Seven Years of Uranium Alloy Development at Weldon Spring, 1959/1966. Page: 17 of 47

4.
would be available on a production basis assuming a useful size and shape could
be produced for direct fabrication. This concept of. by-passing the remelting
to cast an ingot led to the coining of the term dingot to mean "direct ingot."
Scale-up of the bomb reduction operation to produce large-sized reguli of
uranium ultimately led to the selection of a 3300-pound dingot as the standard
production unit. Fabrication procedures-were explored including hammer
forging and press forging in the high alpha temperature range and ultimately
extrusion in the gamma phase at about 1800*F-. -The forged or extruded bars were
then rolled to rod at the Fernald Plant operated by National Lead Company of
Ohio. Sufficient interest was expressed by the reactor sites to justify the
production of fuel cores from dingot metal on a routine basis, and it was
assumed that the desirable target of higher purity in uranium metal had been
satisfied.
A difficulty with dingot metal that became promptly apparent was the
unfavorable level of hydrogen content which ultimately was found to be a
function of the-relative humidity existing at the time of the bomb preparation
and, for a large number of .dingots, to range from as low as approximately 1 ppm
to as high as 11 ppm H2. It is not -the intent of this report to recite in
detail the long-and intensive effort that was made to gain control of the
thermite bomb reaction to yield a low hydrogen dingot. This effort extended
into 1961 and ultimately was terminated with the decision that the simplest
means of control was by a final vacuum out-gassing treatment of core blanks
in the alpha phase following beta heat treatment and prior to final machining.1o
Efforts to devise a method for the refinement of beta heat-treated grain size
proceeded concurrently during this period at a number of sites. Many of these
were concerned with the question of-whether a beneficial recrystallization of
grain size could be obtained by an alpha annealing procedure after rapid cooling
from either the beta or the gamma phase. Work of this nature conducted by John
Riches and associates at Hanford, by Bruce Dunnington and Richard Huntoon and
associates at Savannah River, as well as the group at Weldon Spring were
reported at a classified information meeting held at Ames, Iowa, in May of
1956..41 The outcome of these efforts may be characterized in retrospect by the
following -comments:
1... In general, the cooling rate had to be very rapid if the change
in grain size in recrystallization was to be of a desirable
magnitude, and such cooling rates did not appear to be readily
obtainable in the metal sections of full fuel cores.
-2.- Drastic quenching of uranium from either the gamma or the beta,
phase gave rise to a relatively-fine grained, equiaxed structure
when viewed in a section perpendicular to the thermal gradient-
existing in the quench but showed a pronounced tendency to create
a columnar shape of grain when viewed in a section parallel with-
-the -thermal gradient. Such structures were not viewed as being
favorable for the desired degree of randomness 'of or ientation.4,,534

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Fellows, J. A. Seven Years of Uranium Alloy Development at Weldon Spring, 1959/1966., report, January 1, 1966; Weldon Spring, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc1033773/m1/17/ocr/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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