RMI Nuclear Justice Documents

* -~ wm ore : tow oe FE weSE fercoo : ° . C ~ . - . . - « : a . woe C , . . =~ A ): : . pt 138 This means that the radioactive fall-out for shot No, 5 ofTUMBLERSHAPPER is equivalent to the situation where the two hour old atomic cloud comes in contact with continuous heavy rain which originates at 40,000 to 50,000 ft, ml, It: will be assumed that the rain ‘reaches the ground within 20 or 30 minutes, hence - the fall-out will be completed at Ht3 hrs. If it is assumed that the rain is . ne uniforaly intense throughout the 17,000 square ‘miles, ‘thea the two hour old: -’ atomic cloud will be assumed to have a "hot core® or central area of maximua >. ~.” activity of 1300 square mile cross-section, The shape of the cross-section will> be elliptical with the major.axis of the ellipse parallel to the average hori- .“me zontal wind direction, 4round this central "hot core" there will be less radioe | active areas, 4s a matter of fact Figure 1 would be a good representation of the © cross-section of the atomic cloud from shot No. 5 provided a correction is applied to account for the motion of the cloud top in the first two hours, of COUFBE, oars “an vats tees it way be possible to obtain the same fall-out pattern if we assuned that the more intense radioactive fall-outareas are due to heavy” rain. and the less intense contamination is due to the fact that the rain in theseareas was less intense,’ In other words, if the cloudis assumed homogeneous then it must beassuned. that . the rain is non-homogeneous,“and vice versa, in order to!‘obtain the fall-out’ es patterns shown in the inclosed Figures, This shows that”even if the three hour old atomic cloud is scavenged by heavy rain which originates at the unlikely. height of 40,000 ft., the radioactive fall-out will not ‘present a hazard to iit. There will be a relatively small surface area where the” maximum “dose rate will be as high as’ 2r/hr, but where for the cost part.“the:average maxigum 1298¢ ratetis within the area would be in the order of 200 to 300ar/hr,and the t- ~decay. law would apply.. Certainly“this would pose'a hardship in the‘area “concerned, oe. but it would not, be hazardous to life. It was assumed above,“that: the continuous « type of steady rain originates at 40,000 to 50,000 ft. msl, In reality it would .‘4 be quite rare indeed to find héavy rain originating atsucha high level. Oa-< 7% rare occasions or under some turbulent thunderstorm activity: precipitation may 2°3°% reach such heights, but to make operational plans based on the ‘assumption that :*.% this happens on a continuing basis {s certainly unrealistic, It is thought that |z a more realistic assumption would, be that rain originates from 5000 ft. to 25, 000»& teal wary onLone ft. asl. This’ means the amount of radioactivity scavenged out at He2 or H¢3 | hours would be’ considerably less than that indicatedabove, because the scaveng-: ing would-begin at 25,000'ft. or less, hence raincouldnot possibly. come in - [3 contact with all. of the atonic cloud. As a matter of. fact it is. difficult to-- — see how the average rain. could cone in ‘contact,withthe pushroom of an atoaic 57 cloud formed bythe detonationof,a ‘nominal-(20KT)bomb.” ‘From,the long ‘range’ es ’ Public Health point of viewthe inclosed Figures”‘indicate thatthere ’say be ae hazerd to heith in the areaswhere fall-outis “shown, However, it should be . noted that in’ all of the shots subsequent to shot 5,it was not’possible to find . a measurable ‘amount of radioactivity in the areas concerned two tothree days -~ after shot time. This indicates that the radioactive.fall-out, is further diluted by such "weathering® effects as winds, rain, ete, It"‘was possible to find measur-: able amounts of radiosctivity two weeks after ‘shot No. 5’was detonated. Itisbelieved that the available data from TUMBLER/SNAPPER together with the Indicated calculations has made it possible to determine the order of magnitude of the radioactive contamination that may be scavenged out by rain from the three hour old atomic cloud.. If it is desired_to determine the radioactive fall-out froa |" «. the young atonic cloud then the “rate of decay and the diffusionfactor of the : atomic cloud must be evaluated, The decay factor. is relatively simple to evaluate. r > Le ee Bes, _ . : Se +l AS ~“i° eo bere I Ope we jv. oe 2 eee ee ¥. vine?adsSLLTey ‘Se De ’ “Sat waarSeat we Wy a. = . = 27 Ot? sy eat Do re & AG