Influence of high dose γ irradiation on the calibration characteristics of type K mineral-insulated metal-sheathed thermocouples

Abstract In this paper, the influence of high dose γ irradiation on the thermoelectric drift of the mineral-insulated metal-sheathed (MIMS) thermocouples has been investigated by calibrations from 100 °C to 400 °C and Electron Probe Micro-Analysis (EPMA) composition analysis. The results show that the thermal electromotive force (EMF) of the thermocouples increases dramatically and the highest drift reaches to about +173 μV at 400 °C after γ irradiation. Moreover, the total EMF drift is consisted of reversible and irreversible changes. The reversible drift is positive and has been recovered by annealing at 1070 °C. This is because of the short order arrangement of the positive thermoelement (KP). For the irreversible drift, the EMF decreases −24 μV at 200 °C and increases about +32 μV at 300 °C and +55 μV at 400 °C, respectively. The irreversible changes are attributed to a small amount of oxidation of the KP thermoelement and the aging of the two thermoelements. The deep understanding of the EMF drift mechanism is of crucial importance in terms of the manufacture of thermocouple sensor and the safety operation system in the nuclear reactors.

[1]  R. N. Wright,et al.  Thermophysical properties of Alloy 617 from 25 °C to 1000 °C , 2013 .

[2]  P. B. Coates.  The replacement of type K by nicrosil-nisil thermocouples , 1981 .

[3]  N. Asahi,et al.  Reversible short-range ordering due to the structural relaxation in amorphous Ni-Cr-B alloys , 1991, Journal of Materials Science.

[4]  R. Averback,et al.  Displacement damage in irradiated metals and semiconductors , 1997 .

[5]  Lars-Erik Josefson,et al.  Inhomogeneity Measurements of Long Thermocouples using a Short Movable Heating Zone , 2008 .

[6]  T. Tsuji,et al.  Heat capacity of (Cr1-xNix)3Te4(x=0-0.2) at high temperatures , 2001 .

[7]  R S Pease,et al.  REVIEW ARTICLES: The Displacement of Atoms in Solids by Radiation , 1955 .

[8]  M. Laurie,et al.  Long term out-of-pile thermocouple tests in conditions representative for nuclear gas-cooled high temperature reactors , 2011, 2011 2nd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications.

[9]  P. A. House,et al.  Effects of fusion neutrons on thermocouples , 1981 .

[10]  R. Powell,et al.  The Nicrosil versus Nisil Thermocouple: Properties and Thermoelectric Reference Data , 1978 .

[11]  K. Sloneker.  Life Expectancy Study of Small Diameter Type E, K, and N Mineral-Insulated Thermocouples Above 1000 °C in Air , 2011 .

[12]  G. Coggiola,et al.  Stability of K-, N- and S-type thermocouples in the temperature range from 0°C to 1060°C , 1993 .

[13]  Rl Meltzer,et al.  Electromotive Force Stability of Nicrosil-Nisil® , 1980 .

[14]  A. Fenton.  Errors in thermoelectric thermometers , 1969 .

[15]  K. R. Carr,et al.  Temperature measurement errors with type K (Chromel vs Alumel) thermocouples due to short‐ranged ordering in Chromel , 1975 .