On April 25, 1986, the shutdown of the 4th power unit of the Chornobyl NPP was scheduled for routine maintenance. It was decided to use this opportunity to conduct a series of tests. The purpose of one of them was to check the design mode, which involves the use of coasting (inertia) of the generator turbine to power the reactor systems in case of loss of external power supply. Dazai was in the control department located further from power unit 4 and, receiving information and messages, gave appropriate instructions. Before the start of the experiment, Dazai decided to personally be near the 4th power unit and the reactor operator in order to obtain results from the first sources.