Which fission product gas is a common example found in reactor coolant?

• A. Krypton
• B. Helium
• C. Neon
• D. Argon

Answer: (A)

Fission-product gases come from the fragments that split off when the fuel nuclei fission. Among these fragments, noble gases like krypton are produced directly and are volatile, so they don’t stay trapped in the solid fuel. Krypton is a classic example because it is frequently created as a fission fragment and, being inert, readily moves into the reactor coolant as a gas. This makes krypton a typical fission-product gas you’d expect to find in the coolant system and monitor for safety and efficiency.

Helium can appear but mainly from other processes like alpha decay, not as a primary fission fragment; neon and argon are not produced in significant amounts as direct fission products in ordinary reactor operation, so they’re less representative of fission-product gases in the coolant.