RMI Nuclear Justice Documents

t ¢ ( 2 tw is NGLASSIFIED surface zero with the arrival points of all particles from the same eleva- 2.2.1 sizes will deposit from that originating altitude, in most of the observations made at the Er: e2tok Proving Ground © the winds aloft were not ina steady state. Cignificanatr changes in the winds aloft were observed in as snort a periodes Shr. This variability was probably due to the fact that proper ficing cunditions, which required winds that would deposit the fallozt certh of the proving ground, occurred only during an unstable synoptic situation of rather short curation. It was necessary to correct for this variativc to kee, iracK of the predicted fallout area, especially at great distances from surface zero where as much as 20 hr elapsed before deposition. — tion, are most descriptive for they define the patb along which all particle , CLASSIFIED The heigkt lines describing the fallout from the lower portion of the mushroom immediat ly establish the “hot line." The “hot line" is best defined as that portion of the fallout area wherein the highest levels of activity are found relative to the adjacent areas, Under most meteorological conditions this area is described oy a line from surface zero that coincides with the height lines from the altitude layers that include the base of the mushroum; for the source mode] was so defined to concentrate the activity in this volume. : Time Variation of the Winds Aloft Since this variation could not be forecast, balloon runs were made every 3 hr from H40 to H+24 and each particte trajectory employed the winds as they changed With time. The correct particle trajectories were approached by a method of successive approximations as luliows: Tables 3 through 6 were computed for the four particie sizes and gave their cumulative times of fail sach that starting at any eievation their altitude at any time after H-br could be located. For example, the 75-p particle originating at 70,000 ft extered the 40,000-it layer in 7.18 br and reachec the surface in 19 hr. Since new upper air observations Since the plotted grid of size-lines and height-lines was based on a line source of activity, each particie point must be expanded to the appropriate cloud or stem diameter from which it originated, This expansion, after t2king inte consideration the cadiai particie size irac’ tionation in the source model, defines the perimeter of the drea, One . then has a map indicating the fallout areaand the path of expected highest activity. Curves of time of arrival of fallout through the pattern are estab- were obtained every 3 hr it was assumed that the balloon released at H+0 represented the winds aloft until H+3 hr and the balloon released at H+3 hr represented the winds until H+6 hr ard soon. Therefore, as the particle settled toearth the appropriate winds aictt were applied to it. lished by simply assigning the appropriate value of falling time to each expanded circle about the arrival points and by constructing from this network of values iso-time coziour's that indicate the earliest time at which falloat will arrive at a given distance from the shot point, Similarly, the determination of the time of cessationof fallout at any location may be plotted. However, one is faced with the question of Low to define cessation, Very sm1ll particles that do not contribute significantly to the radiation field continue to arrive for days after time zero, Cansequently, a plot which describes time-to-peak activity seems more meaningful, During the field operation time-to-peak activity was defined as the time of arrival of fallout particles originating in the lower third of the mushroom.” The first step was to slot size-lines for the particles based on the H+@-hr winds. This establisned a fallout plex that assumed the winds would aot change with time. When the 14#3-hr winds became available a similar plot was made based on them. With the aid of Tables 3 through 6 the particles starting at various elevations were located in altitude at E+3-hr points, These H+3-hr points are marked at the proper altitsde oa each size line, The two size lines, HrO and Ht3,are then overlayed sech the: the H+3-hr points are coincident and the combined sixe-lices ceter- muned with the aid of a Kgbt-table. This is done by taking tke upper portion of the H+0-hr size-line and th: lower portion of the H+3-hr sizeline. This first approximation then assumed that the H¢3-—hy winds will remain steady for the remainder of the particles flignt, The process is repeated using the cornbined size-line and the new size ~line for the next set of wind data uct‘] the particle reaches the surface. Therefore for each new wind observation a closer approximation of the corrected time variable plot is made until ultimately the plot is quantitative. This method determines the fallout plot under conditions that do not involve several important meteorclogica! variables. In this’ sense it is most vali for a fallout of short duration and over a relativeiy small area, for-example, a 1-KT surface detonation, Megatca devices and large KT yields deposit primary fallout over long periods and to great distances, To map such extensive deposition of fallout necessitates inclusion of comngl.s meteorological variables and consideration of the fact that clouds from these Large detonations extend to great heights in the atrnosphere. 2.2.2 Space Variation The preceding computations assumed that the winds aloft, as” measured at the point of detonation, ata given time are the same throughout the area for that time. Since the failout can ceposithucdreds of miles * A recent study of available data indicates that the time-to-peak acticity cas be excclicetly defined as twice the Uime of arrival, ~10. wlhls ‘ | | | ! UNCLASSIFIED 7 eeeeee meee ornatecetiet 64 abba eae Dat sparenote cat ty £86ferna STNmer FE ¢ .