Title : Determination of the elemental composition and changes in thermal and electrical conductivity of “Hanford” and GMZ grade graphite depending on the fast neutrons fluence
Abstract:
Graphite used as a key material for heat dissipation in electronic devices and nuclear engineering due to its remarkable thermal properties. Thermal expansion and conductivity of graphite have always been the main scientific parameters in the field of carbon materials. Therefore, paid great attention to theoretical and experimental research in this area.We know that neutron irradiation noticeably reduces the electrical and thermal conductivity of graphite materials. When nuclear graphite is annealed, Wigner energy is released [10]. The thermal conductivity values of individual grades of graphite vary greatly from each other, this is the result of different production processes leading to differences in the microstructure of the final product. Studying the properties of graphite recovered from operating nuclear reactors is vital for predicting the properties and integrity of graphite as part of assessing continued operation and life extension of a nuclear power plant. Reactors have limited space available for monitoring structural materials, so size-constrained samples require reliable and efficient measurement methods. To study the elemental composition, thermal and electrical conductivity, samples of Hanford grade graphite were used, obtained from residual reserves from the construction of the first nuclear reactor B in Hanford. A sample with a diameter of 12 mm and a height of 3.4 mm was irradiated. The mass of the sample was 0.6 g. The size of GMZ grade graphite was 16 mm in diameter, 3.64 mm in height, and weighed 1.3 g. The samples were irradiated with neutrons from the VVR-SM nuclear reactor of the Institute of Nuclear Physics of the Academy of Sciences of Uzbekistan with an integral fast neutron flux of 1017 - 1019 n/cm2. In graphite samples, the concentrations of 15 elements were determined by neutron activation analysis, thermal conductivity and electrical conductivity were measured.
