NV/HES Mtg.-Sept. 26-27, 1968 Page 4 The PHS studies also include air-to-milk ratios and milk-to-forage ratios that can be applied as prediction tools for future tests conducted under similar conditions. PHS data indicate that restricting animals fed in the open to a single feeding after the cloud passage will result twentieth of the peak radioiodine in one-fourth to one- in subsequent milk production that would be seen if there were continous feeding. Similarly, if water is applied to fresh green forage immediately after the cloud has passed over, potential dosage may be reduced by about a factor of ten. Iil. PREDICTION OF I-13] LEVEL ON THE GROUND The Group discussed the need of an improved particle diffusion model as an extension of the PHS prediction scheme in the determination of I-131 deposition on the ground. The D model, currently utilized, is a "close-in'' model that is extended beyond its range of applicability. Differences in wind direction at different heights tend to spread out the radioactive particles and reduce both the cloud concentration and the eventual ground concentration. A new model which determines cross- wind distance in the conventional wind shear fashion used in most close-in prediction models and which brings the particles to the ground er oe by an eddy diffusion process instead of the conventional fallout process would do much toward refining the prediction of I-131 depgsition on the ‘b ground. The Group decided to defer a recommendation that ‘NVOO investigate the applicability of some of the newer diffusion models until after Galetetens "NE SNL 8 76