Study on fluid mixing in a fuel subassembly of a fast reactor; Mixing phenomena with cross flow and applicability of subchannel analysis

Kawamata, Nobuhiro; Miyakoshi, Hiroyuki; Kamide, Hideki 

Sodium experiments were carried out for mixing phenomena in a subassembly of fast reactor. A blockage was installed in a wire wrapped 37-pin subassembly in order to form cross flow around the blockage. Temperature distributions in the subassembly were measured under a condition that only one pin was heated. Investigation on mixing phenomena with the cross flow is useful to predict thermohydraulics in a deformed pin bundle of high burnup core. The subchannel analysis code, ASFRE, was applied to the experimental analyses. The ASFRE solves momentum equations in multi dimensions and has the distributed resistance model for a wire spacer.Following remarks were obtained:1).Measured axial temperature distributions showed that the sodium temperature decreased due to the core flow coming from the cold blockage side. Local peaks were found at the subchannels which have the wire spacer. 2).ASFRE simulated the temperature decreases due to the cross flow and axial temperature profiles were in good agreement with the measured data.3).The local peaks at wire positions were also simulated by ASFRE, however, the peak value was underestimated. ASFRE has high applicability to the mixing phenomena in a wire wrapped subassembly where the cross flow has significant role due to the change of flow area.4).Experimental database for the mixing phenomena with the cross flow were obtained for a subassembly of sodium cooled fast reactor.