Which statement about subcritical, critical and supercritical masses is true?

Which statement about subcritical, critical and supercritical masses is true?

• A. Subcritical mass is the mass of fissile material that would sustain a chain reaction.
• B. Critical mass is the mass that is not enough to sustain a chain reaction.
• C. Supercritical mass is the mass that is more than enough to sustain a nuclear chain reaction.
• D. Subcritical mass is the mass of fissile material insufficient to sustain a chain reaction.

Answer: (C)

Understanding how mass relates to a fission chain reaction helps here. Subcritical, critical, and supercritical describe whether the neutron population sustains, matches, or grows the reaction. Subcritical means there aren’t enough neutrons to keep the chain going, so the reaction tends to die out unless an external source keeps it going. Critical means the neutron production just balances losses, so the reaction can continue at a steady rate. Supercritical means there is more than enough mass for the neutrons produced to exceed losses, causing the reaction rate to rise. The statement about a supercritical mass being more than enough to sustain a nuclear chain reaction matches this idea directly: having extra mass pushes the system into a self-sustaining, growing chain reaction. The other choices misrepresent the meanings—subcritical would not sustain on its own, critical mass is the threshold to sustain rather than “not enough,” and while describing subcritical as insufficient is true, it doesn’t capture the defining behavior of when the reaction actually grows.

Understanding how mass relates to a fission chain reaction helps here. Subcritical, critical, and supercritical describe whether the neutron population sustains, matches, or grows the reaction. Subcritical means there aren’t enough neutrons to keep the chain going, so the reaction tends to die out unless an external source keeps it going. Critical means the neutron production just balances losses, so the reaction can continue at a steady rate. Supercritical means there is more than enough mass for the neutrons produced to exceed losses, causing the reaction rate to rise.

The statement about a supercritical mass being more than enough to sustain a nuclear chain reaction matches this idea directly: having extra mass pushes the system into a self-sustaining, growing chain reaction. The other choices misrepresent the meanings—subcritical would not sustain on its own, critical mass is the threshold to sustain rather than “not enough,” and while describing subcritical as insufficient is true, it doesn’t capture the defining behavior of when the reaction actually grows.