Neutron reflectors – factors affecting reflectivity The effectiveness (reflectivity) of a neutron reflector in a reactor depends primarily on which of the following?

Difficulty: Easy

Correct Answer: All of these

Explanation:


Introduction / Context:
Neutron reflectors are placed around a reactor core to reduce neutron leakage, improve utilization, and flatten power distributions. Reflector performance depends on several interacting factors that influence scattering and absorption.



Given Data / Assumptions:

  • Steady reactor operation.
  • Reflector materials such as graphite, beryllium, water, or steel.
  • Interest in overall reflectivity (return of neutrons into the core).


Concept / Approach:
Reflectivity is governed by (1) material properties (scattering cross section, absorption cross section, atomic mass), (2) geometry and thickness (more mean free paths increase return probability), and (3) neutron energy (fast vs. thermal scattering behavior). Therefore, it is not a single-parameter phenomenon.



Step-by-Step Solution:
Consider material: low absorption, high scattering improves reflection.Consider geometry: sufficient thickness and proper shape minimize leakage paths.Consider energy: moderation and back-scatter depend on neutron energy spectrum.Therefore, “All of these” control reflectivity.



Verification / Alternative check:
Core design calculations and diffusion/transport theory solutions show reflector savings dependent on both material buckling and reflector thickness.



Why Other Options Are Wrong:

  • Any single factor alone is incomplete; real reflectivity arises from their combination.
  • “None” is clearly incorrect.


Common Pitfalls:
Overlooking neutron energy effects; scattering angles and lethargy change per collision matter to return probability.



Final Answer:
All of these

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