ML25353A565
| ML25353A565 | |
| Person / Time | |
|---|---|
| Site: | 99902130 |
| Issue date: | 01/23/2026 |
| From: | NRC/NRR/DANU/UAL2 |
| To: | |
| Shared Package | |
| ML25353A521 | List: |
| References | |
| EPID L-2025-LRM-0111 | |
| Download: ML25353A565 (0) | |
Text
OFFICIAL USE ONLY SECURITY RELATED INFORMATION OFFICIAL USE ONLY - SECURITY RELATED INFORMATION ENERGY NORTHWEST NEW NUCLEAR, LLC. - U.S. NUCLEAR REGULATORY COMMISSION STAFFS FEEDBACK REGARDING THE WHITE PAPER TITLED ACCEPTABILITY OF HISTORICAL INFORMATION - FLOODING (EPID: L-2025-LRM-0111)
SPONSOR INFORMATION Sponsor:
Energy Northwest New Nuclear, LLC.
Sponsor Address:
345 Hills Street Richland, WA 99352 Docket/Project No.:
99902130 DOCUMENT INFORMATION Submittal Date: July 30, 2025 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No.: ML25211A360 Purpose of the white paper: Energy Northwest New Nuclear, LLC. (ENNN) stated that the purpose of this white paper (WP) is to provide ENNNs evaluation of the acceptability of using existing 2016 post-Fukushima flooding hazard reevaluations for the Columbia Generating Station (Columbia) (Reference 1), which were accepted by the NRC (Reference 2) in 2018, satisfying the requirements for assessing flooding hazards in the ENNNs Construction Permit Application (CPA).
Action Requested: ENNN requested that the U.S. Nuclear Regulatory Commission (NRC) staff provide feedback pertaining to the information discussed in the WP titled: Acceptability of Historical Information - Flooding (Document XO125-012). Specifically, ENNN is requesting feedback on ENNNs evaluation of the acceptability of applying the historical information from Columbias post-Fukushima flooding hazard reevaluations to the flooding evaluations necessary for the proposed ENNN project license application.
OFFICIAL USE ONLY SECURITY RELATED INFORMATION OFFICIAL USE ONLY - SECURITY RELATED INFORMATION FEEDBACK AND OBSERVATIONS Note: (( )) denotes security related information.
Introduction:
The NRC staff reviewed ENNNs letter, dated July 30, 2025, titled Acceptability of Historical Information - Flooding, (ML25211A360). The WP, with enclosures, outlines ENNNs process for determining the acceptability of historical information to characterize flooding hazards for its proposed site, which will host up to 12 Xe-100 small modular reactors adjacent to the Columbia Generating Station.
Specifically, ENNN evaluated whether the 2016 post-Fukushima Flooding Hazard Reevaluation Report (FHRR) for Columbia remains applicable to the proposed site. The proposed ENNN site is approximately 1.1 miles east of the Columbia site, toward the Columbia River, and at a higher elevation than the Columbia site. Site elevations range from 455.4 to 470.4 feet NAVD 88 -
about 11 to 26 feet higher than Columbias grade elevation. ENNN concluded that, except for local intense precipitation (LIP) flooding, the 2016 FHRR can serve as the flooding hazard basis for the new site CPA. ENNN stated that the LIP flooding mechanism will require a site-specific evaluation due to elevation, grading, and drainage differences at the proposed location.
The 2016 Columbia flooding reevaluation was conducted in response to the 2011 Fukushima Dai-Ichi accident and addressed multiple flooding mechanisms, including: LIP and site drainage, flooding in streams and rivers, dam failures, storm surge and wind-wave activity, seiche, tsunami, ice-induced flooding, channel migration/diversion, and combined effects (including wind-wave run-up). The 2016 Columbia FHRR concluded that the Columbia site would remain dry during all applicable flooding events with substantial margin, except for LIP. The NRC staff reviewed and approved the FHRR in 2018.
Applicability of Historical Data:
ENNN evaluated the applicability of each flood estimate presented in the 2016 FHRR analysis to the new site using six criteria:
- 1. Regulatory changes
- 2. Analysis methodology
- 3. Scope of analysis
- 4. Site changes
- 5. Quality assurance
- 6. Copy of record A yes response for each criterion confirmed that the 2016 FHRR analysis remains applicable.
For criteria where the response was no, but justified, ENNN provided technical bases supporting the use of the historical analysis despite differences. Based on the evaluation of each flood mechanisms, ENNN concluded that the 2016 FHRR flooding evaluations remain valid for the proposed site, with the exception of LIP flooding, which requires a site-specific analysis to determine the maximum water surface elevations for the proposed site.
OFFICIAL USE ONLY SECURITY RELATED INFORMATION OFFICIAL USE ONLY - SECURITY RELATED INFORMATION REFERENCES
- 1. Columbia Generating Station, Docket No. 50397 Flooding Hazard Reevaluation Report, Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident. October 6, 2016, ML16286A309.
- 2. Columbia Generating Station - Staff Assessment of Response to 10 CFR 50.54(f)
Information Request - Flood-Causing Mechanism Reevaluation (CAC No. MF8455, EPID NO. 000495/05000397/L-2016-JLD-0010). February 21, 2018, ML18051A401.
Principal Contributors: Hosung Ahn (NRR/DEX/EXHB)
Nebiyu Tiruneh (NRR/DEX/EXHB)