Why was Chernobyl unstable at low power?

One of the most crucial causes of the accident is the large positive void coefficient possessed by the nuclear reactor. However, the RBMK reactor used had a positive coefficient, which means that the reactor becomes very unstable at low power levels, and vulnerable to dangerous rises in energy production levels.

Why was the RBMK reactor flawed?

As the disaster showed, the RBMK had some key design flaws. In particular, the location of the control rods, the containment structure, and the reactor’s positive void coefficient proved to be quite unsafe. RBMK reactors operated for decades in Russia after the Chernobyl disaster.

What design flaw caused Chernobyl?

A peculiarity of the design of the control rods caused a dramatic power surge as they were inserted into the reactor (see Chernobyl Accident Appendix 1: Sequence of Events). The interaction of very hot fuel with the cooling water led to fuel fragmentation along with rapid steam production and an increase in pressure.

What flaw caused Chernobyl?

Human error was the overriding cause of the Chernobyl nuclear accident, but the reactor’s design made it a difficult one to manage, according to nuclear safety experts who have read the Soviet Union’s government report on the disaster.

What is a scram button?

A scram or SCRAM is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction. It is also the name that is given to the manually operated kill switch that initiates the shutdown.

Why did RBMK reactors have graphite tips?

A minimum reserve for an RBMK reactor is supposed to be 30 control rods. 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.

Why was the RBMK reactor so dangerous?

However, the RBMK reactor used had a positive coefficient, which means that the reactor becomes very unstable at low power levels, and vulnerable to dangerous rises in energy production levels. This was one of the reasons for the reactor explosion during the Chernobyl accident. Another cause was a flaw in the design of control rods.

What is the Chernobyl reactor design?

The Chernobyl reactor uses a RBMK design, a design that is unique to former Soviet Union and former Eastern Bloc countries. [1,2,5] The RBMK, or the channelized large power reactor, is a boiling water reactor. It does not have any pressure vessels; rather, the fuel assemblies are found in pressurized tubes (1000 or more).

Where did the radioactive fallout from Chernobyl come from?

The majority of the radioactive fallout (an estimated 60\%) landed in Belarus. The Chernobyl reactor uses a RBMK design, a design that is unique to former Soviet Union and former Eastern Bloc countries. [1,2,5] The RBMK, or the channelized large power reactor, is a boiling water reactor.

What is the purpose of the ventilation stacks at Chernobyl?

The ventilation stacks at RBMK power plants are used to discharge gaseous radioactive wastes, chiefly argon-41. At Chernobyl, air sparging was used to clean up the water in the control rod cooling circuit, dissolving a relatively large amount of atmospheric Ar-40 in the water.