165 a Certainly a more exhaustive study of this is indicated for turf, clay and what have you. One of the things which will detere mine the degree of heavy fallout after the attenuation mechanisms have been made operative ig the spectral composition of the fallout, the spectral composition of the radiation from the fallout, Information along these linea in reference to this problem is essentially none existent, though of course there hns been a tremendous amount of theoretical work done on degradation pamna rays. The washdown gituetion seems to be pretty well in hand with the work that NRDL has already performed and is continuing. And lastly, what is a reslistio value of permissible exposure in the event of a major nuclear catastrophe? , This of course, will determine many things, will have many vital effects on the kind of counter measures, the kind of shield~ ing and the economics of protection egainst this, twenty-five, up to fifty or something of

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