In the thermal utilization factor, what does the ratio represent?

In the thermal utilization factor, what does the ratio represent?

• A. The ratio of fast neutrons produced to those absorbed
• B. The ratio of neutrons captured in fuel to total neutrons captured
• C. The ratio of fission cross section to absorption
• D. The ratio of reactor power to neutron production

Answer: (B)

The thermal utilization factor tells you what fraction of absorbed neutrons are captured in the fuel. It is defined as the number of neutrons captured in the fuel divided by the total number of neutrons captured (in fuel and in non-fuel materials) when the neutrons are thermal. So the ratio represents the share of all absorptions that occur in the fuel. This is why the description of neutrons captured in fuel relative to all captured neutrons is the correct interpretation. Other statements describe different ideas (like production of fast neutrons, cross-section ratios, or power relative to neutron production) and do not describe how the absorptions are distributed between fuel and other materials.

The thermal utilization factor tells you what fraction of absorbed neutrons are captured in the fuel. It is defined as the number of neutrons captured in the fuel divided by the total number of neutrons captured (in fuel and in non-fuel materials) when the neutrons are thermal. So the ratio represents the share of all absorptions that occur in the fuel. This is why the description of neutrons captured in fuel relative to all captured neutrons is the correct interpretation. Other statements describe different ideas (like production of fast neutrons, cross-section ratios, or power relative to neutron production) and do not describe how the absorptions are distributed between fuel and other materials.