Gamma irradiation facility optimization for very low dose rates

Many researches, mainly those linked to medicine and biology, sometimes require low dose irradiations. Sources with activity above 3.7 x 1013 Bq, even if the collimate beam good geometry is maintained, do not tolerate irradiations without device modifications. A Co-60 panoramic source, with 8.51 x 1013 Bq, was adapted to allow irradiation range of 0.2-100 Gy with dose rates within the 0.5-1 Gy/min range. In this specific case, some important aspects that allow to offer to the user an adequate dosimetric standard are shown. Some of these aspects consider the accumulated dose during the positioning of the source, the sample rotation and the errors in the lower limits of the required dose range. (author). 2 refs., 3 figs