Benchmarking of experimental setup for pressure drop calculation in a packed pebble bed using RELAP5

Pebble bed reactor (PBR) is one of High Temperature Gas Cooled Reactor (HTGR) having nuclear fuels formed by a number of pebbles containing uranium in the core. The PBR is the focus of this research since this type of HTGR is under development by BATAN in form of Experimental Power Reactor (EPR) since 2014. One of the challenges in designing the EPR as a PBR is to model the pebbles forming a bed in the core, since this pebble bed will determine the flow and heat transfer characteristics under certain core power and gas flow rate. One parameter under consideration is the pressure drop along the pebble bed as a function of gas velocity, which has been analyzed by building an experimental setup having different pebble diameters. The purposes of this work is to develop a model of the pebble bed experimental setup mentioned above using the RELAP5/SCDAP/Mod3.4 in order to study the RELAP5 capability in modelling the pebble bed core based on benchmarking of the simulation with the experimental results. The results show that values in determining the pressure drop coefficient (K) using RELAP5 can be estimated for the 1.25 cm, 2 cm, and 5 cm pebble diameter after comparing with experimental data. Those values, in particular for the 5 cm pebble diameter, which are related to the Reynolds number and different gas velocities, can be used in developing the model of EPR core having pebble diameter not far different from the experiment.