The RAETRAD model of radon generation and transport from soils into slab-on-grade houses.
Remediation planning and 222Rn-related construction zoning require knowledge of how close and strong 226Ra sources can be in different foundation soils under different groundwater conditions without excessively elevating indoor 222Rn levels. A two-dimensional numerical-analytical model was developed to simulate (a) 222Rn emanation, decay, and movement by diffusion and advection in soils around houses and in their understructures; and (b) 222Rn accumulation in a single-zone house. The model represents foundation soils and a house in elliptical-cylindrical geometry. 222Rn may diffuse through its floor slab or may enter via idealized cracks and openings. The model was validated with analytical calculations of two-dimensional air pressure fields and with one-dimensional calculations of 222Rn generation with diffusion and diffusion combined with advection. Agreement generally was within < 1% when finite-difference approximations were minimized. Benchmark comparisons with indoor 222Rn measurements in two test-cell structures under passive and depressurized conditions averaged within 11% of measured values, well within measurement uncertainty. The corresponding average bias was only 3%. Larger variations were observed when applying the model to 50 houses. In this application, a negative bias of nearly 50% was observed due to data gaps and to poorly-characterized floor slabs and crack distributions.
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Rogers and Associates Engineering Corporation, Salt Lake City, UT 84110-0330.
Rogers
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Rogers
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Holt
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D004058:Diffusion; D005431:Florida; D005740:Gases; D006798:Housing; D008962:Models, Theoretical; D010539:Permeability; D011312:Pressure; D011886:Radon; D012987:Soil
D005740:Gases; D012987:Soil; D011886:Radon