Ionizing radiation has high energy which is enough to break the molecular bonds and ionize atoms. As a result, materials exposed to this radiation undergo modification in their physical, chemical and biological properties. At present, the principal industrial applications of this radiation are sterilization of health care products including pharmaceuticals, irradiation of food and agriculture products (for various end objectives, such as dis-infestation, shelf life extension, sprout inhibition, pest control and sterilization etc.) and materials modification (such as chain scission, polymer cross linking and gemstone colorization etc.) A significant impetus was given to the radiation processing industry with the advent of nuclear reactors, which have the capability to produce radioisotopes.
Cobalt-60, the gamma ray emitter is widely used as the radiation source for industrial use mainly because it is readily available from simple nuclear reactions in nuclear reactors and is non-soluble in water. In recent times, the use of electron accelerators as a radiation source (and sometimes equipped with X ray converter) is increasing. However, gamma irradiators standout when it comes to irradiation of non-uniform and high density (thicker) materials. This is due to the deeper penetration of gamma in a given material. This document describes various aspects involved with gamma irradiators, which are used for various radiation processing applications. Gamma processing has several advantages over other treatment methods; for example, sterilization of health care products using either EtO or wet steam as a sterilant. In the case of gamma sterilization, such advantages include :
Products of any shape can be sterilized because powerful gamma rays penetrate right through the package and products.
Being a cold process, heat sensitive plastic medical devices and pharmaceutical products can safely be sterilized.
Flexibility in packaging as the products can be packed individually in sealed bags and sterilized in the fully packed form.
Since sterilization is effected after final packaging, products sterility is retained indefinitely provided the package is undamaged.
This is a continuous, fully automated process with a single parameter to be controlled, namely the time of exposure. Steam sterilization and ETO apart from being batch processes; require more than one parameter to be controlled.
The treated product can be used immediately.
This is a very precise and reproducible treatment process.
Gamma irradiation is one of the three types of natural radioactivity. Gamma rays are electromagnetic radiation,like X-rays. The other two types of natural radioactivity are alpha and beta radiation, which are in the form of particles. Gamma rays are the most energetic form of electromagnetic radiation, with a very short wavelength of less than one-tenth of a nanometer.
Alpha Particles :
Certain radionuclides of high atomic mass(Ra226, U238, Pu239)decay by the emission of alpha particles(two neutrons and two protons each). Alpha particles are emitted with discrete energies characteristics of the particular transformation from which they originate.
Beta Particles :
A nucleus with an unstable radio of neutrons to protons may decay through the emission of a high speed electron called a beta particle. This results in a net changes of one unit of number(z). Beta particles have a negative charge.
Gamma-ray :
A nucleus which is in an excited state may emit one or more photons(packets of electromagnetic radiation)of discrete energies.The emission of gamma rays dose not alter the number of protons or neutrons in the nucleus but instead has the effect of moving the nucleus from a higher to a lower energy state(unstable to stable)
