Validation of COBAYA4/CTF coupling within European NURESIM Platform against MCNP/CTF

Through NURESAFE project, depth modifications were performed in the core simulator from the UPM COBAYA. COBAYA was recoded and integrated into NURESIM platform with all its capabilities. The last version of the code is COBAYA4. Moreover, a new coupling was developed with one of the last versions of the thermal-hydraulic code integrated into NURESIM platform, CTF. After all these depth changes, next step is COBAYA4 and coupling validation. The collaboration was carried out with North Carolina State University (NCSU), Reactor Dynamics and Fuel Modeling Group (RDFMG), to validate coupled system COBAYA4/CTF. RDFMG developed a coupling system MCNP6/CTF and it has been used as a reference solution to validate COBAYA4/CTF. A fuel assembly analysis was performed with both coupled systems. The fuel assembly comes from OECD/NEA UAM-LWR Benchmark. The results obtained from the two coupled systems have to be analyzed carefully. Two different neutronic codes compared were, Monte-Carlo and Neutronic Diffusion code. They use different neutronic solver. The two coupling are different, one is an external coupling and another an internal coupling. Moreover, the thermal-hydraulic models are little different, one is rod center and the other one is sub-channel center. Despite the internal differences, the two solutions are similar