The temperature profile of a cryogenic system for cooling of beryllium filter of a small-angle neutron scattering (SANS) instrument of TRIGA MARK II PUSPATI research reactor was investigated using computational fluid dynamics (CFD) modeling and simulation. The efficient cooling of beryllium filter is important for obtaining higher cold neutron transmission for the SANS instrument. This paper presents the transient CFD results of temperature distributions via the thermal link to the beryllium and simulation of heat
flux. The temperature simulation data are also compared with the experimental results for the cooling time and distribution to the beryllium.