G. Water and Air Background Information Water Contamination of water supplies does not constitute a major source of intake of radioactive fallout debris. In the case of surface water supplies there is a very large dilution factor. In the case of under- ground nuclear detonations the fission products are restricted largely to the immediate vicinity of the detonation due principally to two factors. Firstly, approximately 90 percent of the fission products are fixed in glassy type material formed by the detonation. Secondly, ion exchange between such key fission products as strontium-90 and cesium-137, and the soil results in almost all of the remaining activity being _ perhaps tens of hundyeds absorbed within a matter of feet/away from the source**-. In addition to fission products, tritium may be formed in varying amounts. This radioisotope probably is not greatly influenced by the two factors mentioned in the previous paragraph and must depend upon the dilution factor for reduction of the concentration in the water - at least for underground detonations. For above ground or cratering shots, the tritium largely escapes into the atmosphere where very large dilutions occur. Theoretical calculations suggest it may be possible for above acceptable concentrations of tritium to be present in the amount of water present around ground zero of some underground nuclear detonations? 6a. . 27 ad