Inherent safety analysis of the UO2 fueled pebble lattice at the RDE using SRAC2006 module of PIJ

Reaktor Daya Eksperimental (RDE) is type of High Temperature Gas Cooled Reactor (HTGR) with nominal power 10 MWth that uses pebble bed type of sperical fuel. In the development of the RDE core design, as the earliest stage is to study characteristic of the fuel pebble latice cell, mainly related to the inherent safety. In this study, the inherent safety analysis to the transient effect of fuel temperature and water ingress in the pebble fuel lattice on RDE design core has been done by using Standard Reactor Analysis Code (SRAC2006) Probability I J (PIJ) module. In addition, the nuclide content in the spent pebble fuel lattice was also analyzed. PIJ is code based on the collision probability method applicable to analyze the change of k-inf value when transient occurs at certain fuel burn up point. The analysis was performed to the 17.00% and 8.50% enrichment of UO2 fuel pebble at varying levels of uranium heavy metal loading, i.e 3, 5, 7, and 9 gram. The k-inf value of the fuel pebble lattice has been calculated using branching burn up mode module PIJ through double heterogenity model. Calculation results showed that the higher loading level of heavy metal of uranium then the k-inf value will be smaller. The transient with increasing of the temperature at each particular burn up point or the occurrence of water ingress will also decreas in the k-inf value of fuel pebble lattice. From the analysis result, it can be concluded that pebble lattice fueled with 17% enrichment of UO2 on RDE has inherent safety properties i.e. the decreasing of k-inf value if transient temperature occurs. And when there is water ingress, the inherent safety characteristeic is shown by pebble lattice with maximum loading of 9 g uranium heavy metal.. The percentage of the nuclide content in spent fuel of pebble latice on RDE is similar to the PWR lattice, so it is not possible for a large number of plutonium production. At the transient by increasing of temperature, there are no significant increasing of gaseous fission product production (Xe-135, I-135, Sm-149, Pm-149).