NSUF 25-5238: Improved In-reactor Performance of SiC by n-Doping with Phosphorus and Nitrogen Through Neutron Transmutation Doping and Pre-Irradiation Chemical Vapor Deposition

This project aims to determine the temperature dependence of the extrinsic thermal conductivity of the semiconductor silicon carbide (SiC) doped with nitrogen via chemical vapor deposition (CVD) and phosphorus via neutron transmutation doping (NTD). Thermal conductivity will be determined through measurements of thermal diffusivity by laser flash method, heat capacity by differential scanning calorimetry, and density from literature. The goal is to increase the electrical conductivity of SiC through n-type doping via as-fabricated pre-irradiation doping and in-reactor NTD. Coupled with the inherent semiconductor property of increasing electrical conductivity with increasing temperatures, the project will test the hypothesis that this increase in the electrical transport will lead to an increase in and domination by the electronic heat transfer mechanism contribution to the thermal conductivity resulting in an increase in the total thermal conductivity of the material at elevated temperatures. It is intended to test if a total doping level of about 1.2x1018 atoms/cm3 (~40 parts per thousand) will exhibit a transition temperature to increasing thermal conductivity at some temperature below 1500C. This RTE will stand as a prologue to a more extensive CINR project under review. SiC has long been advocated for use in advanced reactor designs and components for existing reactors due to its superior properties, including low activation, chemical inertness, radiation stability, and very high temperature performance. SiC is currently used as an advanced fuel component in TRISO fuel kernels and it has been suggested for use as cladding material as well as other in-vessel structural components. If the doped SiC, whether through CVD or NTD, can achieve higher thermal conductivity (and potentially improved mechanical properties), the study’s results will be highly significant. It could revolutionize the use of SiC in in-core component structural materials and provide a major advancement for SiC based cladding materials, where enhanced thermal conductivity is highly desirable. It could also position doped SiC as a potential substitute for the SiC component in TRISO fuels. In a nuclear reactor under a thermal neutron flux, 30Si (3% of the natural abundance of Si isotopes) can undergo neutron capture and covert to 31Si, which -decays with a half-life of 2.6 hours to the stable 31P. This phenomenon is known as Nuclear Transmutation Doping (NTP) and is well known in the electronics industry. This RTE project involves determining the temperature dependence of the thermal conductivity for a neutron irradiated SiC sample that was also pre-irradiation doped with nitrogen by CVD technique. The chosen sample has ~1/3 of the doping from phosphorus by NTD and ~2/3 of the doping from nitrogen by CVD. Thermal conductivity values from 5K to 1800K will be obtained by direct measurement and the thermal diffusivity (laser flash) x heat capacity x density method. Whereas defect and impurity accumulation in-reactor strongly act to decrease thermal conductivity through phonon-defect, phonon-impurity, and phonon-electron scattering mechanisms, a positive outcome from the project will demonstrate the relationship between degree of doping and temperature where properties can begin to improve as expressed by an increase in the thermal conductivity.

Informações Adicionais

Campo	Valor
Award Announced Date	2025-08-06T10:07:39.647
Awarded Institution	Idaho National Laboratory
Facility Tech Lead	Alina Montrose
Irradiation Facility
PI	Rory Kennedy
PI Email	[email protected]
Project Type	RTE
RTE Number	None