CFD Analysis on Temperature Homogenisation Performance in Experimental Power Reactor Bottom Plenum (R Andika Putra Dwijayanto1, a), Farisy Yogatama Sulistyo1, b), and Muhammad Subekti1, c)

Abstract. An issue concerning Experimental Power Reactor (Reaktor Daya Eksperimental/RDE), an HTGR-based
experimental-scale nuclear power reactor proposed by National Nuclear Energy Agency (Badan Tenaga Nuklir
Nasional/BATAN), is hot gas temperature deviation. To prevent safety-related problems caused by such deviation, RDE
employs two levels of gas mixing for the heated coolant gas; the first level is bottom plenum and the second is hot gas
chamber. Unlike the latter, bottom plenum is a simple empty column where the heated gas is mixed, but not homogeneous
enough to be considered safe to be flown into the heat exchanger. To understand the mixing phenomena better, this paper
will analyse the temperature homogenisation on the RDE bottom plenum, employing computational fluid dynamics-based
method using FLUENT software. Simulation result shows that the coolant gas heterogeneity is reduced by 139.98°C,
implying temperature homogeneity degree of 55.99%. This value provides insight on coolant gas parameter to perform
more accurate calculation on the hot gas chamber. Temperature deviation pattern at the outlet channels is also discussed.
Keywords: RDE, HTGR, bottom plenum, CFD, temperature homogenisation