Assessment of RELAP/MOD3 Against CCFL tests with full-scale fuel bundle structures

摘要

The purpose of this work is to investigate with the RELAP5/MOD3 (v5m5) code the influence of the structure of the core upper tie plate in a pressurized water reactor on penetration of emergency core cooling system water downwards into the core in the event of a hypothetical loss-of-coolant accident. Stationary air/water countercurrent flow experiments at atmospheric pressure for fuel bundle top area structures of the pressurized water reactors VVER-1000 and VVER-440 were simulated with the RELAP5/MOD3 (v5m5) code both without and with a countercurrent flow limitation (CCFL) correlation. The effects of flow channel size and presence of the unheated fuel rod bundle on countercurrent flow behaviour were observed. Applying the CCFL model has a minor effect on the CCFL curve in the case of our stationary calculations. A comparison with the countercurrent flow limitation in a free-flow channel is also made. The calculational results for the flow channel of a small cross-sectional area show a good agreement with the experimental results. The form of the CCFL correlation has a minor effect on the CCFL curve. (orig.) (3 refs., 47 figs., 14 tabs.). (Atomindex citation 26:053103)