The Chernobyl Disaster: Control Rods
One of the last elements of the Chernobyl disaster can be found in the design of the control rods. Control rods contain compounds comprising elements that are effective neutron absorbers. The Chernobyl RBMK control rods comprised primarily B4C and as a neutron absorber. The problem was not that this material wasn’t appropriate to suitable for use in control rods, it was that the bottom 1 m of the control rods was intended to extend past the bottom of the reactor. The tips of the control rods were, therefore, made of graphite followed by a hollow section before the neutron absorbent material began. Insertion of the control rod thus begins with displacement of water (or perhaps steam) by a rod that improves the neutron moderating capabilities of the system initially. If a large number of rods were inserted into the reactor simultaneously, the “reactivity” of the reactor (the number of fission events per unit time) would increase suddenly before decreasing as intended.
The control rod design was the final small misfortune that condemned the Chernobyl reactor.
Edited April 30, 2008.
Posted: April 29th, 2008 under Chernobyl, Nuclear Power.