Neutronics Modeling and Analysis of the TMSR-SF1 Core with Explicitly Described Fuel Pebble Loadings

摘要

The growing global demand for emission-free energy is creating a market for advanced Generation-IV NPP, and the Fluoride salt-cooled High-temperature Reactor design with a pebble-type fuel is a promising candidate. However, this design also brings unique challenges, namely evaluating the effects of the fuel's distribution and dynamic movement. Generating explicitly described fuel pebble loading patterns is non-trivial. This study serves two main purposes: I) to investigate the neutronic performance of pebble type fuel within the TMSR-SF1, and 2) to conduct a preliminary comparison between pebble coordinate generation methods. The first method of coordinate generation, the Discrete Element Method (DEM), is a particle-tracking model which accounts for inter-particle forces. While this method generates packing distributions closer to real-world scenarios, it is computationally intense. The alternative method analyzed is a mathematical model (MM), which fills arbitrary domains through simple geometric rules on the addition of particles. This method, while less realistic, generates coordinates significantly faster. Afterwards, fuel pebble coordinates from both methods are utilized to generate inputs for high-fidelity neutronics modelling. The results of these simulations, with the aid of various tools within Python, allowed for the neutronic analysis of the core, specifically when considering the eigenvalues of each coordinate set, and the fission power distribution within the fuel pebbles. It was found that the packing fraction in the axial direction to be consistent within the MM coordinate generation method, and the general trends similar between it and DEM-generated coordinates. Additionally, the eigenvalues of the simulated core were found to be proportional to the number of pebbles within the core. Finally, the fission power distribution of the cores was found to be qualitatively consistent both within many sets of MM-generated coordinates, and in comparisons of the two coordinate generation methods.