Chapter 40, Problem 7A

To determine

Whether the supercritical chain reaction is more likely in two separate pieces of U-235 or the same pieces stuck together.

Explanation of Solution

Introduction:

The critical chain reaction is the fission reaction that produces the enough number of neutrons for another one fission reaction. If the number of neutrons produced in critical reaction can initiate more chain reactions then it is called the supercritical chain reaction.

The neutrons in the separate pieces of U-235 reaches the surface and escapes quickly from the surface. So, neutrons in separate pieces are only able initiate subcritical chain reaction.

The distance to reach the surface of stuck pieces of U-235 is more. So, the neutron in the stuck pieces are able to trigger chain reaction in more U-235 atoms in stuck pieces. The more the number of atoms triggered by the neutron for chain reaction more likely the stuck pieces of U-235 for supercritical chain reaction.

Conclusion:

Thus, the stuck pieces of U-235 are more likely to initiate the supercritical chain reaction.