Abstract
The paper describes an experience of the IVG.1M research reactor operation with the core water-cooling system, which includes an auxiliary reactor coolant cooling system, designed for forced coolant cooling in periods of long-term reactor shutdown. The IVG.1M reactor is cooled by a limited amount of coolant circulating in a closed circuit, heated and uncooled during reactor operation. In this regard, duration of continuous operation of the reactor and frequency of startups are restricted due to limited value of water temperature at the core inlet. Prior to commissioning of the reactor coolant cooling system, it was cooled by means of natural heat transfer to the environment, while full-scale reactor startups were conducted with a frequency of approximately once per month. With forced coolant cooling, provided by use of the reactor coolant cooling system, its temperature decreases to acceptable values approximately within a week after the next startup, and, accordingly, full-scale startups of the IVG.1M reactor can be conducted once a week. This significantly expands potential of using the reactor and at the same time accelerates burnup of nuclear fuel and decrease in the reactor reactivity margin. Estimation of the fuel burnup rate will allow organizing timely supply of fresh fuel to replace the burnt out fuel. The paper contains the measurement results of the coolant temperature after a series of reactor startups, based on which it can be concluded that the IVG.1M RCCS has an effect on reducing the reactor downtime time between startups. The obtained results can be used to select and justify options for implementing the reactor campaign and its fuel.