The transmission of neutrons and gamma-rays through air slots

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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:
AA00009214:00001


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UNCLASSIFIED


BNL-2025

Subject Category: PHYSICS



UNITED STATES ATOMIC ENERGY COMMISSION



THE TRANSMISSION OF NEUTRONS AND
GAMMA-RAYS THROUGH AIR SLOTS.
PART VII. THE EFFECT ON THE NEUTRON
TRANSMISSION OF CHANGING THE WALL
MATERIAL OF AN AIR SLOT


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 15 cents. Available from the
Office of Technical Services, Department of Commerce, Wash-
ington 25, D. C.


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-2025


THE TRANSMISSION OF NEUTRONS AND GAMMA-RAYS THROUGH AIR SLOTS


Part VII

The Effect on the Neutron Transmission
of Changing the Wall Material of an Air Slot


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




1 September 1954




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














REACTOR DEPARTMENT

BROOKHAVEN NATIONAL LABORATORY
Associated Universities, Inc.

under contract with the
United States Atomic Energy Commission








Part VII


The Effect of Changing the Wall Material of an Air Slot
on the Neutron Transmission of the Slot


The task of relating experimental information of the type pre-
sented in this series of reports to the particular reactor shield with
which the designer is concerned is often more nearly an art than a science.
In the investigation of the neutron transmission through air slots, we have
made a serious attempt to investigate the effect of varying enough of the
parameters to make the job of the shield designer as simple as possible.
One of those parameters which has been investigated is the material con-
stituting the wall of the slot. This report contains the data which we
have obtained relating to the variation of this parameter.

To obtain a reasonable amount of information with a small number
of measurements, we have used a single slot thickness to investigate the
effect of changing the wall material. When the air slot thickness is large,
it is reasonable to expect the effect of the walls to be less important than
when the slot thickness is small. However, if the slot thickness is made
too small, the construction of the slot will not be sufficiently reproducible
to measure accurately the change in the transmission resulting from an
alteration in the wall material. The slot thickness which was chosen as being
reasonably small and yet readily reproducible was 0.50 inch.

Since steel is the material which usually forms the walls of a
practical air slot, the water equivalent walls of a 0.50 x 34 x 48 inch
straight air slot were replaced with 0.50 inch steel sheet. Thermal neutron
data above the slot with both lucite and steel walls are presented in Figs.
1 and 2. It is evident from the vertical traverses shown in Fig. 2 that the
30 per cent reduction in thermal flux on introducing the steel walls noted
immediately above the slot does not persist as the detector is raised. The
fast neutron flux is not, therefore, materially affected by the change. The
difference between the two curves in the vicinity of Z = 80 inches is be-
lieved to be the result of a difference in the photoneutron background.

Since the effect of changing the wall material is expected to be
more important for an offset slot where the direct transmission has been
greatly reduced, a comparison has been made between a 0.50 x 34 x 48 inch
slot with a 1.80 inch offset located in the middle with lucite and with
0.50 inch steel walls. The thermal neutron traverses above the slot are
presented in Figs. 3 and 4. The vertical traverses in Fig. 4 indicate a
reduction of about a factor of three close to the slot with the effect of
the steel walls becoming much less when the detector was moved several
inches away from the slot. The photoneutron backgrounds are not known with
sufficient accuracy for these special situations to permit an accurate sub-
traction of the effect.

The next step in the investigation was to introduce a
1.8 x 34 x 3 inch steel bar at the offset of the lucite-walled slot, mentioned
above, since it was felt that the material near the offset would probably be







more effective than material located at other positions in the slot. The-
location of the steel bar is indicated in the sketch in Fig. 5. That figure
also shows vertical traverses obtained with a thermal neutron detector above
the slot for three conditions of the slot: (1) no steel in the walls;
(2) the 1.8 x 34 x 3 inch steel bar located at the offset; and, (3) the steel
bar at the offset and a cadmium sheet in the middle of the upper section.
It may be noted that the steel bar has about the same effect on the trans-
mission as the one-half inch steel walls over the entire slot. With the
steel bar in place, the reduction in the fast flux was about 25 per cent.
The introduction of the cadmium further reduced the low energy component
without affecting the fast neutrons,

On the basis of these measurements, we have concluded that the
fast neutron transmission of an air slot is essentially independent of the
wall material. The low energy component, however, can be affected, pre-
sumably by the introduction of material with a large absorption cross section.
In practice, of course, consideration must be given to the introduction of
large amounts of any material which is appreciably less effective than water
as a neutron shield.

At this point, the investigation was terminated since it appeared
that the effects were important only for thermal neutrons.










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