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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Carbon Fiber Reinforced Polyolefin Body Panels

This project addresses an automotive industry desire for a cost-effective, lightweight material for body panels that offers mass reduction compared to steel and aluminum body panels, and a cost savings compared to incumbent polymer body panels. Inexpensive polypropylene (PP) combined with <10 weight % reclaimed/recycled carbon fiber (rCF) have the potential to meet both performance and affordability targets for lightweight, paintable vertical body panels. This project supports DOE and IACMI technical goals of reducing production cost of CF composites >25% in 5 years on a path to >50% in 10 years and demonstrating technologies for >80% recyclability or reuse of fiber reinforced composites in 5 years on a path to >95% in 10 years. Alternative body panel materials must meet all fit and surface finish requirements, and match the appearance of metal body panels adjacent to them. The PP/rCF materials must maintain exterior dimensional requirements with a low co-efficient of thermal expansion, excellent paintability, and mechanical performance. Thermoplastic injection molding offers significant reduction in tooling costs as injection molding dies are typically less than half the cost of stamping dies. This project utilized rCF compounded with special formulations of PPs to produce automotive components that meet requirements for fit, finish, mechanical performance, and paintability while offering significant mass savings over incumbent metal panels. It will also offer a cost savings versus other composite solutions. Fenders were molded at the IACMI – Corktown facility using an existing fender tool. Ford Motor Company was the industry lead for this project and provided project management, testing, painting and adhesion testing, and developed the cost-model/business case. Ford engaged and aggregated cost share with Borealis who provided materials, technical support for process trials, and participated in coordination meetings. Vehicles Technology Area staff in Corktown assisted in project management, process trials, molded fenders, and benchmarked physical characteristics. Over 450 plaques were molded with two different gating systems to look at processing conditions and specimens were excised for mechanical testing. Plaques were also used for paint trials, surface analysis, and dimensional analysis. Subsequently, over 200 fenders were molded at IACMI – Corktown. These fenders were used for paint trials, surface analysis, and dimensional analysis. The PP/rCF systems met all of the requirements except for paint appearance. Additional development of paint primer and top coat is necessary to fulfill automotive OEM paint surface requirements.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

A real-time distributed solid oxide electrolysis cell (SOEC) model for cyber-physical simulation

System integration and dynamic operability between SOEC and balance-of-plant (BoP) components are major technical challenges before realizing rapid load following of SOEC systems. Cyber-physical simulation (CPS) is a leading-edge digital engineering approach and is regarded as the next step beyond Digital Twins. CPS approach can be used to research SOEC system integration and develop dynamic controls prior to actual pilot testing without using a real SOEC. To seamlessly couple with BoP hardware and access non-observable operational parameters (e.g., local temperature gradient) during transients, a distributed one-dimensional (1D) real-time SOEC model was developed. Its real-time execution was demonstrated for 20 to 640 nodes at the fixed time step of 5 ms. A higher excess air ratio enabled smaller local temperature gradients on SOEC solid materials and faster transients upon current density step change from 0.15 to 0.55 A cm -2 . During the transients, the magnitude of the peak temperature gradient nearly doubled in 10 s from -3.5 to -5.9 °C cm -1 . This represents a significant operating risk that can impact the dynamic operability of SOEC systems. In addition, the local temperature gradient was found to change directions on all nodes in SOEC solid materials, with the greatest impact on the upstream nodes. The SOEC model was also tested at the thermal neutral voltage using actual process air flow parameters as variable model inputs. Variable process air temperatures were found to induce alternating local temperature gradients on SOEC solid materials. These are new operational mechanisms for SOEC degradation relevant for load following operational modes yet distinct from previous reports. To mitigate these unfavorable features, the SOEC can be operated at voltages that are slightly (±20 mV) deviated from the thermal neutral voltage. Here, the corresponding net thermal energy change was less than 1.6% of the electric power consumption. This 1D real-time SOEC model established the basis of cyber-physical simulation of SOEC hybrid systems.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

BETO 2021 Peer Review - Bio-Insecticides from Thermochemical Biomass Conversion

This work is developing a sustainable and inexpensive bioinsecticide that leverages the inherent chemical functionality created from thermochemical biomass conversion. The impact of this project lies at the intersection of energy and agricultural sustainability. Thermochemical conversion of biomass to fuels remains an attractive pathway, and bioinsecticides, isolated from a fraction of upgraded bio-oils, are a high-valued coproduct that can increase biorefinery profitability. Existing insecticide products are facing significant pressure from regulators and consumers due to negative health and environmental impacts. Bioinsecticides, produced through the deconstruction of biomass, can offer a safer more environmentally benign alternative due to the chemical homology with biologically degraded lignin. To enable thermochemical coproduction of bioinsecticides insecticidal activity must be competitive with existing products, separations of the bioinsecticide must be technically viable, and the overall process economics must be improved. Using vacuum distillation, we have separated a bioinsecticide active ingredient that has similar activity to current commercial products, and technoeconomic modeling has shown it can be produced at market competitive prices. This work has established a bioinsecticide fraction that is ready for further, more resource intensive development by addressing early technical, economic, and toxicological risks.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Transition of Spent Nuclear Fuel to Dry Storage: Modeling activities concerning aluminum spent nuclear fuel cladding integrity

In 2017, a report was prepared by the Spent Nuclear Fuel Working Group in 2017 and titled “Technical Considerations and Challenges for Extended (>50 Years) Dry Storage” [1-2]. In this report several key scientific issues were identified pertaining to the problem of aluminum spent nuclear fuel (ASNF) and its safe removal from wet storage with subsequent drying and transfer to dry storage at the Department of Energy (DOE) Idaho National Laboratory (INL). This report outlines two modeling analyses performed for aluminum and aluminum oxides. The first analysis examined the solubility of aluminum oxides as a function of temperature and pH. This report presents existing literature produced as far back as the 1950’s and including significant analysis and reporting performed at Alcoa in the 1980’s. The primary technical gap was the lack of solubility data beyond that reported at standard temperature (25°C). The analysis examined these solubility curves as a function of temperature as well as phase type. The pH value of minimum solubility shifted with temperature but was insensitive to the oxide phase type. The solubility increases with temperature as would be expected, where an order of magnitude increase was observed from 25°C and 90°C. This data provides greater information to understand the various conditions experiences by ASNF including in dry storage in cases where water filming may occur. A second thermodynamic analysis was performed to examine the aluminum phase behavior as a function of temperature. This was performed to understand limitations and possible problems with fuel drying at elevated temperatures. Based on what has been established in previous reports, water remains chemically entrained within boehmite until temperatures exceeding 400°C. Analysis showed that significant phase changes occurred with highly alloyed AA6061 and AA5052 while the more pure aluminum (AA1100) showed nearly ideal behavior (i.e. limited phase changes). In the case of the more alloyed AA5052 and AA6061, the phase changes could take place at relatively low temperatures (100°C to 250°C), and thus may have already experienced some of these phase changes in service. As results are thermodynamic in nature, assessment of kinetics will be examined to determine if the phase changes are a concern for the relatively short fuel drying step.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

The Synchronic Web

The Synchronic Web is a distributed network for securing data provenance on the World Wide Web. By enabling clients around the world to freely commit digital information into a single shared view of history, it provides a foundational basis of truth on which to build decentralized and scalable trust across the Internet. Its core cryptographical capability allows mutually distrusting parties to create and verify statements of the following form: “I commit to this information—and only this information—at this moment in time.” The backbone of the Synchronic Web infrastructure is a simple, small, and semantic-free blockchain that is accessible to any Internet-enabled entity. The infrastructure is maintained by a permissioned network of well-known servers, called notaries, and accessed by a permissionless group of clients, called journals. Through an evolving stack of flexible and composable semantic specifications, the parties cooperate to generate synchronic commitments over arbitrary data. When integrated with existing infrastructures, adapted to diverse domains, and scaled across the breadth of cyberspace, the Synchronic Web provides a ubiquitous mechanism to lock the world’s data into unique points in discrete time and digital space. This document provides a technical description of the core Synchronic Web system. The distinguishing innovation in our design—and the enabling mechanism behind the model—is the novel use of verifiable maps to place authenticated content into canonically defined locations off-chain. While concrete specifications and software implementations of the Synchronic Web continue to evolve, the information covered in the body of this document should remain stable. We aim to present this information clearly and concisely for technical non-experts to understand the essential functionality and value proposition of the network. In the interest of promoting discourse, we take some liberty in projecting the potential implications of the new model.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2020

The World’s Largest Wind Tunnels: Their History, Contributions to Aeronautics, and Importance to Flight - A History of the NASA Ames 40- by 80-Foot and 80- by 120-Foot Wind Tunnels

This book describes the history of the facility in some detail. Modifications to the tunnel are described along with much of the research and development testing performed over the years. Often models or aircraft were studied in the facility and then modified and tested again, such that many models and aircraft were tested numerous times over a period of several years. Descriptions generally cover investigations of models that occurred for several years, rather than descriptions of tests performed chronologically. The goal has been to make the descriptions understandable and not particularly technical, but yet clearly state their purposes. Not all tests are described because of the large number of tests performed (on the order of 700), but many representative tests are described that are intended to illustrate the variety and importance of the models and aircraft investigated over the years. A comprehensive list of references is included for those who are interested in more technical details. It should be noted that after the implementation of full-cost recovery, the interest of NASA in producing traditional reports on aerodynamics was substantially reduced. As a result, there were fewer NASA aeronautical reports in later years. This was a disappointing development because of the importance and high quality of the NASA reports and the importance of archiving results of unique experiments. Dates of important events are provided in Appendix A and a list of NFAC tests are provided in Appendix B. This book is organized in four parts: Part I. Design and Construction; Part II. Operation and Management History; Part III. Research History; and Part IV. Concluding Remarks, References, and Appendices.

World’s Largest Wind Tunnels↗
DOE OSTI2016

Feasibilities of a Coal-Biomass to Liquids Plant in Southern West Virginia

This project has generated comprehensive and realistic results of feasibilities for a coal-biomass to liquids (CBTL) plant in southern West Virginia; and evaluated the sensitivity of the analyses to various anticipated scenarios and parametric uncertainties. Specifically the project has addressed economic feasibility, technical feasibility, market feasibility, and financial feasibility. In the economic feasibility study, a multi-objective siting model was developed and was then used to identify and rank the suitable facility sites. Spatial models were also developed to assess the biomass and coal feedstock availabilities and economics. Environmental impact analysis was conducted mainly to assess life cycle analysis and greenhouse gas emission. Uncertainty and sensitivity analysis were also investigated in this study. Sensitivity analyses on required selling price (RSP) and greenhouse gas (GHG) emissions of CBTL fuels were conducted according to feedstock availability and price, biomass to coal mix ratio, conversion rate, internal rate of return (IRR), capital cost, operational and maintenance cost. The study of siting and capacity showed that feedstock mixed ratio limited the CBTL production. The price of coal had a more dominant effect on RSP than that of biomass. Different mix ratios in the feedstock and conversion rates led to RSP ranging from $104.3 - $157.9/bbl. LCA results indicated that GHG emissions ranged from 80.62 kg CO 2 eq to 101.46 kg CO2 eq/1,000 MJ of liquid fuel at various biomass to coal mix ratios and conversion rates if carbon capture and storage (CCS) was applied. Most of water and fossil energy were consumed in conversion process. Compared to petroleum-derived-liquid fuels, the reduction in GHG emissions could be between -2.7% and 16.2% with CBTL substitution. As for the technical study, three approaches of coal and biomass to liquids, direct, indirect and hybrid, were considered in the analysis. The process models including conceptual design, process modeling and process validation were developed and validated for different cases. Equipment design and capital costs were investigated on capital coast estimation and economical model validation. Material and energy balances and techno-economic analysis on base case were conducted for evaluation of projects. Also, sensitives studies of direct and indirect approaches were both used to evaluate the CBTL plant economic performance. In this study, techno-economic analysis were conducted in Aspen Process Economic Analyzer (APEA) environment for indirect, direct, and hybrid CBTL plants with CCS based on high fidelity process models developed in Aspen Plus and Excel. The process thermal efficiency ranges from 45% to 67%. The break-even oil price ranges from $86.1 to $100.6 per barrel for small scale (10000 bbl/day) CBTL plants and from $65.3 to $80.5 per barrel for large scale (50000 bbl/day) CBTL plants. Increasing biomass/coal ratio from 8/92 to 20/80 would increase the break-even oil price of indirect CBTL plant by $3/bbl and decrease the break-even oil price of direct CBTL plant by about $1/bbl. The order of carbon capture penalty is direct > indirect > hybrid. The order of capital investment is hybrid (with or without shale gas utilization) > direct (without shale gas utilization) > indirect > direct (with shale gas utilization). The order of thermal efficiency is direct > hybrid > indirect. The order of break-even oil price is hybrid (without shale gas utilization) > direct (without shale gas utilization) > hybrid (with shale gas utilization) > indirect > direct (with shale gas utilization).

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Detailed Modeling of Physical Processes in Electron Sources for Accelerator Applications

At present, electron sources are essential in a wide range of applications – from common technical use to exploring the nature of matter. Depending on the application requirements, different methods and materials are used to generate electrons. State of-the-art accelerator applications set a number of often-contradicting requirements for electron sources (e.g., high quantum efficiency vs. high spin-polarization, high current density vs. long lifetime, etc). Development of advanced electron sources includes modeling and design of cathodes, material growth, fabrication of cathodes, and cathode testing. The detailed simulation and modeling of physical processes are required in order to shed light on the exact mechanisms of electron emission and to develop new-generation electron sources with optimized efficiency. The purpose of the present work is to study physical processes in prominent electron sources and to develop scientific tools that could be used to predict electron emission from novel nano-structured materials. In particular, the Monte Carlo model has been implemented and used to study photoemission from Negative Electron Affinity (NEA) GaAs widely used to provide spin-polarized electron beams for many accelerator facilities, including Thomas Jefferson National Accelerator Facility. According to our best knowledge, this is the first to date scientific tool to simulate the complete from-excitation-to-emission-into-vacuum photoemission of spin-polarized electrons from NEA GaAs based on the details of material band structure. Moreover, an effective image-processing algorithm has been developed and used to study field emission properties of Nitrogen-incorporated UltraNanoCrystalline Diamond ((N)UNCD) films. The algorithm processes large sets of image micrographs representing field emission sites formed on the anode plate and therefore provides significant information about the field emission area and the current density. The field emission model from convenient semiconductors has been modified and used to study the influence of the space-charge region and the electric-field-dependent electron mobility on the field emission characteristics of (N)UNCD field emitters.

Chubenko, Oksana↗
DOE OSTI2024

Assessment of Condition Monitoring Methods and Technologies for Inservice Inspection and Testing of Nuclear Power Plant Components

This report was prepared for the U.S. Nuclear Regulatory Commission (NRC) to explore the application of advanced technologies toward meeting the current and future regulatory requirements for maintenance and condition monitoring of structures, systems, and components. The advanced technologies considered in this work are advanced sensors and instrumentation, data analytics, machine learning and artificial intelligence (ML/AI), physics-based models, and digital twins (DT). The interest in the application of advanced technologies for condition monitoring in nuclear power plants continues to grow, and current and future licensees are expected to implement advanced technologies as part of their inservice inspection (ISI) and inservice testing (IST) programs. This report delineates the outcomes of an exploratory investigation into the implementation of advanced condition monitoring technologies to address ISI and IST requirements. A thorough review was conducted of the existing regulatory requirements for ISI and IST, along with an analysis of associated industry practices. Additionally, a state-of-the-art assessment was performed on advanced condition monitoring technologies frequently employed in non-nuclear sectors. This research incorporated two nuclear-specific case studies to illustrate the application of these technologies within the current nuclear fleet. The report provides an exhaustive discussion on the technical challenges, considerations, and opportunities associated with the deployment of advanced condition monitoring technologies. The following are key considerations in the application of advanced technologies for the ISI and IST of nuclear power plant components: • Developing adequate verification and validation procedures to confirm the functional and non-functional requirements, • Developing technical capabilities to conduct real-time asset condition monitoring, • Establishing guidance and protocol for modeling and simulation tools to continuously meet regulatory requirements, • Addressing trustworthiness, explainability, and interpretability of ML/AI methods, • Evaluating maintenance activities to maintain an adequate safety margin and avoid undesirable conditions, • Establishing cybersecure condition monitoring programs associated with a computer-based software system, and • Establishing standardized evaluation metrics for advanced condition monitoring programs. Interest in the use of advanced technologies for condition monitoring in ISI and IST programs continues to grow, and the technology is expected to experience rapid and wide industry adoption in the near future. Adoption of advanced technologies for condition monitoring could have novel and unique impacts on regulatory activities associated with ISI and IST programs. The NRC is continuing to explore the regulatory aspects of advanced technologies as part of ISI and IST programs by pursuing additional research in this technical area.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

2026 Annual Molten Salt Reactor Campaign Review

This report documents the 2026 Annual Molten Salt Reactor (MSR) Campaign Review held in Albuquerque, New Mexico, from April 21–24, 2026. The review was organized by Dr. Patricia Paviet, National Technical Director of the Advanced Reactor Technology (ART) MSR program for the U.S. Department of Energy Office of Nuclear Energy (DOE-NE), and included participation from principal investigators, federal managers, developers, regulators, and members of the broader MSR community. The 2026 review expanded beyond the ART-MSR campaign to include related DOE-NE programs supporting molten salt reactor advancement, including the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, the Advanced Materials and Manufacturing Technologies (AMMT) program, Advanced Reactor Safeguards and Security (ARSS), Material Protection, Accounting and Control Technologies (MPACT), and relevant advanced fuels activities. Three days were dedicated to technical presentations and panel discussions covering thermal properties, off-gas management, modeling and simulation, safety and licensing, safeguards and security, materials and corrosion, and irradiation activities. A fourth day was dedicated to technical tours of Sandia National Laboratories and Kairos Power facilities. Attendance was strong and comparable to the prior annual review, with approximately 75 in-person participants per day, 75–80 virtual attendees per day, and approximately 30 participants in the tour day. The review fostered significant technical exchange across national laboratories, universities, industry, regulators, and international participants. This report summarizes the review structure, technical themes, participation, tours, feedback, and conclusions relevant to future planning for the MSR campaign.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

The Scientific Case for Concurrent Neutron and X-ray Scattering and Spectroscopy

The interrogation of materials with X-rays or neutrons to determine the structure, energetics, and dynamics of materials is fundamental to advancing materials' physical and chemical science and developing innovative material technologies. A transcending challenge in developing novel materials is that progress hinges on understanding the structure and dynamics across multiple time and length scales in complex materials that feature multiple components, interfaces, and compositions. Despite the ever-growing demands on materials’ characterization, existing approaches are almost exclusively based on isolated X-ray or neutron scattering, i.e., an approach commensurate with the more narrowly defined needs of fifty years ago. A three-day workshop sponsored by the U.S. National Science Foundation (NSF) analyzed the demand for concurrent neutron and X-ray (NeX) experiments. It was held at the Spring Hill Suites, San Jose, California, from June 2 to 4, 2022. In this workshop, 70 national and international experts ascertained the crucial need to establish NeX capabilities to advance the science of complex materials and systems in the US. Here, we illustrate the need for NeX scattering and spectroscopy experiments by showcasing examples that span areas as diverse as biomaterials, energy science, soft matter, and nanomaterials. To provide NeX capability will require new instrumentation that enables concurrent experiments. Affected areas include chemistry, soft matter, quantum materials, pure and applied chemistry, bioscience, geoscience, and applied materials. NeX benefits research outcomes due to the complementarity of the two techniques, which is essential for better model refinement. While joint refinement of data from separate neutron and X-ray experiments is critical to avoid ambiguities, especially in multiphase-multicomponent materials, concurrent experiments overcome scientific and technical barriers associated with single measurements, separated by location and, thus, time. Among all the examples, these factors introduce uncertainties in the results that complicate data analysis. [1,2] [3] While models are strongly sample-dependent, the principles of joint refinement are generally applicable to these disciplines, including the development of advanced parameterization, modeling, and analysis techniques that also consider the temporal and spatial resolutions of the two methods, leading to unambiguous data interpretation. Solutions for technical barriers must be found to realize NeX experiments, including developing robust sample environments that meet the optical requirements of neutrons and X-rays.

36 MATERIALS SCIENCE↗
DOE OSTI2019

GeoVision Analysis Supporting Task Force Report: Barriers-An Analysis of Non-Technical Barriers to Geothermal Deployment and Potential Improvement Scenarios

This report describes research and analysis performed in support of the U.S. Department of Energy Geothermal Technologies Office for its Geothermal Vision Study. A summary of the study is captured in DOE’s report, GeoVision: Harnessing the Heat Beneath Our Feet and included ground-breaking, detailed research on geothermal technologies. The study projects and quantifies the future electric and nonelectric deployment potentials of these geothermal technologies within a range of scenarios in addition to their impacts on U.S. jobs, the economy, and environment. Coordinated by the U.S. Department of Energy Geothermal Technologies Office, the Geothermal Vision Study development relied on collecting, modeling, and analyzing robust data sets through seven national laboratory partners that were organized into eight technical task force groups. These task forces and their respective principal leading national laboratory are listed in Table F-1. The table also provides a guide to the final research documents produced by each GeoVision task force. In most cases, these were prepared as laboratory reports, and they are referenced accordingly. Consult these external reports for detailed discussions of the topics contained within, which form the basis of the GeoVision analysis.

15 GEOTHERMAL ENERGY↗
DOE OSTI2017

Automatic generation and simulation of urban building energy models based on city datasets for city-scale building retrofit analysis

Buildings in cities consume 30–70% of total primary energy, and improving building energy efficiency is one of the key strategies towards sustainable urbanization. Urban building energy models (UBEM) can support city managers to evaluate and prioritize energy conservation measures (ECMs) for investment and the design of incentive and rebate programs. This paper presents the retrofit analysis feature of City Building Energy Saver (CityBES) to automatically generate and simulate UBEM using EnergyPlus based on cities’ building datasets and user-selected ECMs. CityBES is a new open web-based tool to support city-scale building energy efficiency strategic plans and programs. The technical details of using CityBES for UBEM generation and simulation are introduced, including the workflow, key assumptions, and major databases. Also presented is a case study that analyzes the potential retrofit energy use and energy cost savings of five individual ECMs and two measure packages for 940 office and retail buildings in six city districts in northeast San Francisco, United States. The results show that: (1) all five measures together can save 23–38% of site energy per building; (2) replacing lighting with light-emitting diode lamps and adding air economizers to existing heating, ventilation and air-conditioning (HVAC) systems are most cost-effective with an average payback of 2.0 and 4.3 years, respectively; and (3) it is not economical to upgrade HVAC systems or replace windows in San Francisco due to the city's mild climate and minimal cooling and heating loads. Furthermore, the CityBES retrofit analysis feature does not require users to have deep knowledge of building systems or technologies for the generation and simulation of building energy models, which helps overcome major technical barriers for city managers and their consultants to adopt UBEM.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Infiltration Data Package for the E-Area Low-Level Waste Facility Performance Assessment

The infiltration data package contains the input parameters, the cap design and material properties assumptions, and the modeling results for the Hydrologic Evaluation of Landfill Performance (HELP) infiltration model simulations performed in support of the E-Area Low-Level Waste Facility Performance Assessment (PA). The infiltration estimates establish the upper boundary condition for the PORFLOW vadose-zone model and GoldSim model simulations for the following E-Area disposal unit types: Slit and Engineered Trenches, Low-Activity Waste Vault (LAWV), Intermediate-Level Vault (ILV), Componentin- Grout (CIG) special waste form trench segments, and the Naval Reactor Component Disposal Areas (NRCDAs). The infiltration data package builds upon relevant, foundational PA technical reports and memoranda from the past 15 years and is supported by three important components: the HELP model input parameter datasheets, HELP model input and output filenames and directory structure, and infiltration rates as a function of time for each scenario for each disposal unit type. For Slit and Engineered Trenches, a single best-estimate Bahia-grass case of two-percent slope and 585- foot slope length represents an upper bound on intact closure-cap infiltration rates over a 10,000-year period. Building upon the single, bounding, and intact case, two different approaches were considered for incorporating the effect of localized cap subsidence on infiltration rates in the PORFLOW flow and transport model simulations. In the first approach, a Monte Carlo probabilistic model was developed to calculate infiltration rates for 0.54%, 2%, 3.6%, and 4.9% subsidence scenariosa reflecting historical and future non-crushable content for the Slit and Engineered Trenches. The resulting blended (spatially and slope-length averaged) infiltration rates become an inflow upper boundary condition for the PORFLOW vadose zone model simulations. In the second and preferred approach, a Monte Carlo rectangle packing algorithm (Danielson, 2019) and a simplified equation for the total mass flux of water draining into a subsided compartment (Equation 1) will be employed to implement a weighted blending of radionuclide fluxes to the water table using the results of deterministic PORFLOW vadose zone simulations representative of specific subsidence cases. Finally, HELP-model results from sensitivity studies of the intact infiltration case were fit to a log-logistic function to generate infiltration profiles over a 10,000-year period for most-optimistic, more-optimistic, best-estimate, more-pessimistic, and most-pessimistic cases, for both the intact and four subsidence scenarios. For the LAWV and IL vaults, infiltration rate profiles for a 10,000-year period were developed for both an on-vault (above the concrete/metal vault roof) and an off-vault (10-foot soil zone adjacent to vault walls) scenario. The purpose of the off-vault simulations was to confirm that subsurface runoff from the concrete vault roof will adequately drain through the lowermost backfill layers adjacent to the vault walls. The LAWV and ILV infiltration profiles assume collapse of the concrete roof at relative Years 2,905 and 7,100, respectively. The identical Bahia-grass case with two-percent slope and 585-foot slope length assumed for the Slit and Engineered Trenches will represent an upper bound on intact infiltration rates for the NRCDAs and CIG special waste form as well. While the NRCDA casks are assumed to remain structurally intact (i.e., non-assumed to collapse 300 years after the end of operations. Because both rows of the existing CIG trench segments in ST23 (formerly CIG01) extend across the planned cap crest, the subsided CIG trench segments are treated conservatively in the HELP model as a 100%-subsidence case with zero subsurface run-on. The CIG special waste form trench segment infiltration profile, therefore, consists of an intact-cap period from relative Year 100 to Year 300, followed by a 100%-subsidence period from relative Year 300 to Year 10,100.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗