Hanford Site Research Articles

Effects of flow on uranium speciation in soils impacted by acidic waste fluids

Radioactive acidic liquid waste is a common byproduct of uranium (U) and plutonium (Pu) enrichment and recycling processes whose accidental and planned release has led to a significant input of U into soils and sediments across the world, including at the U.S. DOE's Hanford site (WA, USA). Because of the particularly hazardous nature of U, it is important to predict its speciation when introduced into soils and sediments by acidic waste fluids. Of fundamental importance are the coupled effects of acid-driven mineral transformation and reactive transport on U speciation. To evaluate the effect of waste-fluid residence time and co-associated dissolved phosphate concentrations on U speciation in impacted soils and sediments, uncontaminated surface materials (from the Hanford Site) were reacted with U-containing synthetic acidic waste fluids (pH 2) amended with dissolved phosphate concentrations in both batch (no flow) and flow-through column systems for 7–365 days. By comparing dissolved U behavior and solid phase speciation as a function of flow regimen, we found that the availability of proton-promoted dissolution products (such as Si) to sequester U into uranyl silicates was dependent on waste fluid-sediment contact time as uranyl silicates were not detected in short contact time flow-through systems but were detected in no-flow, long contact time, reactors. Moreover, the dominance of uranyl phosphate as neoprecipitate U scavenger (principally in the form of meta-ankoleite) in phosphate amended systems confirmed the importance of phosphate amendments for an efficient sequestration of U in the soils and sediments. Overall, our experiments suggest that the formation of uranyl silicates in soils impacted by acidic waste fluids is likely to be limited unless reaction products are allowed to accumulate in soil pores, highlighting the importance of investigating soil U speciation in flow-through, transport-driven systems as opposed to no-flow, batch systems. This study provides insights into uranium speciation and its potential changes under acidic conditions for better prediction of risks and subsequent development of efficient remediation strategies.

Impact of dilution-induced precipitates on the filtration of Hanford liquid tank wastes

ABSTRACT To facilitate its vitrification, a portion of the radioactive wastes currently stored at the Hanford Site will be staged and treated using tank-side operations to render their chemistry compliant with the requirements of Hanford’s low-activity waste vitrification facility. Initial sampling of staged feeds indicates that process-water dilution, used to reduce waste feed sodium content to levels acceptable for vitrification (5–6 M Na), may cause precipitation of fine, difficult to settle solids that could affect downstream tank-side filtration and ion-exchange. However, dilution-induced precipitation has not been demonstrated under controlled, rigorous laboratory conditions. This paper presents a set of qualitative and quantitative assessments of dilution-induced precipitation using a nonradioactive, Hanford Tank AP-105 simulated waste. These studies found that dilution of AP-farm waste simulants induced precipitation of up to 150 ppm solids, regardless of whether dilution was done with process water (which contains, among other analytes, naturally occurring Ca and Mg) or deionized water. Naturally occurring process-water analytes appeared to accelerate the rate (and possibly extent) of precipitation. Filtration of diluted waste simulants also found that the precipitated solids challenged prototypic tank-side filter operations; however, the impact to filtration performance was readily managed through waste staging settle/decant operations.

Radiobiology of Select Radionuclides in Hanford Site Tank Waste.

There are several important radionuclides involved in the "clean-up" or environmental isolation of nuclear waste contained in US Department of Energy Hanford Site underground waste tanks that drive many of the decisions associated with this activity. To make proper human health risk analyses and ensure that the most appropriate decisions are made, it is important to understand the radiation biology and the human health risk associated with these radionuclides. This manuscript provides some basic radiological science, in particular radiation biology, for some of these radionuclides, i.e., 3 H, 90 Sr, 137 Cs, 99 Tc, 129 I, and the alpha emitters 239, 240 Pu, 233,234,235,238 U, and 241 Am. These radionuclides were selected based on their designation as "constituents of potential concern," historical significance, or potential impact on human health risk. In addition to the radiobiology of these select radionuclides, this manuscript provides brief discussions of the estimated cost of planned management of Hanford tank waste and a comparison with releases into the Techa River from activities associated with the Mayak Production Association. A set of summary conclusions of the potential human health risks associated with these radionuclides is given.

Ecological information and approaches needed for risk communication dialogs for acute or chronic environmental crises.

Scientists, social scientists, risk communicators, and many others are often thrust into a crisis situation where they need to interact with a range of stakeholders, including governmental personnel (tribal, U.S. federal, state, local), local residents, and other publics, as well as other scientists and other risk communicators in situations where information is incomplete and evolving. This paper provides: (1) an overall framework for thinking about communication during crises, from acute to chronic, and local to widespread, (2) a template for the types of ecological information needed to address public and environmental concerns, and (3) examples to illustrate how this information will aid risk communicators. The main goal is providing an approach to the knowledge needed by communicators to address the challenges of protecting ecological resources during an environmental crisis, or for an on-going, chronic environmental issue. To understand the risk to these ecological resources, it is important to identify the type of event, whether it is acute or chronic (or some combination of these), what receptors are at risk, and what stressors are involved (natural, biological, chemical, radiological). For ecological resources, the key information a communicator needs for a crisis is whether any of the following are present: threatened or endangered species, species of special concern, species groups of concern (e.g., neotropical bird migrants, breeding frogs in vernal ponds, rare plant assemblages), unique or rare habitats, species of commercial and recreational interest, and species/habitats of especial interest for medicinal, cultural, or religious activities. Communication among stakeholders is complicated with respect to risk to ecological receptors because of differences in trust, credibility, empathy, perceptions, world view valuation of the resources, and in many cases, a history of misinformation, disinformation, or no information. Exposure of salmon spawning in the Columbia River to hexavalent chromium from the Hanford Site is used as an example of communication challenges with different stakeholders, including Native Americans with Tribal Treaty rights to the land.

Physics‐Informed Machine Learning Method for Large‐Scale Data Assimilation Problems

AbstractWe develop a physics‐informed machine learning approach for large‐scale data assimilation and parameter estimation and apply it for estimating transmissivity and hydraulic head in the two‐dimensional steady‐state subsurface flow model of the Hanford Site given synthetic measurements of said variables. In our approach, we extend the physics‐informed conditional Karhunen‐Loéve expansion (PICKLE) method to modeling subsurface flow with unknown flux (Neumann) and varying head (time‐dependent Dirichlet) boundary conditions. We demonstrate that the PICKLE method is comparable in accuracy with the standard maximum a posteriori (MAP) method, but is significantly faster than MAP for large‐scale problems. Both methods use a mesh to discretize the computational domain. In MAP, the parameters and states are discretized on the mesh; therefore, the size of the MAP parameter estimation problem directly depends on the mesh size. In PICKLE, the mesh is used to evaluate the residuals of the governing equation, while the parameters and states are approximated by the truncated conditional Karhunen‐Loéve expansions with the number of parameters controlled by the smoothness of the parameter and state fields, and not by the mesh size. For a considered example, we demonstrate that the computational cost of PICKLE increases near linearly (as N1.15) with the number of grid nodes N, while that of MAP increases much faster (as N3.28). We also show that once trained for one set of Dirichlet boundary conditions (i.e., one river stage), the PICKLE method provides accurate estimates of the hydraulic head for any value of the Dirichlet boundary conditions (i.e., for any river stage).

Using Ensemble Data Assimilation to Estimate Transient Hydrologic Exchange Flow Under Highly Dynamic Flow Conditions

AbstractQuantifying dynamic hydrologic exchange flows (HEFs) within river corridors that experience high‐frequency flow variations caused by dam regulations is important for understanding the biogeochemical processes at the river water and groundwater interfaces. Heat has been widely used as a tracer to infer steady‐state flow velocities through analytical solutions of heat transport defined by the diurnal temperature signals. Under sub‐daily dynamic flow conditions, however, such analytical solutions are not applicable due to the violation of their fundamental assumptions. In this study, we developed a data assimilation‐based approach to estimate the sub‐daily flux under highly dynamic flow conditions using multi‐depth temperature observations at a 5‐min resolution. If the hydraulic gradient is measured, Darcy's law was used to calculate the flux with permeability estimated from temperature responses below the riverbed. Otherwise, flux was estimated directly by assimilating multi‐depth temperature data at 1‐ or 2‐hr time intervals assuming one‐dimensional flow and heat transport governing equation. By comparing estimated fluxes with model‐generated synthetic truth, we demonstrated that both schemes have robust performance in estimating fluxes under highly dynamic flow conditions. This data assimilation‐based flux estimation method was able to capture the vertical sub‐daily fluxes using multi‐depth high‐resolution temperature data alone, even in the presence of multi‐dimensional flow. This approach has been successfully applied to real field temperature data collected at the Hanford site, which experiences highly dynamic HEFs. Our study shows the promise of adopting distributed 1‐D temperature monitoring to capture spatial and temporal exchange dynamics in river corridors at a watershed scale or beyond.

Pu distribution among mixed waste components at the Hanford legacy site, USA and implications to long-term migration

Beginning in 1943, process wastes containing approximately 1.85 × 1015 Bq (200 kg) of plutonium (Pu) were released into unlined cribs, trenches, and field tiles at the Hanford Site, Washington, USA. The 216-Z-9 (Z-9) unlined trench received over 4 × 106 L of mixed Pu processing waste from the Plutonium Finishing Plant (PFP) consisting of high ionic strength (∼ 5 M nitrate, ∼ 0.6 M aluminum), acidic (pH ∼ 2.5) solutions, which also contained the organic solvents: tributyl phosphate (TBP), dibutyl butylphosphonate (DBBP), carbon tetrachloride (CCl4), and lard oil. A small fraction of Pu migrated deep into the subsurface vadose zone to depths of 37 m, but the mechanisms controlling Pu migration beneath the trench are unknown. In this study, we determined Pu partitioning behavior in a series of binary and ternary batch experiments containing aqueous, organic, and solid phases representative of the waste constituents and natural sediments of the Z-9 trench in order to develop a conceptual model for the transport of Pu in the subsurface. Our results show that Pu at equilibrium with low pH, high nitrate waste and in the presence of a TBP/organic phase can migrate as a Pu-TBP-nitrate complex in the organic phase as long as the low pH and high nitrate concentrations are maintained. Reducing the nitrate concentrations or increasing the pH will lead to Pu partitioning into the aqueous phase from the organic phase with subsequent sorption to native Hanford sediments. The results of this work suggest that Pu migration in the subsurface is likely driven by weak sorption of aqueous Pu under low pH conditions as well as the formation of Pu-TBP-nitrate complexes in the organic phase. Long-term Pu migration will be limited by the transient nature of the low pH conditions and the dispersion of the nitrate plume.

Technical note: Using long short-term memory models to fill data gaps in hydrological monitoring networks

Abstract. Quantifying the spatiotemporal dynamics in subsurface hydrological flows over a long time window usually employs a network of monitoring wells. However, such observations are often spatially sparse with potential temporal gaps due to poor quality or instrument failure. In this study, we explore the ability of recurrent neural networks to fill gaps in a spatially distributed time-series dataset. We use a well network that monitors the dynamic and heterogeneous hydrologic exchanges between the Columbia River and its adjacent groundwater aquifer at the U.S. Department of Energy's Hanford site. This 10-year-long dataset contains hourly temperature, specific conductance, and groundwater table elevation measurements from 42 wells with gaps of various lengths. We employ a long short-term memory (LSTM) model to capture the temporal variations in the observed system behaviors needed for gap filling. The performance of the LSTM-based gap-filling method was evaluated against a traditional autoregressive integrated moving average (ARIMA) method in terms of error statistics and accuracy in capturing the temporal patterns of river corridor wells with various dynamics signatures. Our study demonstrates that the ARIMA models yield better average error statistics, although they tend to have larger errors during time windows with abrupt changes or high-frequency (daily and subdaily) variations. The LSTM-based models excel in capturing both high-frequency and low-frequency (monthly and seasonal) dynamics. However, the inclusion of high-frequency fluctuations may also lead to overly dynamic predictions in time windows that lack such fluctuations. The LSTM can take advantage of the spatial information from neighboring wells to improve the gap-filling accuracy, especially for long gaps in system states that vary at subdaily scales. While LSTM models require substantial training data and have limited extrapolation power beyond the conditions represented in the training data, they afford great flexibility to account for the spatial correlations, temporal correlations, and nonlinearity in data without a priori assumptions. Thus, LSTMs provide effective alternatives to fill in data gaps in spatially distributed time-series observations characterized by multiple dominant frequencies of variability, which are essential for advancing our understanding of dynamic complex systems.

Impact of feed variability on cesium removal with multiple actual waste samples from the Hanford site

ABSTRACT The Tank Side Cesium Removal (TSCR) system, under development by Washington River Protection Solutions (WRPS), will send initial low-activity Hanford waste tank supernate feeds to the Hanford Waste Treatment and Immobilization Plant (WTP) Low-Activity Waste (LAW) Facility. In addition to entrained solids removal from the supernate, the primary goal of TSCR is to remove cesium-137 (137Cs) by ion exchange, allowing contact handling of the liquid effluent product at WTP. Crystalline silicotitanate (CST) ion exchange media, manufactured by Honeywell UOP (product IONSIV™ R9140-B), was selected as the ion exchange media at TSCR. This lot of material was found to have superior performance in comparison to historic batches of CST. Ion exchange column and batch contact testing with supernate from Hanford tanks AP-105, AP-107 and AW-102 was performed to assess the impact of feed variability on system performance. These tests demonstrated that batch contact measurements provide a reasonable prediction of column capacities with some deviation in performance attributed to column dynamics. In addition, the variability in CST capacity for cesium in the various actual waste samples does not track with historical understanding of the competing cations, suggesting that tank waste samples contain other components that may significantly impact cesium loading.

Heat capacity of complex aluminoborosilicate glasses

ABSTRACTFor nuclear waste vitrification in the Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford site, waste feed is charged into a continuously fed electric melter and the molten glass is poured into stainless steel containers to solidify. The heat from the molten glass must be removed from the facility within plant operating constraints, making knowledge of thermal properties of the waste glasses critical. The heat capacity of Hanford low‐activity waste glasses with systematic variations in composition were studied using complementary thermal analyses – power‐compensated differential scanning calorimetry (pcDSC) at 50–630°C, heat‐flux differential scanning calorimetry (hfDSC) at 200–800°C, and drop calorimetry at 600–1200°C. Variations of the heat capacity with composition have been observed around the transition temperature (Tg) and above, particularly when B2O3 and Al2O3 is varied. Above Tg, all glasses exhibit decreasing heat capacity with increasing temperature. A correlation was found between this curve and the fraction B[4]2O3 in glasses, suggesting boron coordination plays a role in this anomalous behavior. These measurements will be used as critical input to validate the heat balance calculations used for facility design and thus the overall operation of the WTP.

Effect of ion interactions on the Raman spectrum of NO3−: Toward monitoring of low-activity nuclear waste at Hanford

Raman spectroscopy is a valuable in-situ technique for many applications. The concentrations of species in complex ionic mixtures of nuclear waste can be estimated using Raman measurements. However, it has been experimentally observed that ion interactions can cause a modification of Raman peak intensities and positions. The present work explores the nonlinear behavior associated with the nitrate anion, NO3−, which is present in abundance in low activity nuclear waste. We examine changes in the main Raman peak of the nitrate anion in the presence of other ions. A wide range of concentrations are covered, including those expected during direct-feed low-activity waste (DFLAW) processing at the Hanford site in the State of Washington. The experiments showed that the ions interact and associate to form ion pairs, which results in a blue shift (i.e., a shift towards higher wavenumbers) in the main Raman peak of nitrate. The results indicate that cation concentration is a better predictor of the peak shift, compared to ionic strength, both for binary and multicomponent mixtures. These findings have direct implications on the development of spectra-to-composition models for the DFLAW system, since they show deviations from the linearity assumptions used in common chemometric models.

Frustrated Coulombic and Cation Size Effects on Nanoscale Boehmite Aggregation: A Tumbler Small- and Ultra-Small-Angle Neutron Scattering Study

To better understand the effects of solution chemistry on particle aggregation in the complex legacy tank wastes at the Hanford (WA) and Savannah River (SC) sites, we have performed a series of tumbler small- and ultra-small-angle neutron scattering experiments on 20 wt % solid slurries of nanoparticulate aluminum oxyhydroxide (boehmite) with M1+ nitrates of various concentrations and radii. The solutes consisted of H, Li, Na, K, and Rb nitrates at 10–5, 10–3, 10–1, 2, and 4 molal (m) concentrations, as well as in pure H2O. Synthetic boehmite nanoparticles were used with a size range from ∼20 to 30 nm. Tumbler cells were used to keep the solids from settling. Although particles initially form individual rhombohedral platelets, once placed in solution, they quickly form well-bonded stacks, primary aggregates, up to ∼1500 Å long, and a second level of aggregates whose concentration and structure vary as a function of cation type and concentration. Aggregation generally increases with increased solute concentration and with cation radius up to a concentration somewhat above 10–1 m, at which point the trend reverses. Primary aggregates become more rodlike and larger. The Kirkwood-like reversal probably reflects a change from Derjaguin–Landau–Verwey–Overbeek (DLVO)/Debye behavior controlled by surface chemistry to a frustrated Coulombic system controlled by the solution structure. These data suggest that an understanding of the effects of salt concentration and chemistry on nanoparticle aggregate structures provides useful physical insights into the microscopic origin of slurry rheology in the Hanford and Savannah River legacy wastes.

The evolution of hydrated lime-based cementitious waste forms during leach testing leading to enhanced technetium retention

The interaction between radionuclides and cementitious material phases is crucial in the prediction of the long-term disposal behavior of cementitious waste forms. This work focuses on the behavior of technetium-99 (Tc) within a hydrated-lime based waste form developed as a candidate to immobilize high-sulphate containing liquid wastes known to inhibit cement solidification when using a fly ash based formulation. In leach testing, the hydrated-lime based formulation demonstrated improvement in Tc retention over a fly ash containing formulation beginning after 14 d leaching. The mineralogical evolution of the hydrated-lime samples during leach testing showed a decrease in portlandite content and reduction capacity at the onset of the Tc retention improvement. Leach testing upwards of 400 days showed the improved Tc retention was sustained. Samples cured for different lengths of time (28 days vs 60 days) confirmed that the improved Tc retention and mineralogic change was caused by cement – leachant interactions and not the sample curing time. The Tc observed diffusivities in the hydrated-lime samples are amongst the lowest measured in a cement waste form tested for development at the US Department of Energy Hanford site, leading to a possible pathway to improved cement conditioning where contaminants can be retained for long disposal times.

Transition from pore fouling to cake filtration in high level waste dead end filtration

ABSTRACT Treatment of radioactive waste at the Hanford site is dependent upon dead end filtration to prepare feed for ion exchange. Recent testing has indicated that the filter media that will be deployed for this treatment process is susceptible to depth fouling. A model was developed to understand the transition from pore fouling to cake filtration to provide insight into the planned operations of this facility. These results indicate that an initial transition takes place during which the filter is depth fouled. However, after the majority of the pores have been plugged the filter flux is governed by cake filtration on the surface of the fouled filter.

Review: Echoes of Exclusion and Resistance: Voices from the Hanford Region, edited by Robert Bauman and Robert Franklin

This is the third volume in the Hanford History Series from WSU Press. Whereas the first two volumes examined the Manhattan Project and its impact on Hanford, White Bluffs, and Richland, this volume expands the scope to include the broader Tri-Cities region and the social changes that have shaped it. The authors make great use of oral histories, and they deserve much credit for amplifying Native American, Japanese American, and African American voices. This also makes the book’s exclusion of Mexican American voices all the more surprising.The book’s overarching thesis, developed by four authors across six chapters, is straightforward: social diversity, racial conflict, wartime displacement, and civil rights activism shaped the Tri-Cities region from the 1880s to the 1970s, and World War II was the turning point. With less consistency, the authors argue that white residents’ treatment of Plateau Indians and successive waves of Chinese, Japanese, and African American newcomers followed the same patterns of discrimination and segregation, the “echoes of exclusion” that fueled resistance.Thomas Marceau’s opening chapter explores the centrality of the region’s natural resources to the Wanapum people and thus the travesty of the tribe’s displacement from the Hanford Site in 1943. Robert Bauman’s chapter backtracks to survey the racist treatment that Chinese immigrants faced during the late nineteenth century before focusing on Japanese immigrants, their survival strategies, and the injustices that internment policy brought to their doorsteps. The next three chapters turn to African Americans. Robert Franklin examines the wartime opportunities that African Americans perceived and the realities of discrimination and segregation they faced. Laura Arata focuses more tightly on African American women and the “optimism, disappointment, and determination that shaped their experiences” (p. 114). Bauman and Franklin then analyze the region’s civil rights movement, including its courageous leaders, committed opponents, and mixed results. Each of these chapters has much to offer, especially for students of Washington state history. The book as a whole presents a compelling mix of material on racial conflict and the perseverance needed to overcome it.The book also reflects some conceptual shortcomings. Lumping Plateau Indians, Chinese immigrants, Japanese Americans, African Americans, and ethnic Mexicans together as “nonwhites” is problematic. It illuminates patterns, but it says more about white residents’ misguided conflation of tribal, national, racial, ethnic, and immigrant identities. More problematic is the decision to relegate the experiences of ethnic Mexicans to five pages of the final chapter. Their recognition that the history of Latinas/os in the region deserves its own book offers some solace. I eagerly await the fourth volume in this series.

Big Data Analytics for Long-Term Meteorological Observations at Hanford Site

A growing number of physical objects with embedded sensors with typically high volume and frequently updated data sets has accentuated the need to develop methodologies to extract useful information from big data for supporting decision making. This study applies a suite of data analytics and core principles of data science to characterize near real-time meteorological data with a focus on extreme weather events. To highlight the applicability of this work and make it more accessible from a risk management perspective, a foundation for a software platform with an intuitive Graphical User Interface (GUI) was developed to access and analyze data from a decommissioned nuclear production complex operated by the U.S. Department of Energy (DOE, Richland, USA). Exploratory data analysis (EDA), involving classical non-parametric statistics, and machine learning (ML) techniques, were used to develop statistical summaries and learn characteristic features of key weather patterns and signatures. The new approach and GUI provide key insights into using big data and ML to assist site operation related to safety management strategies for extreme weather events. Specifically, this work offers a practical guide to analyzing long-term meteorological data and highlights the integration of ML and classical statistics to applied risk and decision science.

The Importance of Preserving Birds and Their Habitats at Hanford Site and Oak Ridge Reservation: Information and Communication Tools for Governments, Local and Diverse Communities and Others

The Department of Energy (DOE) has one of the largest environmental remediation tasks in the world, cleaning up the radiologic and toxic contamination legacy of nuclear weapons production. DOE has committed itself to accomplish remediation “while protecting human health and the environment”. Many DOE sites are huge, encompassing habitats that are ecologically valuable because they have been protected from human disturbance for 70 years or more. Yet information on the importance of DOE lands for protecting specific ecological resources is often buried in volumes of data. In this paper, we examine the importance of DOE lands as habitats for birds using two sites as examples: the Hanford Site and Oak Ridge Reservation. Our overall goal was to provide a model for communication of key information useful for the public and decision-makers. Birds are conspicuous and familiar features of the landscape, and bird populations are important indicators of habitat quality. As future land use plans evolve, birds can convey important messages about habitat uniqueness and conservation importance and recreational values of designating DOE land for conservation, but only if they are in accessible formats. At the semi-arid Hanford site, shrub-steppe is an important habitat outside the Columbia River corridor. At the wet Oak Ridge Reservation eastern deciduous forest, interior forest is a particularly important habitat. There are different groups of bird species dependent on each habitat. We use two methods for each habitat: 1) a comparison of historical written records and 2) a comparison of land use/land cover data. Habitat loss through development, fragmentation, and degradation is one of the most important causes of avian decline. Importantly, we present the data in a manner suitable for discussion among diverse audiences regarding future use of sites now undergoing remediation. The Hanford Site has recorded 205 bird species, including shrub-steppe species of regional importance. The Oak Ridge Reservation has recorded 213 species of birds, including Neotropical migrants of international concern. In both cases, their respective habitat is key to protection of the unique avian assemblages, and there is a higher percentage of these habitats on the DOE lands than in the surrounding habitats. Our analysis also concludes that these habitats that are of high importance to the rare and declining avian assemblages are mostly increasing on the DOE sites as the once agrarian landscape has reverted to more natural habitat. Since acquisition, DOE has developed about 10% of the land for nuclear and industrial activities, leaving the rest of it as a security buffer for the nuclear production mission. The tables provided in this manuscript can serve as valuable tools in communicating the importance of these lands and protecting these lands for surrounding communities. We commend the DOE for its protection of ecological resources for the regions and the Nation, applaud their mechanisms for ecological protection, and recommend that more of each site’s respective unique and important habitats be designated as preserved in perpetuity as valued ecological resources. This designation entails communicating with Tribes, communities, government agencies and organizations, and the public about the ecological value of their protected lands.

Development of a point-kinetics model in OpenFOAM, integration in GeN-Foam, and validation against FFTF experimental data

Following the growing interest that we observe in the use of OpenFOAM for nuclear reactor analysis, the current work presents a point-kinetics model and associated open-source code that can easily be integrated in existing thermal–hydraulic solvers to streamline the use of OpenFOAM for multi-physics investigations. As a proof of concept, we have integrated the new solver in the GeN-Foam multiphysics platform, and validated it against past experimental measurements from the Fast Flux Test Facility, a 400 MW (th) Sodium-cooled Fast Reactor located at the Hanford Site, Washington, USA. Both steady-state and transient simulations provide satisfactory results, also in view of previous studies with other codes. Overall, the developed point-kinetics model and its integration in GeN-Foam have proven to be suitable for the system-level investigation of nuclear reactor transients, thus enabling a more widespread use by the nuclear community of a major open-source toolkit like OpenFOAM.

A newly proposed isotherm model to predict Cs exchange with crystalline silicotitanate in tank waste simulants

ABSTRACT The Zheng Anthony Miller (ZAM) computer model, a multicomponent ion exchange model used to predict the exchange of Group I metals onto crystalline silicotitanate (CST), has historically been used to predict Cs distribution coefficients from Hanford and Savannah River Site (SRS) tank waste simulants. Comparison of experimentally determined Cs distribution coefficients from tank waste simulants with ZAM isotherm model predictions indicate overprediction of Cs and K distribution coefficients for simple and complex simulants with the engineered form of CST. Additionally, recent changes in chemical composition/manufacturing of IONSIV TM R9140-B have resulted in increased Cs capacity from high-salt, highly alkaline solutions. This work served to assess different isotherm models and refine equilibrium parameters to develop a model that can be applied to Hanford and SRS tank waste Cs removal efforts. Toward this goal, the Campbell Westesen Peterson (CWP) model was developed. This model utilized the experimentally determined Cs capacity, and simplified ZAM equilibria expressions to include only the binary substitution of Cs+ or K+ on the Na+ sites. Equilibrium constants for these equations were refined using experimentally determined distribution coefficients. Overall, the CWP model significantly improved our ability to predict both Cs and K loading capacity from complex matrices.

Speciation of aluminum phases at the Hanford Site

AbstractTreatment of the tank waste at the Hanford Nuclear Reservation in Washington State is one of the largest environmental challenges facing the world today. Disposition of the insoluble solids poses the greatest hurdle to achieving long‐term stabilization of the tank waste. The single largest component of the insoluble solids is aluminum. An assessment of the characterization of this waste has identified that the aluminum is roughly split into thirds between sodium aluminate, gibbsite, and boehmite mineral phases. The largest single source of aluminum in the Hanford tank farms is associated with the tanks located in the southwest corner of the site. These tanks contain relatively high concentrations of aluminum such that the mass of insoluble solids present could be reduced by up to 90% through caustic leaching of the materials in these tanks. Performing such leaching processes would enable the recovery of waste from several leak‐prone single‐shell tanks in that area.