Criticality and Burnup Study on Different TRISO Modelling of HTR Pebble

Abstract

Modeling of high temperature reactor core (HTR) of pebble bed type has been widely developed before, but the calculation of reactor core in equilibrium condition has not been developed much, especially in Indonesia. The initial approach to see the effect of modeling and simplification that will be used in full-scale HTR modeling can start to be done on the smallest level i.e. TRISO and single pebble. The purpose of this study was to analyze the effect of TRISO particle modeling in the HTR fuel pebble using MCNPX. The modeling variations that will be carried out include modeling of complete TRISO particles, modeling using homogenized TRISO coating layers and full homogenized TRISO. Then another variation is on the TRISO dispersion pattern inside pebble that will be modeled uniformly distributed using several types of TRISO unit, HCP, SC, FCC and BCC lattice. For all variations mentioned above, K-INF calculations will be performed and burnup calculation only performed on single pebble modelling. The modeling using fuel kernels and cover (homogenized buffer, PyC and SiC) gives K-INF values that are not much different than the complete TRISO modeling (fuel kernel, buffer, PyC and SiC on each different zone). The different from fully homogenized modeling is the value of K-INF becomes lower than the complete modeling. Then for all types of TRISO unit, modeling using homogenized TRISO requires longer pebble burnup computation time than other modeling, whereas modeling of homogenized cover types gives a shorter pebble burnup computation time.