ML22152A236
| ML22152A236 | |
| Person / Time | |
|---|---|
| Site: | 99902078 |
| Issue date: | 06/03/2022 |
| From: | Vivanco R NRC/NRR/DNRL/NRLB |
| To: | Michael Dudek NRC/NRR/DNRL/NRLB |
| Vivanco R | |
| Shared Package | |
| ML22152A235 | List: |
| References | |
| Download: ML22152A236 (8) | |
Text
June 3, 2022 MEMORANDUM TO:
Michael I. Dudek, Chief New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation FROM:
Ricky Vivanco, Project Manager /RA/
New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE MAY 4, 2022, OBSERVATION PUBLIC MEETING FOR PRE-APPLICATION DISCUSSION OF NUSCALE POWER, LLCS TREATMENT OF DC POWER IN SAFETY ANALYSIS LICENSING TOPICAL REPORT SUBMITTAL The U.S. Nuclear Regulatory Commission (NRC) held an observation public meeting on May 4, 2022, to discuss pre-application topics related to the NuScale Power, LLC (NuScale) method of treatment of DC power in safety analysis for a future Licensing Topical Report (LTR) submittal.
NuScale requested this meeting to provide context for the method as part of the overall design and deterministic safety analysis processes. NuScale also sought feedback from the NRC staff on the methodology approach proposed in the future LTR submittal. This meeting was the second pre-application meeting held on this topic.
The public meeting notice dated May 4, 2022, was posted on the NRC public website, and can be found in the NRCs Agencywide Documents Access and Management Systems (ADAMS) under Accession No. ML22117A074. Information related to NuScale presentation can be found under ML22115A259.
Enclosed are the meeting agenda (Enclosure 1), list of participants (Enclosure 2), overview (Enclosure 3), summary of feedback - non-proprietary version (Enclosure 4) and summary of feedback - proprietary version (Enclosure 5). The complete ADAMS package can be found under ML22152A235.
Docket No. 99902078
Enclosures:
As stated cc: w/encl.: DC NuScale Power CONTACTS: Ricky Vivanco Getachew Tesfaye, NRR/DNRL 301-415-0021 301-415-8013
PKG: ML22152A235 MEMO: ML22152A236
- via eConcurrence NRR-106 OFFICE DNRL/NRLB: PM DNRL/NRLB: LA DSS/SNRB: BC DNRL/NRLB: BC NAME RVivanco*
SGreen*
RPatton*
MDudek*
DATE 05/31/2022 06/01/2022 06/03/2022 06/03/2022
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE MAY 4, 2022, OBSERVATION PUBLIC MEETING FOR PRE-APPLICATION DISCUSSION OF NUSCALE POWER, LLCS TREAMENT OF DC POWER IN SAFETY ANALYSIS LTR SUBMITTAL MEETING AGENDA May 4, 2022 Time Topic Speaker 11:00 - 11:05 PM Introductions and Opening Remarks All 11:05 - 11:10 PM Discussion of NuScales Treatment of DC Power in Safety Analysis NRC/NuScale 11:10 - 11:30 PM Questions from the public NRC/Public Closed Portion 11:30-1:00 PM Continued Discussion of Proprietary Information NRC/NuScale 1:00 PM Adjourn
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE MAY 4, 2022, OBSERVATION PUBLIC MEETING FOR PRE-APPLICATION DISCUSSION OF NUSCALE POWER, LLCS TREAMENT OF DC POWER IN SAFETY ANALYSIS LTR SUBMITTAL LIST OF ATTENDEES May 4, 2022 Name Organization Ricky Vivanco NRC Getachew Tesfaye NRC Michael Dudek NRC Sheila Ray NRC Victor Cusumano NRC Rebecca Patton NRC Antonio Barrett NRC Brian Smith NRC Joseph Donoghue NRC Adam Rau NRC Robert Beaton NRC MJ Ross-Lee NRC Joshua Miller NRC Bruce Bavol NRC Ryan Nolan NRC Rosemary Sugrue NRC Carl Thurston NRC Michael Snodderly NRC Joshua Miller NRC
2 Craig Harbuck NRC Thomas Griffith NuScale Paul Infanger NuScale Andy Lingenfelter NuScale Kristopher Cummings NuScale Meghan McCloskey NuScale Ben Bristol NuScale Kevin Lynn NuScale Robert Gamble NuScale Mark Shaver NuScale David Rickenbach NuScale Kent Welter NuScale Gary Becker NuScale Melissa Bates DOE Yan Peng John Pfabe
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE MAY 4, 2022, OBSERVATION PUBLIC MEETING FOR PRE-APPLICATION DISCUSSION OF NUSCALE POWER, LLCS TREAMENT OF DC POWER IN SAFETY ANALYSIS LTR SUBMITTAL OVERVIEW The U.S. Nuclear Regulatory Commission (NRC) held an observation public meeting on May 4, 2022, to discuss pre-application topics related to the NuScale Power, LLC (NuScale) method of Treatment of DC Power in Safety Analysis LTR submittal. NuScale requested this meeting to provide context for the method as part of the overall design and deterministic safety analysis processes, outline the method described in the tropical report and provide an example of the method as it is applied. NuScale also sought feedback from the NRC staff on the proposed approach in the future topical report submittal. This meeting was the second pre-application meeting held on this topic. The non-proprietary information related to NuScales presentation can be found under ADAMS Accession No. ML22115A259.
The beginning of the meeting was open to the public. NuScale gave opening remarks and a short presentation to summarize what the closed session presentation would cover. Only general questions were posed from the NRC during this time. NuScale clarified that this topical report would be submitted sometime late 2nd quarter or in the beginning of the 3rd quarter of this year. NuScale further clarified that this Topical Report is a new submittal and neither a supplement nor revision to a previous topical report about passive electrical systems. There were no questions posed from the public attendees.
During the closed portion of the meeting, NuScale gave a presentation showing details of their proposed methodology. NuScale also included an example of how the methodology would be applied. The NRC staff provided feedback throughout the presentation (i.e., a non-proprietary version is summarized in Enclosure 4 and the proprietary version in summarized in Enclosure 5). The NuScale personnel and NRC staff agreed a third pre-application meeting may be warranted.
U.S. NUCLEAR REGULATORY COMMISSION
SUMMARY
OF THE MAY 4, 2022, OBSERVATION PUBLIC MEETING FOR PRE-APPLICATION DISCUSSION OF NUSCALE POWER, LLCS TREAMENT OF DC POWER IN SAFETY ANALYSIS LTR SUBMITTAL
SUMMARY
OF FEEDBACK - NON-PROPRIETARY VERSION On May 4, 2022, the NRC staff held a pre-application discussion with NuScale Power, LLC regarding a proposed future LTR for the treatment of DC power in the safety analysis. The staff concluded its comments with the viewpoint that based on the limited information provided to the staff during the meeting, it would be challenged to find the proposed methodology acceptable and appropriate for generic application. Further, the staff stated that it would be difficult to assess that the augmented quality DC power supply (EDAS) is not safety-related without final design information and a safety analysis would be needed that demonstrates acceptable consequences if the EDAS fails during event progression. The staff also explained that determinations on topics like the one proposed in this proposed LTR, or more generically for the crediting of non-safety-related structures, systems and components (SSCs) in the Chapter 15 safety analysis, are reviewed on an event-specific or case-by-case basis. In this case the information the staff needs to make such a finding is either not available (yet) or might not be appropriate for a generic methodology. Finally, it was acknowledged that further engagement on this topic should be considered. The bullets below provide a summary of the specific feedback the NRC staff communicated during the May 4, 2022, public meeting:
Staff stated that consistent with the philosophical approach to design-basis event analysis, it would need to have event-specific information to fully understand the frequency of occurrence of the event and its consequences.
Staff stated that, currently, the regulations and applicable guidance do not allow the exclusion of the consideration of failures of non-safety-related SSCs following event initiation. Title 10 of the Code of Federal Regulations, Part 50.2 definition of safety-related are those SSCs relied upon to remain functional during and following design-basis events.
Therefore, the assessment of availability/need for an SSC is not only required at event initiation, but throughout the entire transient. Absent an event-specific analysis to show that EDAS failure doesnt lead to a more limiting result or result in a figure of merit not being satisfied the staff is not able to conclude the EDAS meets the definition of safety-related. In addition, the staff identified general design criteria (GDC) 1 which requires the quality of the SSCs to be commensurate with the importance of the safety function being performed:
2 NuScale stated that it will justify the EDAS is not safety-related ((. The staff stated that approach appears appropriate for that particular event sequence, (( }}. Staff described a similar topic encountered during the DCA review where the non-safety-related backup main steam isolation valves (MSIVs) were credited for mitigation of steam generator tube failure (STGF) events. NuScale resolved the issue by demonstrating the result of the non-safety-related backup MSIV failing during a SGTF would not result in unacceptable consequences or meet any of the safety-related criteria in 10 CFR 50.2. Staff stated that, in general, assumptions for timing of power-loss scenarios have been reviewed on an event-specific basis when a safety analysis is submitted. The staff reiterated that it would need to review the event progression in order to make determination of how it can be treated. Staff stated that failures identified by a failure modes and effects analysis (FMEA) are used by the staff to find potential single failures of safety-related SSCs. ((
}}. Typically, during Chapter 15 reviews, non-safety-related SSCs are assumed to fail non-mechanistically since they are not appropriately qualified. In these cases, the staff verifies that the non-safety-related SSCs are assumed to operate in a manner which leads to the most limiting results.
Staff stated its approach to crediting of non-safety-related SSCs has been on a case-by-case basis. At a minimum, the credited non-safety-related SSC should not be part of the primary success path (i.e., not needed to meet any acceptable criteria). The staff should be able to reach a conclusion that crediting the non-safety-related SSCs is not needed if it fails during event progression and use of the system only provides additional margin to the acceptable criteria. As such, the staff stated that it would be challenging to reach these conclusions without a final design and safety analysis. Staff stated that there is extensive history regarding the assumption of failures in electrical components. For example, both passive and active single failures of safety-related/Class 1E electrical equipment is assumed at any time during a transient. Also, it may not be appropriate for the NuScale design to use the same simplifications or assumption as operating facilities if the design does not have a Class 1E onsite power system.}}