ML23333A134
| ML23333A134 | |
| Person / Time | |
|---|---|
| Site: | 99902071 |
| Issue date: | 12/04/2023 |
| From: | Dukes O Office of Nuclear Reactor Regulation |
| To: | Michael Wentzel Office of Nuclear Reactor Regulation |
| References | |
| Download: ML23333A134 (1) | |
Text
12/04/2023 MEMORANDUM TO:
Michael Wentzel, Chief Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation FROM:
Ondra Dukes, Project Manager /RA/
Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF THE OCTOBER 24, 2023, OBSERVATION MEETING WITH X ENERGY, LLC, TO DISCUSS NRC STAFF QUESTIONS PERTAINING TO X-ENERGYS ATMOSPHERIC DISPERSION AND DOSE CALCULATION TOPICAL REPORT Meeting Information:
Applicant: X Energy, LLC (X-energy)
Project No.(s): 99902071 Public Meeting Notice Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML23284A341 Meeting Attendees: See the enclosure for a list of meeting attendees.
CONTACT:
Ondra Dukes, NRR/DANU 301-415-0537
Meeting Summary:
The U.S. Nuclear Regulatory Commission (NRC) staff conducted the meeting in accordance with NRC Management Directive 3.5, Attendance at NRC Staff-Sponsored Meetings (ADAMS Accession No. ML21180A271). The meetings objective was to discuss NRC staff questions provided to X-energy by email (ML23264A098) pertaining to X-energy's topical report titled Atmospheric Dispersion and Dose Calculation Methodology, Revision 1. Subsequent to the issuance of the NRC staffs questions, X-energy submitted Revision 2 of the TR (ML23268A454). The main points of discussion during the meeting included:
X-energy staff noted that language has been included in Revision 2 of the subject topical report (TR), Atmospheric Dispersion and Dose Calculation Methodology, in Section 1.2, Scope, to clarify that the TR methodology is not intended for environmental analysis.
X-energy explained that they plan to pursue a 10 CFR Part 50 license, but they may decide to also pursue a 10 CFR Part 52 license for the Xe-100 design in the future. In addition, NRC staff noted differences in the dose metrics in the siting requirements for test reactors as compared to power reactors. X-energy stated that they do not plan to pursue licensing the Xe-100 design as a test reactor.
X-energy stated that the withdrawn Regulatory Guides (RG) 1.3 and 1.4 are not used and those RG references have been removed from the TR in Revision 2. NRC staff confirmed the references have been removed.
X-energy staff discussed that the control room habitability dose criterion comes from the X-energy design principal design criterion (PDC) 19 and is assessed for anticipated operational occurrences (AOOs) and design basis events (DBEs), but the control room dose criterion is not assessed for beyond design basis events (BDBEs) or design basis accidents (DBAs).
X-energy explained that while the subject TR is intended to describe how they determine doses, it is not intended to describe how they will assess integrated risk over all licensing basis events. X-energy is developing a risk integration book to calculate cancer fatality.
X-energy explained that the exclusion area boundary (EAB) and outer boundary of the low population zone (LPZ) are at the same distance. X-energy also noted that updates were submitted in Revision 2, Section 4.5, of the TR to clarify that the EAB and the LPZ are the same distance and that there is only one dose calculated for both EAB and LPZ.
The dose is summed over 30 days from the start of the accident.
X-energy noted that there is a TR on principal design criteria for the Xe-100 design, including PDC 19, currently under NRC staff review which covers the control room radiological habitability criterion and the basis for evaluation of AOOs and DBEs for the purpose of demonstrating control room habitability.
X-energy noted that while the XDIS computer code has a model to predict atmospheric dispersion factors (also called chi-over-q values or /Qs), they do not use this capability. X--energy also clarified that by providing dose methodology verification information in the TR they are attempting to show consistency with the RADionuclide Transport and Removal and Dose Estimation (RADTRAD) accident dose analysis code calculation of offsite doses, but they are not requesting approval of the Gaussian plume
/Q model in the XDIS code through the subject TR.
X-energy discussed that they are using the 2-hour /Q to calculate the exclusion area boundary (EAB) dose over 30 days to bound the EAB dose for any 2-hour period over the accident release as in the requirement. X-energy confirmed that they will perform a site-specific dispersion calculation to confirm that it is within the generic calculation. NRC
staff requested explanation for how the doses would be reported to meet 10 CFR 50.34(a) offsite dose requirements for safety analyses and noted that additional verification would be needed. X-energy also confirmed that because the XDIS code does not calculate dose at the EAB for any 2-hour period, the TR Section 7 verification of the XDIS methodology did not include assumptions that would exercise such a capability.
X-energy stated that there is no difference between deterministic and specifically defined deterministic analyses in Sections 4.4 and 4.5 of the TR. X-energy explained their intention to convey that more conservative assumptions will be used for design basis accident (DBA) analysis than will be used for non--DBA analysis.
X-energy clarified that data logging of transient dose in Section 5.2.1.2, Phenomena Modeled by XDIS, refers to calculation of the dose as a function of time. X-energy also clarified that they do not plan to use this function of the XDIS code or the plume model in XDIS for licensing purposes.
X-energy stated that they have corrected the exponents in Section 7, XDIS Dose Methodology Verification in Revision 2 of the TR.
X-energy confirmed that the non-DBA EAB /Q reduction factors are not used for determining site characteristic atmospheric dispersion factors using site-specific meteorological data because determining site characteristics is outside the scope of the TR, which is focused on determination of generic bounding /Qs.
NRC staff expressed concern with X-energys interpretation of Figure 11 in Section 5.1.1.2.1.1, EAB Dispersion Factors Methodology Assumptions as it relates to the development and use of reduction factors in the atmospheric dispersion calculations, and detailed ongoing review of the reference documents. X-energy stated confidence in their interpretation of Figure 11 and noted the TRs commitment to perform site-specific calculations to confirm that the generic atmospheric dispersion factors are conservative.
NRC staff asked X-energy to discuss any other changes that were incorporated in Revision 2 of the subject TR. X-energy confirmed that Revision 2 of the TR only includes clarifications in response to the NRC staff questions provided (ADAMS Accession No. ML23264A098) and updates to proprietary markings. X-energy indicated that they would submit a letter to the NRC to document response to all NRC staff questions provided via ML23264A098.
No regulatory decisions were made during this meeting.
Project No. 99902071
Enclosure:
List of Meeting Attendees cc: X-energy Xe-100 via GovDelivery
SUBJECT:
SUMMARY
OF OCTOBER 24, 2023, OBSERVATION MEETING WITH X ENERGY, LLC, TO DISCUSS NRC STAFF QUESTIONS PERTAINING TO X-ENERGYS ATMOSPHERIC DISPERSION AND DOSE CALCULATION TOPICAL REPORT DATED: DEC 4, 2023 DISTRIBUTION:
PUBLIC RidsNrrDanuUal1 Resource RidsNrrDanuUal2 Resource RidsNrrDanu Resource Greg Oberson Ian Jung Jason Schaperow Michelle Hart Jason White Nebiyu Tiruneh Lance Kingsbury Inseok Baek Nanette Valliere Michael Wentzel Ondra Dukes Adrian Muniz Jorge Hernandez ADAMS Accession Number: ML23333A134 OFFICE NRR/DANU/UAL2/PM NRR/DANU/UAL2/BC NAME Ondra Dukes MWentzel DATE 12/04/2023 12/04/2023 OFFICIAL RECORD COPY
Enclosure LIST OF MEETING ATTENDEES AT THE OCTBER 24, 2023, OBSERVATION MEETINGS WITH X ENERGY, LLC, TO DISCUSS NRC STAFF QUESTIONS PERTAINING TO X-ENERGYS ATMOSPHERIC DISPERSION AND DOSE CALCULATION TOPICAL REPORT October 24, 2023 Name Organization Ondra Dukes U.S. Nuclear Regulatory Commission (NRC)
Adrian Muniz NRC Nebiyu Tiruneh NRC Jason Schaperow NRC Greg Oberson (He/Him)
NRC Jason White NRC Michelle Hart NRC Ian Jung NRC Lance Kingsbury NRC Inseok Baek NRC Nanette Valliere NRC Maggie Staiger X-energy Jessica Maddocks X-energy Brian Froese X-energy Travis Chapman X-energy Herman van Antwerpen X-energy Patrick X-energy Stephan C. Moen Energy-Northwest Hovhannes Hovhannisyan Holtec Devshibhai Ziyad Holtec Carl Friesen U.S. Department of Energy David Yarwood U.S. Department of Energy Mark Natale U.S. Department of Energy Timothy Stuhldreher U.S. Department of Energy Daniel Strohmeyer MPR Associates Neil Haggerty Member of the public Dominik Muszynski Member of the public