Simulation of Steam Generator Tube Rupture on the Experimental Power Reactor (RDE)

Abstract

As an effort to introduce nuclear power plant in Indonesia, Indonesia’s National Atomic Energy Agency (BATAN) has been developing the small sized pebble- bed reactor of high temperature gas-cooled reactor (HTGR) technology since 2015. The 10 MWt Experimental Power Reactor (Reaktor Daya Eksperimental / RDE) was designed based on the HTR-10 design and is entering the drafting process of detail design document involving a number of calculations, experiment activities and simulations. One of research activities to verify the safety of the RDE design is by performing simulations using RELAP5 thermal hydraulic code starting from the development of RDE model for steady-state condition. One initial event classified in the safety analysis report is the steam generator tube rupture, which is simulated in this paper. The purpose of the simulation is to analyze, how accurate is the available RDE model to predict changes in the thermal behavior, particularly in the primary system. The results of two simulated cases by assuming two helical tubes ruptures, with and without safety system actuations show that the transients of pebble temperatures in the core are still under safety limit of the TRISO pebble fuel of 1230 °C. Both cases also indicate the importance of the pressure limitation devices in the primary system to control the increase of the primary pressure during the event into the allowable operating value. Other issues are still open to address such as the heat sink in the reflector model for the pebble temperature behavior, core positive reactivity due to the water-steam increase and the operation of the steam generator discharge system to mitigate the event. In general, the RELAP5 code is able to simulate the particular event, even the time sequences are different if compared with the THERMIX code.