CORRELATIONS ON DEBRIS FROM SILICATE BURSTS
79
the range was considerably wider. The slope values obtained from the
Johnie Boy and the Small Boy data are in quite good agreement with
each other. The Sedan data are also given for purposes of comparison
along ~with slopes from previous correlations on a high-yield coralsurface burst and on some air bursts. A few interesting points with
regard to &.
of °Np in the 2
. may be mentioned. The nonfractionating behavior
ralexsurface burst is at variance with its behavior in
the ais* bursts,and the silicate bursts. On the other hand, **Mo fractionates in the. M@ar-burstg@ebut not in the other shots. There is an in-
dication of possible sfight fractionationsof ‘4Ge in.Sedan andin the air
bursts. In the silicate bursts ‘Cg fr&etionateg less than '"Cs. The
fractionation -of‘the. latter is explainable ai?the‘basis of its rare-gas
precursor, !*'Xe.”Cegium-136, on the_othen hand, is shiegied; i.c., it
has no preétirsors. A possfite explanatjon#f its fractiongt n behavior
lies in thé basicity
of the alkali-meta¥oxide or hydroxide relative to
the silicate sqil
m.
“*
A reservation ‘should be noted for the slope values repiftted for the
103-, 106-, and 132-mass chains for Johnie Boy and Small Boy. There
is some indication in each of these cases that the datd points belong to
two different families and should not be fitted to the same straight line.
The available data are unfortunately inadequate to resolve the question.
Aside from the **Mo and ?Np anomalies just mentioned, insofar
as the table permits one to judge, the differences in fractionation in
the various kinds of bursts are of degree rather than Kind.
Analysis on many samples separated into sieve fractions displays
the trend of fractionation with particle size in a rough way. Figure 5
shows
an example of these data from the Small Boy shot and also
illustrates the variability of the ratios observed. The ratio of *Sr to
*5Zr has been plotted against the sieve-opening diameter. There is,
of course, no really accurate way of plotting these data. For example,
any point on the right side of the 1580-y line corresponds to a sample
that passed a No. 7 sieve (2800- openings) and was caught on a No. 12
sieve (1580-, opening’); padtinitiiy the.saihple mayciein”particles
up to 2800 yu. The scatteMigat the points is
@iught tape-dge to the
combined effects of heterdgeneit prand wegseial)sarge. size.Atlleast
two kinds of active particles,
Sonia:
a3rregélar particles,
were discernible in these s
;
cemales: ¢
‘Heve4fractions
consisted of only a few parftit ceo
‘pOMMeenS niay nothaveeen
truly
representative
of their“particle--size classes.
If an. dverage
weighted according to sampte masses is taken, one obtaing,the, ints
of Fig. 5 through which a line has been drawn. The figureis quite
representative of the behavior of fractionating nuclides in both Small
Boy and Sedan. The siéve data OR: theJohnie“Boy&pnples were too
few to draw any conclusions relative to particle size.