ML23102A005
ML23102A005 | |
Person / Time | |
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Issue date: | 04/14/2023 |
From: | Kimberly Webber NRC/RES/DSA |
To: | Mike Franovich NRC/NRR/DRA |
Shared Package | |
ML23097A085 | List: |
References | |
Download: ML23102A005 (3) | |
Text
MEMORANDUM TO:
Michael X. Franovich, Director Division of Risk Assessment Office of Nuclear Reactor Regulation FROM:
Kimberly A. Webber, Director Division of Systems Analysis Office of Nuclear Regulatory Research
SUBJECT:
COMPLETION OF HIGH BURNUP FUEL ACCIDENT SOURCE TERM ANALYSIS AND PEER REVIEW In response to Nuclear Reactor Regulation (NRR) User Need 2021-016, Regulatory Research Supporting Licensing of Burnup and Enrichment Extensions in Near-Term Accident Tolerant Fuel (ATF) (ML21145A177), and the planned work discussed in the memorandum Applicability of Source Term for Accident Tolerant Fuel, High Burnup and Extended Enrichment (ML20216G376), the Office of Nuclear Regulatory Research staff (RES) completed an updated in-containment source term analysis for High Burnup/High-Assay Low Enriched Uranium fuel (HBU/HALEU). Staff contracted with Sandia National Laboratories (SNL) to perform MELCOR calculations to extend the NUREG - 1465 alternative source term to address light-water reactors (LWRs) with cores with HBU fuel and different enrichments. The results of the analyses are documented in SAND2023-01313 (ML23097A087). Energy Research, Inc.
(ERI) organized an independent panel of internationally recognized technical experts to peer review the SAND2023-01313 report. The conclusions of the panel are provided in ERI/NRC 23-201 (ML23097A086). These reports are attached to this memo and highlights from the reports are provided below.
MELCOR Source Term Calculations Report (SAND2023-01313; ML23097A087):
This report provides details of MELCOR calculations and source term recommendations for higher fuel burnups with increased enrichment. Representative radiological releases to containment were evaluated with fuel burnups of 60 and 80 GWd/MTU with fuel enrichments of 5% and 8% (peak of 10% for BWR fuel). The MELCOR analyses have found no appreciable change in the fraction of initial core radionuclide inventory released to the containment across the range of burnups and enrichments considered. However, given enhancements to MELCOR developed during the State-of-the Art Reactor Consequence Analyses (SOARCA) uncertainty project, as well as post-9/11, and post-Fukushima regulatory studies, the release of volatile radionuclides (e.g., the halogens) to containment is higher than previously evaluated in NUREG-1465 and SAND2011-0128, Accident Source Terms for Light Water Nuclear Power Plants Using High-Burnup of MOX Fuel (ML20093F003).
CONTACT: Shawn Campbell, RES/DSA (301) 415-0244 April 14, 2023 Signed by Webber, Kimberly on 04/14/23
M. Franovich The larger early releases to the containment are a result of early primary pressure boundary failure. Releases to the containment are significantly reduced if the pressure boundary remains intact.
Source Term Peer Review Report (ERI/NRC 23-201; ML23097A086):
This report provides a summary of the views of the peer review panel to establish if the overall analysis approach, and the specific applications of MELCOR calculations to development of in-containment source term, were technically adequate.
The peer review panel endorsed the approach in SAND2023-01313 and considered the study a significant technical improvement to the SAND2011-0128 source term characterization, building upon comprehensive and peer reviewed SOARCA and post-Fukushima Daiichi studies. The peer review panel did not identify any specific technical errors in the assumptions and interpretation of the analysis results leading to the proposed in-containment source terms documented in the SNL report. They also found that the analysis provides an appropriate technical basis for the fuel pellet/cladding gap and early in-vessel phases used in the in-containment source terms to account for the effects of higher levels of burnup and enrichment.
ML23097A085; Memo ML23102A005 OFFICE RES/DSA/FSCB RES/DSA/FSCB RES/DSA NAME SCampbell HEsmaili KWebber DATE Apr 12, 2023 Apr 12, 2023 Apr 14, 2023