Gamma Irradiation is a physical means of sterilisation or decontamination. Put simply, it kills bacteria. Gamma Irradiation kills bacteria by breaking down bacterial DNA and inhibiting bacterial division. Essentially, energy passes through the treated product disrupting the organic processes that cause contamination.
Gamma Irradiation exposes products or substances to gamma rays. Gamma rays are electromagnetic radiation of very short wave lengths (similar to UV). Gamma rays are used for many purposes from communications (radio waves) to cancer treatment applications.
The most common source of gamma rays for irradiation processing comes from the radioactive isotope Cobalt 60. It is manufactured specifically for the Gamma Irradiation process.
Gamma Irradiation is known as a ‘Cold Process’ as the temperature of the processed product doesn’t significantly increase. It is not dependant on humidity, temperature, vacuum or pressure. Thus, the packaging remains intact, as the seals are not stressed. The only variables are source strength and exposure time.
Products or substances are exposed to gamma rays in a special chamber called the irradiation room. This chamber is constructed of two meters of reinforced concrete. Cobalt 60 pellets are sealed inside stainless steel cylinders known as source pencils. These pencils are arranged in a moveable rack and stored in a pool of pure water. The source rack can only be in one of two positions: the storage position (submerged in a deep pool of water) or the raised operating position.
Products to be processed are loaded onto automatic conveyor systems and transported into the irradiation room. The products are then circulated to ensure an even exposure to ionising energy.
The received dose is determined by product density, and exposure time. It is measured by a Perspex Dosimeter. The darkening or increased optical density indicates the absorbed dose.
