What is the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction called?

What is the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction called?

• A. Critical mass
• B. Half-life
• C. Nuclear Fusion
• D. Fusion energy production

Answer: (A)

The idea being tested is critical mass: the minimum amount of fissile material needed for the neutrons produced by fission to on average cause at least one more fission, so the chain reaction can continue. If the mass is below this, neutrons escape or are absorbed without causing further fission, and the reaction dies out. The exact critical mass depends on how densely the material is packed, its shape, impurities, and whether a neutron reflector is used, all of which affect how many neutrons stay in the material to sustain fission. By contrast, half-life concerns how quickly the material decays over time, nuclear fusion involves joining nuclei rather than splitting them, and fusion energy production is about energy from fusion, not sustaining a fission chain.

The idea being tested is critical mass: the minimum amount of fissile material needed for the neutrons produced by fission to on average cause at least one more fission, so the chain reaction can continue. If the mass is below this, neutrons escape or are absorbed without causing further fission, and the reaction dies out. The exact critical mass depends on how densely the material is packed, its shape, impurities, and whether a neutron reflector is used, all of which affect how many neutrons stay in the material to sustain fission. By contrast, half-life concerns how quickly the material decays over time, nuclear fusion involves joining nuclei rather than splitting them, and fusion energy production is about energy from fusion, not sustaining a fission chain.