28
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
SHORT LIVED FISSION PRODUCT GAMMA RADIATION
curves were again integraled to obtain the
photons/fission-see and energy/fission-sec, and
the results are shown in Table 2.
Tarte 2
‘pimeafter Sssion
[:
‘ fete28"
A Ateraedna
Mev)
(Mev)
7
1.62% 107
wn
nm
ot
2.34% 10-4
5
1.15
Ll?
1. 21
4.90 x 10-3
1.68 x 10-%
4.00 5 16°€)
an
4,48 x 10?
1,53 x 107?
8.97 x 10-3
4.16% 107
1,48 x 10|)
5.11 x 10-¢
PHOTON INTENSITY ( photons /Mev- fission -séc}
117
6.58 x 10-?
3. 88x 10?
1.31% 10-7
7.43 x 10-3
tor?
1.89 x 1a-t
5. 50x 10°?
5.25 x 10-4
3.76 5 10-4
2.26 x 10-4
Lig
1.18
Lu
1.08
94
97
nN
Crossplo(s of the data taken in one phase
of the experiment on those of the other phase
are shown in Figures 4 and 5.
S
1
s
the agreement is quite good.
It is seen that
An additional experiment was performed in
wo
cooperation with R. W. Peelle of this labora-
P|
M
|
mh
"COMPTON SPECTROMETER
ae
* PAIR =~
roe
tory. In this case the equipment used integrated the spectrum over a longer time than
was used in the first experiment. A representative spectrum, representing the integral between
about 0.7 second and about 3 hours after fission
is shown in Figure 6. While it is difficult, to
compare the results of the two experiments
since they cover a different time range, a not
unreasonable extrapolation of the curves from
the first experiment leads to approximately
the same number of photons/fission and en-
ergy/fission as was obtained in the second
experiment.
The authors wish to express their appreciation to Mrs. G. Estabrook for her aid in the
many calculations involved in the analysis of
the data.
DISCUSSION
ee
ae)
20
30
PHOTON ENERGY {Mev}
Figura 3.-—-Fission product photon energy spectrum at 6.2, 40, 100, 2700, and 1,560 sec after fiaston,
W. Zobel and T. A. Love
Voice.
FT wonder if you could describe a
little bit the type of radiation used to produce
29
the fission products described in the first talk,
the duration of this and the spectrum?
Dr. Zonpn. What did you have in mind?
You want the experimental arrangement?
Vorcr. Yes. J would like to find out how
these fission products were produced.
Dr, Zoseu, Small samples of 235 were sent
pneumatically into the graphite reactor and
again pneumatically blown out. The time was
set by an oscillator which was checked with,
if you will, a frequency calculator, so that the
(ime was reproduceable very well. The different bombarding times used, and sample sizes,
the sample sizes varied from 2 milligrams to
32 milligrams the combination of bombarding
time and sample size was chosen so that we
could get the maximum number of counts in
the spectrometer —this is coincidence counts-—
without overloading (he central channel too
horribly.
Are you familiar with the 2 or 3 crystal
spectrometer?
Voice. Yes.
Dr. Zonet. Wehad in the central channel
countrates as high as 150,000 counts a second,
and we just refused to go above that. As you
know, that is bad enough in itself. We ran a
maximum. of about 120 samples in any given
run,
This was all the samples we had.
This
is primarily at the short times, say on the 1.7
seconds, 6.2 seconds and 10.7 seconds runs.
We go to somewhat less samples on some
runs, and the statistics got better. Unfortunately when we first started this, the machine
ran off 1.7 secondsfirst, and this is one of the
first cases. Does that answer your question?
Voice.
Yes.
Dr. Bore (Brookhaven). I would like to
ask one further question to follow up the last
one,
times?
What were the actual bombardment
How long did the fission occur for
the samples that were analyzed 2 seconds
later?
Dr. Zorev.
The bombarding times were
again variable, varying between 1 second and
64 seconds. We tried to keep it so that the
bombarding time and the counting time were
less thanor equal to the time elapsed in between.