Performance of the projected shielding system for the 60C0 multipurpose irradiator from CTR/IPEN, SP, Brazil

The 60Co multipurpose irradiator from the Radiation Technology Centre (CTR) of Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP, Brazil was fully designed and built with national technology. The revolutionary design of this facility consists of a system of continuous transport using containers whose input and output of products is made by a revolving door integrated into the shielding, eliminating the need for constant opening of the irradiation chamber door which decreases the number of climbs and descents of the racks of sources and eliminates the need of labyrinth for products passage by increasing the radiation safety and greater availability of operation of the facility. Shielding calculations were based on the recommendations of NCRP-49 [2] and the NCRP-51 [3], with participation of the team of designers to define some dimensions, such as maximum aperture for the revolving door. These calculations were made in a high conservative way and based on a source with activity of 2000 kCi to limit dose rates on the outside in 0.5 muSv/h. The Multipurpose Irradiator has today a kCi 92 activity of 60Co and the majority of the monitoring points presented values very close to the natural background radiation. Only four points, two on the ceiling and two next to the floor, where it is not foreseen the stay of persons, presented values of dose rates that could lead to overcome the primary dose limits. It was added a small step next to the access door as additional shielding to the initial project to decrease the dose rate in the two points next to the floor