Preliminary Study of DLOFC Accident in HTGR using GRSAC

Abstract

High Temperature Gas-cooled Reactor (HTGR) is one of the Generation-IV reactors that has many advantages and very promising to be utilized in the future. National Nuclear Energy Agency of Indonesia (BATAN) has a program to build a non-commercial power reactor (RDE) that will be based on the pebble-bed type of HTGR. To support this program, the research and development activities in HTGR have been conducting recently. One of the important aspects to be studied is accident analysis to assess the behavior of HTGR during the accident and to anticipate the consequences that might be caused. The purpose of this work is to study the Depressurized Loss of Force Coolant (DLOFC) accident on HTGR by using Graphite Reactor Severe Accident Code (GRSAC). The type of HTGR used as a case study is PBMR-400. This work was begun with the preparation of GRSAC input for reactor parameter including reactor design, core layout design, primary cooling loop design, graphite properties and material properties, cavity design, vessel design, and fission product release. It was assumed that there is an initial event that causes the reactor depressurization and the coolant loss during the time range of 13 seconds. During this time, the reactor pressure dropped from 91.75 kg/cm2 to 1.05 kg/cm2 and the coolant flow reduced from 192.53 kg/s to 0.29 kg/s. Two types of DLOFC event were studied which are DLOFC with scram and DLOFC without scram. The behavior of the fuel temperature was then analyzed during the time range of 100 hours after the DLOFC accident. It was obtained that the maximum fuel temperature was reached at the time of 60 hours after the accident. The maximum temperature after the DLOFC with and without scram accident is 1545oC and 1740oC, respectively. The results of this work were also compared to the results of benchmark work on PBMR-400 conducted by American Nuclear Society and it showed a good comparison. At the end, this work will be very beneficial to be implemented in the RDE program.