Fast breeder reactors — Considering molten sodium as a primary coolant, which statement is correct regarding temperature capability, corrosion, radioactivity, and chemical reactivity?

Introduction:
Liquid sodium is widely used in fast breeder reactors because it has excellent heat-transfer properties and permits high operating temperatures at near-atmospheric pressure. Understanding its true advantages and hazards is essential for reactor engineering.

Given Data / Assumptions:

• Sodium coolants operate near atmospheric pressure while reaching high temperatures.
• Sodium is chemically reactive with air and water.
• Primary-loop sodium can become radioactive mainly by neutron activation (e.g., Na-24), not because of temperature alone.

Concept / Approach:
We examine each statement for accuracy: temperature capability, corrosion behavior, radioactivity origin, and chemical reactivity. The correct evaluation must reflect that radioactivity arises from neutron activation, not heat; sodium can be corrosive to certain materials; and it certainly can attain high temperatures without high system pressures.

Step-by-Step Solution:
Check temperature claim: Sodium permits outlet temperatures in the hundreds of degrees Celsius at low pressure. Thus, saying it cannot attain high temperature is false.Check corrosion claim: Sodium can interact with certain alloys and impurities; asserting it is “not at all corrosive” is incorrect.Check radioactivity claim: Primary sodium becomes radioactive by neutron activation (e.g., forming Na-24), not merely by heating; linking radioactivity to temperature is wrong. However, sodium does react vigorously with air/water, potentially causing fires; the explosive hazard stems from chemistry, not temperature-induced radioactivity.Therefore, the correct choice is that none of the given statements accurately capture sodium’s behavior.

Verification / Alternative check:
Fast reactor literature emphasizes sodium’s low vapor pressure, high thermal conductivity, activation in-core, and strict handling in inert cover gas to prevent air/water reactions.

Why Other Options Are Wrong:

• (a) False: sodium enables high-temperature operation at low pressure.
• (b) False: corrosion compatibility depends on materials and impurities.
• (c) False: radioactivity is due to neutron activation, not temperature; the chemical reactivity part alone is insufficient.

Common Pitfalls:
Confusing temperature effects with neutron activation; underestimating chemical hazards of sodium in air/water.

Final Answer:
none of these