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Fabrication and thermophysical properties of UO2-UB2 and UO2-UB4 composites sintered via spark plasma sintering

Journal Article · · Journal of Nuclear Materials
 [1];  [2];  [1];  [1];  [1];  [1];  [1];  [3];  [4];  [3];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Idaho National Lab. (INL), Idaho Falls, ID (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Rensselaer Polytechnic Inst., Troy, NY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Rensselaer Polytechnic Inst., Troy, NY (United States); Idaho National Lab. (INL), Idaho Falls, ID (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Uranium dioxide (UO2) composites with uranium diboride (UB2) and uranium tetraboride (UB4) have been proposed as advanced fuel candidates due to their high thermal conductivity, high melting point, high fissile density and their ability to incorporate a built-in burnable poison by tailoring the targeted 10B/11B ratio. As such, it is important to assess the fabrication, and thermal and micromechanical properties of such composites. In this work, UO2-UB2 and UO2-UB4 samples with boride phase fractions of 5, 15 and 30 wt% were fabricated to high densities (above 95 % theoretical density) via spark plasma sintering (SPS). This enabled sintering at relatively low temperatures and short timescales. SPS also aided in maintaining the target phase fractions of the samples as reactions between the constituent phases were suppressed due to the short timescales and reducing environment during sintering. Here, thermal diffusivity measurements from 299 to 1273 K were conducted through laser flash analysis (LFA). The diffusivity increased as a function of boride weight fraction, and UB2 additions increased the thermal diffusivity of the composites more than UB4 additions. Assessment of the LFA results indicated in-situ reactions between the UO2 and boride phases that suppress the thermal diffusivity occur above 800 K for all samples. Oxidation of the boride phase was proposed as the underlying reaction. This was supported by thermodynamic assessments from the literature, as well as microstructural, crystallographic, and nanoindentation characterization performed on these samples.
Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
89233218CNA000001; AC05-00OR22725; NE0008532
OSTI ID:
1727414
Alternate ID(s):
OSTI ID: 1747018
OSTI ID: 1776044
Report Number(s):
LA-UR--20-25985
Journal Information:
Journal of Nuclear Materials, Journal Name: Journal of Nuclear Materials Journal Issue: C Vol. 544; ISSN 0022-3115
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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