Which component is used to slow down fast neutrons to prevent them from leaving the reactor core?

Which component is used to slow down fast neutrons to prevent them from leaving the reactor core?

• A. Coolant
• B. Moderator
• C. Regulator Rods
• D. Control Rods

Answer: (B)

When neutrons are born from fission, they are fast. To keep the chain reaction going inside the fuel, these neutrons need to be slowed to thermal energies, where they are much more likely to encounter and cause fission in the fuel. The component that does this slowing is the moderator. It works by elastic collisions with light nuclei (like hydrogen in water or carbon in graphite). These collisions drain the neutron’s energy without absorbing too many of them, so the neutrons stay in the core longer and have a higher chance of sustaining the reaction. The other options don’t primarily slow neutrons. The coolant mainly removes heat from the reactor. The rods labeled as regulator or control rods absorb neutrons to decrease or control the reaction rate, rather than slowing the neutrons down.

When neutrons are born from fission, they are fast. To keep the chain reaction going inside the fuel, these neutrons need to be slowed to thermal energies, where they are much more likely to encounter and cause fission in the fuel. The component that does this slowing is the moderator. It works by elastic collisions with light nuclei (like hydrogen in water or carbon in graphite). These collisions drain the neutron’s energy without absorbing too many of them, so the neutrons stay in the core longer and have a higher chance of sustaining the reaction.

The other options don’t primarily slow neutrons. The coolant mainly removes heat from the reactor. The rods labeled as regulator or control rods absorb neutrons to decrease or control the reaction rate, rather than slowing the neutrons down.