On April 26, 1986, one of the most devastating nuclear disasters in history occurred at the Chernobyl Nuclear Power Plant near Pripyat, Ukraine. An explosion at Chernobyl's reactor number 4 destroyed the facility's protections against nuclear radiation and sent massive quantities of radioactive fallout into the atmosphere. In the aftermath of the disaster, scientists and historians have studied Chernobyl in order to determine exactly what went wrong. Was the catastrophe simply a tragic failure of nuclear safety systems? Or did something more than a mere accident happen at Chernobyl?
A nuclear accident happened at ChernobylShow moreShow less
A combination of technical problems and inadequate safety measures led to a catastrophic explosion.
Chernobyl's reactor number four was an RBMK reactor, an unusual Soviet design with serious flaws that allowed the catastrophic failure to occur. Specifically, RBMK reactors had problems with their void coefficients and control rod design.
Nuclear reactors are powered by nuclear chain reactions that generate heat through the process of fission. Critical components of nuclear reactors include the coolant, which cools the reactor core and transfers heat to electrical generators, and the control rods, which allow operators to control the rate of fission in the reactor in order to keep power levels within normal operating parameters.
The RBMK design used for Chernobyl's reactors used water as a coolant and had a positive void coefficient. The void coefficient refers to the proportion of steam bubbles in the reactor's coolant, and a positive void coefficient means that an increase in steam leads to an increase in reactivity. Reactors with positive void coefficients are highly unstable when operating at low power levels. This is what happened at Chernobyl: reactor number four became unstable when it was operated under very low power. The problem was exacerbated by an inadequate number of control rods, and by the fact that the lengths of the control rods did not match their required specifications.