A study of the concept of a fission-plate converter as a source for an epithermal neutron beam Page: 1 of 10
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BNL-63410
A STUDY OF THE CONCEPT OF A FISSION-PLATE CONVERTER AS A SOURCE
FOR AN EPITHERMAL NEUTRON BEAM
Hungyuan B. Liu, and Robert M. Brugger
Medical Department, Brookhaven National Laboratory, Upton, New York 11973, USA-1 : F.
1. ABSTRACT OCT 1
It has been suggested that a Fission-Plate Converter (FPC) at a reactor can enhance the intense y
of an epithermal neutron beam produced by the reactor. By computer modeling, this concept
has been applied to two sets of reactors to study how effective a FPC might be. The first set
of reactors contains high-powered research reactors and is represented by the Missouri
University Research Reactor and the Georgia Institute of Technology Research Reactor. The
second set combines the FPC into the core of a low-powered reactor, yielding a thin, large area,
reactor that we call a slab reactor. For these reactors, epithermal fluxes above 1 x 109 n/cm2. sec
are predicted while the fast-neutron doses per epithermal neutron are < 3 x 1011 cGy.cm2/n.
2. INTRODUCTION
It has been suggested that a Fission-Plate Converter (FPC) placed near the core of a reactor
might enhance the intensity of a beam of epithermal neutrons that could be produced by the
reactor'. The FPC would allow the source of fission neutrons that are converted into epithermal
neutrons to be moved closer to the patient irradiation position, thus increasing the epithermal
flux. In addition, since the fission neutrons all start from the FPC, instead of the volume of the
core, a lower dose from fast neutrons per epithermal neutron is predicted. With the MCNP
code, different types and sizes of reactors were modeled to test this concept. Two different sets
of reactors were tried. The first set includes high-powered research reactors with FPCs. The
second set comprises a low-powered reactor in which the core has been rearranged to be thin,
but with a large area, to resemble a FPC. This we call a slab reactor.
3. HIGH-POWERED REACTORS
In this study the Missouri University Research Reactor (MURR) and the Georgia Institute of
Technology Research Reactor (GTRR) have been selected to represent high-powered research
reactors. The Brookhaven Medical Research Reactor (BMRR) has been evaluated in another
study2.
3.1 MURR3
The MURR is a research reactor at the University of Missouri campus in Columbia, Missouri,
USA. This reactor operates at 10 MW, 90% of the time to supply neutrons and other radiation
for faculty and other users. It is typical of a high-powered, highly-enriched-fueled, H20-cooled-
and-moderated research reactor. Figure 1 shows a horizontal section of the reactor. Starting
at the center of the reactor with the flux trap, the trap is surrounded by the annulus of fuel and
the fuel is encased in the pressure vessel. Just outside the pressure vessel is a H20 filled space
for the control blades followed by the Be reflector and the graphite reflector wedges. Still inside
D1STRIBURTON OF THIS DOCUMENT IS UNITED M A STER
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A study of the concept of a fission-plate converter as a source for an epithermal neutron beam, article, December 31, 1994; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc688461/m1/1/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.