air, but this dose will usually be small compared to the exposure. or even to . be minuscule compared to natura! backyround levels that follows after the debris is deposited on the pround, nurimal variations of background radiation. G. WATER AND:AIR Be aint ge Savybacette: * ~ BES Backgroynd Information Weter Contamination of water supplies does not constitute » major “*.-gource of intake of radiouctive fallout deuris. In the case of surface water supplies there is a very large dilution factor. In the case of underground nuclear detonations the fission :. products are restricted largely to the immediate vicinity of the detonation due principally to two ‘factors. -Siratly, for underground shots to date approximately 90 percent of the be deposited nor the amount of iodine 1) in nilk.4 Because of the transitory nature of the fallout debris remaining in the gir (and sometimes because of ithe particulac choice of units an used in expressing ita concentration) what may sound Uke alarmingly Jarge amount may, in fuct, result in only minot radiation doses. fission products have been fixed in a’glassy type of material + eas TL, gn cmemne ae aint eb ieeesee | mR, formed by the detonation. Secondly, ion exchange between + such key fiasion products as strontium 80 and cesium 137, . The Dato and the soll resulted in almost al! of the remaining activity in, prediction is by drijling operations. Although these are ev. pensive operations they are carried an extensively at the testing sites. air Aa long as the fallout material from atmospheric tests re- mains in the air some may be inhaled and irradiate the luryzs. This radiation dose to the lungs normally in lesa than external whole body exposure occurring ufter the faliout hus been deposited on the ground. Also in «eneral, tuhalation is only a minor contributor te the intake o. fallout debris into the hody ‘ingestion is the much more important reute. The whole body will also receive some exposure from the penetrating gamma rays while the Fallout material is in the te ee ae pe ia “ The hirhest measured fallout activity in water was at Upper Pahranagat Lake, Nev. in 1985 amounting to ud millionth of acurit per liter? Since this was @ total rosy beta count it it difficult to give a precise estimate of the polential radiation dose. A crude analysis suggests that if this water had bees stored and used as a sole supply for 70 veurs the total dors might be about one roentgen to the bones ond one-quarte; - ground detonations. For above ground or cratering shots, satisfactory method of obtaining the necessary data for this - Water being adsorbed within a matter of perhups tens to hundreds of feet away from the source.” In addition to fission prod: ucts, tritium may be formed in varying amounts. This radio*: isotope probably is not greatly influenced by the two factors mentioned and must depend upon the dilution factor fur reduction of the concentration in the water—at least for under. the tritium largely escapes into theatmosphere where very large dilutions uccur. Theoretical calculations suggest it may be possible for relatively high concentrations of tritium to be present in the amount of water immediately surrounding ground zero of some underground nuclear detonations,’! Essential to predicting potential contamination of ground water is the determination of the water movement. The most How ever, this ratio of doses may not hold for cvents where mos of the radioactivity that escapes beyond the est site isin the: form of gases or finely suspended particles os are confined ' to a relatively shallow layer of air near the sartace, - Measurements of total falluut wctivity in aii (called gros beta counts) provide only a crude alerting: system, It is nes tr a reliable procedure for predicting the amaunt of fallout cay i yoentwen each to the thyroid and lower large intestine. No radiuactive fission products nor luduced activities includ, “ing tritium from underground tests have been found in unden ground water supplies at places of human consumption. an i i The highest concentration of radioactive dcbiis in the air it & populated arenoff-site (except for the Marsiiiliese experienc) where measurements were made only after (he passage of thi cloud) was about 1.5 millionth of a cure per cubic meter aver aged over the 24 hours the activity was present! Thig hap pened at St. George, Utuh, on May 19, bis The estimate: radiation dose to the lungs from inhaled talleat debris was ler than 0.2 roentgen.” The external whole brely exposure fron the fallout while it was atill in the air was coouhly ewtimates to be 0.026 roentgen —only about Yooul the wiiote body exparun that occurred ofter deposition of the fallin Evaluation. The concentrations of fission praducts or toniiy in the waty kupplics have not constituted major sue ot vafiation es posure toman, There is a lacge dilution foot ec owhen sortie THe SER OD ot ¢