Fissionsgasfrisättning

Fissionsgasfrisättning, or fission gas release, refers to the process by which gaseous fission products are generated within nuclear fuel during nuclear fission and subsequently escape from the fuel matrix. When heavy atomic nuclei, such as uranium or plutonium, undergo fission, they split into lighter nuclei and release energy. Among the byproducts of this process are isotopes of various elements that are gases at operating temperatures, such as xenon and krypton.

These fission gases accumulate within the fuel pellet. As the concentration of fission gases increases, they can form bubbles, known as fission gas bubbles, within the fuel microstructure. If these bubbles grow large enough or coalesce, they can create pathways for the gases to migrate towards the surface of the fuel pellet.

The release of fission gases from the fuel is influenced by several factors, including fuel temperature, burnup (the amount of energy extracted from the fuel), fuel microstructure, and the presence of defects. Elevated temperatures accelerate gas diffusion and bubble migration. High burnup leads to a greater inventory of fission gases. The integrity of the fuel cladding is crucial, as it typically contains these fission gases. However, if the cladding is breached, fission gases can escape into the reactor coolant, which can have safety implications by potentially increasing the radioactivity of the primary coolant circuit. Monitoring fission gas release is therefore an important aspect of nuclear reactor operation and safety.