CRESP performs research, strategic assessment and reviews with the goal of developing tools and techniques that enhance the performance and safety of engineered and institutional features of:

• Waste treatment
• Containment
• Tank waste closure
• Storage and land disposal systems for disposition of radioactive waste, used nuclear fuel and special nuclear materials
• Land disposal systems

Projects focus on the disposition of radioactive wastes, used nuclear fuel and special nuclear materials.

Lead Researchers

David Kosson, CRESP Principal Investigator, Vanderbilt University
Kevin Brown, Vanderbilt University
Andrew C. Garrabrants, Vanderbilt University
Martha Grover, Georgia Institute of Technology
Kimberly L. Jones, Howard University
Steven L. Krahn, Vanderbilt University
Florence Sanchez, Vanderbilt University
Kathryn Higley, Oregon State University
Hans Meeussen, Nuclear Research and Consultancy Group (NRG)
Ronald W. Rousseau, Georgia Institute of Technology
Paul Seignette, Consultant
Hans van der Sloot, Consultant
Jane Stewart, NYU
Richard Stewart, NYU

EM Sites Impacted

• Hanford Site
• Savannah River Site
• Idaho Site
• Paducah and Portsmouth Sites

Highlighted Projects

Cementitious Barrier Partnership (CBP)

LEAF – Leaching Environmental Assessment Framework

Current Project Areas

Reducing Uncertainty in Tank Integrity and Performance Under Closure

Project Objectives
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 performance of concrete barriers (tanks and vaults) after closure that contain residual wastes. Specific tasks include:

• 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 (e., dome, walls, and basemat); 2) dual regime column model (laboratory and field conditions), including calibration methodology using bromide tracer test; 3) percolation with radial diffusion to evaluate (cracked) grout within the closed waste tank; and 4) solid-solid interface model (e.g., cementitious waste form in contact with either barrier or surrounding backfill).
• Complete review of regulatory flexibility considerations and technical performance requirements and objectives for the waste tank closure scenario at the Hanford Site, including the intersection, confluence, and potential impacts of the tank closure performance assessments, Tri-Party Agreement (TPA), Waste Acceptance Criteria (WAC), Resource Conservation and Recovery Act (RCRA), etc.;
• 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.;
• 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; and
• Characterize (experimentally) existing tank concrete sidewall cores (to be provided by DOE-ORP or WRPS) for alkalinity; carbonation/pH (g., phenolphthalein); liquid-solid partitioning (USEPA Method 1313; and mass transport (USEPA Method 1315).

Relevance and Impact to DOE:
This research will improve 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 a barrier). “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.

EM Sites Impacted

• Hanford Site
• Savannah River Site

Hanford Tank Waste Treatment: Providing Foundations for Tank Waste Treatment and Disposition Planning

Project Objectives
Evaluate Hanford Site tank waste technical information and analyze legal and regulatory requirements to ensure a complete and accurate understanding of the pertinent facts and constraints to support future decision making associated with the disposition of Hanford Site tank wastes. Develop technical and financial decision tools to support DOE decision making. Specific tasks include:

• Tank Waste Inventory and Uncertainty Analysis (scoping) – review pertinent uncertainties (g., BBI, release, near-field transport) to expand the Hanford Site tank-by-tank inventory analysis and develop an initial Hanford tank stabilization list; to be documented in a scoping white paper in CY 2022;
• Tank Waste Inventory and Uncertainty Analysis (detailed) – review and quantify relevant uncertainties in sufficient detail to 1) inform a detailed Hanford tank-by-tank analysis and detailed Hanford tank stabilization list to support contracting approach (documented in detailed white papers before 30 September 2021) and 2) support “reverse PA” analyses (see below);
• Regulatory Flexibility Evaluation – review and summarize current and historical safety, legal, regulatory, and policy requirements and current and planned facility capabilities, including the potential impacts of Land Disposal Restrictions (LDR) on potential disposal of grouted reprocessing waste from the Hanford Site. Consideration will include regulatory flexibility and precedents from other regional and national cleanup and waste management decisions under RCRA. A summary of the factors that may impact LDR will be provided and CRESP will work with the DOE EM-4.2 HLW Team to determine the specific deliverable on LDR that would be most beneficial to the federal government; and
• Identify potential waste disposition scenario options for planning analysis.

The options evaluated for planning analysis will be defined based on input from a range of stakeholders including DOE-ORP, DOE-EM, State of Washington, EPA, etc. These options will be useful in understanding the implications of changes in key requirements if they were to occur. As indicated above, a Hanford Site tank waste stabilization priority list (ranked from easiest to most difficult) will be developed based on the options evaluated, including prioritization based on technical and regulatory challenges (e.g., bismuth phosphate wastes). As indicated above, a scoping study documented in a white paper will be completed followed by a more detailed white paper.

Relevance and Impact to DOE
The confluence of the (i) lengthy history of tank waste generation and tank waste processing campaigns, (ii) complex set of technical, legal, and policy components and decisions associated with the tank wastes, (iii) changes in Hanford Site mission requirements and clean-up strategies, (iv) impending losses in institutional memory due the aging workforce with direct tank waste experience, and (v) changes in DOE-EM leadership and DOE-ORP responsible personnel, has created challenges in communicating fact-based information and situational awareness to support effective ORP decision making. Furthermore, key information is distributed among a large number of documents that are not readily accessible in useable forms for management-level assessment and decisions. This work is a critical component of effective long-term planning and strategic decision making by DOE-EM and ORP.

EM Sites Impacted

• Hanford Site
• Savannah River Site

Leaching Assessment for Improving Performance Assessment of Glass and Cementitious Wasteforms during Near-surface Disposal

Project Objectives
To develop generalized guidance on the use of leaching tests and leaching assessment frameworks to improve the accuracy and transparency of the evaluation of wasteforms (e.g., Cast Stone and ILAW glass for the Hanford Site and saltstone for the Savannah River Site) and cementitious barriers for US DOE Near-Surface Disposal (e.g., Hanford Site Integrated Disposal Facility (IDF) and Savannah River Site Saltstone Disposal Facility (SDF), including the Saltstone Disposal Units (SDUs)). Specific task objectives include:

• Use EPA Methods 1313 and 1315 for leaching assessment of Hanford ILAW glass in collaboration with PNNL and University of Sheffield (England). Test additional selected Hanford ILAW glasses using appropriate US EPA LEAF methods to provide leaching information relevant to relevant disposal conditions (e.g., IDF) and to provide a defensible basis to estimate vitrified waste leaching rates under anticipated field disposal conditions;
• Evaluate corrosion of “ancient” glasses ( 500 to 3,000 years old) present in the Timna Valley, Negev Desert (Israel) and Jordan Valley in collaboration with PNNL, Tel Aviv University, and U. of Sheffield. The glasses proposed for evaluation were the byproduct of ancient copper production and were disposed under conditions analogous and relevant to planned ILAW glass at Hanford. Samples carefully dated to time of production and with detailed documentation of disposal conditions and climate are readily available from archeological studies at Tel Aviv University. Glass corrosion layers and rates will be characterized and compared to results from corrosion and leaching testing of laboratory glass formulations using the same compositions as the ancient glasses;
• Use geochemical speciation and reactive transport simulation framework developed to evaluate the impacts of aging, water relative saturation, carbonation rate, and oxidation rate on leaching performance to estimate long-term release of key waste constituents (e.g., Tc-99, I-129, nitrate/nitrite, chromium) from grouted wasteforms under realistic field conditions for Hanford and Savannah River Site Near-field Disposal facilities (IDF and SDF, respectively);
• Provide support for the maintenance of the Hanford Integrated Disposal Facility (IDF) Performance Assessment (PA), including addressing bounding and highly conservative assumptions made and their potential orders-of-magnitude impacts on predicted performance;
• Develop and evaluate methods for immobilization using grout and encapsulation of mercury (Hg⁰, Hg²⁺) contained in waste. Testing and evaluation will be done using both traditional testing (e.g., TCLP and SPLP) and the USEPA Leaching Evaluation Assessment Framework (LEAF). This research will provide data and models consistent with the DOE PA approach for low activity waste disposal;
• If requested, provide material leaching research to support PAs reviewed by LFRG and evaluate additional proposed LAW wasteform formulations (e.g., new high-performance grouts, advanced glass formulations);
• Develop a general guidance document describing the use of leaching tests and leaching assessment frameworks to more accurately and transparently evaluate wasteforms and barriers for US DOE Near- Surface Disposal facilities;
• Test and evaluate performance of grout to retain key radionuclides from bismuth phosphate waste; and
• Perform molecular simulation for parameter estimation of contaminant (e.g., Tc, I, Hg) retention in cement systems.

Relevance and Impact to DOE
Performance Assessments show that wasteforms and engineered barriers are needed to limit radionuclide release from nuclear facilities, especially Near-Surface Disposal facilities. Guidance is needed to describe the use of leaching tests and leaching assessment frameworks for the evaluation of wasteforms and barriers. This project will provide data, long-term performance simulations, and guidance describing how leaching tests and leaching assessment frameworks can be used to provide more realistic, reliable, and transparent evaluation of wasteforms and engineered barriers for Near-Surface Disposal facilities. Tools and data will also be provided as bases for incorporation of realistic wasteform retention assumptions (without orders-of-magnitude conservatism) into performance assessments to support regulatory decisions.

EM Sites Impacted

• Hanford Site
• Savannah River Site

On-Line Methods for Monitoring Tank Waste Processing

Project Objectives

• Develop on-line monitoring approaches (IR and Raman spectroscopy, modeling) to track nuclear waste composition for applications at the Hanford LAW Vitrification Facility, as part of the Real Time In-Line Monitoring (RTIM) initiative led by SRNL.
• Combine existing knowledge of on-line monitoring with proposed mass-balance modeling and offline sampling to produce fault detection methodologies.
• Investigate the solution chemistry of the slurries inside the melter feed preparation vessel (MFPV).
• Understand the partitioning of sodium in solid and aqueous phases when waste is mixed with the glass forming chemicals (GFCs).
• Incorporate spectral data in kinetic modeling of Savannah River Site processes, in collaboration with Dan Lambert from SRNL.

Relevance and Impact to DOE
It is important to assess the feasibility of using in situ ATR-FTIR and/or Raman spectroscopy for monitoring the composition of nuclear waste. The methodology has the potential to reduce the number of samples that must be drawn for off-line analysis in the vitrification plant, thereby reducing the need for time-consuming and dangerous sample analysis. The turn-around time for analysis is suitable for the Hanford Direct Feed Low-Activity Waste (DFLAW) Real Time In-Line Monitoring (RTIM) initiative. The integration of the use of spectral data with kinetic models will improve the understanding of redox reactions at SRS and minimize offline data collection.

The planned remediation of the waste at Hanford includes mixing the low activity waste (LAW) with glass forming chemicals (GFCs), followed by vitrification to immobilize the waste as borosilicate glass. The GFC addition is optimized according to the conditions of the incoming waste stream. Therefore, it is crucial to understand the solution chemistry of the slurries inside the melter feed preparation vessel (MFPV) where the liquid simulants are mixed with several solid GFC mixtures.

EM Sites Impacted

• Hanford Site
• Savannah River Site

Nuclear Safety and Waste Processing Facilities

Objectives

• Participate in and evaluate continuing DOE safety management initiatives and understand their impact on the safety and effectiveness of nuclear waste processing activities;
• Develop and maintain understanding of the relationships between DOE safety initiatives and issues, behaviors, and trends at nuclear facilities;
• Compare and contrast DOE experience in management of safety and its impact on facility effectiveness with that of commercial nuclear and other high hazard industries;
• Assist DOE in the evaluation of enhancements to risk management tools, such as the ability to make enhanced use of quantitative risk assessment (QRA)/probabilistic risk assessment (PRA), full use of the insights available in DOE risk/hazards assessments, along with use of insights from DOE programs such as the Occurrence Reporting, Contractor Assurance System (CAS), technology readiness assessment (TRA), and apply them to providing risk-informed insights to management of DOE-EM hazardous operations; and
• Based on the above, develop recommended enhancements (performance measures, potential metrics, improved processes) for use in monitoring the safety and effective operation of nuclear waste processing and nuclear fuel cycle

Significance/Impact to DOE
DOE-EM operates a suite of nuclear chemical processing facilities, including: two plants for processing depleted uranium hexafluoride (UF6) at Portsmouth, Ohio and Paducah, Kentucky; the ARP/MCU, the Defense Waste Processing Facility (DWPF), and Salt Waste Processing Facility (SWPF) & the Saltstone Disposal Facility (SDF) at the Savannah River Site (SRS). The Integrated Waste Treatment Unit (IWTU) at the Idaho National Laboratory (INL) is undergoing commissioning and is scheduled to join these plants in the near future. Further, several new facilities for processing low-activity waste (LAW) from the HLW tanks at Hanford are presently being designed. These facilities share the fact that all perform complex nuclear/chemical processes. For this class of facilities, DOE stands at the intersection of two major industries: the nuclear industry and the chemical processing industry—each with their characteristic approach to safety management and ensuring effective plant operations and each involving the use and processing of highly hazardous materials.

EM Sites Impacted

• Hanford Site
• Idaho Site
• Paducah and Portsmouth Sites
• Savannah River Site

Filtration of High Level Wastes

Project Objectives
The overall objective of this study is to evaluate the potential for using advanced filtration techniques to remove organic constituents from tank waste and to understand the fouling mechanisms of tank waste in a cross-flow filtration system and to develop a simulation model to better predict fouling behaviors and provide fouling control strategies.

• Examine effects of operating parameters on long –term membrane fouling performance during high-level tank waste filtration. Typical operating parameters on long-term fouling and flux decline (crossflow velocity, operating pressure, filtration time) will be investigated. Develop appropriate parameters for a predictive fouling simulation model.

• Develop appropriate fouling management and cleaning strategies for the filtration process that would reduce fouling and increase overall process efficiency.
• Evaluate fouling performance at Hanford and Savannah River and determine optimal operating parameters to minimize fouling.
• Develop an overall fouling reduction plan for crossflow filtration of tank wastes.

Significance/Impact to DOE
Tank waste treatment is a high priority and on-going challenge at both Hanford and Savannah River Sites. Management of organic constituents in tank waste and secondary wastes is central to effective and regulatory compliant use of potential grout treatment options for certain waste fractions. In contrast, vitrification is a critical treatment process for the immobilization of radioactive wastes and eliminates organic constituents through oxidation from the primary wastes to be treated. However, both sites rely on microfiltration membranes to concentrate solids, and the potential exists for use of membrane technology for separation of organic constituents. Therefore, there is a critical need to develop the best suitable solid-liquid and organic constituent separation methods that can be directly used in both sites. Crossflow filtration, specifically microfiltration is one of the principal separation technologies that have been proved to be an effective method to dewater waste by previous work at PNNL (Daniel et al., 2010). However, due to the unique properties of tanks wastes (i.e., high solid content, high pH, and high ionic strength), persistent membrane fouling hinders the treatment process. In addition, the proposed Low Activity Waste Pretreatment System (LAWPS) poses the potential to have significant depth fouling, which is not well understood at this time. Prior studies at the Hanford and Savannah River Sites indicate that typical fouling mechanisms and conventional wisdom involved in planning and operating crossflow membrane systems may not apply to the unique feed streams from high-level waste tanks. When challenged with a synthetic feed, the membrane performance continued to decay at long timeframes and did not reach steady-state. To address this issue and attempt to explain fouling behavior, a new model was proposed to more reasonably match theory and experimental results (Schonewillet al., 2015). Further efforts are needed to determine the mechanistic causes of this behavior in order to recommend modifications to the process to improve filtration performance.

EM Sites Impacted

Hanford Site
Savannah River Site

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All Publications: Waste Processing & Special Nuclear Materials, 2006-2019 (pdf)

Highlighted Publications and Reports

CRESP Waste Processing & Special Nuclear Materials

Kocevska, S, Grover, M & Rousseau, R 2019a, ‘Monitoring the Composition of Low-Activity Nuclear Waste using In-Situ Instrumentation, presentation’, WM ‘2019, WM Symposia, Phoenix, Arizona.

Kocevska, S, Grover, M & Rousseau, R 2019b, ‘Monitoring the Composition of Low-Activity Nuclear Waste using In-Situ Instrumentation, presentation’, Career, Research, and Innovation Development Conference, Atlanta Georgia.

Henry, B, Fortenberry, K, Pierce, E, Echols, R, Edwards, R & Brown, K 2019, ‘Development of the DOE Mercury Management Strategy, Panel’, WM ‘2019, WM Symposia, Phoenix, Arizona.

Greenberg, M, Apostolakis, G, Field, T, Goldstein, B, Kosson, D, Krahn, S, Matthews, R, Rispoli, J, Stewart, J & Stewart, R 2019, ‘Advancing Risk-Informed Decision Making in Managing Defense Nuclear Waste in the United States: Opportunities and Challenges for Risk Analysis’, Risk Analysis, vol. 39, no. 2, pp. 375-388. https://doi.org/10.1111/risa.13135

Zhang, P, Branch, J, Garrabrants, A, Delapp, R, Klein-Ben David, O & Kosson, D 2018, ‘The Effect of Environmental Relative Humidity on Carbonation and Oxidation in a Cementitious Waste Form–18448’, WM’2018, WM Symposia, Phoenix, Arizona. http://toc.proceedings.com/40439webtoc.pdf

Kocevska, S, Rousseau, R & Grover, M 2018, ‘Evaluation of In-Situ Infrared Spectroscopy for Direct Feed Low Activity Waste Processing’, Real-Time, In-Line Monitoring Hanford Program Review, Richland, Washington.

Kocevska, S, Grover, M & Rousseau, R 2018, ‘880 Monitoring the Composition of Low Activity Nuclear Waste using in-situ Measurement Methods, Presentation’, ACSS/SciX Conference, Atlanta, Georgia. https://www.scixconference.org/images/pdfs/program/scix-2018-final-program-wcovers-web.pdf

Brown, L, Allison, PG & Sanchez, F 2018, ‘Use of nanoindentation phase characterization and homogenization to estimate the elastic modulus of heterogeneously decalcified cement pastes’, Materials & Design, vol. 142, pp. 308-318. https://doi.org/10.1016/j.matdes.2018.01.030

Brown, K 2018, ‘Hanford Tank Waste Treatment: Foundations for Waste Treatment and Disposition Planning, Poster Session’, Vanderbilt Conference, Nashville, Tennessee. www.cresp.org

Branch, J, Epps, R & Kosson, D 2018, ‘The impact of carbonation on bulk and ITZ porosity in microconcrete materials with fly ash replacement’, Cement and Concrete Research, vol. 103, pp. 170-178. https://doi.org/10.1016/j.cemconres.2017.10.012

Branch, J 2018, ‘Impact of Aging in the Presence of Reactive Gases on Cementitious Waste Forms and Barriers’, Ph.D. dissertation in Environmental Engineering, Vanderbilt University, Nashville, Tennessee.