The transmission of neutrons and gamma-rays through air slots

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Material Information

Title:
The transmission of neutrons and gamma-rays through air slots
Series Title:
BNL ;
Physical Description:
v. : ill. ; 27 cm.
Language:
English
Creator:
Schamberger, Robert D
Shore, Ferdinand J
Sleeper, Harvey P
Brookhaven National Laboratory
U.S. Atomic Energy Commission
Publisher:
United States Atomic Energy Commission, Technical Information Service
Place of Publication:
Oak Ridge Tenn
Publication Date:

Subjects

Subjects / Keywords:
Nuclear physics   ( lcsh )
Neutrons -- Diffraction   ( lcsh )
Gamma rays   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by Robert D. Schamberger, Ferdinand J. Shore, Harvey P. Sleeper, Jr.
General Note:
Cover title.
General Note:
Originally published 1954.
General Note:
"September 1, 1954."
General Note:
"Subject category: Physics."
General Note:
"Brookhaven National Laboratory, Upton, New York."
General Note:
"Date Declassified: November 21, 1955."--P. 2 of cover.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 004703692
oclc - 432319550
System ID:
AA00009214:00004

Full Text
.47: I2


L CLASSIFIED












0


UNCLASSIFIED


BNL-2021

Subject Category: PHYSICS



UNITED STATES ATOMIC ENERGY COMMISSION



THE TRANSMISSION OF NEUTRONS AND
GAMMA-RAYS THROUGH AIR SLOTS.
PART III. THE TRANSMISSION OF
GAMMA-RAYS THROUGH STRAIGHT
AIR SLOTS IN WATER


By
Robert D. Schamberger
Ferdinand J. Shore
Harvey P. Sleeper, Jr.


September 1, 1954


Brookhaven National Laboratory
Upton, New York


Technical Information Service, Oak Ridge, Tennessee








Date Declassified: November 21, 1955


This report has been reproduced directly from the best
available copy.

Issuance of this document does not constitute authority
for declassification of classified material of the same or
similar content and title by the same authors.

Printed in USA, Price 20 cents. Available from the
Office of Technical Services, Department of Commerce, Wash-
ington 25, D. C.


GPO 822916 I


This report was prepared asa scientific account of Govern-
ment-sponsored work. Neither the United States, nor the Com-
mission, nor any person acting on behalf of the Commission
makes any warranty or representation, express or implied, with
respect to the accuracy, completeness, or usefulness of the in-
formation contained in this report, or that the use of any infor-
mation, apparatus, method, or process disclosed in this report
maynot infringe privatelyowned rights. The Commission assumes
no liability with respect to the use of,or from damages resulting
from the use of, any information, apparatus, method, or process
disclosed in this report.




BNL-2021


THE TRANSMISSION OF NEUTRONS AND GAMiMA-RAYS THROUGH AIR SLOTS


Part III

The Transmission of Gama-rays Through Straight Air Slots in Water


Robert D. Schamberger
Ferdinand J. Shore
Harvey P. Sleeper, Jr.




1 September 1954












REACTOR DEPARTMENT

BROOKHAVEN NATIONAL LABORATORY
Associated Universities, Inc.


Work performed under Contract No. AT-30-2-Gen-16




































Digitized by the Internet Archive
in 2012 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://archive.org/details/transmissionofne0103broo





Page 3


THE TRANSMISSION OF NJEUTROrS AND GAMMA-RAYS THROUGH AIR SLOTS

Part III

The Transmission of Gamma-Rays Through Straight Air Slots in Water


INTRODUCTION

The series of measurements on the transmission of radiation through
air slots in water Was designed primarily to investigate neutron rather than
gamma-ray phenomena The reason for this is, of course, that the medium in
which the measurements were made is a very poor gamma-ray shield. The consequences
of having a poor shielding medium are numerous; all of them, however, may be con-
sidered unfortunate from the standpoint of obtaining accurate information on the
effect of small perturbations in the medium. In spite of these obvious limitations,
the gamma-ray data were taken in the hope that we would obtain some useful in-
formation. They are being published with the hope that this little information
may be of more use to someone than none at all.

This report presents the information which has been obtained on the
gamma-ray dose transmitted by straight air slots. Table I lists the slot di-
mensions, the measurements which are being reported, and the number of the figure
in which the data are presented. The figures also contain background data.

All of the gamma-ray measurements were made with aluminum-walled
ionization chambers in the form of right circular cylinders, 0.94 inches in di-
ameter and 1.75 inches in height. When the location of the ionization chamber
in the tank is given, the position of the bottom of the chamber is specified
rather than the "center of detection", which is located near the center of the
detector.

No attempt has been made to distinguish between that portion of the
dose which traversed the duct as gamma radiation and that portion which was
transmitted as neutrons and then converted near the top of the duct by capture
or inelastic scattering.


Slot Length
(feet)
2



4






6


Slot Thickness
(inches)
3.
1.
0.5
3.
3.
3.
1.5
1.
0.5
0.25
3.
3.
0.5
3.


TABLE I
Traverse

X
x
X
Z
X
X
X
x
X
X
Z
X
X
Z


Position of Traverse
(inches above)
1.75 slot
1.75 slot
1.75 slot
slot center
1.75 slot
2.25 slot
1.75 slot
1.75 slot
1.75 slot
2.25 slot
slot center
1.75 slot
1.75 slot
slot center


Figure

1
1
1
2
3
6
3
3
5
5
4
7
7
8





Page 4


DATA FOR 24-INCH LONG SLOTS

Figure 1 illustrates one of the difficulties which beset this series
of measurements. For the three inch thick slot, which was the greatest thickness
measured, the peak flux was only a little more than twice the background. Pith
the thinner slots it is apparent that the error in estimating the excess trans-
mitted flux is quite large.

A small diagram has been included in the lower left hand corner of
figure 2 to indicate the position of the top of the slot.

DATA FOR 48-INCH LONG SLOTS

The data are presented in figures 3 through 6. Figure 5 indicates a
second difficulty which has appeared frequently during this investigation. The
sensitivity of the ionization chamber appeared to change from one measurement to
another. For the very thin slots there is reason to expect the dose at a reason-
able distance from the slot to be quite independent of the presence of the slot.
For this case, the measurement has been normalized to the accepted background
curve between ten and fifteen inches from the center of the tank. I1hen such a
procedure was not easily justified, the data were not used, Considerable effo"rt
has been expended to correct this situation.

A third trouble is illustrated by the two horizontal traverses pre-
sented for a three-inch slot; one in figure 3 and one in figure 6. The net
transmitted flux obtained from the two measurements differ by about fifteen per
cent. This difference does not appear to be the result of a change in the de-
tector sensitivity. There is no reason that we know of to prefer one measurement
to the other.

DATA FOR 72-INCH LONG SLOTS

The background curve presented in figure 7 was obtained with the ar-
rangement of boxes 1, 2, 3, and 4 indicated in the figure. The data for the
0.5 inch slot, however, were obtained with the upper two feet of the container
consisting of steel rather than aluminum. The background applicable to this
situation has not been measured. To obtain a value for the excess dose, it has
been necessary to estimate the background.

CONCLUSIONS

Figure 9 consists of a plot on log-log paper of the peak excess gamma-
ray dose against the slot thickness, If one assumes that a gamma-ray which enters
the void and leaves it before reaching the top does not contribute to the dose
measured at the top2, one would expect, at least for the four and six foot slots,
that the peak dose would vary approximately as T2 for small values of thickness, T,
where the detector effectively integrates the emergent flux. For values of T which
are large compared with the size of the detector, one would expect the peak values
to vary directly as T. TAhile the data are certainly not good enough to prove that
these expectations are realized, they are not inconsistent with it.





Page 5




On the same basis, one would expect the dependence of the excess dose
on the length of the slot to be L-2. In figure 10, the peak excess dose has been
plotted as a function of the slot length f.r slot thicknesses of three inches and
one-half inch. The data are net incc.nsisternt with an L-' dependence.




1
A description of the apparatus is given in Part I of this series.

2
This assumption is consistent with the gamma-ray data obtcinrid in an inves-
tigation of cylindrical voids, The results of that investigtiion and analysis
appear inpthe Minutes of the May, 195L Shielding Information Meeting.








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