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Williamson, Mark A.

Publications and source records attributed to Williamson, Mark A..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Plutonium oxide melt structure and covalency

Advances in nuclear power reactors include the use of mixed oxide fuel, containing uranium and plutonium oxides. The high-temperature behaviour and structure of PuO 2-x above 1,800 K remain largely unexplored, and these conditions must be considered for reactor design and planning for the mitigation of severe accidents. Here, in this study, we measure the atomic structure of PuO 2-x through the melting transition up to 3,000 +/- 50 K using X-ray scattering of aerodynamically levitated and laser-beam-heated samples, with O/Pu ranging from 1.57 to 1.76. Liquid structural models consistent with the X-ray data are developed using machine-learned interatomic potentials and density functional theory. Molten PuO 1.76 contains some degree of covalent Pu-O bonding, signalled by the degeneracy of Pu 5f and O 2p orbitals. The liquid is isomorphous with molten CeO 1.75 , demonstrating the latter as a non-radioactive, non-toxic, structural surrogate when differences in the oxidation potentials of Pu and Ce are accounted for. These characterizations provide essential constraints for modelling pertinent to reactor safety design. The molten structure of plutonium oxide-a component of mixed oxide nuclear fuels-is measured, showing some degree of covalent bonding. Its atomic structure is similar to that of cerium oxide, which could be a non-radioactive structural surrogate.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Actinide and rare earth drawdown system for molten salt recycle

A method for recycling molten salt from electrorefining processes, the method having the steps of collecting actinide metal using a first plurality of cathodes from an electrolyte bath, collecting rare earths metal using a second plurality of cathodes from the electrolyte bath, inserting the collected actinide metal and uranium into the bath, and chlorinating the inserted actinide metal and uranium. Also provided is a system for recycling molten salt, the system having a vessel adapted to receive and heat electrolyte salt, a first plurality of cathodes adapted to be removably inserted into the vessel, a second plurality of cathodes adapted to be removably inserted into the vessel, an anode positioned within the vessel so as to be coaxially aligned with the vessel, and a vehicle for inserting uranium into the salt.

Willit, James L.↗
DOE OSTI2021

Method to produce salts containing actinide halides

A method of producing uranium halides is disclosed in which chlorine gas is introduced into a liquid uranium-nickel alloy. NaCl salt is surrounding the crucible containing the liquid uranium-nickel alloy, producing a eutectic mixture of NaCl—UCl3. Upon chlorination, the metal halide dissolves in the matrix salt forming a solution. Adding the reactant metal, uranium to the nickel, the alloy is able to remain molten throughout processing. The liquid metal alloy may be removed from the salt bath, while the halogen gas continues to enter the system through the sparge until the desired composition of NaCl—UCl3—UCl4 is achieved. The method and system can be used to produce other metal halide salts such as actinide, lanthanide or transition metal halides contained in a matrix salt consisting of alkali and/or alkaline earth halides.

Williamson, Mark A.↗
DOE OSTI2021

Multielectrode sensor for concentration and depth measurements in molten salt

A multi electrode sensor that provides in-situ, real time measurements for molten salts and other process fluids such as real-time concentration and salt level measurements for nuclear systems such as molten salt reactors, nuclear reprocessing facilities utilizing molten salts and concentrated solar power systems. The sensor has multiple electrodes with unique lengths which are connected to a potentiostat. Measurements are taken when the electrodes are immersed in the process fluid.

Hoyt, Nathaniel C.↗
DOE OSTI2021

Multielectrode Array Sensors to Enable Long-Duration Corrosion Monitoring and Control of Concentrating Solar Power Systems

Molten mixtures of MgCl2-KCl-NaCl are promising heat transfer fluid (HTF) candidates for the next generation of concentrating solar power systems (Gen3 CSP), because of their low cost, high decomposition temperature, and favorable heat transfer characteristics. However, if the chemistry of the salts is not properly controlled, molten chlorides can cause corrosion of high-temperature metal alloys, such as Inconel (R), in CSP systems. Here we demonstrate a corrosion monitoring system that can be used to monitor the health of the structural alloys over long durations. The monitoring system includes a multielectrode array voltammetry sensor that measures the redox potential of molten MgCl2-KCl-NaCl mixture as well as the presence of corrosion products and impurities. The sensors have been successfully operated in static molten salt environments for long durations, and are capable of detecting corrosion products, such as Cr2+ and Fe2+, quantitatively at low concentrations (i.e., approximately 100 ppm) with less than 4% error.

Concentrated solar power↗
DOE OSTI2020

Ceramic waste form production from used nuclear fuel

According to one aspect of the invention, a method to create a ceramic waste form from used nuclear fuel. An active metal salt waste, a rare earth metal waste, and raw materials are received. The active metal salt waste is combined with the rare earth metal waste, forming a waste salt. The waste salt is then heated to approximately 500° C. The raw materials are also heated to approximately 500° C. The waste salt and raw materials are then blended to form a homogenous waste mixture. The homogenous waste mixture is heated to a first predetermined temperature for a predetermined amount of time, creating a ceramic waste form. The ceramic waste form is cooled to a second predetermined temperature.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Actinide and rare earth drawdown system for molten salt recycle

A method for recycling molten salt from electrorefining processes, the method having the steps of collecting actinide metal using a first plurality of cathodes from an electrolyte bath, collecting rare earths metal using a second plurality of cathodes from the electrolyte bath, inserting the collected actinide metal and uranium into the bath, and chlorinating the inserted actinide metal and uranium. Also provided is a system for recycling molten salt, the system having a vessel adapted to receive and heat electrolyte salt, a first plurality of cathodes adapted to be removably inserted into the vessel, a second plurality of cathodes adapted to be removably inserted into the vessel, an anode positioned within the vessel so as to be coaxially aligned with the vessel, and a vehicle for inserting uranium into the salt.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Synthesis of Molten Chloride Salt Fast Reactor Fuel Salt from Spent Nuclear Fuel (CRADA 2017-17170 Final Report)

Elysium Industries USA, Inc. aims to produce safe, cost effective, carbon conscious energy through the development of an advanced liquid-fueled reactor technology. The Elysium liquid-fueled reactor concept comprises a molten chloride salt fueled fast spectrum nuclear reactor, which can accept fissle material recovered from used nuclear fuel and excess fissile material from defense applications. A key technology development need for the system is demonstrating the feasibility of a low cost, efficent method to produce the chloride fuel salt from used nuclear fuel. This approach not only provides a pathway for the disposition of used nuclear but more efficient use of uranium resources for energy production.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Fluid Structure of Molten LiCl–Li Solutions

Molten mixtures of lithium chloride and metallic lithium (LiCl-Li) play an essential role in the electrolytic reduction of various metal oxides. These mixtures possess unique high temperature physical and chemical properties that have been investigated for decades. However, due to their extreme chemical reactivity, no study to date has been capable of definitively proving the basic physical nature of Li dissolution in molten LiCl. In this study, the evolution of the structure of molten LiCl-Li is probed as metallic Li is electrochemically introduced into the melt in situ, using synchrotron radiation experiments based on high energy wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The time-resolved scattering results indicate the formation of transient Cl- ion cages surrounding low-density voids with a periodicity of similar to 8.3 angstrom, which suggests the formation of metastable Li nanocluster. The structure of the LiCl-Li nanoclusters in the solution is modeled using ab initio molecular dynamics (AIMD) simulations. We report the simulation results are in agreement with the X-ray diffraction measurement and suggest the nanoclusters are predominantly Li-8, along with smaller clusters.

25 ENERGY STORAGE↗
DOE OSTI2019

Integral U/TRU recovery cathode system for electrorefining used nuclear fuel, method for electrorefining and harvesting metal from used nuclear fuel

The invention provides a system for collecting metal in an electrorefining process, the system having a hollow cathode; and a container defining an upwardly extending surface adapted to be received by the hollow cathode. An embodiment of the invention provides for metal reduction to occur on laterally facing and medially facing surfaces of the cathode such that electrolyte resides between surfaces of the cathode. Also provided is a metal electrorefining process having the steps of subjecting molten salt containing metal moieties to electrolysis wherein reduced metal accumulates in a cathode-cup construct in a first position; raising the construct to a second position above the molten salt while subjecting the construct to heat from the molten salt; withdrawing the cathode from the construct into a vestibule to the electrorefiner to a third position; and removing the cathode and cup from the electrorefiner to a fourth position.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Consumable anode and anode assembly for electrolytic reduction of metal oxides

An anode assembly is provided having a pair of channels; anodes in slidable communication with the channels; conduit to direct carrier gas to the anode; and conduit to remove reaction gas from the anode. Also provided is a method for continuously feeding anodes into a electrolytic bath, the method having the steps of stacking the anodes such that all of the anodes reside in the same plane and wherein the stack includes a bottom anode; contacting the bottom anode with the electrolytic bath for a time and at a current sufficient to cause the bottom anode to be consumed during an electrolytic process; using gravity to replace the bottom anode with other anodes defining the stack.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Conceptual Design of a Pilot-Scale Pyroprocessing Facility

Argonne National Laboratory and Merrick & Company introduced the conceptual design of a pilot-scale (100 T/year) pyroprocessing facility for the treatment of used fuel generated by commercial light water reactors and subsequent treatment of waste streams generated during the process. The primary purpose of this study was to perform sufficient engineering for the pilot facility conceptual design so that credible capital and operating cost estimates could be developed. Initial safety, safeguards, and security assessments were also completed to provide a detailed evaluation in these areas that can significantly affect both capital and operating costs. Electrorefining-based pyroprocessing resulted in a compact hot-cell facility with few process equipment systems. The process equipment and support systems were estimated to cost $93 million and the facility $305 million for a project total cost of $398 million. The annual operating cost was estimated at $53 million/year Scaling up to a commercial-scale (400 T/year) was also assessed and the capital cost was estimated at $911 million with annual operating cost of $90 million/year.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Modular cathode assemblies and methods of using the same for electrochemical reduction

Modular cathode assemblies are useable in electrolytic reduction systems and include a basket through which fluid electrolyte may pass and exchange charge with a material to be reduced in the basket. The basket can be divided into upper and lower sections to provide entry for the material. Example embodiment cathode assemblies may have any shape to permit modular placement at any position in reduction systems. Modular cathode assemblies include a cathode plate in the basket, to which unique and opposite electrical power may be supplied. Example embodiment modular cathode assemblies may have standardized electrical connectors. Modular cathode assemblies may be supported by a top plate of an electrolytic reduction system. Electrolytic oxide reduction systems are operated by positioning modular cathode and anode assemblies at desired positions, placing a material in the basket, and charging the modular assemblies to reduce the metal oxide.

25 ENERGY STORAGE↗
DOE OSTI2017

Communication—Quantitative Voltammetric Analysis of High Concentration Actinides in Molten Salts

Previous electroanalytical studies have shown that cyclic voltammetry can provide accurate quantitative measurements of actinide concentrations at low weight loadings in molten salts. However, above 2 wt%, the techniques were found to underpredict the concentrations of the reactant species. Here this work will demonstrate that much of the discrepancy is caused by uncompensated resistance and cylindrical diffusion. An improved electroanalytical approach has therefore been developed using the results of digital simulations to take these effects into account. This approach allows for accurate electroanalytical predictions across the full range of weight loadings expected to be encountered in operational nuclear fuel processing equipment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Investigation of molybdate melts as an alternative method of reprocessing used nuclear fuel

Here, an investigation of molybdate melts containing sodium molybdate (Na 2 MoO 4 ) and molybdenum trioxide (MoO 3 ) to achieve the separation of uranium from fission products by crystallization has been performed. The separation is based on the difference in solubility of the fission product metal oxides compared to the uranium oxide or molybdate in the molybdate melt. The molybdate melt dissolves uranium dioxide at high temperatures, and upon cooling, uranium precipitates as uranium dioxide or molybdate, whereas the fission product metals remain soluble in the melt. Small-scale experiments using gram quantities of uranium dioxide have been performed to investigate the feasibility of UO 2 purification from the fission products. The composition of the uranium precipitate as well as data for partitioning of several fission product surrogates between the uranium precipitate and molybdate melt for various melt compositions are presented and discussed. The fission products Cs, Sr, Ru and Rh all displayed very large distribution ratios. The fission products Zr, Pd, and the lanthanides also displayed good distribution ratios (D > 10). A melt consisting of 20 wt% MoO 3 -50 wt% Na 2 MoO 4 -30 wt% UO 2 heated to 1313 K and cooled to 1123 K for the physical separation of the UO 2 product from the melt, and washed once with Na 2 MoO 4 displays optimum conditions for separation of the UO 2 from the fission products.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Presence of Li clusters in molten LiCl-Li

Molten mixtures of lithium chloride and metallic lithium are of significant interest in various metal oxide reduction processes. These solutions have been reported to exhibit seemingly anomalous physical characteristics that lack a comprehensive explanation. ln the current work, the physical chemistry of molten solutions of lithium chloride and metallic lithium, with and without lithium oxide, was investigated using in situ Raman spectroscopy. The Raman spectra obtained from these solutions were in agreement with the previously reported spectrum of the lithium cluster, Li 8 . Furthermore, this observation is indicative of a nanofluid type colloidal suspension of Li 8 , in a molten salt matrix. It is suggested that the formation and suspension of lithium clusters in lithium chloride is the cause of various phenomena exhibited by these solutions that were previously unexplainable.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Electrorefiner system for recovering purified metal from impure nuclear feed material

An electrorefiner system according to a non-limiting embodiment of the present invention may include a vessel configured to maintain a molten salt electrolyte and configured to receive a plurality of alternately arranged cathode and anode assemblies. The anode assemblies are configured to hold an impure nuclear feed material. Upon application of the power system, the impure nuclear feed material is anodically dissolved and a purified metal is deposited on the cathode rods of the cathode assemblies. A scraper is configured to dislodge the purified metal deposited on the cathode rods. A conveyor system is disposed at a bottom of the vessel and configured to remove the dislodged purified metal from the vessel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗