Methodological errors in in-reactor temperature measurements

The requirement of increased reliability and economy of atomic power stations necessitates high accuracy of in-reactor measurements of the fuel-element temperature. Thermoelectric converters are mainly used as the primary temperature converters for this purpose. There are longitudinal holes in the fuel element, into which the thermoelectric converter is introduced directly or as part of a thermometric assembly, where the converter is placed in a technological (protective) sleeve. The changes in thermoemf observed over time suggest that one cause of such changes, in addition to integral effects, may be the presence of methodological errors due to radiational energy liberation in the constructional materials of thermoelectric converters and the technological sleeve. Variation in the contact thermal resistance between the working junction of the converter and the fuel leads to oscillation of the methodological errors. A theoretical-experimental method is proposed for the estimation of the methodological errors of thermoelectric-converter readings in conditions of steady operation of a nuclear reactor, ensuring that the whole set of relevant factors is taken adequately into account