Application of the implicit Eulerian method (ICECO) to fast reactor containments

Applications of the implicit Eulerian method to predict the response of the fast reactor containment to HCDAs are described. In addition to destructive phenomena, the method is also capable of analyzing the sodium-spillage problem. It uses the implicit treatment of density variation of the ICE technique and is applicable to both compressible and incompressible flows. The basic equations used are the full, time-dependent, nonlinear equations of fluid dynamics. The governing equations are approximated by finite-difference equations with respect to the Eulerian cell. Substitution of the advanced-time densities and velocities into the difference form of the mass equation leads to a set of Poisson's equations in the advanced-time pressure that is solved iteratively. The containment wall can be considered either as rigid or deformable. In the deformable-wall analysis, the vessel is treated as a thin shell in which the analysis accounts for the membrance and bending strength of the vessel, and large deflections under dynamic loading conditions. The vessel material to be considered is elastic plastic and strain hardening. The method has been extended to include the treatment of (a) internal solid material for modeling the core barrel and core-support structures, (b) wall opening and outflow boundaries for performing sodium-spillage analyses, (c) irregular cells and arbitrarily shaped boundaries for approximating the reactor bottom, and (d) moving boundaries for handling plug-jump and response of containment vessel. These special capabilities are incorporated with basic hydrodynamic technique in ICECO. Three sample problems are given: response of primary containment to a low-energy excursion, slug impact and sodium spillage and the motion of the core-gas bubble in the primary containment