What were the tips of the control rods in Chernobyl?
The control rods slipped into the reactor to slow reactivity. The boron slowed the reactions down, but the graphite tips initially increased the rate of fission. This was a design flaw, was one of the main factors that caused the explosion.
Why did Chernobyl rods have graphite tips?
Graphite facilitates the fission chain reaction in a graphite reactor by slowing neutrons. Coolant water in such a reactor absorbs neutrons, thus acting as a poison. When the 205 control rods began driving into the surging Number 4 reactor, the graphite tip went in first.
Why are boron control rods tipped with graphite?
The graphite is a moderator and slows neutrons mostly to generate more fission reactions. The graphite tip makes the control rod tip act like a cap to the hole the control rod is in if the rod is pulled fully out, which means the cap is all that is left in the hole.
What does graphite mean in Chernobyl?
Although the Chernobyl reactor was also cooled by water, the water was essentially only used for cooling, but not slowing down the neutrons. Instead, enormous blocks of graphite surrounded the fuel and were used to slow down the neutrons. The graphite blocks caught fire causing more heat and damage.
Is graphite cheaper than boron?
In either case, the carbon tip moderates the change in criticality as the rod is withdrawn. Graphite is glorified coal (carbon C) and pretty cheap. Boron (B) is a relatively rare element and probably more expensive. Both are used in controlling nuclear reactors, but their properties are not the same.
Why did the Chernobyl reactor explode?
The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel. The resulting steam explosion and fires released at least 5\% of the radioactive reactor core into the environment, with the deposition of radioactive materials in many parts of Europe.