Bottom reflooding of a 37 tight lattice rod bundle for future PWRs

Results regarding preliminary reflooding experiments with a 37 rod bundle in the geometry of future PWRs (coolant-to-fuel ratio equal to 1.1) are presented. It is shown that overall quench times and maximum cladding temperatures exhibit the same parametric trends as already observed for standard PWR. Comparison to experiment performed with standard PWR geometry as well as with a very tightened lattice (coolant-to-fuel ratio equal to .6) showed that, under the same initial and boundary conditions, the smaller the lattice, the more difficult the cooling. Reasons for such a tendency are analyzed. First calculations with Cathare code 1.3, adjusted to be confirmed over a wider range of parameters