Melting behavior of (Th,U)O2 and (Th,Pu)O2 mixed oxides

Ghosh, P. S.; Kuganathan, Navaratnarajah; Galvin, C.O.T.; Arya, A.; Dey, G. K.; Dutta, B.K.; Grimes, Robin W.

doi:10.1016/j.jnucmat.2016.06.037

Cited by 33 publications

(13 citation statements)

References 51 publications

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“…10b,c we notice that the MOX formation energies are lower than the pure members, suggesting that there can be an enhancement for MOX cation diffusion at lower temperatures. This can be significant for fission product mobility and it may also effect the melting temperatures of MOX26.…”

Section: Discussionmentioning

confidence: 99%

Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

Galvin

Cooper

Rushton

et al. 2016

Sci Rep

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Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Thx,Pu1−x)O2 (0 ≤ x ≤ 1) between 300–3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Thx,Pu1−x)O2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Thx,Pu1−x)O2 is explained in terms of lower oxygen defect formation enthalpies for (Thx,Pu1−x)O2 than PuO2 and ThO2, while links are drawn between the superionic transition temperature and oxygen Frenkel disorder.

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Section: Discussionmentioning

confidence: 99%

Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

Galvin

Cooper

Rushton

et al. 2016

Sci Rep

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“…The Gd-O parameters employed in this study have been used successfully to model oxygen diffusion in strained Gd doped ceria [44]. The CRG approach accurately reproduces the experimentally determined thermal expansion, elastic constants and melting points of UO 2 , PuO 2 and ThO 2 [17]. This is important as to describe oxygen transport properties the potential must describe the thermal expansion accurately [44].…”

Section: Potential Modelmentioning

confidence: 82%

“…There are~40 reactors worldwide licensed to use MOX [4]. Understanding how the compositions of these mixed oxides affect their thermophysical properties is of importance for safe and efficient reactor operation and a substantial body of experimental and modelling work is being carried out to investigate these properties [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Oxygen diffusion in Gd-doped mixed oxides

Galvin

Cooper

Rushton

et al. 2018

Journal of Nuclear Materials

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Molecular dynamics simulations have been performed to investigate oxygen transport in (U x Pu x−1) 0.95 Gd 0.05 O 1.975 , (U x Th x−1) 0.95 Gd 0.05 O 1.975 and (Pu x Th x−1) 0.95 Gd 0.05 O 1.975 between 1000-3200 K. Oxygen diffusivity and corresponding activation energies are examined and compared to values for the undoped (U x Pu x−1)O 2 , (U x Th x−1)O 2 and (Pu x Th x−1)O 2 systems where compositions between end members display enhanced diffusivity. Below the superionic transition oxygen diffusivity for the Gd doped systems is orders of magnitude greater compared to their undoped counterparts. However, enhanced diffusivity for doped mixed actinide cation compositions is not observed compared to doped end members. Changes in activation energy suggest changes in diffusion regime, which correspond to the creation of thermally activated oxygen defects.

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“…The melting point of thorium-plutonium fuels can be estimated from earlier studies which evaluated the melting point of such fuels using different molar fraction ratios. Fresh fuel's melting point can be estimated to be around 3400 K but will likely decrease as the fuel gets irradiated [33]. Hence 3100 K is used as a conservative estimate of the fuel melting temperature.…”

Section: Control Rod Drop Accidentmentioning

confidence: 99%

Analysis of Control Rod Drop Accidents for the Canadian SCWR Using Coupled 3-Dimensional Neutron Kinetics and Thermal Hydraulics

Salaun

Novog

2018

Science and Technology of Nuclear Installations

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The Canadian Supercritical Water-cooled Reactor (SCWR), a GEN IV reactor design, is a hybrid design of the well-established CANDU™ and Boiling Water Reactor with water above its thermodynamic critical point. Given the batch fueled design, control rods are used to manage the reactivity throughout the fuel cycle. This paper examines the consequences of a control rod drop accident (CRDA) for the Canadian SCWR. The asymmetry generated by the dropped rod requires an accurate 3-dimensional neutron kinetics calculation coupled to a detailed thermal-hydraulic model. Before simulating the CRDAs, the proper implementation of the 3D reactivity feedback was verified and various sensitivity studies were performed. This work demonstrates that the proposed safety systems for the SCWR core are capable of terminating the CRDA sequence prior to exceeding maximum sheath and centerline temperatures. In one instance involving a rod on the periphery of the core, the proposed trip setpoint (115% FP) was not exceeded and a new steady state was reached. Therefore it is recommended that the design also include provisions for a high-log rate and/or local Neutron Overpower Protection (NOP) trips, similar to existing CANDU designs such that reactor shutdown can be assured for such spatial anomalies.

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Melting behavior of (Th,U)O2 and (Th,Pu)O2 mixed oxides

Cited by 33 publications

References 51 publications

Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

Oxygen diffusion in Gd-doped mixed oxides

Analysis of Control Rod Drop Accidents for the Canadian SCWR Using Coupled 3-Dimensional Neutron Kinetics and Thermal Hydraulics

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