RMI Nuclear Justice Documents

mob ow tain RADIATION STANDARDS, INCLUDING FALLOUT 57 clusively. Finally, the lowest curve reflects the geographical distribution of S. debris added to the lower equatorial stratosphere in the summer of 1958 id also deposited in 1959. The year 1959 was chosen to compare it with the viet fallout curve as well as for other reasons. It is based on tungsten 185 aich was a unique tracer for the U.S. Pacific 1958 tests. An arbitrary but asonable relationship between tungsten 185 and strontium 90, derived from study by Hardy of the AEC, permits one to compute the strontium fallout. It is clear that fallout from the equatorial source is distributed more widely an the Soviet fallout and close scrutiny will again reveal peaks in the temrate zones of each hemisphere. The 1959 fallout in the Northern Hemisphere om the U.S. tests was about twice that in the Southern Hemisphere. For mparison with the 80 percent of the Soviet fallout, the fraction of strontium from the 1958 U.S. Pacific tests which was deposited during 1959 was about percent thus refiecting the faster fallout from polar than from equatorial elear clouds. : Dee weytnnes SEASONAL VARIATIONS Figure 7 shows the seasonal variation of Northern Hemisphere fallout for 4 year 1959. The horizontal axis is time in months, with the spring season ided and the vertical axis shows strontium 90 fallout per month, increasing ward. The uppermost line shows the total amount of deposition in the rthern Hemisphere while the middle and lowest lines show the fallout atribution to the total from the U.S.S.R. 1958 and U.S. 1958 Pacific tests spectively. All three curves indicate that during 1959 the spring season was » period of heaviest fallout. Che table on the placard indicates that during the spring of heaviest fallout or to 1962, that is in 1959, of the total fallout, 73 percent was of Soviet tober 1958 origin, about 13 percent could be identified as U.S. Hardtack nmer 1958 origin marked by the tungsten and the remaining 14 percent m all other sources. fhe seasonal variation of Northern and Southern Hemisphere fallout from 58 to the most recent period of data availability is displayed on figure 8. e horizontal axis is time with the calendar year labeled below and the vertical is shows the amount of strontium 90 fallout per month, increasing upward. .@ spring for each hemisphere is identified. The lower curve displays the uthern Hemisphere fallout picture. If the spring were always the time of ‘ximum fallout, the lower curve should peak at each Southern Hemisphere ‘ing and dip at each Southern Hemisphere fall through which it passes. ly in the latter half of 1960 and onward is this true however. so eelavesteteoeca.cernsiey eclechiegsttebtede dis ee sueieddeltnpsesSsbannes PsySabetgEeRMARRNCORI The dashed “tion of this curve (in late 1961), is based on incomplete data. In the Northern Hemisphere, the upper curve, one finds a very clear-cut ‘sonal trend with each April-May showing a maximum and October-Novem‘as a minimum. This, it should be noted, is true even though in 1960 and il there were no atmospheric nuclear tests during the previous fall. It had nn speculated that a possible explanation for the spring maximums prior to 30 was a delay in the fallout from Soviet tests the previous autumn. This ‘ms now not to be the case, although it is clear that the presence of large ounts of Soviet stratospheric debris, as in 1959, greatly enhances the magnile of the spring peak. Since it appears likely that the spring peak is meteorologically induced (it years in other stratospheric tracers like cosmie ray created beryllium 7 ulyzed by Gustafson at Argonne and by the British), why does it not occur ularly in the Southern Hemisphere? There are two likely explanations. ‘st, it is noted that until 1960, the Northern Hemisphere troposphere conned much more radioactivity than the Southern Hemisphere, as evidenced the upper versus the lower curves. There is other evidence of cross-equatorial xing which can bring radioactivity from the more contaminated to the less itaminated hemisphere. Thus, the Southern Hemisphere may have had two irces of strontium 90, the first from the stratosphere which may be showing sonal regularity and a second source, the Northern Hemisphere troposphere, h an entirely different season of injection into the Southern Hemisphere posphere. Then, in 1960 and 1961, when the air content or both hemispheres ‘ded to equality in the troposphere (see fig. 8), as well as in the stratosphere ted earlier), the controlling seasonal factor in the Southern Hemisphere ‘ame the stratosphere. : fence, the appearance of seasonal regularity in the Southern Hemisphere, The other explanation i ich many meteorologists expected, in 1960 and 1961.