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Impedance spectroscopy characterization of neutron irradiated thermoelectric modules for space nuclear power

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journal contribution
posted on 10.06.2019, 09:14 by R Mesalam, H Williams, R Ambrosi, D Kramer, C Barklay, J Garcia-Canadas, D Weston
The European Space Agency is currently supporting the research and development of advanced radioisotope power systems utilising thermoelectric modules. The performance of thermoelectric modules following exposure to neutron radiation is of significant interest due to the likely application of radioisotope thermoelectric generators in deep space exploration or planetary landers requiring prolonged periods of operation. This study utilises impedance spectroscopy to characterise the effects of neutron irradiation on the performance of complete thermoelectric modules, as opposed to standalone material. For a 50 We americium-241 radioisotope thermoelectric generator design, it is estimated that the TE modules could be exposed to a total integrated flux of approximately 5 × 1013 neutrons cm-2 (>1 MeV). In this study, an equivalent neutron dose was simulated experimentally via an acute 2-hour exposure in a research pool reactor. Bi2Te3-based thermoelectric modules with different leg aspect ratios and microstructures were investigated. Gamma-ray spectroscopy was initially used to identify activated radionuclides and hence quantify irradiation induced transmutation doping. To evaluate the thermoelectric properties pre- and post-irradiation, impedance spectroscopy characterization was employed. Isochronal thermal annealing of defects imparted by the irradiation process, revealed that polycrystalline based modules required significantly higher temperature than those with a monolithic microstructure. Whilst this may indicate a greater susceptibility to neutron irradiation, all tested modules demonstrated sufficient radiation hardness for use within an americium-241 radioisotope thermoelectric generator. Furthermore, the work reported demonstrates that impedance spectroscopy is a highly capably diagnostic tool for characterising the in-service degradation of complete thermoelectric devices.

Funding

Funding for RM was provided in part via EPSRC grants EP/L505006/1, EP/M506564/1 and EP/M508081/1. JGC acknowledge financial support from the Spanish Agencia Estatal de Investigación under the Ramón y Cajal program (RYC-2013-13970) and from the Universitat Jaume I under the project UJI-A2016-08. The authors gratefully acknowledge the assistance provided by, the Ohio State University Research Reactor team, the European Space Agency and the role of the EPSRC TE Network in fostering the collaboration.

History

Citation

AIP Advances, 2019, 9, 055006

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Engineering

Version

VoR (Version of Record)

Published in

AIP Advances

Publisher

American Institute of Physics

issn

2158-3226

Acceptance date

26/04/2019

Copyright date

2019

Available date

10/06/2019

Publisher version

https://aip.scitation.org/doi/10.1063/1.5095619

Notes

See supplementary material ftp://ftp.aip.org/epaps/aip_advances/E-AAIDBI-9-009905 for the gamma and impedance spectroscopy data required to reproduce these findings.

Language

en

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