Both beta as well as gamma rays are suitable for sterilization. The main difference between them lies in their penetration capabilities for materials and the dose rates.
The energy-rich beta or gamma rays destroy the DNA of microorganisms and thus render them harmless. Therefore, radiation sterlization is the only process that enables products to be sterilized in their packages without any significant increase in temperature and without the use of chemicals, which always involves the risk of residues. Even the inner surfaces of closed packages or components with complex geometrical shapes are safely and reliably sterilized by high-energy radiation. These benefits make radiation sterilization a simple, effective and environmentally friendly alternative to other methods.
Beta rays are characterised by their ability to irradiate individual packages within a few seconds. In this way, under optimal conditions a complete truckload can be sterilized within a few hours. Your advantage: Products can be processed promptly, without storage and related costs. The limited penetration capability makes it necessary that products in their cartons from the transport pallets have to be packaged, processed and restocked. At our location in Saal, a fully automatic plant handles large quantities of goods within a very short time.
Beta rays or accelerated electrons are generated by electron accelerators, which can be compared to a cathode ray tube. A hot cathode emits electrons which are accelerated in a strong electrical field and a high vacuum. If energies greater than 5 MeV are required, BGS uses resonance accelerators of the Rhodotron® type. In these, electrons are accelerated in a cyclic alternating field in several stages to a maximum energy of 10 MeV. On leaving the accelerator, the electron beam is deflected in an alternating magnetic field so that it reaches the products to be irradiated as a fan-shaped beam.
The products are conveyed through the irradiation field by an appropriate handling system. The process characteristics of beta radiation differ fundamentally from irradiation using gamma rays. The products generally pass through the irradiation process in their final packaging as individual cartons, as loose bulk goods, or as ‘endless’ (continuous) products unwound and re-wound from reels. The irradiation process only lasts a few seconds. The height to which goods can be stacked for irradiation depends on their density, the packing scheme and the energy of the electrons.
Unlike the electron accelerators, in which the irradiation process is completed in a few seconds, irradiation in the gamma plant takes several hours. The gamma rays result from the decay of the radioactive isotope Cobalt-60 (60Co). They have a high penetration capability and can penetrate complete pallets or lots. The products to be irradiated can generally be conveyed directly through the irradiation process on the pallets they were delivered on, without repacking (industrial pallets: 1.20 x 1.00 m, euro-pallets: 1.20 x 0.80 m, heights up to 1.90 m).
A conveyor system transports the pallets into the plant, where they are then conveyed around the source rack which houses the radiation sources. The controls ensure that each pallet completes the number of cycles specified for it. In this way, the total gamma irradiation dose that has been fixed for each product is exactly adhered to. At the BGS gamma plant, different products requiring different doses can be irradiated at the same time. In order that the irradiation plant can be entered without danger, the source rack is lowered into a water basin over eight meters deep, the water column of which serves as a shielding medium.