SUMMARY
Fricke dosimetry was performed in radiation fields of 60Co and 137Cs, corresponding to the Gammabeam 651PT irradiator loaded with new 60Co sources and a new Gammacell-3000 Elan self-irradiator with 137Cs. This last irradiator was purchased with funds from CONACYT. The gamma photons of 60Co from Gammabeam are using for sterilization of industrial products as well as in studies of physical and chemical properties changes of solid and aqueous solutions samples which are of the interest in research at the National Autonomous University of Mexico (UNAM). However, the difference in energy of the gamma photons from 60Co (1.17, 1.33 MeV) and 137Cs (0.66 MeV) makes interesting changes in research samples such as polymers, new dosimetric materials, organic compounds, etc., which are currently researching at the Nuclear Science Institute (ICN-UNAM). In order to use the radiation fields of irradiators, it is important to determine the exposure dose. In this paper, a successful methodology by using Fricke chemical dosimeter is reported. In this dosimeter is carried out the oxidation reaction in acid to ferric ion of ferrous. Dose rates distribution, less than 99 Gy/min, was determined in the Gammabeam irradiator. In the case of 137Cs irradiator, 10.89 Gy/min, at the center of the irradiation chamber was obtained. This value is in agreement to that certified measurement given by the Gammacell-3000 supplier. Because the sources are nonpoint, the uncertainties associated to the gamma doses were determinated. The two irradiators have adequate dose rates to continue supporting scientific research on different substances and materials, and offer the irradiation service at semi-industrial scale.