Aspects to increase source efficiency of 60Co irradiator

Increasing source efficiency is the core of Co-60 irradiator design. This paper introduces several aspects about it. In the two irradiation modes, the perpendicular distance of the product and the rack affects the efficiency very much, so the irradiator should have an optimal distance. Product carrier width is another import factor. Wider carrier can bear more products to be irradiated, but it will increase the absorbed dose uniformity ratio (DUR), which may descend the efficiency. Source distribution in rack is also an important factor of efficiency. There are several principals to arrange source rods in the rack. In product overlapping mode, put more source pencils in the middle (vertical direction) area of the rack. In source overlapping mode, put more source in the top and bottom area of the rack. In both modes, put more source pencils in the middle (horizontal direction) area of the rack. (authors)