tdown. Since the auxiliary diesel engines would automatically engage when power was reduced they were disconnected from the emergency safety system. This allowed the operators to test whether the rundown unit could provide sufficient energy to the cooling pumps during the transition to diesel engine power. As the test began the operator of the control rods lowered them too much which caused a drop in power. At low power levels a process called xenon poisoning takes place within the reactor. This process prevents the reactor from regaining high-level output because xenon absorbs the neutrons needed to create thermal energy. Still determined to complete the test the operators raised the rods in order to maintain sufficient energy output. At 1:23am the steam valves to the turbines were closed and the turbine began to spin down (Medvedev Legacy 11). This point marked the beginning of the sequence of events that would lead to the meltdown of the core. Conditions within the core quickly became dangerously unstable. The spin down of the turbine did not supply sufficient energy to maintain a safe level of coolant circulation through the core. As water circulation within the core decreased the steam pressure within the core began to rise rapidly creating a 'positive void coefficient' (Medvedev Legacy 30). The increased steam leads to an increase in power, which leads to more heat and more steam pressure. This condition coupled with the decrease in cooling led to a massive power surge, which could not be controlled by the operators. The above events occurred over a 36 second time frame from the beginning of the test at 1:23am. At this point the chief operator pressed the emergency shutdown button, lowering the rods, and decreasing the power. This act was insufficient to stem the crisis that had developed. At 1:24am, 20 seconds after the emergency button was pressed, the first explosion rocked the core, displacing the ...