THE PREPARATION OF HIGHLY ENRICHED U$sub 3$O$sub 8$ FOR THE HIGH FLUX ISOTOPE REACTOR CORE Page: 3 of 11
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METHOD OF PREPARATION
Uranium fuel for the core of the High Flux Isotope Reactor (HFIR) was prepared in
the form of a sintered U308 with a size range of 44 to 88 microns. The basic prep-
aration method consisted of the precipitation of a solution of uranyl nitrate with
hydrogen peroxide, followed by calcining and sizing operations. The process was
essentially a batch-type operation utilizing laboratory-type equipment because of
the geometry restrictions imposed by nuclear safety and the availability of the
equipment from other oxide production programs. This report details the process-
ing steps that were required to produce the material.
Conversion of Uranium Metal Turnings to U308 and Dissolution in Nitric Acid
Uranium machine turnings were burned with oxygen to U308 in a water-cooled
stainless steel burner. The construction material for the burner was Type 304L
stainless steel, five-inch Schedule 40 pipe, with an overall length of 40 inches.
The charge of turnings was limited to five kilograms. When burning was completed,
the oxide was removed with a vacuum gulper system.
The U308 was dissolved in nitric acid to produce concentration of approximately
250 grams of uranium per liter.
Precipitation of Uranyl Nitrate Solution with Hydrogen Peroxide
One kilogram of uranium as uranyl nitrate solution was transferred to the precipitator
(Figure 1) and diluted to a concentration of approximately 8 percent. The pH of the
solution was adjusted to 2.0 0.1 with nitric acid or ammonium hydroxide.
Thirty percent hydrogen peroxide was added to the precipitator with sufficient
ammonium hydroxide to control the pH at 2.0 0.1. The cooling water was adjusted
to maintain temperature conditions in the range of 28 - 320C. When the hydrogen
peroxide no longer lowered the pH, an additional 500 milliliters was added and
agitation continued for an additional 15 minutes.
The precipitated material was centrifuged in a Sharples Super Centrifuge and the
cake was then transferred to platinum boats (2" deep x 4 1/2" x 8") (The peroxide
filtrate contains a uranium concentration of 100 - 200 ppm and is economically
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Barkman, J.R. THE PREPARATION OF HIGHLY ENRICHED U$sub 3$O$sub 8$ FOR THE HIGH FLUX ISOTOPE REACTOR CORE, report, February 1, 1966; Oak Ridge, Tennessee. (digital.library.unt.edu/ark:/67531/metadc1025137/m1/3/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.