[en] A radioactive tracer method for studying the effectiveness of various materials to mitigate the explosively driven dispersal of radioactive substances into air has been developed and applied. Experiments are conducted in a facility call CON-CON (for Conical Containment) 1 which simulates the effects of a 23 lb (10.5 kg) spherical high explosive charge. Up to 3.7 x 10⁷ Bq (10 mCi) of ²⁴Na tracer in the form of <325 mesh sodium titanate powder is used in each test. Airborne tracer which breaches the mitigator is collected using cascade impactor air samplers and analyzed by gamma ray counting. Detection sensitivity for the tracer is about 1 part in 10⁹ to 10¹⁰ of the original tracer. Experiments have been conducted with air, dry sand and aqueous foam mitigators. The dry sand decreases the amount of tracer collected by about a factor of 10 to 100 and foam by factors of 2000 to 4000 relative to baseline (no mitigator) tests