ML21202A235
| ML21202A235 | |
| Person / Time | |
|---|---|
| Site: | 99902049 |
| Issue date: | 07/30/2021 |
| From: | Gregory Cranston NRC/NRR/DNRL/NRLB |
| To: | Getachew Tesfaye NRC/NRR/DNRL/NRLB |
| Cranston G | |
| Shared Package | |
| ML21202A234 | List: |
| References | |
| Download: ML21202A235 (8) | |
Text
July 30, 2021 MEMORANDUM TO:
Getachew Tesfaye, Acting Branch Chief New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation FROM:
Gregory V. Cranston, Project Manager /RA/
New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF THE JULY 13, 2021, PUBLIC MEETING TO DISCUSS THE HOLTEC SMALL MODULAR REACTOR, SMR-160, REQUEST FOR ADDITIONAL INFORMATION ON LICENSING TOPICAL REPORT: ELIMINATION OF LARGE BREAK LOCA AND ESTABLISHMENT OF LOCA ACCEPTANCE CRITERIA On July 13, 2021, an Observation Public Meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and SMR, LLC, a Holtec International Company (Holtec), regarding NRC staffs request for additional information regarding licensing topical report HI-2201064R2, Elimination of Large Break Loss-of-Coolant Accident (LOCA) and Establishment of LOCA Acceptance Criteria, (Agencywide Documents Access and Management Systems (ADAMS)
Accession No. ML21068A255). The meeting summary is provided in Enclosure (3). The public meeting notice can be found in ADAMS under Accession No. ML21190A136 and was also posted on the NRCs public Web site.
Enclosed are the meeting agenda (Enclosure 1), list of attendees (Enclosure 2), and the meeting summary (Enclosure 3). In the meeting summary for the June 16, 2021, meeting (ADAMS Accession No. ML21180A465), NRC stated that the information in Enclosures 3 and 4 to the June 16, meeting summary could be discussed with Holtec, if clarification is needed, at a future public meeting. This meeting provided that clarification.
Docket No. 99902049
Enclosures:
- 1. Meeting Agenda
- 2. List of Attendees
- 3. Meeting Summary CONTACT: Gregory Cranston, NRR/DNRL 301-415-0546
PKG: ML21202A234 MEMO: ML21202A235 MEETING NOTICE: ML21190A136
SGreen ABuford*
DATE 07/21/21 07/21/21 07/22/21 OFFICE NRR/DNRL/NPHP: BC NRR/DSS/SNRB: BC NRR/DNRL/NRLB: BC (Acting)
NAME MMitchell*
RPatton*
GTesfaye*
DATE 07/22/21 07/29/21 07/29/21 OFFICE NRR/DNRL/: DD NRR/DNLR/NRLB: PM NAME ABradford*
GCranston*
DATE 07/29/21 07/30/21
SUMMARY
OF THE JULY 13, 2021, PUBLIC MEETING TO DISCUSS THE HOLTEC SMALL MODULAR REACTOR SMR-160 REQUEST FOR ADDITIONAL INFORMATION ON LICENSING TOPICAL REPORT: ELIMINATION OF LARGE BREAK LOSS-OF-COOLANT ACCIDENT AND ESTABLISHMENT OF LOCA ACCEPTANCE CRITERIA July 13, 2021 Meeting Agenda Time Topic Organization 1:00 p.m. - 1:10 p.m.
Introductions and Opening Remarks NRC and Holtec 1:10 p.m. - 2:30 p.m.
SMR-160 Licensing Topical Report Discussion - Open Session NRC and Holtec 2:30 p.m.
Adjourn
SUMMARY
OF THE JULY 13, 2021, PUBLIC MEETING TO DISCUSS THE HOLTEC SMALL MODULAR REACTOR SMR-160 REQUEST FOR ADDITIONAL INFORMATION ON LICENSING TOPICAL REPORT: ELIMINATION OF LARGE BREAK LOSS-OF-COOLANT ACCIDENT AND ESTABLISHMENT OF LOCA ACCEPTANCE CRITERIA July 13, 2021 List of Participants Name Affiliation Morin, Tammy Holtec Trotta, Rick Holtec Hickey, Kevin Holtec Rajkumar, Joseph Holtec Ball, Erick ERI Khatib, Mohsen ERI Glunt, Nathan EPRI Sterling, Lance Certec Barrett, Antonio NRC Brown, Christopher NRC Buford, Angie NRC Caldwell, Bob NRC Cranston, Greg NRC Dudek, Michael NRC Hsu, Kaihwa NRC Kim, Leslie NRC Li, Yueh-Li NRC Manoly, Kamal NRC Mitchell, Matthew NRC Nolan, Ryan NRC Patton, Rebecca NRC Rudland, David NRC Scarbrough, Thomas NRC Sugrue, Rosemary NRC Sweeney, Zach NRC Tesfaye, Getachew NRC Tsao, John NRC Tseng, Ian NRC Villarreal, Tristan NRC Wittick, Brian NRC
SUMMARY
OF THE JULY 13, 2021, PUBLIC MEETING TO DISCUSS THE HOLTEC SMALL MODULAR REACTOR SMR-160 REQUEST FOR ADDITIONAL INFORMATION ON LICENSING TOPICAL REPORT: ELIMINATION OF LARGE BREAK LOSS-OF-COOLANT ACCIDENT AND ESTABLISHMENT OF LOCA ACCEPTANCE CRITERIA July 13, 2021 Meeting Summary On July 13, 2021, an Observation Public Meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and SMR, LLC, a Holtec International Company (Holtec), to discuss NRC staffs request for additional information (RAI) regarding licensing topical report (LTR) HI-2201064R2, Elimination of Large Break Loss-of-Coolant Accident (LOCA) and Establishment of LOCA Acceptance Criteria, (Agencywide Documents Access and Management Systems (ADAMS) Accession No. ML21068A255). The public meeting notice can be found in ADAMS under Accession No. ML21190A136 and was also posted on the NRCs public Web site.
Holtec is requesting that postulation of a break of the steam generator (SG) to reactor pressure vessel (RPV) forged connection (planar inter vessel forging or PIF) and the SG riser be excluded from design-basis LOCA considerations for the SMR-160 such that any breaks associated with the forged connection and SG riser be considered a beyond design-basis event. The SG is connected directly to the RPV by a single forging with concentric fluid flow paths.
The forged connection goes from the RPV to the SG bottom head. The SG riser extends from the bottom tubesheet to the top tubesheet and is welded to the tubesheets. The riser is continuously supported and guided throughout its length. Coolant heated by the core (hot leg) flows through the inner duct of the PIF to the SG tubesheet and coolant returning to the RPV flows through the outer annulus of the PIF (cold leg). The inner duct is not part of the reactor coolant pressure boundary On June 16, 2021, a public and closed meeting (ADAMS Accession No. ML21180A465) was held with Holtec to discuss the response Holtec provided (ADAMS Accession No. ML21147A532) to the NRC staffs RAI 9832). In the June 16, meeting summary memorandum, the NRC staff stated that the information in Enclosures 3 and 4 to the June 16, meeting summary could be discussed with Holtec, if clarification is needed, at a future public meeting. This public meeting provides clarification to Holtec. RAI 9836 can be found in ADAMS (ADAMS Accession No. ML21123A187).
The public meeting commenced with opening remarks and an introduction of participants. There were members of the public attending but there were no public comments. During the meeting, Holtec asked questions for clarification regarding statements made in Enclosure (4) of the June 16, meeting summary. The key clarification points from the June 16, are discussed below. The below points are clarifications and are not intended to change the information being requested in Enclosure (4) of the June 16, meeting summary. It was pointed out to Holtec that even after providing a supplemental response to RAI-9832 there could still be additional questions or an additional RAI as the review of the LTR proceeds.
2
- 1.
In the June 16, meeting summary, the NRC staff stated that the requirements in Title 10 of the Code of Federal Regulations (10 CFR) 50.46, Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors, are applicable if either (1) the locations are considered pipes for purposes of 10 CFR 50.46 (note this is independent from the applied American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code) and designation of the locations), or (2) the locations are not considered pipes, but warrant special considerations for inclusion in 10 CFR 50.46 based on special safety significance related to the combined vessel design and configuration. The subject locations primarily act as conduits to transfer fluid therefore rendering their consideration for the purpose of 10 CFR 50.46 applicability as pipes. However, even if the staff did agree that the locations were part of a combined vessel the staff would consider whether there was a matter of special safety significance to the locations that would require compliance with 10 CFR 50.46. Holtec requested clarification if these are two separate pathways depending on the designation of the components. The NRC staff reiterated that the same exemption would be required regardless of how the components are designated (pipe or vessel). In either case, because 10 CFR 50.46 and General Design Criteria 35, Emergency Core Cooling, are applicable, if compliance is not intended for the SMR-160, an exemption is needed and Holtec could describe the criteria in the LTR that would be used for a future exemption request. The NRC staff stated the criteria must consider both probability and consequences.
- 2.
Regarding consideration of break locations, Holtec asked if a LOCA will just be considered at the welds and not in the body of the forging and the SG riser. The NRC staff stated that the applicability of 50.46 is not specific as to where a LOCA occurs; it is a non-mechanistic, arbitrary loss of coolant. Consequently, it doesnt matter where the break occurs. However, the NRC staff noted the focus of the RAI is generally on welds.
In addition, ASME inservice inspections focus on the welds.
- 3.
In the RAI response, Holtec stated that information from Section XI of the ASME BPV Code will be used for preservice and inservice inspection. However, that provides no detailed criteria for inspections because the prescriptive nature of Section XI of the ASME BPV Code specifies no inspections or definition for the type of the component/weld configuration such as forging to SG weld and the SG riser welds. The NRC staff said in the June 16, meeting summary that Holtec should specify and commit to the inspection method, frequency and acceptance criteria which will apply to the subject welds. Holtec stated that the forging does not fit exactly into ASME BPV Code requirements and asked if it is acceptable to specify that the welds will meet criteria of a certain part of the Code. The NRC staff stated that it would be acceptable for Holtec to cite areas of the Code and specify, for example, that the weld will satisfy the requirements of an examination category and examination item in lWB-2500 (Table B-2500-1 of the ASME BPV Code,Section XI), and will follow specified frequency of inspections, examination methods, and acceptance criteria. There is no need to define a whole new category.
- 4.
Holtec requested clarification on the NRC staff statement that there is no objective evidence that 100 percent volumetric examination (by ultrasonic inspection) for inservice inspection can be achieved for these welds. The NRC staff clarified that 100 percent volumetric examination is needed on the required volume as defined per the ASME BPV
3 Code. Information should be provided that identifies the locations of inspections and makes a commitment that inspections will occur on those portions of the welds which fall into the required examination category and examination item similar to IWB-2500 of the ASME BPV Code,Section XI.
- 5.
The NRC staff stated during the June 16, meeting that the RAI response did not provide sufficient bases to demonstrate that stress corrosion cracking is not an issue. Holtec asked if stating that industry practices, such as NRC Regulatory Guide 1.44, Control of the Processing and Use of Stainless Steel, would be acceptable. The NRC staff stated that Holtec, in addition to citing these documents, could, for example, specify an appropriate water chemistry program in accordance with industry guidelines (e.g.,
Electric Power Research Institute (EPRI) guidance), specify the materials that meet NRC regulatory guidelines, and minimize applied and residual stresses in the design of the subject components to reduce the possibility of stress corrosion cracking.
- 6.
The NRC staff stated during the June 16 meeting that no information was provided regarding how field welding will be performed and that Holtec should provide specific details and commitments regarding the field welds. Holtec stated that the applicant for a license will be required to specify how the welds are fabricated using a qualified fabricator. Holtec stated that there will be post weld heat treatment to reduce residual stress. The NRC staff requested that additional information be included that provides general guidelines on the fabrication methods to be used that would ensure sufficient quality to establish a basis of why these welds would fall under break exclusion. In addition, the ASME BPV Code only provides general requirements, which may include several methods and allowances/exemptions (for example, post weld heat treatment exemptions), and therefore any statements should be specific (i.e., post weld heat treatment will be performed and will not be exempted as allowed by Section III of the ASME BPV Code). Holtec should be as specific as possible in the description of its welding design and fabrication, and the welding processes (e.g., gas tungsten arc welding, etc.).
- 7.
Holtec asked if all information provided in an RAI response needs to be incorporated into the LTR. Holtec noted, and NRC staff confirmed that all RAIs, including responses, typically are attached as an appendix to the LTR. The NRC staff clarified that any criteria or commitments that Holtec makes in the RAI, including any supplements, that the staff will rely on to make its safety finding, will need to be included in the body of the LTR.
- 8.
The NRC staff stated during the June 16, meeting that NRC staff has additional concerns regarding the location and number of riser welds because it might experience loadings from pressure differential, temperature differential, and environmental conditions (primary water on one side and secondary water on the other side of the riser). Holtec stated that they will provide additional information on the riser welds, but needed clarification on what is meant by environmental conditions. The NRC staff stated that if the specific number of welds in the riser is not known at this time, Holtec can specify the bounding conditions (number and locations) of the welds. The NRC staff clarified that they are looking for the total stress state of the component, the environmental conditions experienced by the component, and the specific material used to determine any degradation mechanisms. The stress state should include all loads, such as pressure differential, temperature differential, residual stresses, operational loads, deadweight, and seismic. Environmental conditions should include the highest
4 temperature of the component and the water chemistry. In addition, regarding water chemistry, NRC staff said that Holtec should specify a water chemistry program with associated guidelines (e.g., EPRI) to minimize the potential for stress corrosion cracking.
- 9.
The NRC staff stated during the June 16, meeting that Holtec should provide more specific details on the similarity and differences of the proposed excluded welds from current operating plants. Holtec asked if this request is this just for the riser. The NRC staff said the statement applies to all of the subject components, including the entire forged fittings.
- 10.
The NRC staff stated during the June 16, meeting that Holtec should describe deterministic and probabilistic fracture mechanic analyses (methodology and acceptance criteria) to demonstrate that the forging and SG riser welds have a sufficiently low probability of failure. Holtec asked if they could just say they will follow criteria in the ASME BPV Code, Appendix G. The NRC staff responded that Holtec should also specify the applicable guidance provided in the ASME BPV Code, Appendices A, C, E, and H, and should provide more specificity on what guidance will be used and the acceptance criteria. Holtec can choose whether to specify and describe deterministic and/or probabilistic methodologies.
- 11.
The NRC staff stated during the June 16, meeting that Holtec should provide additional justification and commitments regarding why the forging is or is not susceptible to thermal (aging) embrittlement or hydrogen embrittlement. Holtec stated that this concern applies to cast materials thermal embrittlement and not forgings. The NRC staff said that Holtec can specify they wont have cast materials so thermal embrittlement will not applicable. Also, Holtec should add that it will follow the specific industry practices regarding preventing hydrogen embrittlement to be used in welding and include any applicable references.
- 12.
Holtec had a question on stress state as stated in the NRC June 16, letter. The NRC staff said the stress state is related to applied stresses that should satisfy the ASME BPV Code stress limits. The stress state should include all loads, such as pressure differential, temperature differential, residual stresses, operational loads, deadweight, and seismic. The NRC staff stated that Holtec needs to provide a qualitative assessment, if a quantitative assessment is not available at this time, of the forging (connection duct) and the SG riser and their associated welds to demonstrate that the subject components/welds are designed for low probability of failure. The NRC staff also stated that Holtec should describe how the components/welds are different or similar to operating reactor vessel welds. This information is needed in order to fully understand the basis for the Holtec position that these welds have sufficiently low probability of failure and how they are similar/different from operating reactor vessel welds.
- 13. Holtec stated that they had no questions regarding local leakage detection, comprehensive vibration assessment program, water hammer and steam hammer issues as stated in the NRC June 16, letter. The NRC staff stated that Holtec should be specific in the LTR as to what design features, criteria, methods, programs, or commitments will be met by a future applicant to analyze, detect, or monitor these issues.