When a free neutron collides with a uranium-235 nucleus and causes that nucleus to fission, the collision fragments contain a total of 2.5 free neutrons, on average, including the original free neutron. The critical mass for uranium-235 is about 50 kilograms. Suppose that another radioactive material, fundamentium-999, undergoes fission when struck by a neutron and the collision fragments contain a total of 0.5 neutrons, on average, including the original free neutron. What would be the critical mass of fundamentium-999?
A) Infinite. No chain reaction could occur in fundamentium-999.
B) About 10 kilograms
C) About 50 kilograms
D) About 250 kilograms

Question

Quizplus · Accepted Answer

For a chain reaction to be sustained, each fission event must produce at least one new neutron to continue the reaction. Since fundamentium-999 produces only 0.5 neutrons on average, it cannot sustain a chain reaction, implying an infinite critical mass.

When a Free Neutron Collides with a Uranium-235 Nucleus and Causes