Finite element techniques have offered a substantial modelling improvement capability over the more classical mechanical equilibrium codes. They can be used for evaluating stresses, strains and displacement of components for different accident situations. They can model both static and dynamic effects. They can be used to evaluate the failure mode of structures, e. g. containments under increasing loadings (IAEA-TECDOC-752, 1994).

It is considered desirable (Sammarato et al., 1992) that the methodologies for future advanced containment should be based on ‘best estimate’ approaches. The more advanced codes all offer this capability. The traditional modelling approaches were generally much more conservative.

The development of improved codes can only be realised if there are corresponding improvements in input data. There is a need therefore for ensuring that adequate materials data are available.

Dynamic load modelling under severe accident loads is now within the capabilities of the computer codes but the problem may be in specifying the appropriate boundary conditions, e. g. in assessing the load resulting from a hydrogen detonation. The thermo-mechanical assessment of core catchers is also a modelling requirement for the assessment of advanced containments. This has been investigated in France (Millard et al., 1992) and Italy (De Rosa et al., 1992).