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Applied Sciences
Volume 16
Issue 15
10.3390/app16157853
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Low-Temperature EMF Stability of Mineral-Insulated Thermocouples for Pressurized Water Reactor Core Outlet Temperature Measurement

by
Jie Chen
1,2,3,*,
Xiaodong Peng
2,
Min Liu
3,
Anzhong Zhao
3,
Meiliang Huang
4 and
Shuzhi Chen
4
1
School of Intelligent Manufacturing and Automobile, Chongqing Polytechnic University of Electronic Technology, Chongqing 401331, China
2
Department of Material Science and Engineering, Chongqing University, Chongqing 400044, China
3
Chongqing Material Research Institute Co., Ltd., Chongqing 400707, China
4
China Nuclear Power Engineering Co., Ltd., Shenzhen 518116, China
*
Author to whom correspondence should be addressed.
Appl. Sci. 2026, 16(15), 7853; https://doi.org/10.3390/app16157853
Submission received: 2 June 2026 / Revised: 3 August 2026 / Accepted: 5 August 2026 / Published: 6 August 2026
Versions Notes

Featured Application

The stability of the electromotive force (EMF) of K-type thermocouples used for measuring the core outlet temperature in PWRs is studied. The selection of optimized materials, the preparation of pre-oxidized wires, and the implementation of a stabilization treatment effectively suppress EMF drift under abnormal temperature conditions. The results can be directly applied to the design, manufacturing, and qualification of nuclear-grade thermocouples to improve the accuracy and reliability of temperature monitoring of instruments and control systems in nuclear power plants.

Abstract

The core outlet temperature is an important safety parameter for pressurized water reactors (PWRs), and its accurate determination depends on highly reliable thermocouple sensors. In this study, two typical commercial K-type thermocouple alloys (de1 and de2) were used to fabricate mineral-insulated metal-sheathed (MIMS) thermocouples. A comparative severe accelerated aging test at 500 °C for 168 h was performed to investigate electromotive force (EMF) stability under high-temperature exposure conditions. After aging, both alloy types exhibited obvious positive EMF drift, and the maximum drift magnitude appeared at the calibration temperature of 400 °C. The measured irreversible EMF drift of de2 thermocouples was lower than that of de1 thermocouples. For the same de2 alloy, thermocouples fabricated with pre-oxidized thermoelement wires presented smaller irreversible drift than those made of bright wires. Reversible EMF drift and heating–cooling calibration hysteresis were more significant for de1 specimens. Stabilization treatment at 570 °C for 2 h followed by furnace cooling effectively reduced the thermal hysteresis of both alloys during temperature cycling. This study provides straightforward experimental data and practical processing references for optimizing the manufacturing route of nuclear-grade MIMS thermocouples with improved high-temperature EMF stability.
Keywords: thermocouple; electromotive force (EMF) drift; stability thermocouple; electromotive force (EMF) drift; stability

Share and Cite

MDPI and ACS Style

Chen, J.; Peng, X.; Liu, M.; Zhao, A.; Huang, M.; Chen, S. Low-Temperature EMF Stability of Mineral-Insulated Thermocouples for Pressurized Water Reactor Core Outlet Temperature Measurement. Appl. Sci. 2026, 16, 7853. https://doi.org/10.3390/app16157853

AMA Style

Chen J, Peng X, Liu M, Zhao A, Huang M, Chen S. Low-Temperature EMF Stability of Mineral-Insulated Thermocouples for Pressurized Water Reactor Core Outlet Temperature Measurement. Applied Sciences. 2026; 16(15):7853. https://doi.org/10.3390/app16157853

Chicago/Turabian Style

Chen, Jie, Xiaodong Peng, Min Liu, Anzhong Zhao, Meiliang Huang, and Shuzhi Chen. 2026. "Low-Temperature EMF Stability of Mineral-Insulated Thermocouples for Pressurized Water Reactor Core Outlet Temperature Measurement" Applied Sciences 16, no. 15: 7853. https://doi.org/10.3390/app16157853

APA Style

Chen, J., Peng, X., Liu, M., Zhao, A., Huang, M., & Chen, S. (2026). Low-Temperature EMF Stability of Mineral-Insulated Thermocouples for Pressurized Water Reactor Core Outlet Temperature Measurement. Applied Sciences, 16(15), 7853. https://doi.org/10.3390/app16157853

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