What is one of the ways a fission reaction can get out of control? when there are too many neutrons when the neutrons are slowed down when there is a chain reaction when there is critical mass

Out of the following given choices;

A)when there are too many neutrons

B)when the neutrons are slowed down

C)when there is a chain reaction

D)when there is critical mass

The answer is A. A fission nuclear reactor is controlled by regulating the number of neurotoxins produced in the chain reaction. Too many neutrons cause an accelerated chain reaction that causes enormous heat to be generated in a short amount of time which could cause an explosion. Control rods , made of “neutron poisons”, e.g. cadmium, are put in the reactors to control the number of neutrons at any one time

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