Monte Carlo validation of the irradiator parameters of the Portuguese gamma irradiation facility after its replenishment

In December 2003 the irradiator of the Portuguese 60Co irradiation facility, UTR, was replenished. Monte Carlo simulation studies were used to characterize the facility. Comparison of simulation results with experimental measurements were useful in estimating where the source elements were positioned and what the total activity was. For this purpose the MCNPX code was used. From the experimental point of view ionization chambers and PMMA dosemeters were used.The results indicate that the geometry of the irradiator used for simulation studies shows a shift on the vertical dimension relative to the actual geometry of approximately 8 cm, but with reduced influence on the irradiation process. Considering the uncertainties of the experimental and simulated approaches the activity of the irradiator stated by supplier has been confirmed.