4.1 A variety of irradiation or treatment processes use low energy electron processors to modify product characteristics. Dosimetry requirements, the number and frequency of measurements, and record keeping requirements will vary depending on the type and end use of the products being processed. Dosimetry measurements are often used in conjunction with physical, chemical, or biological testing of the product, to help verify specific treatment parameters.

NOTE 1 - In many cases reference data may be developed, comparing dosimetry results with other quantitative product testing; for example, gel fraction, melt flow, modulus, molecular weight distribution, or cure analysis tests can be used to estimate radiation dose in specific relevant materials.

4.2 Radiation processing specifications usually include a minimum or maximum absorbed dose limit, or both. For a given application these limits may be set by government regulation or by limits inherent to the product itself.

4.3 Critical process parameters must be controlled to obtain reproducible dose distribution in processed materials. The electron beam energy (in eV or keV), beam current (in mA), spatial distribution of the beam, and exposure time or process line speed all affect absorbed dose.

NOTE 2 - In some liquid-to-solid polymerization applications (often referred to as radiation curing), the residual oxygen level during irradiation must be controlled to achieve consistent results. A high level of residual oxygen can affect product performance in these curing applications, but does not affect the absorbed dose. However, oxygen effects on the response function of the dosimeter used in the measurement of dose should be taken into account.

4.4 Before any radiation process system can be utilized, it must be validated to determine its effectiveness. This involves testing of the process equipment, calibrating the measuring instruments, and demonstrating the ability to deliver the desired dose within the desired dose range in a reliable and reproducible manner.