| Abstract: | Analytical model requirements for core natural convection analyses are reviewed. Then results from current modeling on intra-assembly flow and heat redistribution are compared with several sources of experimental data. Also, data are described on low flow rod bundle hydraulic characteristics. Numerous sensitivity studies are also presented which show the effect and importance of various parameters on core temperatures during natural circulation, including inter-assembly flow redistribution, pump flow coastdown, rod size and fuel type, control system scram worth and shutdown power level. A system of codes for making the natural circulation predictions is also described, i.e., a plant-wide dynamic code, a whole-core system dynamic code and a hot channel dynamic analysis code. The overall approach of verifying the core related codes is presented, along with the interaction and linkage between all the codes. Confirmation of this system of three codes will bee through prototypic data obtained from EBR-II and FFTF natural circulation experiments. |
