What are the three fission product barriers?

• A. Containment; Moderator; Shielding
• B. Fuel pellet and cladding; Shielding; Containment
• C. Fuel pellet and cladding; Reactor Coolant System (RCS) pressure boundary; Containment
• D. Control rods; Moderator; Containment

Answer: (C)

Three fission product barriers are the fuel with its cladding, the reactor coolant system pressure boundary, and the containment. The first barrier is the fuel itself plus the cladding that surrounds it; fission products are produced inside the fuel pellets, and the cladding keeps them from escaping into the reactor environment unless the fuel is breached. The second barrier is the reactor coolant system pressure boundary, which includes the reactor vessel and connected piping; if fuel cladding is breached, the coolant boundary limits how far any released fission products can spread within the primary system. The third barrier is containment, a robust structure designed to prevent or greatly reduce any release of radioactive material to the surrounding environment during normal operation and accidents. Shielding and moderator don’t serve as barriers to release of fission products, and control rods are used for reactivity control rather than containing fission product release. This combination—fuel and cladding, the RCS pressure boundary, and containment—matches the three barriers described.