Migration of fission gas atoms through the metal cladding is known as which phenomenon?

• A. Primary Fission Product Barrier
• B. Tramp Uranium
• C. Fuel Gas Diffusion
• D. Cladding Defects

Answer: (C)

The main idea here is the diffusion of fission gas atoms through the metal that makes up the cladding. In a reactor, fission events produce gases like xenon and krypton inside the fuel. Those gas atoms can move through the metal lattice of the cladding, especially at high temperatures, following concentration gradients and along defects or grain boundaries. This diffusion through the cladding is what we call fuel gas diffusion. It matters because as these gases migrate and accumulate, they can form gas bubbles, raise internal pressures, and influence cladding integrity and the potential for release to the coolant. The other terms describe different concepts—barriers to fission product release, impurities, or cladding imperfections—but they don’t specifically describe the migration of fission gas atoms through the cladding.