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:
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:
Common Pitfalls:
Overlooking neutron energy effects; scattering angles and lethargy change per collision matter to return probability.
Final Answer:
All of these
Discussion & Comments