ML25055A081
| ML25055A081 | |
| Person / Time | |
|---|---|
| Issue date: | 02/25/2025 |
| From: | Hayden T NRC/NRR/DNRL/NRLB |
| To: | |
| References | |
| Download: ML25055A081 (1) | |
Text
Non-Proprietary 1
Presentation to the ACRS Subcommittee Staff Review of NuScale Licensing Topical Reports TR-0516-49416, Rev. 4, Non-LOCA Analysis Methodology TR-124587, Rev. 0, XPC Methodology March 4, 2025 (Open Session)
Non-Proprietary 2
Presentation to the ACRS Subcommittee of the Staffs Review of NuScale Non-Loss-of-Coolant Accident Analysis Methodology, TR-0516-49416, Rev 4.
March 4, 2025 (Open Session)
Non-Proprietary 3
NuScale Non-LOCA LTR Review Technical Reviewers
- *Zhian Li, NRR/DSS/SNRB
- Antonio Barrett, NRR/DSS/SNRB
- Adam Rau, NRR/DSS/SNRB
- Peter Lien, NRR/DSS/SNRB
- Ryan Nolan, NRR/DSS/SNRB
- Sean Piela, NRR/DSS/SNRB
- Carl Thurston, NRR/DSS/SNRB
- Dong Zheng, NRR/DSS/SNRB
- Joshua Miller, NRR/DSS/SNRB
- Rosie Sugrue, NRR/DSS/SNRB
- Upendra Rohatgi, RES consultant
- Andrew Dyszel, SNRB contractor
- Marvin Smith, SNRB contractor Project Managers
- Thomas Hayden, NRR/DNRL/NRLB
- Getachew Tesfaye, Lead, NRR/DNRL/NRLB Contributors
Non-Proprietary 4
NuScale Non-LOCA LTR Review NuScale submitted the Non-Loss-of-Coolant Accident (Non-LOCA)
Evaluation Model Topical Report (TR-0516-49416-P), Rev. 4 on January 5, 2023. The topical report was formally accepted for review on July 31, 2023.
NRC conducted an audit of the topical report from March 2023 to August 31, 2024.
49 audit issues were resolved in the audit For items not resolved during the audit, 7 RAIs were generated 1 RAI remains Open There are 2 significant differences between the draft SER submitted to ACRS on February 4, 2025, and the draft SER published on February 26, 2025 Overview
Non-Proprietary 5
NuScale Non-LOCA LTR Review 1 Open Item remaining RAI Non-LOCA.LTR - 50
- Issue description:
- Staff is working to understand changes made to NRELAP5 (v1.7) and the NPM basemodel:
- Modeling changes to DHRS models
- Modeling of core flow distribution
- Path forward:
- NRC and NuScale continue to discuss these modeling changes and have high confidence the issue will be resolved shortly, with minimal impact to the SE Open Item(s)
Non-Proprietary 6
NuScale Non-LOCA LTR Review 2 significant differences
- Section 3.5.3.7, NIST-2 Steam Generator - Decay Heat Removal System (DHRS) Integral Effects Test
- Expanded explanation of NIST-2 DHRS scalability
- Due to closure of Open item RAI NonLOCA.LTR-3,9,18,19,20,21,69
- Section 3.9, Quality Assurance and Section 4.0, Limitations and Conditions
- Removed Limitation and Condition No. 10
- Inserted finding of reasonable assurance related to the implementation of Quality Assurance controls consistent with RG 1.203 for the Non-LOCA EM Significant differences between previously submitted SER
Non-Proprietary 7
NuScale Non-LOCA LTR Review Considered design changes from NPM-160 to NPM-20 Applicability of Phenomenon Identification and Ranking to NPM-20 Use of bounding assumptions for primary coolant release in the radiological analysis instead of calculating primary side mass release Updated critical heat flux (CHF) screening for subchannel analyses Updated initial conditions and biasing scheme for each Non-LOCA event Changes from LTR Rev. 3 (NPM-160) to LTR Rev. 4 (NPM-20)
Non-Proprietary 8
NuScale Non-LOCA LTR Review NRELAP5 revised to version 1.7 NRELAP5 basemodel updated for NPM-20, some system models updated Updated DHRS information with new tests (used in Non-LOCA, LOCA, XPC LTRs)
NIST-2 tests for validation of NRELAP5 for DHRS performance Test results and code predictions of oscillation Reviewed scaling and distortion Long-term progression of non-LOCA events is covered in the XPC LTR Changes from LTR Rev. 3 (NPM-160) to LTR Rev. 4 (NPM-20)
Non-Proprietary 9
NuScale Non-LOCA LTR Review 1)
Applicable to NPM-20 only 2)
Changes to LOCA LTR may require changes to Non-LOCA LTR 3)
Types of analyses approved for Non-LOCA EM 4)
DHRS heat transfer uncertainty 5)
Credit for Non-Safety MSIVs 6)
Separate approval required for single failures, electric power assumptions and operator actions 7)
Approved for NRELAP5v1.7 in conjunction with NPM-20 basemodel Rev. 5 8)
Separate approval required for analytical limits and actuation delays; Applicant must assess for changes to event-specific bias directions 9)
Separate approval required for inputs to radiological consequence analysis not derived from transient analyses Limitations and Conditions
Non-Proprietary 10 NuScale Non-LOCA LTR Review While there are some differences between the current and previous revision, the staff found that the applicant provided sufficient information to support the staffs safety finding.
The staff found that an applicant that references this topical report with the limitations and conditions will meet relevant regulatory requirements pending review and approval of the application.
Conclusions
Non-Proprietary 11 NuScale Non-LOCA LTR Review Questions?
Non-Proprietary 12 Presentation to the ACRS Subcommittee of the Staffs Review of NuScales Extended Passive Cooling and Reactivity Control Methodology (XPC) Topical Report, TR-124587, Revision 0 March 4, 2025 (Open Session)
Non-Proprietary 13 NuScale XPC LTR Review Technical Reviewers
- *Antonio Barrett, NRR/DSS/SNRB
- Dr Rosie Sugrue, NRR/DSS/SNRB
- Dr John Lehning, NRR/DSS/SNRB
- Dr Adam Rau, NRR/DSS/SNRB
- Dr Peter Lien, NRR/DSS/SNRB
- Carl Thurston, NRR/DSS/SNRB
- Dr Len Ward, SNRB contractor
- Marvin Smith, SNRB contractor
- Chis Boyd, RES/DSA
- Jason Thompson, RES/DSA/CRAB II
- Justin Coury, RES/DSA/CRAB II
- Dr Andrew Bielen, RES/DSA/FSCB Project Managers
- David Drucker, PM, NRR/DNRL/NRLB
- Getachew Tesfaye, Lead PM, NRR/DNRL/NRLB Contributors
Non-Proprietary 14 NuScale XPC LTR Review NuScale submitted the Extended Passive Cooling and Reactivity Control Methodology (XPC) Topical Report, TR-124587, Revision 0 on January 5, 2023. The topical report was formally accepted for review on July 31, 2023.
NRC conducted an audit of the topical report from March 2023 to August 31, 2024.
25 audit issues were resolved in the audit For items not resolved during the audit, 8 RAIs were generated 2 RAIs remain open Significant differences between the draft SER submitted to ACRS on February 4, 2025, and the draft SER published on February 26, 2025, are discussed in Slide 16 Overview
Non-Proprietary 15 NuScale XPC LTR Review 2 Open Items remaining RAI XPC.LTR - 6
- Issue description:
- Staff is working to resolve issues with subcriticality considering downpowers and low decay heat RAI XPC.LTR - 21
- Issue description:
- Staff is working to resolve issues related to the incorporation of Nuclear Reliability Factors Path forward:
- NRC and NuScale continue to discuss both of these issues and have high confidence they will be resolved shortly, with minimal impact to the SE Open Items
Non-Proprietary 16 NuScale XPC LTR Review Significant difference
- Sections 4.8.4, Critical Boron Concentration Evaluation and 4.8.7, Boron Precipitation Methodology Assessment, explain why Limitation and Condition No. 10 and No. 11 respectively were added
- Section 5, Limitations and Conditions
- Limitation and Condition No. 10 added to require an applicant to provide technical specification controls to ensure adequate boron concentration is maintained
- Limitation and Condition No. 11 added to require an applicant use a specific initial boron concentration Significant differences between previously submitted SER
Non-Proprietary 17 NuScale XPC LTR Review Long Term Cooling and Reactivity Control
- DCA LTC Technical Report and FSAR Evaluations
- SDAA New XPC Topical Report Methodology and new design features Criticality Evaluations
- DCA has return to power under some conditions with evaluations
- SDAA precludes return to power with use of XPC methodology and design features Relevant Changes from NPM-160 (DCA) to NPM-20 (SDAA)
Non-Proprietary 18 NuScale XPC LTR Review Revised Reactor Design
- Increased number of riser holes to promote mixing between the downcomer and riser to help address potential for recriticality
- Revised Reactor Vent Valve design
- NPM-160 RVV with IAB
- NPM-20 RVV without IAB
- Long Term Cooling enhancements
- Riser holes, containment boron addition and containment mixing tubes contribute to boron redistribution and transport during DHRS and ECCS cooling Relevant Changes from NPM-160 (DCA) to NPM-20 (SDAA)
Non-Proprietary 19 NuScale XPC LTR Review Relevant Design Changes from NPM-160 to NPM-20 Riser Holes ESB RVV Mixing Tubes
Non-Proprietary 20 NuScale XPC LTR Review XPC TR reviewed as an extension of the LOCA and non-LOCA TRs Independent Phenomenon Identification and Ranking Table evaluation Reviewed computational tools used - NRELAP5, SIMULATE5 and MATLAB Reviewed NRELAP5 Test Assessment Basis
- NIST-2 LTC, LOCA ECCS, Non-LOCA Tests
- Reviewed validation and uncertainties Reviewed NRELAP5 LTC model used for thermal-hydraulic response
- Reviewed LTC NRELAP5 model validation vs LOCA base model Review and evaluation of lower riser hole flow assessment Review of evaluated events for collapsed liquid level, DHRS and ECCS heat removal capabilities and boron transport Review Highlights
Non-Proprietary 21 NuScale XPC LTR Review Review of boron transport subcriticality methodology
- Thermal hydraulic conditions
- Boron transport and mixing model assumptions
- Critical boron concentration and Nuclear Reliability Factors Review of boron transport precipitation methodology
- Thermal hydraulic conditions
- Boron transport and mixing model assumptions Review Highlights
Non-Proprietary 22 NuScale XPC LTR Review Updated Nuclear Reliability Factor review portion Add limitation/condition for requiring enough boron to account for integral down powers and xenon impacts for subcriticality analysis applications Add limitation/condition to require the zero power maximum operational limit boron concentration (no xenon) at the beginning of cycle is used as an initial condition for precipitation analysis applications Safety Evaluation Report Differences
Non-Proprietary 23 NuScale XPC LTR Review 1)
Changes to LOCA or Non-LOCA LTR may require changes to XPC LTR 2)
Applicable US460/NPM-20 only 3)
Maintain insignificant non-condensable gas in containment 4)
Consider the density difference between the borated and unborated liquid 5)
Methodology limited to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> 6)
RVV compressible flow qualification 7)
Initial test program (first module only) for dissolution testing 8)
Approved for NRELAP5v1.7 in conjunction w/NPM-20 Basemodel Rev. 5 9)
Separate approval required for single failures, electric power assumptions and operator actions Limitations and Conditions
Non-Proprietary 24 NuScale XPC LTR Review
- 10) Account for integral down powers and xenon for subcriticality
- 11) Zero power maximum operational limit boron concentration (no xenon) at the beginning of cycle is used as an initial condition for precipitation Limitations and Conditions
Non-Proprietary 25 NuScale XPC LTR Review The staff found that the applicant provided sufficient information to support the staffs safety finding.
The staff found that an applicant that references this topical report, and satisfies the limitations and conditions, will meet relevant regulatory requirements pending review and approval of the application.
Conclusion
Non-Proprietary 26 NuScale XPC LTR Review Questions?