Abstract
The relevance of the study is related to the of nuclear control safety. Determining the temperature coefficient of reactivity (TCR) experimentally is a rather difficult problem. One of the main difficulties is to heat up the reactor from two (or more) heat sources with different temperatures for a long time, sufficient for the isothermal heating of all reactor parts. The proof of the reactor isothermal heating may be the equalization of the coolant temperature in the distribution header (at the reactor inlet) and in the drain header (at the reactor outlet) for a time sufficient to stabilize the reactor critical state and the position of the regulatory authorities accordingly. The essence of the study method is related to the fact that during the experiment to determine the TCR, the conditions were created under which barometric (hydrodynamic) and power effects affecting the research reactor reactivity were excluded. The significance of the results is the fact that the TCR, one of the important safety assessment parameters for the IVG.1M reactor, was determined experimentally after the reactor was converted from highly enriched (HEU) to low enriched uranium (LEU) fuel.