Fuel Performance Modelling and Simulations: Oxide Fuel Performance Modelling and Simulation

In order to ensure the safe and economic operation of fuel rods, it is necessary to be able to predict their behaviour and life-time. The accurate description of the fuel rod¿s behaviour, however, involves various disciplines ranging from the chemistry, nuclear and solid state physics, metallurgy, ceramics, and applied mechanics. The strong interrelationship between these disciplines, as well as the non-linearity of many processes involved calls for the development of computer codes describing the general fuel behaviour. Fuel designers and safety authorities rely heavily on these types of codes since they require minimal costs in comparison with the costs of an experiment or an unexpected fuel rod failure. The codes are being used for R&D purposes, for the design of fuel rods, new products or modified fuel cycles and to support loading of fuel into a power reactor, i.e. to verify compliance with safety criteria in safety case submissions. In principle, our spatial problem is three-dimensional (3D). However, the geometry of a cylindrical fuel rod (a very long, very thin rod) suggests that any section of a fuel rod may be considered as part of an infinite body, i.e. neglecting axial variations. By further assuming axial-symmetric conditions because of the cylindrical geometry, the original 3D problem is reduced to a one-dimensional one. Analysing the fuel rod at several axial sections with a (radially) one-dimensional description is sometimes referred to as quasi 2D or 1 1/2D. Most fuel rod performance codes fall into this category. Real 2D codes such as for instance the FALCON code 1 offer the possibility to analyse r-z problems (no azimuthal variation) and r- problems (no variation in axial direction). An example of a 3D code is TOUTATIS 2 and DRACCAR 3 and is dealt with in Chapter 74. DRACCAR is addressed later in 3.1.2. Generally, 2D or 3D codes are used for the analysis of local effects, whereas the other codes have the capability to analyse the whole fuel rod during a complicated, long power history.JRC.E.3-Materials researc