TABLE 3.8 = Activity Concentration of Shot 4,
How, Liquid Fallout
“Wine AfterShot
~Ketivity Concentration
(mr)
Mf - 3
(c/min/ml)
3.2 x 104
BR 5
8 - 9
4e3 x 104
520 x 104
9 -10
10 -l
lL +12
3.7
72 x 103
7.9 x 102
1.8 x 10%
BETA ENERGY MEASUREXENTS
Aluminumabsorbers, inserted between the sample and tube window
very near to the tube window, were used on selected samples to determine the maximum range and energy of the beta radiation.
A plot was
made of activity vs absorber thickness; sufficient absorbers were used
to obtain the gamma background associated with the beta activity.
A
sample plot is shown in Fig. 3.23.
The maximum range, R, of the beta radiation was determined by
visual inspection of the point on the curve where the gamma contribution ceased to be the sole contributor to the total activity. The
beta energy, E, was calculated using the relation.14/
where
BE =1.85R # 0.245
E * maximum energy in Mev
(3.21)
R = maximum range in aluminum in mg/cm
The results are presented in Table 3.9.
Absorption methods for the determination of beta energies for
fission product samples are subject to error due to the presence of a
significant amount of gamm activity which overshadows the activity of
high energy beta emitters present in the samples. Determination of
the range by visual inspection of the curves when gamma backgrounds
are present will yield an apparent range which ie less than the actual
rangee
:
The data indicate that the apparent maximum beta energy of sev~-
eral Shot 1 samples increased from 1.7 Mev to 2.2 - 2.5 Mev during the
period from 9 to 70 days after the shot. The Hunter-Ballou curves15/
indicate that 9 days after fission the contributors hayine the highest
energies are Lal4C_ (1.7 Mev) and Pri44 (2.97 Mev). La+“
contributes
12 per cent and Pri44
0.3 per cent of the total activity at the time.
Shot 1 absorption data taken 9 days after the shot indicate the pre-
sence of Lat40, As the time after the detonation increased, the
curves indicated that the contribution of Prl44 to the total activity
increased (1.6e, 0.9 per cent ami 2.4 per cent at 24 and 70 days
73