Describe the difference between a controlled chain reaction and an uncontrolled chain reaction in nuclear fission.

A controlled chain reaction occurs in a nuclear reactor where control rods absorb excess neutrons to regulate the fission rate, ensuring a steady release of energy. In contrast, an uncontrolled chain reaction happens when there is no regulation, leading to a rapid increase in fission events and potentially an explosion.

This question assesses the ability to distinguish between two types of chain reactions in nuclear fission. A strong answer clearly outlines the mechanisms of control and the consequences of uncontrolled reactions, which is essential for understanding nuclear safety.