Applications of diffusion board concepts in the development of less costly methods for containment of gaseous and particulate emissions from reactor accidents or releases from other nuclear processes are discussed. In the diffusion board concept, a porous building structure would be erected over the reactor or be included in adjacent reactor building walls in the manner of conventional steel containment vessels. It permits steam and radioactive gases and particulates to be decontaminated during passage through the board and yet relieves the stored energy without pressure buildup. Results are reported from evaluation tests of 0.5-in.-thick mineral diffusion board samples for air flow resistance, particulate removal, and iodine removal. (C. H.)