Investigation on thermohydraulics optimization in the lower plenum of large scale FBR

not registered; not registered

In-vessel thermohydraulic analysis using a multi-dimensional code AQUA was conducted to investigate thermohydralic conditions in the lower plenum of a large scale liquid metal fast breeder reactor (LMFBR). In the investigation, it was focused in a effective mixing volume in the plenum and in a loose parts trapping by hydraulic forces. Through the analysis by the AQUA code and discussions based on their results, the following results have been obtained: [In-Flow Allotment Characteristics at the Truss] (1)Mass flow rate between lower flow holes and side flow holes to the truss was balanced in the case of 22.5 for the coolant inlet angle to the plenum under a full flow condition. (2)The above result did not change with the transient conditions simulating a manual reactor trip event. [Effective Mixing volume] (1)From the transient calculation, it was clear that the effective mixing volume was corresponded to 77-79% of the total volume in the plenum. [Loose Parts Trapping] (1)A condition (W1.0m/s) to trap loose parts by hydraulic forces was not satisfied under parametric calculations only considered here.