The Chernobyl experiment was not ordered by scientists. It was ordered by a political appointee who wanted to exceed his boss's expectations and show that the plant could also generate useful power at low neutron densities. The onsite engineers protested to no avail. Unfortunately, the reactor graphite core did not shut down evenly. Instead, full neutron current ran in small sections of the graphite without adequate cooling. When the graphite reached the temperature to dissociate water, the free oxygen ignited a granite/hydrogen explosion which blew about 190 MT of fissionables out of the containment and into the environment.
I'm one of the proposers of an international nuclear intervention process for nuclear disaster like Chernobyl.