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:
AA00009214:00006


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UNCLASSIFIED


BNL-2023

Subject Category: PHYSICS



UNITED STATES ATOMIC ENERGY COMMISSION



THE TRANSMISSION OF NEUTRONS AND
GAMMA-RAYS THROUGH AIR SLOTS.
PART V. THE EFFECT OF THE VERTICAL
POSITION OF A SINGLE OFFSET ON THE
NEUTRON TRANSMISSION 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 Extension, 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
may not 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-2023


THE TRANSMISSION OF NEUTRONS AND GAMA-RAYS THROUGH AIR SLOTS


Part V

The Effect of the Vertical Position of a Single Offset
on the Neutron Transmission of an Air Slot


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




1 September 1954












REACTOR DEPJiRTMENT

BROOKHAVEN NATIONAL LABORATORY
Associated Universities, Inc,


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




Part V

The Effect of the Position of a Single Offset on
the Neutron Transmission of an Air Slot in Water


In designing a stepped air slot which penetrates a hydrogenous
shield, the question arises as to where to place the offset in order to
minimize the neutron transmission. An experiment was performed with a
single offset of a few slot thickness units since the results of Part IV
of this series indicated that the neutron transmission should be compara-
tively small and relatively independent of offset magnitude. Any effects
which could be ascribed to the position of the step would then most probably
correspond to those which would arise in practical situations where one had
designed for minimum transmission. For a step dimension in the region of
zero to unit slot thickness one could, of course, calculate the effect of
varying the position by the methods of Part IV; but by making the offset
somewhat larger, a more interesting situation, the simple calculations
would not be adequate.

The slot system which was used is indicated in Fig. 1. The over-
all length was 48 inches with slot thickness of 0.5 inches and offset magni-
tude of 1.8 inches. Owing to the fact that the aluminum slot holder boxes
were multiples of 12 inches in length, it was convenient to vary the position
bf the offset by 12 inch increments in the length direction; i.e., the
vertical. Vertical traverses were made in the water above the upper slot
along the slot centerline with the results shown in Fig. 2. The detectors
were 1 x 6 inch BF3 counters placed with their axes horizontal in the slot
width direction. Several of the runs were made with lucite in the portion
of the slot below the offset. These runs record those neutrons emergent
from the top section which have traversed water equivalent material before
entering the top section. Corresponding traverses made in the horizontal
direction at Z values of about 54 inches are shown in Fig. 3.

A summary of the general features of the emergent flux variation
with slot position is given in Fig. 4. The offset positions are indicated
schematically in the lower part of the figure. Ordinates are thermal flux
per unit pile power and abscissae are length of section B in inches. The
data are separated into two sets according as to whether the detector was
at 54 or 60 inches above the tank bottom corresponding to water separation
between detector center and slot of respectively 1.5 and 7.5 inches. The
data obtained at Z = 54 inches are, therefore, characteristic of slower
neutrons than the data at Z = 60 inches.

One notices immediately that for both sections A and B empty the
emergent flux is a minimum when the offset position is near the middle of
the 48 inch span. That there should be such a minimum is, of course, obvious
since with section B either zero or 48 inches long one has a straight slot
with maximum transmission. One might suppose that the flux emergent from
the top of A is the sum of four components which are defined as follow:
Component I is that flux which enters the detector with both sections A and
B filled with water; Component II is the flux obtained with just B filled
with water minus I; Component III corresponds to having A filled less I; and,
Component IV is that due to interaction of A and B when both are empty.
2






In addition to the total flux detected, components I and II are
presented in Fig. 4. It is seen that for short lengths of B, neglecting I
which is very small, the total flux is not greatly different from component II.
For a length of 24 inches, however, the slower neutron flux, Z=54 inches data,
is markedly decreased on filling B, whereas the faster flux, Z=60 inches data,
is decreased by a much smaller factor. The same is true for longer sections
of B. One expects that as B increases component II will decrease and com-
ponent III will increase. Unfortunately, data were not taken on component III
so that more cannot be said quantitatively about the relative importance of
the various components.

The experiment demonstrates that the most effective position of
the offsq is near the middle and that providing an offset of this magnitude;
i.e., three to six slot thicknesses, is more effective for fast neutrons than
for slow neutrons -- a result which was apparent in Part IV of this series.





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