-10-
of U235 ag depicted by Hunter and Ballou (1951).
From their Figure
1 the following approximate slopes were obtained graphically: 20-100
days,
-1.2; 200-547 days, -1.8; 2-6 years, -1.3; 10-25 years, -0.7;
150-180 years, -3.7.
Thus, the mean slope for the Eniwetok samples is slightly
steeper than that of Hunter and Ballou up to 100 days; then,
period from 2 to 6 years,
in the
the Eniwetok samples tend to be at first
less steep, and toward the end of the period, steeper.
Future counting
may show whether these curves will level slightly to -0.7 as does
Hunter and Ballou's curve at about 10 years.
For the first six curves (Table 1) of pre-Mike samples involving
products of the Greenhouse tests the curves tend to be steeper than for
TaN
corresponding periods for post-Mike samples.
Contamination of post-
Mike samples by the older products from Greenhouse would tend to produce an effect in this direction, but so marked an effect is rather sur-
prising.
In contrast to the general tendency as noted above for the average
of the slopes to become steeper after 3 years, certain curves showing
a slower decay than average may be of special importance.
Curve 49
for rat muscle decayed most slowly of all those studied,
with a half
life during the
In gamma
last 3 years,
of more than 30 years.
spectroscopy of this plate only Cs!37 was detected.
A listing of those