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DOE OSTI2020

Materials Data on UCd(MoO4)4 by Materials Project

UCd(MoO4)4 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. U6+ is bonded to seven O2- atoms to form distorted UO7 pentagonal bipyramids that share corners with two equivalent CdO7 pentagonal bipyramids. There are a spread of U–O bond distances ranging from 1.84–2.41 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.75–2.41 Å. In the second Mo6+ site, Mo6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mo–O bond distances ranging from 1.75–2.41 Å. Cd2+ is bonded to seven O2- atoms to form CdO7 pentagonal bipyramids that share corners with two equivalent UO7 pentagonal bipyramids. There are a spread of Cd–O bond distances ranging from 2.31–2.46 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Cd2+ atom. In the second O2- site, O2- is bonded in a linear geometry to one U6+ and one Cd2+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two Mo6+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Mo6+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two equivalent Mo6+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mo6+ and one Cd2+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to two Mo6+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Mo6+ and one Cd2+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one U6+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K2U(MoO4)3 by Materials Project

K2U(MoO4)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.78–3.07 Å. U4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.28–2.57 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.76 Å) and two longer (1.85 Å) Mo–O bond length. In the second Mo6+ site, Mo6+ is bonded in a distorted tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.74–1.93 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one U4+, and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+ and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent U4+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one U4+, and one Mo6+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on U(MoO4)2 by Materials Project

UMo2O8 crystallizes in the trigonal P3 space group. The structure is three-dimensional. there are five inequivalent U4+ sites. In the first U4+ site, U4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of U–O bond distances ranging from 2.31–2.50 Å. In the second U4+ site, U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six MoO4 tetrahedra. There are three shorter (2.20 Å) and three longer (2.21 Å) U–O bond lengths. In the third U4+ site, U4+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of U–O bond distances ranging from 2.34–2.45 Å. In the fourth U4+ site, U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six MoO4 tetrahedra. All U–O bond lengths are 2.20 Å. In the fifth U4+ site, U4+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six MoO4 tetrahedra. All U–O bond lengths are 2.19 Å. There are six inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 26°. There are a spread of Mo–O bond distances ranging from 1.77–1.86 Å. In the third Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 21°. There are a spread of Mo–O bond distances ranging from 1.77–1.87 Å. In the fourth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 37°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. In the fifth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. In the sixth Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share a cornercorner with one UO6 octahedra. The corner-sharing octahedral tilt angles are 30°. There are a spread of Mo–O bond distances ranging from 1.77–1.85 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one U4+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to one U4+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the tenth O2- site, O2- is bonded in a linear geometry to one U4+ and one Mo6+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the fourteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the fifteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the sixteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the seventeenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the eighteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the nineteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twentieth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twenty-first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twenty-second O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twenty-third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one U4+ and one Mo6+ atom. In the twenty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one U4+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on U(MoO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on U(MoO4)2 by Materials Project

36 MATERIALS SCIENCE↗

DOE OSTI2021

Fission Induced Radiolysis of Uranyl Sulfate Solutions

At Argonne National Laboratory, an experimental pilot facility is being tested for the production of the medical isotope molybdenum-99 ( 99 Mo). AMORE (Argonne Molybdenum Research Experiment) is an experimental pilot facility in which a 40 MeV electron beam from the LINAC strikes a depleted uranium (DU) target. The target generates high energy neutrons, which are thermalized in an 18-liter uranyl sulfate solution of low enriched uranium (LEU). Thermalized neutrons fission the uranium-235 ( 235 U) to produce 99 Mo as well as many other fission products. The 99 Mo is recovered from the uranium solution and purified. The goal of our work is to reduce the use of highly enriched uranium (HEU) for the production of this isotope.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2020

Impact of uranium oxide (UO 2 ) fuel with molybdenum (Mo) inserts on pressurized water reactor performance and safety

This work investigates nuclear reactor performance and safety characteristics of UO 2 with high thermal conductivity Mo insert structures by using multiphysics modeling techniques. Additionally, the purpose of this study is to use scoping analyses to quantify the impact of using Mo inserts from neutronic and heat transfer standpoints. Attention is given to reactor performance parameters, such as cycle length, maximum fuel temperature, temperature gradients in the fuel, and stored energy in the fuel. The finite-element code BISON and the Monte Carlo particle transport code Serpent were used to perform sensitivity analyses on the Mo insert geometry to optimize the insert design and inform larger scale modeling that required the homogenization of the UO 2 and Mo. Although BISON is often used as a fuel performance analysis tool, it is used in this context for heat transfer analysis only. Fuel performance optimization is outside the scope of the current study, but would be important for future work focused on this concept. The results showed that the insert had little impact on neutronic performance and that homogenizing the UO 2 and Mo was acceptable for reactor physics calculations. Reactivity temperature coefficients calculated using homogeneous UO 2 -Mo were shown to be relatively similar to UO 2 , but higher Mo content and 235 U enrichment can reduce the worth of soluble boron and control rods. The effect of insert geometry on heat transfer was much greater, and an approximately 15–20% difference in maximum fuel temperature was predicted between the best and worst performing heat transfer geometries. Furthermore, thermal conductivity calibration based on the finite element analysis results was performed to improve the accuracy of temperature predictions in reactor analysis models that homogenized the UO 2 -Mo fuel. Compared with UO 2 in a pressurized water reactor (PWR), the optimized UO 2 -Mo design increased the margin to fuel melt by 13–32% across the fuel cycle, but it requires the 235U enrichment to exceed 5% to match the cycle length of conventional UO 2 .

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2020

Materials Data on MgU(MoO4)4 by Materials Project

MgU(MoO4)4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Mg2+ is bonded to seven O2- atoms to form MgO7 pentagonal bipyramids that share corners with four MoO6 octahedra, corners with two equivalent UO7 pentagonal bipyramids, and edges with two MoO6 octahedra. The corner-sharing octahedra tilt angles range from 24–27°. There are a spread of Mg–O bond distances ranging from 2.14–2.33 Å. U6+ is bonded to seven O2- atoms to form UO7 pentagonal bipyramids that share corners with four MoO6 octahedra, corners with two equivalent MgO7 pentagonal bipyramids, and edges with two MoO6 octahedra. The corner-sharing octahedra tilt angles range from 25–30°. There are a spread of U–O bond distances ranging from 1.86–2.35 Å. There are four inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to six O2- atoms to form distorted MoO6 octahedra that share corners with three MoO6 octahedra, a cornercorner with one MgO7 pentagonal bipyramid, a cornercorner with one UO7 pentagonal bipyramid, an edgeedge with one MoO6 octahedra, and an edgeedge with one UO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 7–42°. There are a spread of Mo–O bond distances ranging from 1.76–2.25 Å. In the second Mo6+ site, Mo6+ is bonded to six O2- atoms to form distorted MoO6 octahedra that share corners with three MoO6 octahedra, a cornercorner with one MgO7 pentagonal bipyramid, a cornercorner with one UO7 pentagonal bipyramid, an edgeedge with one MoO6 octahedra, and an edgeedge with one UO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 7–42°. There are a spread of Mo–O bond distances ranging from 1.76–2.25 Å. In the third Mo6+ site, Mo6+ is bonded to six O2- atoms to form distorted MoO6 octahedra that share corners with three MoO6 octahedra, a cornercorner with one MgO7 pentagonal bipyramid, a cornercorner with one UO7 pentagonal bipyramid, an edgeedge with one MoO6 octahedra, and an edgeedge with one MgO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 7–48°. There are a spread of Mo–O bond distances ranging from 1.75–2.26 Å. In the fourth Mo6+ site, Mo6+ is bonded to six O2- atoms to form distorted MoO6 octahedra that share corners with three MoO6 octahedra, a cornercorner with one MgO7 pentagonal bipyramid, a cornercorner with one UO7 pentagonal bipyramid, an edgeedge with one MoO6 octahedra, and an edgeedge with one MgO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 7–48°. There are a spread of Mo–O bond distances ranging from 1.75–2.26 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Mo6+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to two Mo6+ atoms. In the third O2- site, O2- is bonded in a distorted linear geometry to two Mo6+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two Mo6+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to one Mg2+ and one U6+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Mo6+ atoms. In the eighth O2- site, O2- is bonded in a linear geometry to one Mg2+ and one U6+ atom. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two Mo6+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one U6+ and one Mo6+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one Mo6+ atom. In the twelfth O2- site, O2- is bonded in a distorted linear geometry to two Mo6+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two Mo6+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one U6+ and one Mo6+ atom. In the fifteenth O2- site, O2- is bonded in a distorted linear geometry to two Mo6+ atoms. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two Mo6+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Impact of U-10Mo HALEU Fuel Element Tolerances on the Massachusetts Institute of Technology Reactor safety and operational performance – Neutronics

The U.S. is coordinating efforts for the conversion of six U.S. high performance research reactors (USHPRR), including one critical assembly from highly enriched uranium (HEU) to low-enriched uranium (LEU). In order to continue the mission of these reactors, including the Massachusetts Institute of Technology Reactor (MITR), and achieve similar performance, high assay low-enriched uranium (HALEU) with a high-density metallic alloy of uranium with 10 wt% molybdenum (U-10Mo) is being considered. Following the preliminary design of the proposed MITR LEU fuel elements using the U-10Mo monolithic alloy, the impact of the fabrication specification was assessed. This work focuses on the analysis of select neutronics characteristics of the MITR LEU core as a function of the variation of the relevant fuel specification parameters (e.g., U-10Mo composition, fuel plate thickness, etc.). A separate article submitted to this journal addresses the impact on the thermal hydraulic performance. The analyses in these works are performed based on an all-LEU conversion management plan identified in previous work, in which only the proposed elements are utilized for achieving the conversion of MITR. The variations of two main neutronics characteristics are assessed as a function of the variability of the specification parameters resulting from the fabrication process: the MITR LEU core reactivity and the fuel cycle length. The main findings of this work show that the MITR core can meet the operational requirements during the LEU transition plan under the limiting fabrication parameter combinations considered. In addition, the analyses show that the dependency of the core neutronics characteristics on the specification parameters is highly linear within the specification tolerances. The rates of variation are reported in detail for each parameter and can serve as a powerful tool for future MITR fuel management in cases such as when HALEU supply is established that may allow additional cycle length or other operational benefits.