Evaluation and application of the fission matrix based burnup methodology on the TRIGA reactorPungerčič, Anže (Avtor) Snoj, Luka (Mentor) Haghighat, Alireza (Komentor) Nuclear Fuel DepletionFission MatrixbRAPIDTRIGA ReactorNuclide InventoryExperimental ValidationNuclear fuel depletion calculations for TRIGA research reactors are addressed in the thesis. Complete operational history of the TRIGA Mark II reactor at "Jožef Stefan" Institute was recorded and analyzed, enabling depletion simulations. Burnup effects of the TRIGA fuel were studied using deterministic TRIGLAV and stochastic Serpent-2 codes. Main conclusions are that because the reactor core is small and compact, 3D depletion has to be done, dividing the fuel in at-least 15 axial depletion zones. The analysis also verified an approximation of simulating operational history only after 1991 on P=250 kW. Knowing the depletion history, a novel fission matrix-based burnup methodology bRAPID, based on the RAPID Code System, was applied to the depletion model of JSI TRIGA reactor. The methodology allows for calculation of nuclear fuel depletion by combination and interpolation of RAPID's burnup dependent fission matrix (FM) coefficients to take into account core changes due to burnup. Main part of the thesis is the verification and validation of the bRAPID methodology. Verification was performed by comparison to experimentally validated Serpent-2 Monte Carlo depletion calculations. The results show that the burnup methodology is capable of accurately calculating the k_eff changes with burnup, 3D fission source re-distributions and pin-wise, axially dependent fuel burnup and nuclear fuel nuclide composition. Experimental validation was carried out on three different experiments: excess reactivity measurements, and two fuel rod reactivity worth experiments. For all measured parameters RAPID with its bRAPID methodology was within 1sigma of measured uncertainty, indicating great agreement. Finally, both bRAPID and Serpent-2 were applied for depletion calculations of three experiments at JSI TRIGA in which discrepancies were resolved by taking into account fuel depletion. Results from both codes indicated a better agreement (6 %) in absolute measured values of three dosimetry reactions, showing the importance of knowing TRIGA fuel. Main outcome of the thesis is having an experimentally validated new depletion methodology, which retains the accuracy of the Monte Carlo code with a speed-up factor of 600, if fission matrix database is pre-calculated. Such methodology is capable of spent nuclear fuel characterization on the fly while the reactor is in operation and is applicable to other research, small modular, and micro reactors.20242024-07-05 08:15:04Doktorsko delo/naloga159277sl