Fast breeder reactor essentials: which option best summarizes core features of a typical fast breeder reactor (FBR) used in nuclear power R&D?

Introduction / Context:Fast breeder reactors (FBRs) are designed to operate with a fast-neutron spectrum and breed more fissile fuel than they consume. They are central to long-term fuel-cycle strategies because they can convert abundant fertile isotopes into useful fissile material while generating electricity.

Given Data / Assumptions:

• Fast spectrum implies no moderator.
• Fertile blanket commonly uses U-238 → Pu-239 breeding.
• Liquid sodium is the canonical coolant due to high thermal conductivity and low pressure operation.

Concept / Approach:FBR physics depends on maintaining high-energy neutrons; moderators would thermalise neutrons and defeat this purpose. The blanket captures excess neutrons to transmute U-238 to Pu-239, providing breeding. Sodium coolant supports excellent heat transfer and does not significantly slow neutrons, preserving the fast spectrum.

Step-by-Step Solution:Confirm (a): fast neutrons are the defining feature.Confirm (b): breeding from U-238 to Pu-239 is standard.Confirm (c): molten sodium is a common FBR coolant.Therefore, choose “All of the above.”

Verification / Alternative check:Design summaries of experimental and prototype FBRs (e.g., FBTR, BN-series, Phénix) consistently show these three features, with minor variations across programs.

Why Other Options Are Wrong:Each single statement (a), (b), (c) is true but incomplete alone; the best summary is their combination.Heavy water moderation: inconsistent with a fast spectrum; moderators are absent in FBRs.

Common Pitfalls:Assuming “breeder” implies any moderated reactor with a fertile blanket; true fast breeders must avoid moderators to maintain fast-neutron physics.

Final Answer:All of the above: (a), (b) and (c)