32
SHORT LIVED FISSION PROPUCT GAMMA RADIATION
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
distribution from weapons is more that representing high energy neutron fission?
different from that encountered in weapons?
when he showed me different nuclide distribu-
distribution, as well.
Dr. Zonet. I am afraid I don’t know. Lf
the fissioning process is the same, I see no
reason why it should be different. That is for
the U-235 fission product. If there is an
appreciable amount of fast fission which
uraniumor U-235 is not very different from the
slow neutronfission spectrum.
product distribution in your test might be
This would, or course, affect the gamma ray
© COMPTON DAT:
@ PAIR DATA
might lead to different levels, I do not know.
Dr. Bora. Perhaps I can add a small bit
to the last answer. The fission product distri-
bution curves afterfission in different materials
photons/Mev- fission
are noticeably different. Fisstoning in plutonium as against uranium shifts the curve.
Fissioning with high energy neutrons as opposed
to low energy neutrons will raise the value of
the distribution curvefor these who are familiar
with such a curve. If some of the nuclides
which are emitting important gamma spectra
are on the portion of the curve shifted, there
might bea significant difference in the gamma
spectrum that results.
Dr. Sint. Is there any possibility of venturing a guess as to the magnitude of this
effect?
|
;
9
to
20
30
ENERGY (Mev!
Fravae 6-—Typical spectrum of fission product gamma rays from a rotation fuet belt.
33
In other words, for the 1.7 seconds run, the
equipment was set to bombard 1 second, wait
1 second, count 1 second.
Dr. Sir (University of California), Was
there any reason to believe that the fission
Isn’t it likely that the fission product
Dr. Bora.
Yes.
I] must admit I am not
much of an expert along these lines, I think
the answer is probably ves. J] have asked this
question myself of Dr. Spence at Los Alamos
tion curves. He threw up his hands andsaid
itis hard to know. There are so many nuclides
that arc radiating that the chauces are good that
these spectra are similar for each case, and that
the fast spectrum of plutonium or natural
Dr. Cronxirg.
Are there any further ques-
tions?
Mr. Koca (Bureau of Standards).
Howdid
vou evaluate your absolute numbers of fissions
and how accurate do you think your numbers
are?
Dr. Zosgev. That right now is the biggest
source of error that we can see, The number
of fissions is calculated and it is crudely caleujJated, admittedly. We have taken the weight
of the sample, we have taken the cross section,
and we have measured the flux. It is calcu-
lated on that basis. We expect to make a
better analysis of the source and we expect
that this will then bring the error down a fair
amount. We hope that the final error will be
of the order of maybe 15 percent.
think we can reduce it below that.
I don’t