Nielson K K, Rogers V C, Rogers V, Holt R B
Rogers and Associates Engineering Corporation, Salt Lake City, UT 84110-0330.
Health Phys. 1994 Oct;67(4):363-77. doi: 10.1097/00004032-199410000-00007.
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.
修复规划和与氡-222相关的建筑分区需要了解在不同地下水条件下，不同地基土壤中镭-226源的距离和强度在何种程度时，不会过度提高室内氡-222水平。开发了一个二维数值分析模型，用于模拟：(a) 房屋周围土壤及其下部结构中氡-222的析出、衰变以及通过扩散和平流的迁移；(b) 单区房屋中氡-222的积累。该模型采用椭圆-圆柱几何形状来表示地基土壤和房屋。氡-222可能通过楼板扩散，也可能通过理想化的裂缝和开口进入。该模型通过二维气压场的解析计算以及氡-222生成的一维扩散计算和扩散与平流相结合的计算进行了验证。当有限差分近似最小化时，一致性通常在<1%以内。在被动和减压条件下，与两个测试单元结构中的室内氡-222测量值进行的基准比较平均在测量值的11%以内，完全在测量不确定度范围内。相应的平均偏差仅为3%。将该模型应用于50所房屋时，观察到了较大的差异。在这种应用中，由于数据缺口以及楼板和裂缝分布特征不佳，观察到了近50%的负偏差。
