TY - JOUR
T1 - Influence of microstructure and phase morphology on the stability of high temperature irradiation resistant thermocouples
AU - Riley, Scott
AU - Holloway, Kyle
AU - Bateman, Allyssa
AU - Skifton, Richard
AU - Jaques, Brian J.
N1 - Funding Information:
This work was prepared as an account of work sponsored by the U.S. Department of Energy , Office of Nuclear Energy Advanced Sensors and Instrumentation program under DOE Idaho Operations Office Contract DE-AC07-05ID14517 . Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness, of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.
Publisher Copyright:
© 2023
PY - 2023/6
Y1 - 2023/6
N2 - Development of in-core instrumentation is driven by the pursuit of safer and more economic energy production from both existing nuclear reactors and Generation IV reactor designs. Idaho National Laboratory (INL) has developed high temperature irradiation resistant thermocouples (HTIR-TCs) for temperature sensing inside Generation IV nuclear reactors. These thermocouples are composed of phosphorus-doped niobium (Nb-P) and lanthana-doped molybdenum (Mo-LaO) thermoelements, an alumina (Al2O3) insulation, and a niobium sheath. HTIR-TCs require an initial heat treatment exceeding the maximum service temperature to stabilize the generated electromotive force (EMF) signal; however, the mechanism behind this stabilization is not well understood. This work evaluates the impact of the stabilization heat treatment on the thermoelements' microstructures, chemical stability, and electrical properties to determine the mechanisms by which the EMF signal stabilization occurs. Accordingly, during the preliminary heat treatment, a secondary Nb3P phase formed within the Nb-P, along with an interaction region at the Al2O3/niobium interface. The formation of secondary phases within the niobium leg of the thermocouple causes an increase in the Seebeck coefficient. Stabilization of the HTIR-TC EMF signal was found to be dependent upon both the equilibrium of a diffusion interaction region at the Nb-P/Al2O3 interface and the formation of Nb3P precipitates.
AB - Development of in-core instrumentation is driven by the pursuit of safer and more economic energy production from both existing nuclear reactors and Generation IV reactor designs. Idaho National Laboratory (INL) has developed high temperature irradiation resistant thermocouples (HTIR-TCs) for temperature sensing inside Generation IV nuclear reactors. These thermocouples are composed of phosphorus-doped niobium (Nb-P) and lanthana-doped molybdenum (Mo-LaO) thermoelements, an alumina (Al2O3) insulation, and a niobium sheath. HTIR-TCs require an initial heat treatment exceeding the maximum service temperature to stabilize the generated electromotive force (EMF) signal; however, the mechanism behind this stabilization is not well understood. This work evaluates the impact of the stabilization heat treatment on the thermoelements' microstructures, chemical stability, and electrical properties to determine the mechanisms by which the EMF signal stabilization occurs. Accordingly, during the preliminary heat treatment, a secondary Nb3P phase formed within the Nb-P, along with an interaction region at the Al2O3/niobium interface. The formation of secondary phases within the niobium leg of the thermocouple causes an increase in the Seebeck coefficient. Stabilization of the HTIR-TC EMF signal was found to be dependent upon both the equilibrium of a diffusion interaction region at the Nb-P/Al2O3 interface and the formation of Nb3P precipitates.
KW - Differential scanning calorimetry
KW - Electron backscatter diffraction
KW - High temperature irradiation resistant thermocouple
KW - Seebeck coefficient, resistivity
KW - Thermoelectric drift
UR - https://www.scopus.com/pages/publications/85152144045
UR - https://www.mendeley.com/catalogue/8b875b17-4c42-3bbf-83f2-07c7913ed5a2/
U2 - 10.1016/j.mtcomm.2023.105972
DO - 10.1016/j.mtcomm.2023.105972
M3 - Article
AN - SCOPUS:85152144045
SN - 2352-4928
VL - 35
JO - Materials Today Communications
JF - Materials Today Communications
M1 - 105972
ER -