Assessment of CFD for the Canadian SCWR bundle with wire wraps

• Bare and wire wrapped bundles are simulated using CFD commercial code, STAR-CCM+.
• Sensitivity analysis of turbulence models is performed for supercritical flows.
• Wire wraps resulted in reduced wall temperatures compared to that of bare bundles.

Within the Generation-IV (Gen-IV) International Forum, Atomic Energy of Canada Limited (AECL) is leading the effort in developing a conceptual design for the Canadian supercritical water-cooled reactor (SCWR). AECL proposed a new fuel bundle design with two rings of fuel elements placed between the central flow tube and the pressure tube. In the current paper, both the bare-rod and wire-wrapped bundle geometries were tested for the proposed fuel bundle design at 25 MPa using STAR-CCM + CFD code to predict the sheath temperature variation along the axial direction. SST k–ω and Reynolds-stress based turbulence models were compared with each other to assess their capability in predicting wall-to-fluid heat transfer in supercritical flows including the heat transfer deterioration (HTD) phenomenon. Using the turbulence model identified from the sensitivity analysis, the mesh refinement for the bare-rod geometry was performed in accordance with the ASME CFD numerical accuracy guidelines. Following these assessments, the recommended CFD model was then applied to simulate the Canadian SCWR fuel bundle with wire wraps. Predictions for the velocity and temperature variation in bare-rod and wire-wrapped geometries were compared. As a result of this study, it was found that wire wraps reduces the maximum temperature variation significantly for the current SCWR bundle design.