ML24298A032
| ML24298A032 | |
| Person / Time | |
|---|---|
| Site: | PROJ0735 |
| Issue date: | 01/15/2025 |
| From: | Chris Mckenney NRC/NMSS/DDUWP/LLWPB |
| To: | |
| Shared Package | |
| ML24296A001 | List: |
| References | |
| Download: ML24298A032 (1) | |
Text
SUMMARY
OF U.S. NUCLEAR REGULATORY COMMISSION AND U.S. DEPARTMENT OF ENERGY VIRTUAL PUBLIC MEETING TO DISCUSS TECHNICAL CLARIFICATION OF NRC REQUEST FOR ADDITIONAL INFORMATION ON IDAHO NATIONAL LAB CALCINE STORAGE FACILITY WIR EVALUATION DATE:
September 10, 2024 ATTENDEES (NRC):
Chris McKenney, Duane White, Cynthia Barr, Louis Caponi, Maurice Heath, Cardelia Maupin ATTENDEES (NRC CONTRACTOR):
Osvaldo Pensado, Stuart Stothoff ATTENDEES (DOE):
Valerie Kimbro, Gregery Balsmeier, David Thorne, Erik Simpson, William Kirby, Rodrigo Lobos, Richard Chang, Arthur Rood, James McCarthy General On October 20, 2023, the Department of Energy (DOE) submitted the Draft Basis for Section 3116 Determination for Closure of the Calcined Solids Storage Facility (CSSF) at the Idaho National Laboratory Site for the NRC to review. The DOE submittal to the NRC is required under Section 3116 (a) of the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA).
On April 8, 2024, NRC issued a Request for Additional Information (RAI) to DOE regarding its Draft Waste Incidental to Reprocessing (WIR) Evaluation for the Closure of the Calcined Solids Storage Facility at the Idaho National Laboratory Site (ML24095A110). The purpose of the public meetings is to discuss DOEs intended responses to the RAIs and provides an opportunity for NRC and DOE to ask clarifying questions. The public meeting outcome establishes a common understanding of the information that is needed for the NRC to complete its review. The RAI public meeting supports NRCs consultation role as defined in Section 3116 of the NDAA.
On September 10, 2024, the NRC held a virtual public meeting with DOE and stakeholders to discuss NRC RAIs on performance assessment screening analysis, corrosion rates, degradation, inadvertent intruder analysis, and site stability. The public meeting was noticed on the NRC public meeting schedule webpage https://www.nrc.gov/pmns/mtg. The public meeting presentation slides are in NRCs Agencywide Documents Access and Management System (ADAMS) - ML24296A001.
Agenda Item 1. Clarification of RAI PA-1 NRC discussed the need for additional information regarding the performance assessment (PA) screening criteria. NRC's concern was that screening analysis were not sufficiently conservative, such that all potentially risk-significant radionuclides were evaluated in the detailed analysis (e.g., engineered and natural system performance assumptions). NRC also sought clarification on the dose threshold chosen by DOE of 4 mrem. DOE indicated that they had typographical errors in the PA that may have led to confusion on the amount of credit being taken for engineered barriers.
2 After further discussion with NRC regarding its concerns, DOE understands the RAI and plans to provide additional supporting analyses to support its selection of radionuclides for detailed modeling or uncertainty/sensitivity analysis for radionuclides that could have been screened in with more conservative assumptions. DOE also stated the basis for the 4 mrem/year screening threshold is provided in the PA, which is the 4 mrem/year dose equivalent in 40 Code of Federal Regulations 141. NRC stated that the drinking water regulations in 40 CFR 141 are based on different internal dosimetry and do not consider all dose pathways similar to the performance objectives in 10 CFR Part 61, Subpart C. Additionally, the 4 mrem limit for each radionuclide could lead to an exceedance of the dose limit if more than 6 radionuclides are screened out at the limit.
Agenda Item 2. Clarification of RAI PA-2 NRC discussed the need for additional information regarding the assumed corrosion rates for stainless-steel bins in its PA. The corrosion rates were based on measurements in benign conditions that are similar to passive corrosion rates and applied for hundreds of thousands to millions of years.
DOE indicated that some of the higher corrosion rate data NRC listed in its RAI from the literature were not representative of the benign service conditions expected with the calcine bin sets at INL. NRC stated that DOE essentially assumed a passive corrosion rate for long periods of time and needed to present information ruling out more aggressive corrosion mechanisms.
The large range in performance of the steel liner assumed in an earlier version versus the current PA, suggests there is significant uncertainty in the performance of the steel liner. Given the uncertainty in PA assumptions regarding natural and engineered system performance over long time frames and potential difficulty providing support for PA assumptions, in some cases uncertainty may need to be managed with conservative assumptions.
DOE understands the RAI and plans to provide additional analyses similar to the one factor at a time analyses in the current version of the PA to address uncertainty in the performance of the steel liners in DOEs PA (see RAI PA-3).
Agenda Item 3. Clarification of RAI PA-3 NRC discussed the need for additional information to address uncertainty in engineered system performance including consideration of alternative scenarios with more aggressive degradation mechanisms and more discrete failure of cementitious and steel liner materials (e.g., presence of preferential pathways and enhanced corrosion leading to more rapid release of radioactivity to the environment).
DOE understands the RAI and plans to provide results of additional alternative scenarios including one factor at a time and multiple factor at a time sensitivity analyses to address comments on the potential for more aggressive corrosion conditions, preferential flow pathways and pulse releases from the engineered system among other technical concerns.
Agenda Item 4. Clarification of RAI PA-5 NRC discussed the need for additional information related to the biosphere parameters and assumptions in the intruder analysis. NRC discussed the need for additional information
3 regarding planned closure activities, removal of infrastructure below ground surface, potential plugging of transfer lines and any plans for validation of inventory in transfer lines, any planned barriers or controls to decrease the risk to inadvertent intruders.
DOE understands the RAI and plans to provide information regarding a comparison of the biosphere parameters used, Tier I and II closure plans, and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) closure plans. Additionally, DOE plans to provide additional data and results related to the inadvertent intruder analysis, intrusion scenarios considered, and more detailed results by exposure pathway and radionuclide.
Agenda Item 5. Clarification of RAI SS-1 NRC discussed the need for additional information regarding the insufficient information for NRC to evaluate the 10 CFR 61.44 performance objective, Stability of the disposal site after closure. NRC is looking for additional information on evaluation of features, events, and processes important to site stability and details on closure and grout filling designs/strategies, including final grade levels.
DOE understands the RAI and plans to provide additional information necessary to evaluate the site stability performance objective in 10 CFR 61.44. DOE also plans to prepare a Tier 1 and Tier 2 closure documentation for the CSSF. The Tier 1 and Tier 2 closure documents will define any bounding parameters of the CSSF closure action. Specific criteria will be developed regarding grout filling designs/strategies.
Conclusions In October 2023, DOE submitted the Draft Basis for Section 3116 Determination for Closure of the Calcined Solids Storage Facility at the Idaho National Laboratory Site for the NRC to review.
In April 2024, NRC issued RAIs to DOE. NRC conducted a virtual public meeting to provide clarification on the RAIs issued to DOE on the Draft Basis for Section 3116 Determination for Closure of the Idaho National Laboratory Calcined Solids Storage Facility. These RAI public meeting supports NRCs consultation role as defined in Section 3116 of the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005.
The meeting provided an opportunity for NRC and DOE to ask clarifying questions and establish a common understanding of the information that is needed for the NRC to complete its review.
DOE responded that the RAI questions were clarified, and DOE believes they have a path forward for responding to theRAIs. DOE, by letter dated June 7, 20024, stated they will respond to NRC RAIs no later than January 30, 2025 (ML24163A018).
ML24296A001; ML24298A032 OFFICE NMSS/DUWP
/LLWPB NMSS/DUWP/RTAB NMSS/DUWP
/RTAB NMSS/DUWP/RTAB NAME MHeath LCaponi CBarr CMcKenney DATE Oct 28, 2024 Dec 31, 2024 Jan 2, 2025 Jan 2, 2025 OFFICE NMSS/DUWP
/LLWPB NAME DWhite DATE Jan 15, 2025