Nuclear Filters

Radioactive contaminant filters are used in nuclear ventilation systems, containment ventilation, exhaust air filtration, hot cells, isotope laboratories, decontamination units, decommissioning work, and temporary negative-pressure zones. Selection should be based on air flow rate, allowable pressure drop, contaminant class, contaminated filter handling method, housing leakage class, and integrity test requirements.

This category includes rectangular or cylindrical containment housings manufactured from stainless steel 304L/316 or coated carbon steel, with provision for prefilters from G2 to H10, HEPA/ULPA elements, and carbon beds. For critical-duty service, safe-change or bag-in/bag-out arrangements are used so that filter replacement can be carried out without direct operator exposure to radioactive, toxic, or biological loading.

Cylindrical HEPA push-through elements are intended for housings requiring repeatable positive sealing by seal rings and can operate in either vertical or horizontal orientation. Versions are referenced to ES_0_1735_2, individually tested, with efficiency above 99.9925% to BS 3928 Sodium Flame Test and initial pressure drop up to 250 Pa. HEPA canisters are used for lower flow rates, including 5 and 25 l/s units, with efficiency above 99.99% to BS 3928.

For gas-phase duty and radioisotope retention, divided-bed activated carbon filters are applied, using deep-bed cells and a flow path arranged to increase air-carbon contact time. Technical assessment should include face velocity, relative humidity, temperature, breakthrough behavior, and compatibility of impregnated carbon with the target contaminant.

For maintenance work or temporary containment, mobile filter units (MFU) incorporate a HEPA safe-change housing, fan, prefilter, control panel, and differential pressure instrumentation. Where contaminated filters are routed to incineration, incinerable HEPA elements reduce non-combustible residue; compatibility with the housing, sealing arrangement, and final disposal procedure should be verified during specification.