Coupled MCNP6/CTF code: Development, testing, and application

This paper presents the development and testing of a high fidelity Monte Carlo based multi-physics code. The coupling was done between the Monte Carlo neutronics code MCNP6 and the thermal-hydraulic sub-channel code CTF. The coupling for the MCNP6/CTF code was done internally at the pin level. On-The-Fly cross sections were used to decrease the complexity of the coupled code as well as to decrease the memory requirement. The relaxation acceleration technique was applied to the coupled code and was shown that it could satisfy much stricter convergence criterions. The technique can also guarantee convergence and be used as a tool to decrease the computational time. The coupled code was tested against two other coupled Monte Carlo/thermal-hydraulic sub-channel codes and the results were similar. The coupled code was also tested on a full assembly problem.