title: The RAETRAD model of radon generation and transport from soils into slab-on-grade houses.
abstract: 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.
authors.affiliation: Rogers and Associates Engineering Corporation, Salt Lake City, UT 84110-0330.
authors.forename: K K
authors.initials: KK
authors.lastname: Nielson
authors.forename: V C
authors.initials: VC
authors.lastname: Rogers
authors.forename: V
authors.initials: V
authors.lastname: Rogers
authors.forename: R B
authors.initials: RB
authors.lastname: Holt
mesh_terms: D004058:Diffusion; D005431:Florida; D005740:Gases; D006798:Housing; D008962:Models, Theoretical; D010539:Permeability; D011312:Pressure; D011886:Radon; D012987:Soil
chemical_list: D005740:Gases; D012987:Soil; D011886:Radon