Purpose of reflectors in nuclear reactors In power reactors, installing a reflector layer around the core primarily ________ neutron leakage.

Introduction / Context:
Neutron reflectors surround the active core region to improve neutron economy. By scattering escaping neutrons back into the fuel region, reflectors reduce leakage and can enhance reactivity and fuel utilization.

Given Data / Assumptions:

• A reflector made of suitable material (e.g., graphite, water, beryllium) is placed outside the core.
• Steady-state reactor operation is assumed.
• Interest: net effect on neutron leakage.

Concept / Approach:
Reflectors present additional scattering paths beyond the core boundary, increasing the probability that outward-moving neutrons are redirected inward before being lost. This effectively decreases net leakage and provides reflector savings in core design (allowing a smaller critical core or flatter flux).

Step-by-Step Solution:
Consider boundary without reflector → higher leakage probability.Add reflector → more back-scattering and moderation.Therefore, leakage decreases with an effective reflector.

Verification / Alternative check:
Diffusion theory solutions show reduced neutron current out of the boundary when reflector regions are included; measured flux maps confirm higher edge flux and lower leakage.

Why Other Options Are Wrong:

• Increase/no effect contradict typical reflector behavior.
• “Randomly changes” is not consistent with predictable transport physics.
• Reversing flow “permanently” is not meaningful in this context.

Common Pitfalls:
Assuming any material works as a reflector; absorption cross section matters. Poor reflector materials could reduce benefits, but proper reflectors decrease leakage.

Final Answer:
decreases