DEVELOPMENT AND VALIDATION OF A NEW NEUTRONIC MODEL OF THE TRIGA MARK II REACTOR: Thesis

This thesis work discusses the development and validation of an updated neutronics model for the reactor TRIGA Mark II of the University of Pavia. This work finds its basis on a preceding model developed in the past with the Monte Carlo code Serpent and based on the reactor fresh fuel configuration. The model has been adapted in order to be as close as possible to reactor present conditions and, for this purpose, data coming from MCNP burnup calculations up to September 2013 and a new core configuration regarding the same year have been employed and implemented in Serpent-compatible input files. The updated model underwent a code-to-code comparison to MCNP for the first full power criticality configuration and for the core excess simulation. For these same cases a validation via a benchmark analysis with experimental data was performed as well. In both circumstances the results were in good agreement with experimental data. The model was then employed to calibrate two control rods. Two datasets were exploited to compare simulation results, one collected in 2015 and one collected in 2018. The results obtained through Serpent appeared to be in good agreement with experimental data for what concerns the 2015 experimental data; this can be stated for results pertaining 2018 as well. Simulations regarding criticality configurations for both datasets were run as well, obtaining results compatible in both cases with experimental ones, even though reactivity values for the year 2018 resulted in being slightly higher. Despite this last consideration, all criticality simulations outputs resulted in being acceptable if considering systematic uncertainties, whose minimum value had been quantified with previous studies. In conclusion, the updated model can be defined as a valid reactor analysis tool.