Chapter 40, Problem 31A

To determine

Whether a piece of uranium in pancake shape is more likely or less likely for supercritical chain reaction and the reason for this.

Explanation of Solution

Introduction:

The chain reaction in which primary fission reaction produces the large amount of neutrons that can produce more subsequent chain reactions is called supercritical reaction.

The chances of a chain reaction to be supercritical reaction depends on the time and distance for the neutron before escape the surface of radioactive material.

The distance for the neutron in uranium piece increases due to flattening of the uranium piece. The time to escape the surface of uranium piece also increases. So, the neutron can trigger more fission of the other pieces and supercritical chain reaction become more likely than in a normal piece.

Conclusion:

Thus, the supercritical chain reaction is more likely in flattened piece of uranium due to more distance and time for neutron before escaping the surface of piece.