Authors: P. F. Niemand, C. G. du Toit
Year: 2025
Industry: Nuclear & SMR
Keywords: Mention FSE, RCCS
ABSTRACT
The reactor cavity cooling system (RCCS) removes decay heat from the reactor cavity. This system is simulated along with the rest of the reactor for licensing purposes. Experimental facilities provide measurements of proposed RCCS designs. An RCCS experimental facility was constructed at the University of Wisconsin (Madison). This facility consisted of a scaled down version of a water-cooled RCCS design, with the heat removal occurring by means of three riser tubes. The three riser tubes were connected by steel fins dividing the reactor cavity into front and back cavities. The present study focused on the numerical modelling of the flow and heat transfer in the front and back cavities of the heated section. The radiation and total heat transfer, velocity vectors, temperature profiles and the convection heat transfer coefficients were considered. A hypothetical model was also simulated in which the steel fins were omitted and, in this way, evaluate the effects of the fins. In the finned configuration the fins contributed 55.47% of the heat transferred to the water in the riser tubes, the front sides of the riser tubes 38.54% and the back sides of the riser tubes 6.08%. In the configuration without fins the front sides of the riser tubes contributed 53.51% of the heat transferred to the water and the back sides of the riser tubes 46.49%. In the configuration without fins the riser tubes were therefore heated more uniformly. In the finned configuration it was found that parts of the flow in the riser tube transitioned from mixed convection to free convection halfway up the riser tubes, whilst in the case of the configuration without fins the flow in the riser tubes remained in the mixed convection regime.