Other studies explain that the second explosion was produced by the rapid heating of the structural materials of the nucleus, caused by the loss of water after the first explosion. The hydrogen was formed by the reaction of graphite – used by this type of reactor as a neutron moderator – and water vapour at very high temperatures.
A few seconds later, there was a second, stronger explosion, probably caused by the combustion of the hydrogen, which had accumulated inside the reactor. First, there was a steam explosion that created cracks in the reactor and allowed oxygen to enter the core. When the experiment itself began, the reactor suffered a sudden increase in power, at least up to ten times more than was anticipated in the reactor design, and all the cooling water evaporated in a few moments. However, these actions by the Chernobyl operators left the reactor in a highly unstable state they were not quite aware of. In a nuclear reactor, control rods are used as a safety mechanism because they absorb a large amount of neutrons, so adjusting their position is the easiest way for operators to control the amount of fission reactions occurring within the core. To correct the situation, the operators decided to disconnect most of the control rods from the automatic regulation system, which they removed manually, and reduced the injection of cooling water. This caused the power to drop below the limits required for the experiment. A delay in the start of the experiment caused contamination by xenon-135, an element that absorbs neutrons and therefore slows the fission rate in the reactor. To do this experiment, the reactor had to be operating at very low powers. Paradoxically, nuclear reactors require external electrical power to operate the control rooms and hydraulic pumps that circulate the water inside the reactor core and extract the heat generated within. In the early hours of 26 April 1986, the operators of the Chernobyl nuclear power plant were preparing to carry out an experiment to check whether, after a power outage, the turbine was capable of generating enough electricity to operate the safety systems.
0 kommentar(er)
