ISO/TC 142/JWG 10 - Joint ISO/TC 142 - ISO/TC 85/SC 2 WG: Aerosol filters for nuclear applications

ISO 16170:2016 specifies in situ test methods for high efficiency particulate air filters used to limit releases towards the environment (e.g. from nuclear facilities or facilities with aerosol toxic or biological releases). This applies where installations of these filters are used to clean effluent air before discharge to the environment from industrial (including nuclear) installations where toxic/radioactive/biological materials are handled or processed. It excludes the application already covered by ISO 14644‑3. The scope of ISO 16170:2016 includes detail of two methods, either of which applies to the periodic testing of high efficiency filters which are used in demanding applications aiming at protecting the environment, such as the nuclear industry. In the case of nuclear applications, ISO 16170:2016 is applicable to installations covered by ISO 17873 (applications other than nuclear reactors) and ISO 26802 (nuclear reactors). The two reference methods specified in ISO 16170:2016 are not equivalent, but related to, the requirements to be addressed by the test results. The choice of which of the two methods is adopted in any specific case depends on whether the outcome requires an integrity test or a statutory efficiency accountancy test. For industries handling or processing radioactive or toxic materials giving rise to a risk of possible release, the main goal of the tests is to confirm that the filter installation is fit for purpose. In the case of integrity tests (Annex B), this is to confirm that no significant leakage of toxic aerosols through the filter installation is possible. In the case of efficiency accountancy tests (Annex C), the test is designed to make an accurate measurement of decontamination factor with respect to the MPPS size range of particles. The reference method described in Annex B (integrity test) requires a test aerosol of dispersed oil particles mainly submicrometre in size range, which is stable during the test procedure and compatible with other installation components. Particle concentrations are measured in real time by light scattering instrumentation (optical detectors). The reference method described in Annex C (efficiency accountancy test) requires a test aerosol of particles having a narrow size range centred on MPPS size range for HEPA filter media. Their concentration both upstream and downstream the filters is measured by fluorimetric analysis of aqueous solution obtained by washing the membrane sampling filters. It should be noted that the requirements for an efficiency accountancy test also cover the requirements of an integrity test, which is considered to be a minimum requirement. Test methods developed in ISO 16170:2016 do not cover the other in situ performance requirements, such as mechanical resistance, bursting resistance or humidity resistance. Specific systems operating at high temperature or with specific gaseous effluents might require specific test methods. The engineering design of HEPA and ULPA filter installations does not fall within the scope of ISO 16170:2016. NOTE In the field of filters for general ventilation applications, ISO 29462 is a detailed and comprehensive description of a method which uses scanning and particle counting methods to evaluate the performance of a filter in terms of particle grade efficiency, as well as pressure drop. Such a method and procedure would not be applicable in those nuclear installations where quantification of the decontamination factor at MPPS size is needed.