Chapter 24.3, Problem 23SSC

Interpretation Introduction

Interpretation:

The process that occurs during a nuclear chain reaction in a nuclear reactor needs to be explained.

Concept introduction:

Nuclear fission produces the energy generated by nuclear reactors. This energy is primarily used to generate electricity at nuclear power plants. The fuel used in nuclear power plants is enriched to contain 3% uranium-235, the amount required to sustain a chain reaction, and is called enriched uranium. Certain rods, mostly made of cadmium or boron, regulate the cycle of fission within the reactor by absorbing the neutrons emitted during the reaction.

Answer to Problem 23SSC

In a chain reaction, one fission reaction produces two neutrons, these two produces two additional fissions. That means these two fissions discharge four more neutrons and forms four more fissions.

Explanation of Solution

If one fission reaction produces two neutrons, these two neutrons can cause two additional fissions. If those two fissions release four neutrons, those four neutrons could then produce four more fissions. This self-sustaining mechanism is called a chain reaction, in which one reaction initiates the next. When a critical mass is present, the neutrons released in one fission cause other fissions to occur. If much more mass than the critical mass is present, the chain reaction rapidly escalates. This can lead to a violent nuclear explosion. A sample of fissionable material with a mass greater than the critical mass is said to have supercritical mass. It needs careful monitoring and constant adjustment of the control rods to maintain the chain reaction running while preventing it from speeding out of control.

Conclusion

The number of fissions and the quantity of energy discharge can rise rapidly in the chain reaction. The blast from an atomic bomb is an example of an uncontrolled chain reaction.