SCWR subchannel code ATHAS development and CANDU-SCWR analysis

A subchannel code (ATHAS) is developed for preliminary analyses of flow and enthalpy distributions and cladding temperatures at supercritical water conditions. The code is applicable for transient and steady state calculations. A number of heat-transfer correlations, frictional resistance correlations, and mixing models have been implemented into the code as options for sensitivity analyses. In addition, a 3D heat conduction model has been introduced to establish the cladding temperature. The results show that (1) a CANFLEX [Inch, W.W.T., Thompson, P.D., Suk, H.C., 2000. Introduction of the new fuel bundle CANFLEX into an existing CANDU reactor. In: Proceedings of the 12th Pacific Basin Nuclear Conference, October 29–November 2, Seoul, Korea.] bundle is appropriate for use in the CANDU supercritical water-cooled reactor (SCWR) based on heat transfer analysis, (2) the selection of heat transfer, friction, and mixing correlations has a significant impact on the prediction of the maximum cladding-surface temperature, and (3) the inclusion of the 3D heat conduction in the calculation has provided a more realistic prediction of the maximum cladding-surface temperature than assuming a uniform cladding temperature due to the heterogeneous characteristic of rods.