Nuclear fuel is subjected to substantial forces and material changes, which affect the endurance of the fuel rods. Some phenomena are inevitable, but R&D has improved fuel performance considerably since the first commercial operation of nuclear reactors in the 1950s. In this section, the main phenomena affecting fuel rod endurance are briefly addressed and illustrated with examples from the experimental program of the OECD Halden Reactor Project where applicable. Associated modelling is treated in Chapter 14.

The extent to which phenomena affecting fuel rod endurance are allowed to develop is limited by safety criteria and rules for normal operation. When formulating safety criteria, the general goal is to ensure that nuclear power is used safely, but details and specific limits differ between countries. An overview is given by NEA (2003).