Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

Evitts, L. J.; Middleburgh, Simon C.; Kardoulaki, Erofili; Ipatova, Iuliia; Rushton, Michael; Lee, William

doi:10.1016/j.jnucmat.2019.151892

Cited by 12 publications

(4 citation statements)

References 57 publications

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“…Previously, it was noted that point defects in alloys such as HEAs cannot be represented by a single formation energy [ 9 , 116 ], rather because of the variation in the local coordination and symmetry considerations, a range of energies for vacancies, interstitials and substitutional defects result in a range of solution, Schottky, Frenkel and anti-site energies. In addition to point defect computations, DFT calculations that involve the computation of phonons (e.g., to predict thermal properties such as thermal expansion) are more complicated in HEAs [ 167 ] compared to simpler systems due to the symmetry considerations that can be exploited in simple systems that vastly reduce the computational expense of methods such as the quasi-harmonic and harmonic approximations (e.g., Reference [ 168 ], which also captures electronic effects related to thermal and phonon properties). Other methods can be used instead (including molecular dynamics methods [ 169 , 170 ]), but these are not necessarily more computationally efficient or robust when combined with DFT, providing a significant hurdle to modelling HEAs.…”

Section: Challenges and Opportunities For Hea Developmentmentioning

confidence: 99%

High-Entropy Alloys for Advanced Nuclear Applications

Pickering

Carruthers

Barron

et al. 2021

Entropy

192

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The expanded compositional freedom afforded by high-entropy alloys (HEAs) represents a unique opportunity for the design of alloys for advanced nuclear applications, in particular for applications where current engineering alloys fall short. This review assesses the work done to date in the field of HEAs for nuclear applications, provides critical insight into the conclusions drawn, and highlights possibilities and challenges for future study. It is found that our understanding of the irradiation responses of HEAs remains in its infancy, and much work is needed in order for our knowledge of any single HEA system to match our understanding of conventional alloys such as austenitic steels. A number of studies have suggested that HEAs possess ‘special’ irradiation damage resistance, although some of the proposed mechanisms, such as those based on sluggish diffusion and lattice distortion, remain somewhat unconvincing (certainly in terms of being universally applicable to all HEAs). Nevertheless, there may be some mechanisms and effects that are uniquely different in HEAs when compared to more conventional alloys, such as the effect that their poor thermal conductivities have on the displacement cascade. Furthermore, the opportunity to tune the compositions of HEAs over a large range to optimise particular irradiation responses could be very powerful, even if the design process remains challenging.

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Section: Challenges and Opportunities For Hea Developmentmentioning

confidence: 99%

High-Entropy Alloys for Advanced Nuclear Applications

Pickering

Carruthers

Barron

et al. 2021

Entropy

192

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“…Ultra‐high temperature ceramics (UHTCs) are candidate materials for use in extreme environments such as those demanded by next generation hypersonic flight vehicles and nuclear reactors 1,2 . UHTCs are defined by melting temperatures exceeding 3273 K and are generally comprised of borides, carbides, and nitrides of the transition metals.…”

Section: Introductionmentioning

confidence: 99%

“…Ultra-high temperature ceramics (UHTCs) are candidate materials for use in extreme environments such as those demanded by next generation hypersonic flight vehicles and nuclear reactors. 1,2 UHTCs are defined by melting temperatures exceeding 3273 K and are generally comprised of borides, carbides, and nitrides of the transition metals. In particular, ZrB 2 -based ceramics are of interest due to their high thermal conductivity (up to ~140 W/m K) 3 , strength at elevated temperatures (675 MPa at 1873 K) 4 , and melting temperature (3523 K).…”

Section: Introductionmentioning

confidence: 99%

Measurement of the melting temperature of ZrB₂ as determined by laser heating and spectrometric analysis

et al. 2021

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The melting temperatures of two different ZrB2 ceramics were studied using laser induced melting. ZrB2 having a low Hf content, produced by reaction hot pressing, had a melting temperature of 3546 K and a commercial grade ZrB2 had a melting temperature of 3553 K. Uncertainty of the temperature measurements was 1% of the absolute temperature, or ~35 K for both materials based upon 2‐sigma and a 95% confidence interval. While these values were consistent with the previously reported ZrB2 melting temperature of 3518 K, this study was able to measure Tm with less uncertainty than previous studies (±45 K). Furthermore, this study assessed the effect of Hf content on melting temperature, finding that melting temperature did not change significantly for hafnium contents of 1.75 to 0.01 at%. This study also measured a normal spectral emissivity of 0.34 for ZrB2 at 3000 K. The emissivity decreased to 0.28 at the melting temperature, then, stabilized at 0.30 in a liquid phase.

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“…UB 2 has a higher uranium density compared to uranium dioxide (11.68 g cm −3 and 9.67 g cm −3 , respectively [1]), similar to other accident tolerant fuels/advanced technology candidate fuels (ATFs) such as U 3 Si 2 (11.31 g cm −3 [2]). UB 2 also has a much higher thermal conductivity compared to UO 2 [3,4], which will result in a lower fuel centre-line temperatures during normal operating conditions and a significantly flatter temperature profile across the pellet. This has a number of beneficial effects: (1) reducing the rate of the temperature-dependent release of fission products, (2) reduction in the pellet strain as a result of thermal expansion (which is similar to that of UO 2 ), (3) a reduction in the amount of thermal energy stored inside the fuel and importantly (4) a significant increase in the margin to centre-line melting.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of candidate advanced technology fuel: Uranium diboride (UB2) via carbo/borothermic reduction of UO2

Turner

Martini

Buckley

et al. 2020

Journal of Nuclear Materials

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The synthesis of uranium diboride (UB 2 ) from uranium dioxide (UO 2 ) has been carried out for the first time after a coordinated experimental and theoretical investigation. The reliable conversion of UO 2 to UB 2 is of importance when considering commercially relevant products (e.g. as an advanced technology fuel -ATF), avoiding the use of uranium metal as a reactant. UO 2 was reduced and borated in-situ through careful combination with boron carbide (B 4 C) and graphite (carbo/borothermic reduction). The reaction is observed to only be favourable at low partial pressures of CO, here made possible through use of a vacuum furnace at temperatures up to 1800 • C. At higher partial pressures of CO, the product of the reaction is UB 4 . For phase pure UB 2 , excess B 4 C is required due to the formation of volatile boron oxides that are released from the reaction mixture as is observed when synthesising other borides through similar routes.

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Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

Abstract: Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

Cited by 12 publications

References 57 publications

High-Entropy Alloys for Advanced Nuclear Applications

High-Entropy Alloys for Advanced Nuclear Applications

Measurement of the melting temperature of ZrB₂ as determined by laser heating and spectrometric analysis

Synthesis of candidate advanced technology fuel: Uranium diboride (UB2) via carbo/borothermic reduction of UO2

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Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

Abstract: Influence of boron isotope ratio on the thermal conductivity of uranium diboride (UB2) and zirconium diboride (ZrB2)

Cited by 12 publications

References 57 publications

High-Entropy Alloys for Advanced Nuclear Applications

High-Entropy Alloys for Advanced Nuclear Applications

Measurement of the melting temperature of ZrB2 as determined by laser heating and spectrometric analysis

Synthesis of candidate advanced technology fuel: Uranium diboride (UB2) via carbo/borothermic reduction of UO2

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Measurement of the melting temperature of ZrB₂ as determined by laser heating and spectrometric analysis