-6The Bectar teet (May 14, 1953) vas used as the date of
origin except where othervise iadicated, but earlier shots alse
contributed redicactivity to the samples studied. Especially
the Bikini (March 1, 1958) shot con‘ributed greatly to seme of
the seaples. Resid) long-lived products from eariier ietanetienes peior to 195% rendered the curves leas steep than they
would have been as @ result of the 1954 series sisme.
The treads of activity as releted to time are of two kinds,
the physicel decay of individual samples, and the rate of chaage
im activity of ea certain type of sample et a certain locality.
fe distinguish it from ohysical decey. the latter tread will be
Preferred to tn this report as decline.
Results are shown es grephs of the relationship of 1
ithm of rediocactivity to logarithm of time of collection
detonation. The date of origin used may deviate somewhat from
detonation day or the true origin without markedly effecting
linearity of the plot over the period of study. Phe slope is
changed according to the date of origin selected, but if the
same origin is used for both decay and decline, the two may be
compared.
Hunter and Ballou (1951) show on logarithmic plot the
theoretical decay of mixed slow-neutroninitiated fission products of J-235
over a period from 1 to 1000 days as a
slightly curving line vith a predoat-
nantly
below)
downward curvature (concave
and ®@® generel slope varying
from -1.0 to -1.7, averaging -1.2 (Pig. 2).
A similar presentation of the trends of
radioactivity observed in the present
study facilitates comparison with this
curve and within the study itself.
In log-log graphs it will be conwentent to speak of slopes or rates of
decline and decay as becoming more or
less steep vith the pessage of time, and
| ap ie aren tome a a
when the terms steepening or leveling are
applied to the trends, the log-log
relationship is implied. A single
Pig. 2. Mixed fission
product decay, gross
rithmically gives a straight line,
and Ballou).
half life when plotted semiloga-
while on the same plot a aixture of
half lives results in a line of
increasing steepness.
beta.
(After Hunter
In the declines shown as streight lines on log-log plots
possible fluctuations of a cyclic nature attributable to season
or other variables are ignored.