Lead Investigators: Kevin G. Brown, Chen Gruber (Vanderbilt University), Jiannan (Nick) Chen (University of Central Florida), David S. Kosson (Vanderbilt University)

Additional Investigators: Andy C. Garrabrants (Vanderbilt University), Hans Meeussen (Nuclear Research and Consultancy Group, Energy Research Centre of The Netherlands), and Hans van der Sloot (Hans van der Sloot Consultancy, The Netherlands)

Project Objectives
The goal of this project is to perform integrated experimental and modeling studies in support of waste tank and vault closure at the Hanford Site (DOE-ORP). These studies will support risk-informed tank waste retrieval at DOE-ORP by improving the evaluation basis for the performance of concrete barriers (tanks and vaults) after closure that contain residual wastes. Specific tasks include:

• use LeachXS/ORCHESTRA (LXO) reactive transport models (verified and validated as indicated above) as parameterized for residual waste leaching from closed and grouted waste tanks to assess impacts of aging (carbonation and oxidation), degradation (cracking), etc.
• evaluate the data obtained from the PNNL characterization of existing tank 241-A-106 concrete sidewall cores for alkalinity; carbonation/pH (e.g., phenolphthalein); liquid-solid partitioning (USEPA Method 1313; and mass transport (USEPA Method 1315). CRESP researchers completed a review on the PNNL test plan in July 2022.

• complete verification and validation (V&V) and documentation for the following reactive transport (LeachXS/ORCHESTRA) models: 1) carbonation ingress and reaction in waste tank shell (i.e., dome, walls, and basemat); and 2) solid-solid interface model (e.g., cementitious waste form in contact with either barrier or surrounding backfill).
• perform “inverse PA modeling” to evaluate the relationship between the amount of residual waste in the tanks, conditions in and around the tanks, and potential contaminant releases to the environment to assess and estimate the maximum allowable tank residuals to meet performance objectives for Hanford Site waste tanks under closure scenarios.

Significance/Impact:
This research will improve the characterization of uncertainties and allow resulting reductions in conservatisms in contaminant release and near-field transport predictions from Hanford Site waste tanks after closure (including tank integrity as an additional defense-in-depth barrier). The research will be complemented by the DOE NNLEMS Developing a Hanford Grout Modeling Framework and Property Database for Performance Assessments project to provide a transformational change in reducing unnecessary conservatism in PA modeling of grout and improve the representativeness of grout behavior in long-term predictions. The information obtained will be used to parameterize the models used. “Inverse PA modeling” will provide defensible estimates of maximum allowable tank waste residuals to satisfy risk-based closure objectives (technical basis only) and to support risk-informed decision-making under uncertainty.

Public Benefits:
Models developed for this research will be used to better understand cement and concrete performance of buried structures for a range of non-DOE applications. Collaboration with the PNNL-led NNLEMS Project: Developing a Hanford Grout Modeling Framework and Property Database for PAs will generate a centralized property database curated for general use in future Machine Learning grout model development.

References: (* indicates CRESP publication)

*Gruber, C, Kosson, D, Brown, KG, DeLapp, R, Matteo, E, Meeussen, J, Klein-BenDavid, O, Bar-Nes, G, Brown, L, Ayers, J, Taylor, A, Chven, M & Pyrak-Nolte, L 2023, ‘Characterization and Simulation of Cement–Rock Interface Long-Term Performance’, WM’2023, WMSymposia, Phoenix AZ, Feb 26-Mar 3.

*Gruber, C, Steen, M, Brown, KG, DeLapp, R, Taylor, R, Ayers, J, Kosson, DS, Matteo, E, Klein-BenDavid, O, Bar-Nes, G, Meeussen, JCL, 2022, ‘Cement-carbonate rock interaction under saturated conditions: from laboratory to modelling,’ Cement and Concrete Research, Volume 160, October 2022, 106899. https://doi.org/10.1016/j.cemconres.2022.106899

*Gruber, C, Brown, KG, Garrabrants, AC, Meeussen, JCL, van der Sloot, HA & Kosson, DS 2020 ‘Modeling Interfaces to Support Low-Level Waste Disposal System Performance Assessments – 20366’, WM Symposia 2020, Phoenix, AZ, March 8-12, 2020.

*Brown, KG, Garrabrants, AC & Kosson, DS 2020 ‘Predicting Saturated Hydraulic Conductivity over Time for Degrading Saltstone Vault Concrete – 20376’, WM Symposia 2020, Phoenix, AZ, March 8-12, 2020.

Klein-BenDavid, O, Harlavan, Y, Levkov, I, Teutsch, N, Brown, KG, Gruber, C & Ganor, J 2019, ‘Interaction between spent fuel components and carbonate rocks,’ Science of the Total Environment, 689(2019), 469-480. https://doi.org/10.1016/j.scitotenv.2019.06.396.

*Gruber, C, Steen, M, Brown, KG, DeLapp, R, Matteo, EN, Klein-BenDavid, O, Bar-Nes, G, Meeussen, JCL, Ayers, J & Kosson, DS 2019, ‘Cementitious Materials Aging in Carbonate-Rock/Cement-Paste Interfaces with Implications for Deep Geological Disposal Sites’, Mechanisms and Modelling of Waste / Cement Interactions 2019, Karlsruhe, Germany, March 25-27, 2019.

*Garrabrants, AC, Brown, L, Zhang, P, van der Sloot, HA, Brown, KG, Gruber, C & Kosson, DS 2019, ‘Experimental and modeling efforts to predict long-term geochemistry of vault concrete – salt waste interfaces at U.S. DOE disposal sites’, International Workshop on Mechanisms and Modeling of Waste/Cement Interactions 2019. Karlsruhe, Germany.

ASME NQA-1-2015. 2015. Quality Assurance Requirements for Nuclear Facility Applications. New York, NY: American Society of Mechanical Engineers.

DOE Order 414.1D, Quality Assurance. Available at: https://www.directives.doe.gov/directives-documents/400-series/0414.1-BOrder-d (17 September 2015).

Rast, RS 2011, ‘Analytical Test Plan for the Removed 241-C-107 Dome Concrete and Rebar,’ RPP-PLAN-48753, Rev. 0, Washington River Protection Solutions, Richland, Washington.