A set of computer codes based on different physical models has been developed for the investigation of effects that are essential for the analysis of pressure fields and structural loads and responses during pressurized water reactor (PWR) blowdown. The main aspects under investigation are:

  1. two- and three-dimensionality, nonequilibrium two-phase flow
  2. advanced structural models
  3. fluid-strueture interaction.
The goal of separate investigation of these aspects is to establish guidelines for the development of an integrated model. Which effects must be represented? Which effects should be neglected because they only insignificantly influence the result? Some of the results of these investigations are as follows: Two-and (in certain areas) three-dimensional representation of the fluid flow and pressure field is essential in the PWR downcomer. Fluid structural coupling is an effect that must be taken into account. The structural model must be able to resolve the steep pressure gradients in the neighborhood of the broken nozzle. Homogeneous equilibrium two-phase models are adequate except in the immediate vicinity of the broken nozzle.