Effect of Core Size on Temperature Reactivity Feedback of Indonesia Experimental Power Reactor (RDE) (Taswanda Taryo1*, Wahid Luthfi1 and Zuhair 1)

Abstract. BATAN (the National Nuclear Energy Agency) and its national stakeholders are now developing an
experimental power reactor, so called Reaktor Daya Eksperimental (RDE) 10 MW thermal (MWth) and the reactor is a
high temperature gas cooled reactor (HTGR) Gen IV-type power reactor. The RDE is a graphite-moderated and heliumcooled
pebble bed reactor and uses uranium with the enrichment of 17%. There are a lot of safety analysis regarding RDE
reactor, but there has not yet been a neutronic analysis focused on the effect of core size to influence the temperature
reactivity feedback in the RDE reactor core. To begin with, RDE core reactor should be modeled in such 4 regions, fuel
pebble and dummy, coolant, radial refelctor and cone and axial refelctor and shield. For all computation, continuous
energy-nuclear data library ENDF/B-VII were then employed by differing the 4-region model and the famous Monte Carlo
Neutron Perturbation 6 (MCNP6) was applied. The calculated temperature reactivity feedback dealing with Doppler
temperature coefficient (DTC), moderator temperature coefficient (MTC) and reflector temperature coefficient (RTC) of
reactivity has been utilized as well. For this simulation, it is assumed that an accident in the RDE core was defined if the
core has the temperature in the range of 800 0K (526.85 0C) to 1,800 0K (1,526.85 0C). The KCODE and KSRC, a main
part of the MCNP6 code, were then applied to generate cross section (XS) using the nuclear data library ENDF/B-VII.0
in the temperature ranges of 800 0K (526.85 0C) to 1,800 0K (1,526.85 0C). For whole calculations, instead of defining
four regions, dry air and helium coolant were also implemented. The RDE core depth has also been decided starting from
79.023 cm as bottom core to 201.16 cm as full core. The simulation results showed the total of temperature reactivity
feedback in the RDE reactor core is negative and hence the RDE reactor core is totally safe during the defined accident
takes place.
Keywords: Core size, temperature reactivity feedback, RDE, MCNP6, ENDF/B-VII.