integrated Evaluations 2.1.2 - Summary of PRA Results 7.2 - Special Treatment Essential to the LMP-Based 4.1 - Overall Plant Risk Requirements for NSRST SSCs Affirmative Safety Case (3) Performance Summary (7)
- 1) Deviations from NEI 18-04 and RG 1.233 7.3 - Descriptions for NSRST SSCs 2.2 - Source Term (4) 4.2 - Defense-in-Depth 2) PRA scope and methods
- 3) Pointers to PRA results 2.3 - DBA Analytical Methods 4) Source term methodology 8 - Plant Programs Description of the PRA 5) Uses of the PRA in design; success criteria 2.4 - Other Methodologies and 6) Absolute risk significant event sequences 8.1 - Maintenance Program PRA results 7) Cumulative risk metrics Analyses
- 8) Absolute risk significant SSCs (F-C Target 8.2 - Other Programs Other and cumulative risk metrics)
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 13
NEI 21-07 (TICAP)
Section 2.1.1, Overview of PRA, p. 24 At the CP stage, neither the plant design nor the PRA is expected to have the level of maturity that will be necessary to support an OL application.
At the CP application stage, the applicant should describe its ultimate intended approach for qualifying the PRA. If conformance to ASME/ANS RA-S-1.4-2021 is planned, a simple statement to that effect should be sufficient. If the applicant intends to use another PRA methodology, that planned approach for establishing PRA technical adequacy should be described.
In either case, the applicant should address the last five items in the Section 2.1.1 list, consistent with the state of the plant design and the PRA at the time of CP application.
Staff: Change five to six.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 14
NEI 21-07 (TICAP)
Section 2.1.1, Overview of PRA, pp. 22-23 The discussion should include the following items:
A statement that describes how the applicant used the non-LWR PRA Standard ASME/ANS RA-S-1.4-2021 to establish the technical adequacy of the PRA, including the scope of technical requirements that were addressed.
A statement that a peer review was completed following the non-LWR PRA Standard and the guidance in NEI 20-09, Rev. 1, Performance of PRA Peer Reviews Using the ASME/ANS Advanced First 4 items; Non-LWR PRA Standard Only apply to OL application A summary of the peer review scope and approach relative to the scope of the PRA. Peer review findings and associated actions are to be documented consistent with the non-LWR PRA Standard requirements for PRA configuration control and available in plant records. The findings and associated actions are not required for inclusion in the SAR.
Discussion of how the NRC regulatory guide that endorses the non-LWR PRA standard was implemented (pending finalization of the regulatory guide)
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 15
NEI 21-07 (TICAP)
Section 2.1.1, Overview of PRA, pp. 22-23 Identification of the sources of radionuclides addressed and the sources of radionuclides that were screened out What does it mean to address or Discussion of how multi-reactor scenarios were addressed, if applicable include in the PRA?
Identification of the internal and external hazards that were included and the ones that were screened out Identification of the plant operating states that were included and those that were screened out Discussion of the software and analytical tools that were used to perform the event sequence modeling Last 6 items; and quantification, determine the mechanistic source terms, and perform radiological consequence Apply to CP evaluations, reported in the SAR as stated below:
and OL o All non-DBA LBEs in Chapter 3 that involved a 30-day EAB dose of 2.5 mrem TEDE or greater radiological consequences to the public o The cumulative dose and risk calculations in Section 4.1 The discussion should include identification of the methods and a high-level description of how they are applied to the radiological consequence evaluation.
Description of the site characteristics modeled or assumed in the radiological consequence evaluations covered by the previous bullet.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 16
NEI 21-07 (TICAP)
Chapter 3, Licensing Basis Events, p. 38 For a CP application, Chapter 3 should mirror the COL guidance but will reflect the preliminary nature of the design information. The PSAR should describe the methodology to be used in determining the initial set of LBEs and specifically address the conservative DBA calculation used to demonstrate DNRL-ISG-2022-01, App. A., p. 3: It is essential that the 25 rem TEDE dose limit in 10 CFR 50.34 is met to support the site suitability requirements. The structure of the chapter and sections should that all credible design-basis transients and follow the structure for the COL guidance. The discussions should be accidents be considered and evaluated during the sufficiently robust so the reader can clearly see how the methodology will lead to a final set of LBEs to be used in developing the final design, safety CP application stage.
margins, operational program content, and FSAR content. The discussion should clearly describe the role of the PRA in determining the initial set of DBEs. The PRA methodology described in Chapter 2 should be used to determine the preliminary assessments of the Licensing Basis Events, as NEI 18-04, Rev. 1, p. 14: In many cases, it is described in the COL guidance for Sections 3.3 through 3.6 above. (Note that ASME/ANS RA-S-1.4-2021 includes guidance on the performance of PRAs at expected that the initial selection of SR SSCs and various design stages.) selection of the DBAs will be based on a PRA that The discussions in the various sections of this chapter should provide includes internal events but has not yet been preliminary assessments of the AOOs, DBEs, and BDBEs, and the basis for expanded to address external hazards. With the those preliminary assessments. Any analyses performed and the methods used in those analyses should be described. The methods and analytical tools understanding that SR SSCs are required to be (if different from those described in Chapter 2) to be used in deriving the DBAs from the DBEs should be described in Section 3.6. capable of performing their RSFs in response to external events within the DBEHL, there will be no To the extent tests, experiments, or analytical enhancements are planned to support the FSAR LBE evaluations, those plans should be described in Chapter new DBAs introduced by external hazards.
2 or Chapter 3 of the PSAR, as applicable.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 17
NEI 21-07 (TICAP)
Chapter 5, Safety Functions, Design Criteria, and SSC Safety Classification,
- p. 56 For a CP application, Chapter 5 includes preliminary determination of the DNRL-ISG-2022-01, App.
RSFs and PDC (which include a quality assurance criterion, the RFDC, and the A., p. 4: A CP should CDC), safety classification of SR and NSRST SSCs, and specific NSRST SSC identify the safety design requirements. The LMP methodology for assessing safety functions, categorization and design design criteria, and SSC safety classification, as described in Chapter 5 of the classification of the COL guidance, draws on results from the initial PRA. The PRA methodology proposed facility SSCs.
described in Chapter 2 should be used in the preliminary determination of RSFs, determination of RFDC, CDC, and SSC safety classification.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 18
ASME/ANS RA-S-1.4-2021 (NLWR PRA Standard)
Section 3, Risk Assessment Application Process Provides a five-stage process to establish the capability of a PRA to support a particular risk-informed application.
Stage A: The plant life cycle stage is characterized as well as the PRA application or applications to be supported in this stage.
Stage B: The relevant portions of the PRA are examined to determine whether the PRA scope and level of detail and the risk metrics calculated by the PRA are sufficient for the application.
Stage C: An evaluation is performed to determine whether the capability requirements for the SRs from this Standard for each relevant portion of the PRA are sufficient to support the application.
Stage D: Each relevant portion of the PRA is compared to the appropriate SRs in this Standard for the Capability Category needed to support the application as determined in Stage A.
Stage E: The relevant portions of the PRA, supplemented by additional analyses if necessary, are used to support the application. This activity is outside the scope of this Standard.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 19
10 CFR 50.69 Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors
§ 50.69(b)(2) - A licensee voluntarily choosing to implement this section shall submit an application for license amendment under § 50.90 that contains the following information:
(ii) A description of the measures taken to assure that the quality and level of detail of the systematic processes that evaluate the plant for internal and external events during normal operation, low power, and shutdown (including the plant-specific probabilistic risk assessment (PRA), margins-type approaches, or other systematic evaluation techniques used to evaluate severe accident vulnerabilities) are adequate for the categorization of SSCs.
§ 50.69(c) SSC Categorization Process. (1) SSCs must be categorized as RISC-1, RISC-2, RISC-3, or RISC-4 SSCs using a categorization process that determines if an SSC performs one or more safety significant functions and identifies those functions. The process must:
(i) Consider results and insights from the plant-specific PRA. This PRA must at a minimum model severe accident scenarios resulting from internal initiating events occurring at full power operation. The PRA must be of sufficient quality and level of detail to support the categorization process, and must be subjected to a peer review process assessed against a standard or set of acceptance criteria that is endorsed by the NRC.
(ii) Determine SSC functional importance using an integrated, systematic process for addressing initiating events (internal and external), SSCs, and plant operating modes, including those not modeled in the plant-specific PRA. The functions to be identified and considered include design bases functions and functions credited for mitigation and prevention of severe accidents. All aspects of the integrated, systematic process used to characterize SSC importance must reasonably reflect the current plant configuration and operating practices, and applicable plant and industry operational experience.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 20
RG 1.247 TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities FROM SECTION C.1 - An Acceptable PRA:
Scope of a PRA: The scope of a PRA is defined in terms of (1) the metrics used to characterize risk, (2) the POSs for which the risk is to be evaluated, and (3) the causes of initiating events (hazard groups) that can potentially challenge and disrupt the normal operation of the plant and, if not prevented or mitigated, would eventually result in a radioactive release. The scope of a PRA is determined by its intended use for representing the as-built and as-operated plant or the as-designed, as-to-be-built, and as-to-be-operated plant. 5 Level of detail of a PRA: The level of detail of a PRA is defined in terms of the resolution of the modeling used to represent the behavior and operations of the plant. A minimal level of detail is necessary to ensure that the impacts of designed-in dependencies (e.g., support system dependencies, functional dependencies, and dependencies on operator actions) are correctly represented. This minimal level of detail is implicit in the elements comprising the PRA and their associated characteristics and attributes.
Elements of a PRA: The PRA elements are defined in terms of the fundamental technical analyses needed to develop and quantify the PRA model for its intended purpose (e.g., determination of a specific risk metric). The characteristics and attributes of the PRA elements define specific criteria for successfully performing those technical analyses and achieving a defined objective.
Plant representation and PRA configuration control: Plant representation is defined in terms of how closely the PRA represents the plant as it is designed, built, and operated. In general, PRA results used to support applications after a certificate, approval, permit, or license has been issued should be derived from a PRA model that represents the as-designed, as-to-be-built, or as-to-be-operated plant or as-built, as-operated plant. Consequently, the PRA should be maintained and upgraded, where necessary, to ensure it represents the as-built and as-operated plant through an acceptable configuration control process. Regulatory Position C.1.4 provides guidance on plant representation in the PRA.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 21
RG 1.247 TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities FROM SECTION C.1.1 - Scope of a PRA:
All radiological sources at the plant (e.g., reactor cores, spent fuel, fuel reprocessing facilities for molten salt reactors) should be addressed, including accident scenarios that lead to a radioactive release from multiple radiological sources.
All internal and external hazards should be addressed. For licensing activities, a PRA for the seismic hazard group must always be developed; other hazards should also be included if they cannot be screened out with appropriate justification. Appendix B to this RG lists hazards to consider when developing the PRA.
All POSs (e.g., at-power and low-power and shutdown (LPSD) types of POSs) should be addressed.
The frequencies of event sequences should be developed based on the occurrence of an initiating event, evaluation of plant response, evaluation of releases of radioactive material, and the consequences that result from those releases (i.e., an NLWR PRA should address all levels of PRA analysis, analogous to Level 1, 2, and 3 PRAs for LWRs).
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 22
RG 1.247 TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities FROM SECTION C.3.1 - PRA Scope, Level of Detail, and Degree of Plant Representation (PRA Acceptability for an Application):
The scope of a PRA needed to support an application will depend on the application-specific regulatory requirements, and the acceptability of the scope will be measured in terms of whether the applicant or holder of a license, certification, or permit meets those requirements. Application-specific guidance documents are expected to provide direction on meeting such requirements.
For plants in the preoperational stages of the plant life cycle, the PRA and its results used to support an application are expected to reflect the as-designed, as-to-be-built, or as-to-be-operated plant.
For operating plants, the PRA should reflect the as-built and as-operated plant. When used for risk-informed decision-making, the PRA should always reflect the best available information for the plant. For most applications, an applicant or holder of a license, certification, or permit should address all radiological sources, all hazards, all POSs, and all levels of analysis, as discussed in Regulatory Position C.1.1 of this RG.
The staff will assess the appropriateness of the justification for any deviations from this scope.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 23
A F Addressing All Sources, Hazards, and POSs in the Risk Evaluation E SSC Classification C LBE Selection SR SSCs DBAs Disposition
- Classified using the LMP process Reactor Non-Reactor
- Classified using deterministic B
Identification Internal At-Power PRA PRA/SE2 PRA/SE DBAs processes
- Hazards D BDBE
- POSs Other At-Power PRA/SE/DBHL PRA/SE/DBHL OR AOOs DBEs s Hazards1 NSRST SSCs LPSD PRA/SE/DBHL PRA/SE/DBHL DG-1413 NEI 18-04, RG 1.233
- Absolute risk significance
- Other risk-informed approaches 1Other hazards means hazards other than internal events (e.g., internal fires, NSR SSCs seismic) DBHLs 2Risk-informed supplemental evaluation (SE)
Preliminary Design G I CP Application ARCOP Detailed Design and Construction
- Description of the PRA and its results H
- Preliminary SSC classi"ca ons
- Preliminary reliability and capability design bases PRA Maintenance and Upgrade3
- Description of the Reactor Non-Reactor targets (PSAR or plant records)
- Final LBEs
- Final SSC M
- Final design
- Concurrent risk-informed and PRA Updated Screened-out Sources, Hazards, and POSs applications NEI 21-07 (TICAP),
- Optional approval of 3Full implementation of LMP implies full-scope PRA
- Optional request for finality of design features K selected design NEI 21-07 features (TICAP), DG-1404, OL Pre-Application Engagement ARCAP ISGs 24
Recent License Amendment to Use 10 CFR 50.69 (ANO-1, 6/23/2022, ML22138A431)
Entergy is approved to implement 10 CFR 50.69 using the processes for categorization of Risk-Informed Safety Class (RISC)-1, RISC-2, RISC-3, and RISC-4 Structures, Systems, and Components (SSCs) using: Probabilistic Risk Assessment (PRA) models to evaluate risk associated with internal events, including internal flooding, and internal fire; the The specific evaluation shutdown safety assessment process to assess shutdown risk; the Arkansas Nuclear One, methods (PRA and non-Unit 2 (ANO-2) passive categorization method to assess passive component risk for Class PRA-type) used to support 2 and Class 3 SSCs and their associated supports; the results of the non-PRA evaluations that are based on the IPEEE Screening Assessment for External Hazards updated using the SSC classification are external hazard screening significance process identified in ASME/ANS PRA Standard RA- identified as a license Sa-2009 for other external hazards except wind-generated missiles and seismic; the condition.
tornado safe shutdown equipment list for wind-generated missiles; and the alternative seismic approach as described in the Entergy submittal letter dated May 26, 2021, and all its subsequent associated supplements, as specified in License Amendment No. 277 dated June 23, 2022.
Changes to approved Prior NRC approval, under 10 CFR 50.90, is required for a change to the categorization methods require a license process specified above (e.g., change from a seismic margins approach to a seismic PRA approach). amendment.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 25
Summary All sources, hazards, and POSs should be identified and dispositioned in the CP application:
Modeled in the PRA, or Addressed using risk-informed supplemental evaluations, or Dispositioned using design-basis hazard levels (DBHLs) for hazards other than internal events, or Screened out.
As a minimum, the CP application should be based on an internal events, reactor at-power PRA model.
The acceptability of the CP PRA must be demonstrated; however, a peer review is not necessary.
The CP application should provide a preliminary, yet complete, set of LBEs.
The CP application should provide a preliminary, yet complete, SSC classifications.
The CP application should provide a plan for maintaining and upgrading the PRA during construction.
Example: Replacing a seismic DBHL with a seismic PRA CP holders are encouraged keep the staff advised of changes to the PRA completion plan that significantly affect the design.
The TICAP guidance implies the PRA will be full-scope (i.e., all sources, all hazards, all POSs) and peer reviewed in support of the OL application.
PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 26
Next Steps Staff will consider public feedback from this meeting General concepts and approach Clarifications and interpretations of the LMP guidance and TICAP Editorial comments (with emphasis on the diagrams)
Staff will develop guidance to complement DG-1404 (proposed new RG 1.253, which will endorse TICAP - NEI 21-07, Rev. 1)
Potential workshops PUBLIC MEETING ON PRA IMPLEMENTING LMP FOR 04/18/2023 NON-LWR CP APPLICATIONS UNDER 10 CFR PART 50 27