4.1 Various products and materials routinely are irradiated at predetermined doses in gamma irradiation facilities to reduce their microbial population or to modify their characteristics. Dosimetry requirements may vary depending upon the irradiation application and end use of the product. Some examples of irradiation applications where dosimetry may be used are:

4.1.1 Sterilization of medical devices,

4.1.2 Treatment of food for the purpose of parasite and pathogen control, insect disinfestation, and shelf life extension,

4.1.3 Disinfection of consumer products,

4.1.4 Cross-linking or degradation of polymers and elastomers,

4.1.5 Polymerization of monomers and grafting of monomers onto polymers,

4.1.6 Enhancement of color in gemstones and other materials,

4.1.7 Modification of characteristics of semiconductor devices, and

4.1.8 Research on materials effects.

NOTE 3-Dosimetry is required for regulated irradiation processes such as sterilization of medical devices and the treatment of food. It may be less important for other industrial processes, for example, polymer modification, which can be evaluated by changes in the physical and chemical properties of the irradiated materials.

4.2 An irradiation process usually requires a minimum absorbed dose to achieve the intended effect. There also may be a maximum absorbed dose that the product can tolerate and still meet its functional or regulatory specifications. Dosimetry is essential to the irradiation process since it is used to determine both of these limits and to confirm that the product is routinely irradiated within these limits.

4.3 The absorbed-dose distribution within the product depends on the overall product dimensions and mass, irradiation geometry, and source activity distribution.

4.4 Before an irradiation facility can be used, it must be qualified to determine its effectiveness in reproducibly delivering known, controllable absorbed doses. This involves testing the process equipment, calibrating the equipment and dosimetry system, and characterizing the magnitude, distribution and reproducibility of the absorbed dose delivered by the irradiator for a range of product densities.

4.5 To ensure consistent and reproducible dose delivery in a qualified process, routine process control requires documented product handling procedures before and after irradiation, consistent product loading configuration, control and monitoring of critical process parameters, routine product dosimetry and documentation of the required activities.