BOIL-MOISTURE PREDICTION METHOD FOR NRDL INDUCED-ACTIVITY PREDICTION SYSTEM

摘要

Part of the military problem of predicting the gamma-radiation doses at 3 feet above the ground produced by the radioactivity induced in soil elements by neutrons emitted from nuclear air bursts is that of predicting the moisture content in the top soil layer of interest. The greater the moisture content in this layer, the closer to the surface lies the major part of the thermal neutron flux, since hydrogen atoms in the water are highly effective in thermalizing neutrons. Thus, there is less attenuation of the resulting gamma radiation by the soil. A method of predicting the soil moisture content in the top 8 inches of soil is described. The method, whose computational procedure follows a simplified "bookkeeping" form, is based on soil textures and experimental values on daily moisture accretion and depletion for different seasons of the year. The method is applicable to both free and impeded drainage conditions. The method is demonstrated by simple and complex examples.