Trends and needs in experimentation and numerical simulation for LWR safety

摘要

The very complex phenomena that need to be considered in safety analyses require use of sophisticated analytical tools. Basically, one-dimensional (1D) system codes have been used for a long time and have reached a degree of maturity. There are, however, limits to their capabilities and further developments are underway; these are outlined. The development of new generations of tools and methods can profit from the availability of increasingly powerful computers and advances in multiphase flow, information technology and numerical techniques. Three-dimensional (3D) situations need also to be addressed more frequently now. Certain developments in these directions that are already taking place in various EURATOM research programs and elsewhere are briefly reviewed; case studies of applications are discussed and lessons drawn. Future safety analyses for nuclear power plants may include use of Computational Fluid Dynamics (CFD) for parts of the primary system and the containment. First applications in this direction have already been made. Although 3D, single-phase CFD computations are commonplace, the size of the systems considered make these quite challenging. The real challenges lie, however, in two-phase flow CFD applications that are still at their very infancy. Coupling of neutronic and thermal-hydraulic codes is also necessary for certain problems.