Thermal Transport in Actinide Oxide Fuels With Interstitial Defects

2019 ◽  
Author(s):  
Katherine Mitchell ◽  
Hunter Horner ◽  
Alex Resnick ◽  
Jungkyu Park ◽  
Eduardo B. Farfán ◽  
...  
Keyword(s):  
Point Defects ◽  
Thermal Transport ◽  
Nuclear Reactor ◽  
Nuclear Reactors ◽  
Reactor Operation ◽  
Oxygen Interstitial ◽  
Interstitial Defects ◽  
Actinide Oxides ◽  
Non Equilibrium Molecular Dynamics ◽  
Thermal Conductivities

Abstract Molecular displacement occurs in the oxide fuels of nuclear reactors during operation. This causes several types of point defects to be generated inside the oxide nuclear fuels. To improve the safety and efficiency of nuclear reactor operation, it is necessary to better understand the effects of point defects on the properties of the oxide fuels. In this study, we examine the effects of interstitial defects on thermal transport in two representative actinide oxides used in modern reactors (UO2, and PuO2). Reverse non-equilibrium molecular dynamics (RNEMD) is employed to approximate the thermal conductivities for the aforementioned fuels at several sample lengths and at defect concentrations of 0.1%, 1%, and 5%. The results show that alterations to the lattice structures of these fuels reduce their thermal conductivities significantly. For example, oxygen interstitial defects at concentrations even as low as 0.1% decreased thermal conductivity by 20% at 100 units for each fuel.

scholarly journals Thermal transport study in actinide oxides with point defects

2019 ◽  
Vol 51 (5) ◽  
pp. 1398-1405 ◽  
Author(s):  
Alex Resnick ◽  
Katherine Mitchell ◽  
Jungkyu Park ◽  
Eduardo B. Farfán ◽  
Tien Yee
Keyword(s):  
Point Defects ◽  
Thermal Transport ◽  
Transport Study ◽  
Actinide Oxides

In-plane thermal transport in black phosphorene/graphene layered heterostructures: a molecular dynamics study

2018 ◽  
Vol 20 (32) ◽  
pp. 21151-21162 ◽  
Author(s):  
Ting Liang ◽  
Ping Zhang ◽  
Peng Yuan ◽  
Siping Zhai
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Thermal Transport ◽  
Single Layer ◽  
Black Phosphorene ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Non Equilibrium ◽  
Thermal Conductivities

We use non-equilibrium molecular dynamics simulations to study the in-plane thermal conductivities of black phosphorene/graphene heterostructures and single-layer black phosphorene in black phosphorene/graphene heterostructures.

Thermal Transport in Thorium Dioxide

2017 ◽  
Author(s):  
Jungkyu Park ◽  
Eduardo B. Farfán ◽  
Christian Enriquez ◽  
Nicholas Kinder ◽  
Matthew Greeson
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Low Temperatures ◽  
Nuclear Reactors ◽  
Mean Free Path ◽  
Thorium Dioxide ◽  
Long Wavelength ◽  
Fuel Pellets ◽  
Different Temperatures ◽  
Non Equilibrium Molecular Dynamics

Thorium is more abundant in nature than uranium and thorium fuels can breed fissile U-233 fuel that can be used in various types of nuclear reactors. Moreover, thorium dioxide has drawn interest from researchers due to its relatively superior thermal properties when compared to conventional uranium dioxide fuel pellets. In this study, thermal transport in thorium dioxide is investigated using reverse non-equilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K and the phonon mean free path was estimated to be between 7 ∼ 8.5 nm at 300 K. It was also observed that the thermal conductivity of thorium dioxide has a strong dependency on temperature; the thermal conductivity decreases with an increase in the temperature. Moreover, by simulating thorium dioxide structures with different lengths at different temperatures, it was also identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.

scholarly journals A Thermal Transport Study of Branched Carbon Nanotubes with Cross and T-Junctions

2021 ◽  
Vol 11 (13) ◽  
pp. 5933
Author(s):  
Wei-Jen Chen ◽  
I-Ling Chang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Thermal Management ◽  
Thermal Transport ◽  
Topological Defects ◽  
Branch Length ◽  
Phonon Transport ◽  
Heat Current ◽  
Transport Mechanisms ◽  
Non Equilibrium Molecular Dynamics

This study investigated the thermal transport behaviors of branched carbon nanotubes (CNTs) with cross and T-junctions through non-equilibrium molecular dynamics (NEMD) simulations. A hot region was created at the end of one branch, whereas cold regions were created at the ends of all other branches. The effects on thermal flow due to branch length, topological defects at junctions, and temperature were studied. The NEMD simulations at room temperature indicated that heat transfer tended to move sideways rather than straight in branched CNTs with cross-junctions, despite all branches being identical in chirality and length. However, straight heat transfer was preferred in branched CNTs with T-junctions, irrespective of the atomic configuration of the junction. As branches became longer, the heat current inside approached the values obtained through conventional prediction based on diffusive thermal transport. Moreover, directional thermal transport behaviors became prominent at a low temperature (50 K), which implied that ballistic phonon transport contributed greatly to directional thermal transport. Finally, the collective atomic velocity cross-correlation spectra between branches were used to analyze phonon transport mechanisms for different junctions. Our findings deeply elucidate the thermal transport mechanisms of branched CNTs, which aid in thermal management applications.

Japan's Post-Fukushima Energy Politics

2015 ◽  
Vol 07 (02) ◽  
pp. 109-116
Author(s):  
Tai Wei LIM
Keyword(s):  
Democratic Party ◽  
Nuclear Reactor ◽  
Prime Minister ◽  
Nuclear Reactors ◽  
Liberal Democratic Party ◽  
The Political ◽  
Political Arena ◽  
Liberal Democratic ◽  
Energy Politics ◽  
Gubernatorial Election

A 2011 earthquake damaged the Fukushima nuclear reactor and provided a galvanising point for anti-nuclear resistance groups in Japan. Their public cause slowly faded from the political arena after the Democratic Party of Japan fell out of power and anti-nuclear politicians lost the 2014 Tokyo gubernatorial election. The current Liberal Democratic Party Prime Minister Abe holds a pro-nuclear position and urges the reactivation of Japan's nuclear reactors after all safeguards have been satisfied.

Exploring the Use of Alumina Nanofluid as Emergency Coolant for Nuclear Fuel Bundle

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
A. S. Chinchole ◽  
Arnab Dasgupta ◽  
P. P. Kulkarni ◽  
D. K. Chandraker ◽  
A. K. Nayak
Keyword(s):  
Heat Transfer ◽  
Nuclear Fuel ◽  
Nuclear Reactor ◽  
Cooling System ◽  
Nuclear Reactors ◽  
Electrical Heating ◽  
High Dose ◽  
Potential Candidate ◽  
Alumina Nanofluid ◽  
Core Cooling

Abstract Nanofluids are suspensions of nanosized particles in any base fluid that show significant enhancement of their heat transfer properties at modest nanoparticle concentrations. Due to enhanced thermal properties at low nanoparticle concentration, it is a potential candidate for utilization in nuclear heat transfer applications. In the last decade, there have been few studies which indicate possible advantages of using nanofluids as a coolant in nuclear reactors during normal as well as accidental conditions. In continuation with these studies, the utilization of nanofluids as a viable candidate for emergency core cooling in nuclear reactors is explored in this paper by carrying out experiments in a scaled facility. The experiments carried out mainly focus on quenching behavior of a simulated nuclear fuel rod bundle by using 1% Alumina nanofluid as a coolant in emergency core cooling system (ECCS). In addition, its performance is compared with water. In the experiments, nuclear decay heat (from 1.5% to 2.6% reactor full power) is simulated through electrical heating. The present experiments show that, from heat transfer point of view, alumina nanofluids have a definite advantage over water as coolant for ECCS. Additionally, to assess the suitability of using nanofluids in reactors, their stability was investigated in radiation field. Our tests showed good stability even after very high dose of radiation, indicating the feasibility of their possible use in nuclear reactor heat transfer systems.

scholarly journals Temperature and interlayer coupling induced thermal transport across graphene/2D-SiC van der Waals heterostructure

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Md. Sherajul Islam ◽  
Imon Mia ◽  
A. S. M. Jannatul Islam ◽  
Catherine Stampfl ◽  
Jeongwon Park
Keyword(s):  
High Temperatures ◽  
Thermal Transport ◽  
Van Der Waals ◽  
Thermal Conductance ◽  
Interlayer Coupling ◽  
Phonon Modes ◽  
Out Of Plane ◽  
System Temperature ◽  
Non Equilibrium Molecular Dynamics ◽  
Increasing Temperature

AbstractGraphene based two-dimensional (2D) van der Waals (vdW) materials have attracted enormous attention because of their extraordinary physical properties. In this study, we explore the temperature and interlayer coupling induced thermal transport across the graphene/2D-SiC vdW interface using non-equilibrium molecular dynamics and transient pump probe methods. We find that the in-plane thermal conductivity κ deviates slightly from the 1/T law at high temperatures. A tunable κ is found with the variation of the interlayer coupling strength χ. The interlayer thermal resistance R across graphene/2D-SiC interface reaches 2.71 $$\times$$ × 10–7$${\text{Km}}^{2} /{\text{W}}$$ Km 2 / W at room temperature and χ = 1, and it reduces steadily with the elevation of system temperature and χ, demonstrating around 41% and 56% reduction with increasing temperature to 700 K and a χ of 25, respectively. We also elucidate the heat transport mechanism by estimating the in-plane and out-of-plane phonon modes. Higher phonon propagation possibility and Umklapp scattering across the interface at high temperatures and increased χ lead to the significant reduction of R. This work unveils the mechanism of heat transfer and interface thermal conductance engineering across the graphene/2D-SiC vdW heterostructure.

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