Function of using reflector in nuclear reactor is to

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Examoogle · Accepted Answer

Send back the escaping neutrons

Explanation: A reflector in a nuclear reactor is a layer of material placed around the reactor core to reduce neutron leakage. Its primary function is to scatter or 'reflect' escaping neutrons back into the core, thereby maintaining the chain reaction and improving neutron economy.

Working Principle: Reflectors utilize materials with high scattering cross-sections and low absorption cross-sections, such as graphite, beryllium, or heavy water. When fast neutrons strike the nuclei of the reflector material, they undergo elastic scattering, which redirects them back toward the fuel region. This process essentially increases the effective size of the reactor, allowing it to achieve criticality with less fuel mass.

Key Formulas: $P = \Sigma_a \Phi$; $\eta = \frac{
u \Sigma_f}{\Sigma_a}$

Key Points: Reflectors significantly decrease the critical mass required for the reactor.; Common materials include Graphite, Beryllium, and Beryllium Oxide.; A good reflector must have a high scattering cross-section and a very low absorption cross-section.; It helps in maintaining a more uniform neutron flux distribution across the reactor core.

Advantages: Reduces fuel enrichment requirements; Flattens the neutron flux distribution; Increases the efficiency of fuel utilization

Disadvantages: Adds complexity to the reactor vessel design; Subject to radiation damage (Wigner effect in graphite); Increased bulk and weight of the core assembly

Applications: Graphite-moderated reactors; Fast breeder reactors; Research reactors

Additional Info: Option B is incorrect because a reflector must specifically avoid absorbing neutrons, as absorption would decrease the neutron population available for fission.. The 'Reflector Saving' is a concept that quantifies the reduction in critical dimensions due to the use of a reflector.

Answer: A is correct — The reflector is designed to scatter escaping neutrons back into the core, minimizing loss and increasing reactor efficiency.

Exam Tip: Always remember: In reactor physics, materials are classified by their scattering properties (moderators/reflectors) versus absorption properties (control rods/poisons). Never confuse the two!

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