ML25267A014
| ML25267A014 | |
| Person / Time | |
|---|---|
| Issue date: | 09/25/2025 |
| From: | Sean Meighan NRC/NRR/DRA/ARCB |
| To: | |
| References | |
| EPID L-2025-LRM-0108 | |
| Download: ML25267A014 (1) | |
Text
U.S. NRC Staff Presentation - Items to Improve the Efficiency and Effectiveness of Accident Dose Consequence Analysis in License Amendment Request Safety Evaluations Pre-Submittal Meeting Regarding a Proposed LAR for Increased Enrichment and Burnup September 25, 2025 Sean Meighan Radiation Protection and Consequence Branch Division of Risk Assessment Office of Nuclear Reactor Regulation
Introduction Disclaimer: NRC staff statements at the meeting should not be interpreted as new or revised NRC positions that would result in backfitting, forward fitting, or affect issue finality. The NRC staff may provide guidance, identify NRC requirements, or provide information for consideration. The licensee, sponsor, or applicant is not required to consider NRC comments made during the meeting. The NRC staff will evaluate an application against NRC regulations if it is submitted to the NRC for review.
Items identified in the following slides would be helpful for the staffs review but are not required to be part of the license amendment request. If included, the items discussed in this presentation would support the efficiency and effectiveness of the NRCs review.
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Values Table The NRC staff found it helpful to perform a review when the applicants provide a values table, which lists all initial conditions, inputs, and assumptions for each of the design basis accidents (DBAs).
- A useful example of a values table, can be found in Attachment 11 of the Vogtle AST LAR (ML22181B066). Note that 3 categories/columns comprise the table.
o Value in the License Amendment Request (LAR) o The Current Licensing Basis (CLB) value o Change/no change column If there is a change from CLB, describe the change.
If there is a change to the last docketed calculation (LDC) under 50.59, describe the change.
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Values Table Example
- This is an example of a section of a values table and is not prescriptive of inputs/assumptions to be included in the amendment request.
Control Room Leakage, Source Term, and Dispersion
- Identify if there is a change from the CLB in assumed unfiltered in-leakage to the control room (or more specifically, the last docketed calculation (*LDC)).
- If so, will the licensee provide tracer gas tests? (The last 3 tests would be best for trending if assumed value is near the TS limit).
- Identify if licensee is developing a new source term.
- If so, will the licensee be using ORIGEN?
- Identify if the atmospheric dispersion coefficients (/Qs) will be revised.
- If so, will the ARCON data supporting the change be submitted with the LAR?
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- NOTE: LDC denotes that the NRC staff has reviewed this change, which was submitted on the docket, it is in ADAMS and was most likely reviewed during a past LAR.
CLB may include changes made under 50.59 and may include changes that the NRC staff has not reviewed.
DBA Path, DBA Precedent, and Other Calculation Files Will the application include doses contributions for each DBA broken down by pathway? (e.g., containment, ESF, shine, etc.)
Will the licensee provide information on the most recent LAR that revised the dose analysis for any of the submitted DBA(s)?
Will the LAR include Microshield dose assessment results? If so, will the licensee provide the associated Microshield files?
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RADTRAD RADTRAD use is not required but if it is used the staff finds it helpful when the applicant
- provides decks (*.psf or *.med with supporting files)
- output files
- Ensure that TSC is included if applicable Which version of RADTRAD is licensee using?
Will licensee provide the RADTRAD output file (*.pdf) attached to end of LAR?
Will licensee provide the following statement in the proposed LAR (or something similar)?
Unless otherwise noted below, initial conditions, inputs, and assumptions used for the analysis remain the same as provided in the current UFSAR Chapter (15) and/or in previously submitted DBA analysis of record. (this should go just before the Values Table described above) inclusion of this statement allows us to focus on the initial conditions, inputs, and assumptions that have changed from CLB.
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Margins and Defense-in-Depth Will the licensee provide a tabulation/treatment of key safety margins (e.g., unfiltered control room leakage, containment leakage, ESF leakage)?
Will the licensee provide a tabulation/treatment of major contributors to defense in depth, diversity, and redundancy (e.g., assuming additional failure outside of single failure, modeling only 2 MSLs (deposition and holdup), assuming additional passive failures)?
This information is helpful to the staff because it can be used as a basis to make risk-informed regulatory findings.
Will the licensee address the other design basis accidents (DBAs)?
Those DBAs that were affected by the change in the LAR but did not trip the more than minimal increase in dose and can be addressed in 50.59 space.
In the past, staff have inquired about DBAs that did not meet the amendment threshold in a 50.59 screening in audits and/or RAIs. It is helpful to the staff when licensees address this question in their applications.
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Use of Alternative Technical Approaches Licensees may propose alternative technical approaches for NRC staff review, provided those approaches offer an acceptable method for meeting regulatory requirements, even if they differ from those outlined in approved Regulatory Guides 9
Conclusion
- The NRC staff is not making any regulatory decisions at todays meeting.
- Consistent with NRC policy as described in NRR Office Instruction LIC-101, once the proposed license amendment request is received, the NRC staff will conduct its review to determine whether there is reasonable assurance that regulatory requirements will be met. All regulatory decisions will be documented in writing and made in accordance with the established review schedule.
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