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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

A low-temperature, one-step synthesis for monazite can transform monazite into a readily usable advanced nuclear waste form

It has been demonstrated that monazite-type materials are excellent candidates for nuclear waste forms, and hence, their facile synthesis is of great importance for the needed sequestration of existing nuclear waste. The synthesis of monazite, LaPO 4 , requires inconveniently high temperatures near 1000°C and generally involves the conversion of the presynthesized rhabdophane, LaPO 4 •nH 2 O, to the LaPO 4 monazite phase. During this structure transformation, the rhabdophane converts irreversibly to the thermodynamically stable monoclinic monazite structure. A low-temperature (185° to 260°C) mild hydrothermal acid-promoted synthesis of monazite is described that can both transform presynthesized rhabdophane or assemble reagents to the monoclinic monazite structure. The pH dependence of this reaction is detailed, and its applicability to the LnPO 4 (Ln = La, Ce, Pr, Nd, Sm-Gd), Ca 0.5 Th 0.5 PO 4 , and Sr 0.5 Th 0.5 PO 4 systems is discussed. The crystal growth of Ca 0.5 Th 0.5 PO 4 and Sr 0.5 Th 0.5 PO 4 is described, and their crystal structures were reported. In situ x-ray diffraction studies, performed as a function of temperature, provide insight into the structure transformation process.

Biogeochemistry↗
DOE OSTI2021

Evaluation of Tritium Behavior in Forest Vegetation for the Purpose of Determining Appropriate Non-Zero Deposition Velocities for Tritium Oxide

Modeling and field measurements have been conducted between 2019 and 2021 to assess the practicality of using a non-zero deposition velocity for safety basis estimates of tritium oxide fate and transport modeling. A model was developed which used a complex deposition algorithm designed to assess how tritium oxide would mix based on the turbulent motions and wind speed effects that the forest canopy has on the atmosphere. The model was driven based on measurements of wind and turbulence taken from the Aiken AmeriFlux Tower which measures these properties at five levels located within and just above the forest. The model was then validated against a series of field experiments which were designed to test the model predictions and estimate the deposition velocity occurring over the forest environment at the Savannah River Site. The field releases used deuterium oxide as a surrogate for tritium oxide and was released as a fine mist which rapidly evaporated, creating a gaseous tracer in the atmosphere. Using air samplers, the elevations in deuterium concentration in the air relative to background measurements was assessed and then modeled. Generally, the numerical model tended to underpredict the amount of deuterium being mixed from above the canopy to the forest floor, indicating that the predictions it provides are still conservative relative to what was measured during the field experiments. Across a suite of modeling runs, the 95 th and 99 th percentile deposition velocities were estimated to be 1.2 and 0.7 cm s -1 , respectively. Estimated deposition velocities in the 2021 field experiments, which specifically assessed a release above the forest canopy and its mixing to the surface, predicted deposition velocities ranging from 1.75 to 6.61 cm s -1 . While these field releases do not cover all possible meteorological conditions, it seems appropriate to use a non-zero deposition velocity when performing safety-basis modeling of tritium oxide. The recommendation presented in this report is to use 1.0 cm s -1 . This is between the 95 th and 99 th percentile value estimated from the modeling study, suggesting it should be appropriate for the majority of release scenarios given the model’s apparent conservatism relative to field measurements.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

NNSA-IAEC Area: Workshop on Nuclear Waste Management and Subsurface Science (8-10 November 2022)

The 7 th workshop of the NNSA-IAEC collaboration was conducted on November 8-10 2022. The workshop was held at the geologic survey of Israel, Jerusalem. The IAEC hosted the workshop. The main topic of the workshop evolved around the results of the characterization borehole drilled in the Yamin plain during 2022 and associated experimental work and modeling results. The new data will be integrated for the applicability analysis of intermediate depth borehole (IDB) disposal for spent fuel in the Yamin plain. The first day of the workshop (November 8 th ) was dedicated to a geological field trip in the Judea desert depicting a similar cross section to that found in the Yamin plain. During the 9 th and 10 th of November the characterization BH results were presented, results of new work on the Miocene Hazeva fm. were presented, and this year’s outcome of the different collaboration groups were given.

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

Verification and Validation of the STAT7 Code

This document presents the verification and validation of the STAT7 Version 1.1 code, which has been developed to perform the steady-state thermal hydraulics (TH) safety calculations required to support conversion of the Massachusetts Institute of Technology Research Reactor from highly enriched uranium fuel to low- enriched uranium fuel. The key capabilities of the code, including statistical processing, water property generation, and TH solution, are verified independently. While the first two capabilities are checked using statistical tests and NIST data tables, each component of the TH solution is verified using simple geometry test problems. The comparison between results obtained by the code and by hand calculations on these problems shows that each of these components works correctly. Additionally, a comprehensive comparison between STAT7 Version 1.1 and PLTEMP/ANL Version 4.3 Revision 162 calculations is performed for the validation. Good agreement is achieved between the results obtained with the two codes for all TH parameters belonging to the fuel core region.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

Tools for Assessing Performance (TAP) Project: FY2023 Quarter 2 Report

LANL personnel presented TAP-sponsored work at the 103 rd Annual Meeting of the American Meteorological Society, which was held in Denver, CO in January 2023. There were four different presentations related to TAP-sponsored work that were given by LANL staff and studentsat this meeting: (1) Gloeckler, T., M. Nelson, H. Shah, M. Deshler, L. Wedell, R. Linn, N. Duboc, S. Pol, P. Bieringer, A. Annunzio, B. Martin, and H. Tinnesand, 2023. Testing Validity and Limitations of a Low-Order Diffusive Wake Model. 15 th Symposium on the Urban Environment, January 8-12, 2023, Denver, CO, U.S.A. (2) Nelson, M., H. Shah, T. Gloeckler, M. Deshler, L. Wedell, A. Ortega, R. Linn, N. Duboc, P. Conry, S. Pol, and H. Tinnesand, 2023. The Isolated Building Wake Experiment. Paper 1A.1. 24 th Symposium on Boundary Layers and Turbulence, January 8-12, 2023. Denver, CO, U.S.A. (3) Shah, H., M. Nelson, S. Pol, R. Linn, N. Duboc, and H. Tinnesand, 2023. Detailed Measurement of a Building Wake Under Real-World Atmospheric Conditions. Poster 102. 24 th Symposium on Boundary Layers and Turbulence, January 8-12, 2023, Denver, CO, U.S.A. (4) Wedell, L., M. Nelson, H. Shah, T. Gloeckler, M. Deshler, R. Linn, S. Pol, H. Tinnesand, 2023. The Isolated Building Wake Experiment: Using a Rotating Building to Mulitply the Number of Wake Measurement Locations without Moving the Instruments. Paper 1A.4A. 24 th Symposium on Boundary Layers and Turbulence, January 8-12, 2023, Denver, CO, U.S.A.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

The 2024 Run in the Injectors

The injectors provided polarized protons to RHIC for most of Run 24. That was followed by 3 weeks of Gold at 9.8 GeV/n using Tandem. Physics with PP was first declared on May 1 st and the PP portion of the run ended on Sept. 30 th . The standard BU4/AU4 setup was used for most of it. Although, from Sept. 7 th to 30 th the AGS skew quad setup (BU4/AU6) was used instead. More work was done on the Split/Merge setup (BU3/AU3) initially developed in Run 22. A two Linac pulse setup was also developed this run (BU4/AU2). As far as PP work in the injectors goes this note will focus on the standard, Split/Merge, and Two Linac pulse setups. The 9.8 GeV/n Tandem Au setup was essentially the same as in Run 23. The injector setup for Helium-3 from EBIS (BU7/AU7), which was used for an APEX study in RHIC on August 7 th , will be covered as well.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Highly-detailed neutronic and thermal-hydraulic coupled calculations for OPAL reactor using diverse codes and approaches

The industry-standard approach for designing and operating research reactors cores relies on well-established methodologies that consider uncoupled neutronic calculations and a subchannel analysis of the Thermal-Hydraulic (TH) associated problem. Advancements in computing power and codes allow detailed Multiphysics approaches to be implemented, thereby reducing conservatism. In this study, a comparative analysis of results from diverse detailed neutronic-TH coupled core approaches is developed. To address a realistic application case, the comparison is made for a reported critical configuration from the Open Pool Australian Lightwater research reactor (OPAL) at Hot Full Power (HFP) and low burnup. Both cell-core and stochastic methodologies for neutronics are evaluated, whereas two different subchannel codes are considered for TH. In conclusion, the convergence of the coupled schemes, and the consistency of the main parameters are discussed, showing the compatibility of the alternative methods and their ability to offer critical insights not captured by standard practices.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2020

Materials Data on DyTh by Materials Project

ThDy is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Th is bonded in a body-centered cubic geometry to eight equivalent Dy atoms. All Th–Dy bond lengths are 3.47 Å. Dy is bonded in a body-centered cubic geometry to eight equivalent Th atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThGe2 by Materials Project

ThGe2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Th is bonded to twelve equivalent Ge atoms to form a mixture of distorted edge and face-sharing ThGe12 cuboctahedra. There are eight shorter (3.18 Å) and four longer (3.51 Å) Th–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to six equivalent Th and three equivalent Ge atoms. There are two shorter (2.54 Å) and one longer (2.69 Å) Ge–Ge bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThAu2 by Materials Project

ThAu2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Th is bonded to twelve equivalent Au atoms to form a mixture of face and edge-sharing ThAu12 cuboctahedra. All Th–Au bond lengths are 3.27 Å. Au is bonded in a 9-coordinate geometry to six equivalent Th and three equivalent Au atoms. All Au–Au bond lengths are 2.78 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th2Cu by Materials Project

CuTh2 is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Th is bonded in a 4-coordinate geometry to four equivalent Cu atoms. All Th–Cu bond lengths are 3.09 Å. Cu is bonded in a 10-coordinate geometry to eight equivalent Th and two equivalent Cu atoms. Both Cu–Cu bond lengths are 2.89 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThSb by Materials Project

ThSb is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Th is bonded in a body-centered cubic geometry to eight equivalent Sb atoms. All Th–Sb bond lengths are 3.34 Å. Sb is bonded in a body-centered cubic geometry to eight equivalent Th atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThGe by Materials Project

ThGe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Th is bonded to six equivalent Ge atoms to form a mixture of edge and corner-sharing ThGe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Th–Ge bond lengths are 3.04 Å. Ge is bonded to six equivalent Th atoms to form a mixture of edge and corner-sharing GeTh6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThGa2 by Materials Project

ThGa2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Th is bonded to twelve equivalent Ga atoms to form a mixture of face and edge-sharing ThGa12 cuboctahedra. All Th–Ga bond lengths are 3.26 Å. Ga is bonded in a 9-coordinate geometry to six equivalent Th and three equivalent Ga atoms. All Ga–Ga bond lengths are 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th2Pd by Materials Project

Th2Pd is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Th is bonded in a 4-coordinate geometry to four equivalent Pd atoms. All Th–Pd bond lengths are 3.13 Å. Pd is bonded in a 10-coordinate geometry to eight equivalent Th and two equivalent Pd atoms. Both Pd–Pd bond lengths are 2.98 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThIr2 by Materials Project

ThIr2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to twelve equivalent Ir atoms. All Th–Ir bond lengths are 3.20 Å. Ir is bonded to six equivalent Th and six equivalent Ir atoms to form a mixture of face, edge, and corner-sharing IrTh6Ir6 cuboctahedra. All Ir–Ir bond lengths are 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThB12 by Materials Project

ThB12 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Th is bonded in a 1-coordinate geometry to twenty-four equivalent B atoms. All Th–B bond lengths are 2.83 Å. B is bonded in a 7-coordinate geometry to two equivalent Th and five equivalent B atoms. There is one shorter (1.75 Å) and four longer (1.81 Å) B–B bond length.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThPt by Materials Project

PtTh crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Th is bonded in a 7-coordinate geometry to seven equivalent Pt atoms. There are five shorter (3.02 Å) and two longer (3.28 Å) Th–Pt bond lengths. Pt is bonded in a 5-coordinate geometry to seven equivalent Th atoms.

36 MATERIALS SCIENCE↗