Coupled neutronics/thermal-hydraulics of CANDU-SCWR fuel channel

At supercritical pressure condition, the thermal-hydraulics behavior of water differs strongly from that at subcritical pressure due to a rapid variation of the thermal-physical properties across the pseudo-critical line. A coupling of neutronics and thermal-hydraulics has become necessary for SCWR, because of the strong link between the water density and the neutron spectrum and subsequently the power distribution. The neutronics code MCNP (Monte Carlo N-Particle code) and the subchannel code ATHAS (Advanced Thermal Hydraulics Analysis Subchannel) are used in a coupled way to better understand the design characteristics of a pressure tube type SCWR fuel channel. The results show that: The developed coupled code system can be used to analyze pressure tube type SCWR fuel bundles; improved radial fuel enrichment profile will optimize the coolant and cladding temperature distribution to meet the design criteria; Smaller pressure tube pitch will result in more flatten axial power distribution and more uniform radial power distribution. (author)