Pseudo-transient coupled simulations of a IPR-R1 Triga Mark I fuel pin

In this work, a fine-mesh 1:1 Computational Fluid Dynamics (CFD) - Monte Carlo Neutron Transport (MC) coupled calculations for a IPR-R1 TRIGA MARK I fuel pin was performed. Coupled calculations lead to more accurate results, that is, results closer to the real behavior of nuclear systems. The used kind of coupling and its codes allows optimization analysis, since this numerical simulations provide results with accuracy and detail. The proposed methodology allowed the simulation of the fuel pin behavior in a pseudo-transient state. The power given to the system using MC code has changed during coupled iterations in order to reproduce real reactor operational conditions. The given power varied from 2000 to 7930 W. The velocities were changed according to the iteration given power. The keff, temperature and power density profiles were monitored during the coupled iterations. The pseudo-transient analysis allowed the evaluation of the stability of the implemented coupled scheme. Serpent Nuclear Code was used for neutronics simulations, while OpenFOAM was used for thermal-hydraulics calculations. OpenFOAM simulations were made by using a modified chtMultiRegionFoam solver, developed to read Serpent output correctly. This coupling method produced smooth power density profiles with a constant number of neutron histories through the coupled iterations. The outcome suggests application of this methodology for TH detailed profiles. However, noise could still be observed in the achieved power density profiles. The results were encouraging, however, the methodology should be employed on the study of problems with increased complexity for further assessment. (author)