-10-
of U235 as 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,
the Eniwetok
in the
samples tend to be at
less steep, and toward the end of the period, steeper.
first
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
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 last 3
In gamma
years,
of more than 30 years.
spectroscopyof this plate only Cs!37 was detected.
A listing of those