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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

The feasibility study of small long-life gas cooled fast reactor with mixed natural Uranium/Thorium as fuel cycle input

A conceptual design study of Gas Cooled Fast Reactors with Modified CANDLE burn-up scheme has been performed. In this study, design GCFR with Helium coolant which can be continuously operated by supplying mixed Natural Uranium/Thorium without fuel enrichment plant or fuel reprocessing plant. The active reactor cores are divided into two region, Thorium fuel region and Uranium fuel region. Each fuel core regions are subdivided into ten parts (region-1 until region-10) with the same volume in the axial direction. The fresh Natural Uranium and Thorium is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and the each region-1 is filled by fresh natural Uranium/Thorium fuel. This concept is basically applied to all regions in both cores area, i.e. shifted the core of i{sup th} region into i+1 region after the end of 10 years burn-up cycle. For the next cycles, we will add only Natural Uranium and Thorium on each region-1. The calculation results show the reactivity reached by mixed Natural Uranium/Thorium with volume ratio is 4.7:1. This reactor can results power thermal 550 MWth. After reactor start-up the operation, furthermore reactor only needs Natural Uranium/Thorium supply for continue operation along 100 years.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2012

Uncertainty evaluation for the matrix 'solidified state' of fissionable elements

In case of the analysis of the radioactive liquid samples, no matter the relative physical analysis method used, two impediments act that belong to the behavior in time of the dispersion state of the liquid samples to be analyzed and of the standard used in the analysis. That is, one of them refers to the state of the sample to be analyzed when being sampled, which 'alter' during the time elapsed from sampling up to the analysis of the sample. The other impediment is the natural change of the dispersion state of the standard radioactive solutions, due to the occurrence and evolution in time of the radiocolloidal and pseudo-radiocolloidal states. These radiocolloidal states are states of aggregation and they lead to the destruction of the homogeneity of the solutions. Taking into consideration the advantages offered by the relative physical methods of analysis as against the chemical or the radiochemical ones, different ways of eliminating these impediments have been tried. We eliminated these impediments processing the liquid reference materials (the solutions calibrated in radionuclides of interest), immediately after the preparation. This processing changes the liquid physical state of the reference materials in a 'solidified state'. Through this procedure the dispersion states of the samples, practically, can no longer be essentially modified in time and also ensure the uniform distribution of the radionuclides of interest in the elemental matrix of the samples 'state solidified'. The homogeneity of the distribution of the atoms of the radionuclides from the samples 'solidified state' was checked up through the track micromapping technique of the alpha particles. Through this technique, in the chemically etched track detectors that were put in direct contact with the sample for a determined period of time, the alpha exposure time of the detectors, micromaps of alpha tracks were obtained. These micromaps are retorts through tracks of the distributions atoms of fissionable elements (Thorium e.g.), of which, heavy charged particles, in this case the alpha radiations naturally emitted, were registered in the CR-39 track detectors. The density of alpha track from the obtained track micromaps was studied through common optic microscopy. Micromaps were studied counting the tracks on equal areas, in different measurement points. For the study of the foils prepared within the paper, the studied area was of 4.9 mm2, formed of 10 fields of 0.49 mm2 area each. The estimation of the uncertainty was carried out for all the sizes that were measured within the paper, no matter if they participate, directly or indirectly, in the estimation of the uncertainty regarding the homogeneity of the Thorium atoms distribution in the 'solidified state' foils of the standard solution calibrated in Thorium, such as: i) the weighted masses, ii) the dropped volumes of solution, iii) the alpha duration of exposure of the detectors, iv) the area studied on the surface of the micromap and v) the densities of alpha tracks. The procedure suggested allowed us to considerate that the homogeneity of alpha tracks distribution, on the surface and in thickness, is within the limits of 3.1%.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides {sup 232}Th, {sup 238}U and {sup 237}Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Pebble fuel design for the PB-FHR

This paper presents the results of parametric studies of pebble fuel that can guide the design of future PB-FHR cores. The pebble fuel designs are assessed using the following performance characteristics: burnup, reactivity feedback, transient response, timescale to reach equilibrium cycle, and protection of structural components. The performance of a thorium pebble blanket is assessed by comparing against a seed-only system and system that utilizes a graphite pebble reflector instead of a thorium blanket. This paper presents the functional requirements and a methodology to assess these fuel pebble designs. This paper identifies a feasible design space for low enriched uranium pebbles and selected a baseline pebble design for safe, economic energy generation. Furthermore, this study finds a thorium blanket does not increase the performance of the system significantly with respect to a graphite pebble reflector. Therefore, a graphite pebble reflector is recommended in the baseline full-core design to extend the lifetime of the outer solid graphite reflector to the life of plant. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2012

A Novel Fuel/Reactor Cycle to Implement the 300 Years Nuclear Waste Policy Approach - 12377

A thorium-based fuel cycle system can effectively burn the currently accumulated commercial used nuclear fuel and move to a sustainable equilibrium where the actinide levels in the high level waste are low enough to yield a radiotoxicity after 300 years lower than that of the equivalent uranium ore. The second step of the Westinghouse approach to solving the waste 'problem' has been completed. The thorium fuel cycle has indeed the potential of burning the legacy TRU and achieve the waste objective proposed. Initial evaluations have been started for the third step, development and selection of appropriate reactors. Indications are that the probability of show-stoppers is rather remote. It is, therefore, believed that development of the thorium cycle and associated technologies will provide a permanent solution to the waste management. Westinghouse is open to the widest collaboration to make this a reality. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

NORM in Building Materials: A Case Study in Releasing and Disposing of Building Debris within the DOE System - 18123

In 2013, the Office of Management and Budget issued Memorandum 2013-02, clarifying its 'Freeze the Footprint' policy. Memorandum 2013-02 requires that all federal agencies maintain or reduce their total square footage, within each subsequent year, from a FY2012 baseline. Memorandum 2013-02 also requires that total square footage remain constant with respect to the type/intended use of a building. At Los Alamos National Laboratory (LANL), this means that new construction cannot occur without demolition of equivalent (both in type and square footage) building(s). Since 2013, decommissioning and demolition of aging, unused facilities at LANL has increased. In 2016, the TA16-280 building complex was scheduled for demolition. TA16-280 is a former high explosives (HE) processing facility that consists of six buildings connected to each other via weatherproof walkways. It was constructed in the 1950's and has been subsequently used for HE shipping, receiving, and storage. Interviews with radiation protection staff suggest that some of the buildings within the complex may have been used to store depleted uranium metal parts in a non-dispersible form. It is LANL policy to conduct decommissioning surveys for radioactive materials when building history cannot confirm that a structure is radiologically non-impacted. LANL follows the Multi-Agency Radiation Survey and Assessment of Materials and Equipment (MARSAME) process to develop its surveys and clear structures from radiological control. After clearance, a structure may be dispositioned as non-regulated waste, at a significant cost savings compared to regulated disposition pathways such as low-level waste. MARSAME measurements conducted in the 16-280 complex were elevated compared to reference measurements of surrogate materials, and a majority of the survey units failed to pass indistinguishable from background (IFB), which is LANL's unregulated clearance criteria. Further measurements conducted both in situ and in the laboratory indicated the presence of naturally-occurring thorium in several building materials including: poured concrete, the glaze atop ceramic blast tiles, and the porcelain enamel on the exterior of blast-proof ceiling lamps. Other than naturally-occurring thorium, there were no elevated radionuclide concentrations detected in building materials. It should be noted that there was no history of thorium use in the 16-280 complex, and the material in question was in all cases fixed to and within the building materials in question. Except in certain specific cases, such material is exempt from regulation under the Atomic Energy Act of 1954 [3], as amended, and is therefore exempt from regulation under the Nuclear Regulatory Commission, the Department of Energy, and agreement state regulatory frameworks. Despite this regulatory exemption, disposition of material from the 16-280 complex proved to be challenging, principally because local industrial landfills stipulate 'No radioactive material' in their Waste Acceptance Criteria. This disconnect between what is regulated and what is disposable creates a situation where some DOE sites find it easier to disposition property as Low Level Waste in lieu of pursuing a non-regulated disposition pathway. This presentation will explore the specifics of the 16-280 decommissioning project as well as the implications of the release/disposition disconnect for naturally occurring radioactive material and project planning at LANL. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Incorporation of 40 CFR 192 as an ARAR when Implementing MARSSIM (USACE Input to the MARSSIM Committee for MARSSIM Revision 2) - 18526

One example special case for Final Status Surveys (FSSs) occurs at Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA) sites at which the radioactive materials are from the processing of uranium or thorium ores for their source material content. At these sites, EPA's Health and Environmental Protection Standards for Uranium and Thorium Mill Tailings, in 40 CFR 192, are applicable. Also, 40 CFR 192 may be invoked at non-UMTRCA sites through the CERCLA as an Applicable or Relevant and Appropriate Requirement (ARAR) due to the presence of radium (Ra)-226 or Ra-228, even though the source of residual radioactive material was not a uranium or thorium mill tailings facility. However, the regulatory requirements in these standards infringe on some of the recommendations in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). Specifically, the soil cleanup standards for Ra-226 or Ra-228 are specified as averages over an area of 100 square meters (m{sup 2}). Note that in the 40 CFR 192 rulemaking, an averaging area of 100 m{sup 2} was used as a reasonable footprint for a home. One goal of the 40 CFR 192 standards was to protect future homes from indoor radon, and the specified averaging area was a component implemented for the protection of health. In addition, 40 CFR 192 is silent regarding elevated measurement criteria (EMC)-type requirements for smaller areas of elevated radioactive material within the 100-m{sup 2} footprint. At UMTRCA sites and CERCLA sites where UMTRCA is an ARAR, the following approach for FSSs is acceptable: - Survey units (SUs) may be classified, as appropriate, and survey activities may be adjusted accordingly for Class 1, Class 2, or Class 3 SUs. - Class 1 soil SUs should provide for evaluation of portions that are no greater than 100 m{sup 2} in size, consistent with the 40 CFR 192 standards. - Class 2 and 3 soil SUs are not expected to exceed the 40 CFR 192 soil cleanup standard, so they do not require evaluation of portions that are no greater than 100 m{sup 2} in size. - Compliance with 40 CFR 192 can be demonstrated through analysis of soil samples or composite soil samples from each SU, in conjunction with gamma radiation scanning or in situ gamma radiation measurements of each SU. When appropriate, these gamma radiation scans or in situ measurements correlated to soil sampling may be used in place of soil sampling. - By demonstrating that the average over 100 m{sup 2} meets the 40 CFR 192 soil cleanup standard, the EMC criteria for small elevated areas of activity are not required for the purposes of MARSSIM, but may be developed. These minor modifications to the standard MARSSIM radiological survey approach are acceptable for UMTRCA sites or CERCLA sites where UMTRCA is an ARAR. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

Fission-Fusion: A new reaction mechanism for nuclear astrophysics based on laser-ion acceleration

We propose to produce neutron-rich nuclei in the range of the astrophysical r-process around the waiting point N = 126 by fissioning a dense laser-accelerated thorium ion bunch in a thorium target (covered by a CH{sub 2} layer), where the light fission fragments of the beam fuse with the light fission fragments of the target. Via the 'hole-boring' mode of laser Radiation Pressure Acceleration using a high-intensity, short pulse laser, very efficiently bunches of {sup 232}Th with solid-state density can be generated from a Th target and a deuterated CD{sub 2} foil, both forming the production target assembly. Laser-accelerated Th ions with about 7 MeV/u will pass through a thin CH{sub 2} layer placed in front of a thicker second Th foil (both forming the reaction target) closely behind the production target and disintegrate into light and heavy fission fragments. In addition, light ions (d,C) from the CD{sub 2} layer of the production target will be accelerated as well, inducing the fission process of {sup 232}Th also in the second Th layer. The laser-accelerated ion bunches with solid-state density, which are about 10{sup 14} times more dense than classically accelerated ion bunches, allow for a high probability that generated fission products can fuse again. The high ion beam density may lead to a strong collective modification of the stopping power, leading to significant range and thus yield enhancement. Using a high-intensity laser as envisaged for the ELI-Nuclear Physics project in Bucharest (ELI-NP), order-of-magnitude estimates promise a fusion yield of about 10{sup 3} ions per laser pulse in the mass range of A = 180-190, thus enabling to approach the r-process waiting point at N = 126.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Bioleaching of rare earth elements from monazite sand: Bioleaching of Rare Earth Elements from Monazite

Three fungal strains were found to be capable of bioleaching rare earth elements from monazite, a rare earth phosphate mineral, utilizing the monazite as a phosphate source and releasing rare earth cations into solution. These organisms include one known phosphate solubilizing fungus, Aspergillus niger ATCC 1015, as well as two newly isolated fungi: an Aspergillus terreus strain ML3-1 and a Paecilomyces spp. strain WE3-F. Although monazite also contains the radioactive element Thorium, bioleaching by these fungi preferentially solubilized rare earth elements over Thorium, leaving the Thorium in the solid residual. Adjustments in growth media composition improved bioleaching performance measured as rare earth release. Cell-free spent medium generated during growth of A. terreus strain ML3-1 and Paecilomyces spp. strain WE3-F in the presence of monazite leached rare earths to concentrations 1.7-3.8 times those of HCl solutions of comparable pH, indicating that compounds exogenously released by these organisms contribute substantially to leaching. Organic acids released by the organisms included acetic, citric, gluconic, itaconic, oxalic, and succinic acids. Abiotic leaching with laboratory prepared solutions of these acids was not as effective as bioleaching or leaching with cell-free spent medium at releasing rare earths from monazite, indicating that compounds other than the identified organic acids contribute to leaching performance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Self-Assembly of Hexanuclear Clusters of 4f and 5f Elements with Cation Specificity

Six hexanuclear clusters of 4f and 5f elements were synthesized by room-temperature slow concentration experiments. Cerium(IV), thorium(IV), and plutonium(IV) each form two different hexanuclear clusters, among which the cerium and plutonium clusters are isotypic, whereas the thorium clusters show more diversity. The change in ionic radii of approximately 0.08 Å between these different metal ions tunes the cavity size so that NH4+ (1.48 Å) has the right dimensions to assemble the cerium and plutonium clusters, whereas Cs+ (1.69 Å) is necessary to assemble the thorium clusters. If these cations are not used in the reactions, only amorphous material is obtained.

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

Charge-Coupled Substituted Garnets (Y 3-x Ca 0.5x M 0.5x )Fe 5 O 12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y 3+ = Ca 2+ + M 4+ , where M 4+ = Ce 4+ or Th 4+ . Single-phase garnets Y 3–x Ca 0.5x M 0.5x Fe 5 O 12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57 Fe–Mössbauer spectroscopy indicated that M 4+ and Ca 2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe 3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

Guo, Xiaofeng↗
DOE OSTI2020

Unraveling the structural stability and the electronic structure of ThO 2 clusters

Unraveling the correlations between the geometry, the relative energy and the electronic structure of metal oxide nanostructures is crucial for a better control of their size, shape and properties. Here, we investigated these correlations for stoichiometric thorium dioxide clusters ranging from ThO 2 to Th 8 O 16 using a chemically-driven geometry search algorithm in combination with state-of-the-art first principles calculations. This strategy allows us to homogeneously screen the potential energy surface of actinide oxide clusters for the first time. It is found that the presence of peroxo and superoxo groups tends to increase the total energy of the system by at least 3.5 eV and 7 eV, respectively. For the larger clusters, the presence of terminal oxygen atoms increases the energy by about 0.5 eV. Regarding the electronic structure, it is found that the HOMO–LUMO gap is larger in systems containing only bridging oxygen atoms (~2–3.5 eV) than for systems containing oxo groups (~1–3 eV), peroxo groups (~0–2 eV), and superoxo groups (~0–1 eV). Furthermore, while the LUMO is always dominated by thorium orbitals, the composition of the HOMO changes in the presence or the absence of oxo, peroxo and/or superoxo groups: in the presence of peroxo groups, it is dominated by thorium orbitals, in all other cases, it is dominated by oxygen orbitals, and is rather localized in the presence of terminal oxo or superoxo groups. These correlations are of great interest for synthesizing clusters with tailored properties, especially for applications in the field of nuclear energy and heterogeneous catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Passive and active neutron signatures of 233 U for nondestructive assay

The thorium fuel cycle is emerging as an attractive alternative to conventional nuclear fuel cycles, as it does not require the enrichment of uranium for long-term sustainability. The operating principle of this fuel cycle is the irradiation of 232 Th to produce 233 U, which is fissile and sustains the fission chain reaction. 233 U poses unique challenges for nuclear safeguards, as it is associated with a uniquely extreme γ-ray environment from 232 U contamination, which limits the feasibility of the γ-ray-based assay, as well as more conservative accountability requirements than for 235 U set by the International Atomic Energy Agency. Consequently, instrumentation used for safeguarding 235 U in traditional fuel cycles may be inapplicable. It is essential that the nondestructive signatures of 233 U be characterized so that nuclear safeguards can be applied to thorium fuel-cycle facilities as they come online. In this work, a set of 233 U 3 O 8 plates, containing 984 g 233 U, was measured at the National Criticality Experiments Research Center. A high-pressure 4 He gaseous scintillation detector, which is insensitive to γ-rays, was used to perform a passive fast neutron spectral signature measurement of 233 U 3 O 8 , and was used in conjunction with a pulsed deuterium-tritium neutron generator to demonstrate the differential die-away signature of this material. Furthermore, an array of 3 He detectors was used in conjunction with the same neutron generator to measure the delayed neutron time profile of 233 U, which is unique to this nuclide. These measurements provide a benchmark for future nondestructive assay instrumentation development, and demonstrate a set of key neutron signatures to be leveraged for nuclear safeguards in the thorium fuel cycle.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Final Report on Actinide Glass Scintillators for Fast Neutron Detection

This is the final report of an experimental investigation of actinide glass scintillators for fast-neutron detection. It covers work performed during FY2012. This supplements a previous report, PNNL-20854 “Initial Characterization of Thorium-loaded Glasses for Fast Neutron Detection” (October 2011). The work in FY2012 was done with funding remaining from FY2011. As noted in PNNL-20854, the glasses tested prior to July 2011 were erroneously identified as scintillators. The decision was then made to start from “scratch” with a literature survey and some test melts with a non-radioactive glass composition that could later be fabricated with select actinides, most likely thorium. The normal stand-in for thorium in radioactive waste glasses is cerium in the same oxidation state. Since cerium in the 3+ state is used as the light emitter in many scintillating glasses, the next most common substitute was used: hafnium. Three hafnium glasses were melted. Two melts were colored amber and a third was clear. It barely scintillated when exposed to alpha particles. The uses and applications for a scintillating fast neutron detector are important enough that the search for such a material should not be totally abandoned. This current effort focused on actinides that have very high neutron capture energy releases but low neutron capture cross sections. This results in very long counting times and poor signal to noise when working with sealed sources. These materials are best for high flux applications and access to neutron generators or reactors would enable better test scenarios. The total energy of the neutron capture reaction is not the only factor to focus on in isotope selection. Many neutron capture reactions result in energetic gamma rays that require large volumes or high densities to detect. If the scintillator is to separate neutrons from gamma rays, the capture reactions should produce heavy particles and few gamma rays. This would improve the detection of a signal for fast neutron capture.

Actinide Glass↗
DOE OSTI2010

Characterization of High Level Waste from a Hybrid LIFE Engine for Enhanced Repository Performance

In the interest of providing unlimited greenhouse gas-free energy at low cost, the Laser Inertial Fusion Energy (LIFE) project provides a testbed for inertial confinement fusion technology. Proposed designs are a pure fusion reactor or a hybrid fusion-fission reactor, which includes a subcritical blanket of fissionable material to be irradiated by neutrons from the fusion reaction. Two possible fuels are considered: (1) used fuel from current reactors; (2) thorium. Amounts of high level waste (HLW) generated per kilowatt-hour (kW*h) produced are lower relative to current Light Water Reactors (LWR), but potential hazard associated with 1 ton of HLW from LIFE is superior. The scope of this study is to combine quantities and qualities of HLW from LIFE and determine the repository space required relative to HLW from LWR for a once through fuel cycle. Repository space was determined in terms of number of canisters required disposal of waste in the production of 1 kW*h. HLW properties were determined using the Oak Ridge Isotope GENeration code (ORIGEN-S) and waste was conditioned and stored in borosilicate glass. For a LWR, the fuel was burnt to 50 gigawatt-days per tonne heavy metal (GWd/tHM) then reprocessed through Plutonium Uranium Extraction (PUREX). For LIFE, fuel burnup varied from 478.6 to 971.8 GWd/tHM and both PUREX reprocessing and conditioning with no separation were analyzed. HLW load per canister was determined for each fuel by combining mass, decay heat, and composition constraints, but the decay heat constraint was eliminated, allowing the spent fuel to cool before solidification. If PUREX reprocessing is applied, LIFE requires 1.47E-10 and 1.39E-10 canisters per kW*h for used fuel and thorium fuel, respectively. A LWR requires 1.56E-10 canisters per kW*h. Limiting constraints for LIFE spent fuel were mass of the canister, mass fraction of the glass frit, or molybdenum trioxide mass fraction. If uranium and plutonium are not separated from LIFE spent fuel, then 2.10E-10 and 1.96E-10 canisters are required per kW*h, for the used fuel and thorium fuel, respectively. Required number of canisters decreases with increased fuel burnup. HLW waste disposal of LIFE is not only feasible, but more efficient than LWR with separation per kW*h. High burnups of LIFE offer the greatest waste performance benefit. Limitations of the study include assumption of generic processing or PUREX extraction for LIFE fuel. Future work will include environmental impact after canister failure.

42 ENGINEERING↗
DOE OSTI2026

Quantum enabled precision measurements of the 229Th nuclear isomer transition (final report)

The existence of the nuclear isomer transition in thorium-229 was first inferred from keV lines in the gamma spectrum of uranium-233 decay more than 40 years ago. Over the years, the value of the transition energy has been refined with indirect measurements using nuclear physics techniques, and the current evidence points to transition energy in the laser-accessible vacuum ultra-violet region of the spectrum. At the start of this project, the two best measurements of the transition energy were 7.8±0.5 eV and 8.28±0.17 eV from high precision gamma ray spectroscopy and kinetic energy of internal conversion electrons, respectively. This project aimed to reduce the uncertainty in the transition energy to 10 meV using direct calorimetric measurements of the decay energy with superconducting nanowire single photon detectors (SNSPDs). Specifically, the method that was pursued was to generate thorium-229 in the excited isomer state by the alpha decay of uranium-233, embed the excited state thorium into an SNSPD, then detect the energy released when the isomer deexcites.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1993

Th-230 - U-238 series disequilibrium of the Olkaria rhyolites Gregory Rift Valley, Kenya: Petrogenesis

Positive correlations of (U-238/Th-230) versus Th show the rhyolites to be products of partial melting. Positive correlations of U and Cl and U and F show that the U enrichment in the rhyolites is associated with the halogen contents which may be related to the minor phenocryst phase fractionation. Instantaneous Th/U ratios exceed time integrated Th/U ratios providing further evidence of the hydrous nature of the Olkaria rhyolite source. Excess (U-238/Th-230) in the subduction related rocks has been associated to the preferential incorporation of uranium in slab derived fluids, but no evaluation of the size of this flux has been made. The majority of the Naivasha samples show a (U-238/Th-230) less than 1 and plot close to the subduction related samples indicating the Naivasha rhyolites may also have been influenced by fluids during their formation. In general samples with high (U-238/Th-230) ratios reflecting recent enrichment of uranium relative to thorium have high thorium contents, thereby the high (U-238/Th-230) ratios are restricted to the most incompatible element enriched magmas and, hence, are a good indication that the rhyolites were formed by partial melting. If a fluid phase had some influence on the formation of the rhyolites then the uranium and thorium may have some correlation with F and Cl contents which can be mirrored by the peralkalinity. Plots of uranium against F and Cl contents are shown. The positive correlation indicates that the uranium enrichments are associated with the halogen contents. There seems to be a greater correlation for U against Cl than F indicating that the U may be transported preferentially as Cl complexes.

Black, S.↗
NASA NTRS2014

Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide-humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

humic acid↗