In this paper, the parameters thermal to epithermal neutron flux ratio (f) and thermal neutron flux (Φth) are estimated (assuming α = 0) for the periphery irradiation positions (G3-G4) available at Nuclear Research Reactor IAN-R1 that belongs to the Colombian Geological Survey. This estimation was performed by measuring the induced activity, from neutron capture reactions (n, γ) in two reference soils, which were irradiated (n = 4) together with Al-Au monitors. Four referencecapture reactions were considered in soils, which involve isotopes of elements with certified mass fraction and 1/v behavior for cross section variation in the range of thermal neutron energy. An average value of 33 (CV = 9%) for f was found, considering 8 positions in the irradiation container; this value is comparable with measurements reported for periphery irradiation channels of TRIGA type reactors. the average thermal neutron flux determined for the 8 position of thecontainer resulted in 1,5×1011 n cm-2 s-1 (CV = 4 %).