HTR-10 OTTO Cycle Depletion Simulation Using Discrete Element Method Coupled Monte Carlo

Abstract

Pebble bed reactor core contains 27,000 pebbles placed in a random position. Since the pebble insertion relies on gravity, the pebble placement pattern is irregular. Discrete Element Method used to simulate the pebble interaction and pebble movement during HTR-10 operation. Even though pebbles distributed randomly, the random generation of pebble positions used in most research does not mimic the actual pebble position and pebble surface contact. The Discrete Element Method provides a realistic interpretation of the pebble position by considering the pebble surface contact and gravity force. Each pebble coordinates from the Discrete Element Method obtained to construct Monte Carlo geometry of the HTR-10 core realistically. By coupling the DEM simulation with Monte Carlo simulation, it is possible to calculate the depletion while considering the core dynamic characteristic. The OTTO recirculation depletion calculation scheme with steady 10MW power for 368 days was constructed and demonstrated in this work. The DEM coupled Monte Carlo method allow one to track and predict each depleted fuel composition. Although the flux distribution change is slight in every timestep, the relation between flux and depleted U235 and Xe135 composition deserves to be taken into account. The calculation model in this work is comparable with the other calculation, but the timestep adjustment is needed to provide more accurate and representative results. Flux calculation and depletion simulation performed using the OpenMC program with ENDF/B-VIII.0 cross-section data. Please refer to digital version to view graph.