Improvement of CANDU safety parameters by using the CANFLEX fuel

In this study, the use of the CANFLEX fuel bundle in the CANDU6 reactor has been investigated with high-fidelity Monte Carlo simulations in view of major safety parameters. The CANFLEX fuel bundle is designed such that it has a smaller linear power and flatter bundle power distributions than those of the standard design. This results in a significantly lower average fuel temperature. In addition, with slightly larger coolant flow area than the standard design, the CANFLEX bundle is expected to improve fuel temperature coefficient (FTC) and coolant temperature coefficient (CTC) during normal operation. This study presents 2-D neutronic lattice evaluations of these safety parameters of the CANDU6 reactor loaded with CANFLEX fuel bundle against with the standard fuel design. To adequately model the equilibrium CANDU6 core, a number of different 2-D fuel bundle lattices were simulated on a huge number of neutron histories. For a reasonably accurate evaluation of the FTC, thermal motion of 238U was considered with the Doppler Broadened Rejection Correction (DBRC) scheme. Based on these numerical evaluations, it can reasonably be concluded that the CANFLEX fuel design can possibly enhance safety of the CANDU6 reactor as its PCR is clearly negative for a wide range of reactor power. All depletion calculations were completed using the Monte Carlo Serpent2 code with ENDF/B-VII.0 library.