ML25098A041
| ML25098A041 | |
| Person / Time | |
|---|---|
| Issue date: | 04/17/2025 |
| From: | Jacqueline Thompson NRC/NRR/DEX/EXHB |
| To: | Hayes B NRC/NRR/DEX/EXHB |
| References | |
| Download: ML25098A041 (7) | |
Text
April 17, 2025 MEMORANDUM TO:
Barbara Hayes, Chief External Hazards Branch Division of Engineering and External Hazards Office of Nuclear Reactor Regulation FROM:
Jenise Thompson, Geologist
/RA/
External Hazards Branch Division of Engineering and External Hazards Office of Nuclear Reactor Regulation
SUBJECT:
U.S. Nuclear Regulatory Commission Meeting Summary
Title:
Proposed Use of Offsite Meteorological Data for Safety Reviews and Atmospheric Dispersion Modeling, #ADVANCENRC Meeting Identifier: 20250247, Agencywide Documents Access Management System (ADAMS)
Accession No. ML25049A299 Date and Time of Meeting: Thursday, March 6, 2025; 2:00 pm to 3:30 pm Location: Teams Meeting/Teleconference Type of Meeting: Information Meeting with Question and Answer Purpose of Meeting: To discuss the proposed use of offsite meteorological data for safety reviews and atmospheric dispersion modeling Meeting Summary:
The U.S. Nuclear Regulatory Commission (NRC) staff provided opening remarks and the meeting agenda. NRC Staff Presentation Slides are available in ADAMS at ML25058A252.
Nuclear Energy institute(NEI)presentation slides are available in ADAMS at ML25064A310.
NRC Presentation The NRC staff presentation was given by Jenise Thompson and Kevin Quinlan.
The NRC staff provided a general description of the ADVANCE Act, status of activities, outreach efforts, and contact information.
The NRC staff provided a summary of an initial graded approach depending on three levels of proposed radiological emissions (i.e., none, minimal, or non-minimal) to be confirmed by NRC staff and implications of each. The NRC staff posed a related discussion question: What other
factors need to be considered to determine if atmospheric dispersion modeling and meteorologic (Met) monitoring is needed? If so, for what emission release level?
NEI responded that regardless of the size of the release, the representativeness of offsite meteorological (Met) data should be the determining factor. There are a lot of available sources of data and if it is representative, applicants should be able to use offsite data regardless of the release type. The NRC staff responded that there are many Met data sources and if the data are deemed to be representative, they could be used with the appropriate and necessary data processing.
NEI also noted that if there is a site boundary emergency planning zone (EPZ), that should be factored into the determination as well. The NRC staff noted that this was under consideration.
The NRC presentation addressed the content of Regulatory Guide (RG) 1.23 and that onsite data is preferred but guidance also allows for alternate approaches. The NRC staff also provided a high-level summary of some of topics that would need to be considered in determining if data is representative of onsite conditions including being context specific to various dispersion models, algorithms, and how modeling results are used. No initial questions were asked.
The NRC staff summarized several examples of technical information needed based on RG 1.23 and other industry guidance including compliance with and departures from RG 1.23. The NRC staff posed the following discussion question: What other general factors should be considered to demonstrate the representativeness of offsite Met data for use in onsite dispersion analyses?
Jon Facemire (NEI) commented that while the considerations listed on the slide are good, what is the plan going forward? RG 1.23 is the standard, but the language is prescriptive regarding the amount of data needed for certain applications. Is the path forward to update RG 1.23 to allow for alternative data?
The NRC clarified that is it still determining the path forward and clarified that while the NRC plans to get more guidance out, it has not been decided if it will be in the form of updated or new guidance.
Adam Stein (The Breakthrough Institute) asked what is the purpose of the NRC wanting to know the original purpose of the Met data that is being proposed for use. The NRC clarified that the staff are doing their due diligence to see if the data is appropriate and compatible for use in the models since different sources of Met data may have different collection and processing methods (e.g., airport Met data is focused on aviation needs). In a follow-up question, Dr. Stein noted that regardless of why the data is collected, as long as it is appropriate, it shouldnt matter for the purpose it was collected. It was also noted that the use of the strict comparison of offsite to onsite meteorology data as a means to show representativeness could still result in the need to put up the Met tower. The NRC staff provided some initial thoughts on ways that the representativeness of offsite Met data alone for a site can been shown.
Erwin Prater (Sargent & Lundy) asked for the NRCs thoughts on data from airports or other sources and alternative methods to calculate atmospheric stability since most other sources dont use delta T. NRC staff acknowledged that other methods are used such as the U.S.
Environmental Protection Agency (USEPA) methods and this is an area the NRC staff is looking
into further. The stability issue was also addressed later in the open discussion section of the meeting.
The NRC staff summarized initial thoughts including the possible need for different statistical tests, acceptance criteria, and Met monitoring strategies, as well as the important distinction between Met data used for dispersion modeling and climate-related descriptions. Staff also discussed distinctions between dispersion models and results for onsite and offsite receptors due to accidents, and for dispersion analyses of routine release impacts at offsite receptors. The NRC staff also noted that separate statistical tests and acceptance criteria may be needed for safety-and environmental purposes. The NRC staff also recognized the possible need to establish an onsite Met monitoring program during operational phase and for emergency preparedness (EP) planning and response in lieu of continued reliance on offsite Met monitoring data.
NRC staff posed the following discussion question: What would be considered appropriate safety-and environmental-related correlations or other statistical comparisons and acceptance criteria for each applicable Met parameter and type of dispersion model used?
Erwin Prater commented that at minimum, there should be a linear correlation analysis of possible data sites, which might include comparisons among several locations surrounding or near a given site to establish similarity of conditions in the area.
Jon Facemire (NEI) asked how is Met monitoring being considered if you have an onsite EPZ versus an offsite EPZ? The NRC staff clarified that if there are no releases, an onsite Met tower may not be needed and will need to determine how to satisfy the obligation for the Met monitoring data required to support emergency response. A follow-up question noted that Appendix E does have some specific requirements where 10 CFR 51.60 has different approaches that should be explored further. An additional comment indicated that a separation of the parameters may be possible to address both dispersion and emergency preparedness. The NRC staff noted that it should be possible from an EP standpoint to use the RASCAL code and its capabilities. However, possible modifications to that code may be needed depending on the offsite Met data source proposed to be used. A final comment noted that potential localized terrain might not be easily correlated to regional weather.
NEI Presentation The NEI presentation was given by Jon Facemire (NEI) and Erwin Prater (Sargent & Lundy).
NEI noted that they have submitted numerous papers to the NRC regarding microreactors that may be applicable to the discussion on the use of offsite Met data. Jon Facemire (NEI) questioned what the best mechanism would be to transmit the NEI report to NRC in the near future. The NRC staff discussed the possible options for transmitting the report and mentioned that in addition to the report being related to the ADVANCE Act it can also be tied to Division of Engineering and External Hazards (DEX) effort on developing the graded approach to site characterization. The NRC staff also asked if the document is coming in for endorsement or consideration. NEI clarified that this is still under discussion.
The NEI presentation also suggested reverting to the original seven stability classes identified by Turner if offsite Met data source only classifies stability to current 6 classes.
Open Discussion Jeffrey Merrifield (Pillsbury Winthrop Shaw Pittman) asked if the NRC staff is preparing a paper for the Commission to consider cases moving from large light-water to microreactors if the EPZ is at the site boundary and there is no outside dose. The NRC staff discussed the ongoing efforts related to developing a graded approach that addresses the issues across all hazards.
The NRC staff also suggested that Mr. Merrifield provide a formal question to the agency.
Jon Facemire reiterated the importance of the Met data issue and that there is a lot of interest by industry. The Met tower is critical path (cost and schedule). He suggests that it should not be the critical path if there are good sources of Met data available. The NRC staff agreed that this is an important issue and is proceeding with efforts to address it.
Adam Stein mentioned (1) EPAs AERMOD model was integrated into MACCS (Melcor Accident Consequence Code System); (2) an option for an applicant to forgo weather data by providing a bounding analysis of potential /Qs for a specific location and design using ARCON noting that this was submitted as a question during RG 1.249 public comments; (3) stated that there is no public danger from radiological releases during construction; and (4) reiterated the concern that establishing an onsite Met monitoring program is a critical path item. Erwin Prater and Adam Stein also discussed the integration of AERMOD into MACCS. The NRC staff did not discuss these topics further.
The NRC staff discussed the difference between the environmental review vs. the safety review.
Jeffrey Merrifield (Pillsbury Winthrop Shaw Pittman) asked the staff to consider possible categorical exclusions of facilities that dont require Met towers. The NRC staff indicated that categorical exclusions are currently covered under 10 CFR Part 51 for implementing the National Environmental Policy Act (NEPA).
The NRC staff provided some summary comments on the presentations, thanked the presenters and participants, and indicating that the NRC staff is looking forward to receiving NEIs report when more detailed comments would be provided. Three key points or takeaways to recognize from todays meeting: (1) the fundamental difference between offsite Met data used to describe climatological characteristics expected at a given site and offsite Met data proposed for use in dispersion modeling analyses; (2) the need to address the technical differences between NRCs method for classifying atmospheric stability and how it was used in developing the current NRC-approved dispersion models versus other stability classification methods and indicating one such difference between centerline dispersion factors (X/Qs) for short-term averages being 2.5 times higher and directly proportional to dose for G stability compared to F stability; and (3) potential technical and logistical issues that need to be addressed for possible deployments of advanced reactor designs in locations subject to extreme and persistent cold conditions such as in Alaska.
Erwin Prater asked about a copy of Mike Mazaikas slide presentation on cold region Met monitoring and dispersion modeling during the 2023 Regulatory Information Conference (RIC).
He also wonders about the rationale of the changes to the preferred methods of calculating atmospheric stability over the years. The NRC staff provided a link to the video of the
presentation at the 2023 RIC (TH20) and noted that the video presentation begins at 21:46 and runs until about 51:00. The slides from Mr. Mazaikas RIC (TH20) presentation can be accessed in ADAMS at ML25069A620.
Jon Facemire (NEI) thanked Mr. Mazaika for the comments, will review the RIC presentation, and decide if any updates will be made to the NEI report before submittal to the NRC. NEI appreciates the engagement today.
The NRC thanked everyone for their participation and adjourned the meeting.
Enclosure:
- 1. List of Attendees
KQuinlan*
DATE 04/17/2025 04/17/2025
Name Affiliation Name Affiliation Aaron McCraw NRC Jeffrey Merrifield Pillsbury Law Firm Addison Hall Services 6 Michelle Hayes NRC Allen Fetter NRC Mike Mazaika NRC Beth Dalick TerraPower Milton Valentin NRC Billy Gleaves NRC Jill Monahan No affiliation stated Cristina Reid No affiliation stated Nebiyu NRC David Louis Daigle No affiliation stated Nicolas Mertz No affiliation stated Angela Sabet NRC Niko McMurray No affiliation stated Christopher Balbier No affiliation stated Nolan Bartlow No affiliation stated Anthony Torres NRC Paul Guinn NuScale April Rice No affiliation stated Peter Clark No affiliation stated James Ashe No affiliation stated Alex Polonsky No affiliation stated Kati Austgen NEI Emily Portanova No affiliation stated Bryson Roberson No affiliation stated Erwin Prater Sargent and Lundy Josh Coulbeck Enteng Maury Pressburger No affiliation stated Daniel Stout No affiliation stated Kevin Robinson No affiliation stated Darrell Gardner Kairos Sean Gallagher No affiliation stated Deb Luchsinger No affiliation stated James Edward Smiley No affiliation stated Jon Facemire NEI Spencer Toohill No affiliation stated Ashley Harper No affiliation stated Andrea Sterdis No affiliation stated Ryan Donald Henderson No affiliation stated Joseph Stoney No affiliation stated Amy Hsieh DEP Thomas Wood VI No affiliation stated Ingrid Nordby No affiliation stated Timothy Eichler No affiliation stated Jack Giessner NRC Timothy Williamson No affiliation stated Jason White NRC Yoshinori Takechi NRA Japan Jessie Quintero NRC Chihiro Suzuki No affiliation stated Joe Kanney NRC Sarah Lopas NRC Kevin Quinlan NRC Adam Stein Breakthrough Institute Laura Klein No affiliation stated Jenise Thompson NRC Russell Light No affiliation stated James Ashe No affiliation stated Ryan Lighty No affiliation stated Nicole Schlichting No affiliation stated Luis Betancourt NRC Erin Wisler TerraPower Saya Lee No affiliation stated Jill Magnusson NuScale Lisa Matis No affiliation stated Rachel Turney No affiliation stated Julianne McCallum No affiliation stated Tyler Beck NuScale Megan Chambers No affiliation stated Peter Shaw NuScale Lawrence Denney No affiliation stated