Investigation of the IGR research reactor’s uranium-graphite fuel's high-temperature corrosion by a combination of thermal analysis and mass-spectrometry methods

Abstract

The National Nuclear Center of the Republic of Kazakhstan (NNC RK) operates two unique research reactors – IVG.1 M and IGR, both of which are undergoing a conversion program to reduce nuclear fuel enrichment from 90 % to 19.75 % by ²³⁵U In 2023, the conversion of the IVG.1 M reactor was successfully completed. NNC RK is currently conducting various studies related to the conversion to a new uranium-graphite fuel for the IGR reactor. One such study focuses on the corrosion processes of the fuel surface under normal operating conditions and in various emergency situations, associated with the penetration of oxygen and water vapor into the reactor core. The study of changes in the basic physical and chemical properties of uranium-graphite fuel during interaction with chemically active gases and vapor-gas mixtures is crucial for predicting material behavior under various operating conditions.

This paper presents the results of the study of high-temperature corrosion of unirradiated uranium-graphite fuel of the IGR research reactor, using a combination of thermal analysis and mass spectrometry methods. During the experiments, data were obtained on the sample temperature, sample mass, heat flux to the sample, and changes in the composition of the reaction gas (vapor-gas mixture) in the chamber, which was purged throughout the experiment. The results of the high-temperature corrosion experiments of experimental, highly enriched uranium-graphite fuel in the reaction chamber of a thermogravimetric analyzer, with different compositions of chemically active gases, are presented. An analysis of the experimental data enabled the identification of corrosion mechanisms and the determination of the parameters of these processes.