Seven Years of Uranium Alloy Development at Weldon Spring, 1959/1966. Page: 31 of 47
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X-Ray Preferred Orientation Panel
The pronounced interest in means of measuring and expressing the amount of
preferred orientation existing within a fuel core led to the informal organi-
zation of a group which met regularly for a number of years to exchange
information and data.33-40 The meeting place for this exchange of ideas was
rotated between the interested sites, and a report of the proceedings of each
meeting was issued by the home site. (One exception to this practice was a
meeting held in Connecticut in December of 1962-which has not been reported.)
The purpose of the panel was to devise the most effective methods for
expressing preferred orientation and to standardize the experimental techniques
for determining it. It was particularly desirable that -the participating sites
be able to exchange data with confidence that the results reflected'the
influence of manufacturing process or material composition and not a variance
in experimental procedure. The deliberations of thepanel evolved a
succession of techniques for expressing the texture to be discovered within
uranium. This progression represented the improvements in method as ihe
experimentors gained sophistication in the use of X-ray diffraction equipment.
In this progression, the early practice of plotting inverse pole figures,5 'and
listing texture coefficients52 gave way to the quotation of growth index values
which was in turn replaced by G2 and G3 values.54 Still later, the J factor57
(an orientation parameter with a value of 1.00 for a completely random structure)
has been routinely reported to supplement the Gx or G3 value since it became
evident that in the circumstance of two'-pronounced textures which offset each
other, the growth index calculation' could yield a value of 0 (implying a
completely random structure), whereas the J factor would reflect the true
Even more recent has been the practice' of calculating "axis distribution
coefficients," symbolized by Q a, Qb, and Q-. For an ideally random structure,
all three coefficients would have the same value of 0.333 and in any case the
sum of the three coefficients must equal unity. The values for a particular
specimen therefore reveal whether there is an excess 'or a deficiency in align'
ment of a given crystal axis with a specific dimensional direction of the fuel
core. A value of Sb well in excess of 0.333 for instance in the axial' direction
of a core would imply that a real potential existed for longitudinal growth under
Precision of Texture Measurements
The .growing need for reliable predictions of dimensional behavior during
irradiation naturally led to an active interest in the precision attainable in
the texture parameter calculations.28 Results were therefore compared between
duplicate samples and between successive scans of the same sample, repolishing
and realigning in the diffractometer each time the data indicated that J
factor values conformed to a precision of + 2 to-+ 6% while the texture
coefficients (Pi) showed a precision of + 12 to + 20%,"both at a 95% confidence
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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/m1/31/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.