Critical dimensions of systems containing /sup 235/U, /sup 239/Pu, and /sup 233/U: 1986 Revision Page: 35 of 205
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URANIUM OF VARIOUS ENRICHMENTS
Tables 9 and 10 give critical data for homogeneous liydrogei-noderated units of ira-
niumn enriched in 2U to var;oius degrees. In addition to UO2F; solutions, there are solid
uranium-bearing mixtures iii which the hydrogenous iiaterial is polyethylene, paraffin, or
Sterotex (glycerol tristearate, [(C H35COO)3C3Hsj. In the tables there has been no at-
tempt to convert to a common composition. In Table 9, critical values of one-dimensional
forms (spheres, infinite cylinders and infinite slabs) are obtained from Oak Ridge reports
of critical experiments. They are derived from quoted values of buckling, extrapolation
distance and reflector savings. Results of other experiments at various enrichments appear
in Table 10.
Reports of Ul(4.89), U(3.00) and 1)(2.00) systems give values of buckling, extrapolation
distance, and reflector saving, from which spherical equivalents are derived (as well as
equivalent infinite cylinders and slabs). Otherwise, listed spherical equivalents are as re-
ported with the original data or as they appear in Ref. 14. The entries for U(95.3) and
U(29.8) are from the only heterogeneous systems for which there is sufficient experimental
information to permit correction to homogeneous compositions.
Critical masses and critical volumes of hydrogen-moderated spheres of U(93), U(30.3),
U(4.89), U(3.00), and 1(2.00) are displayed in Figs. 14 anid 15. Values for U(3.00) and
U(2.00) include those listed in Table 9 for U(3.00)F4-paraffin and U(2.00)F4-paraffin com-
pacts. Dashed curves that extend beyond experimental ranges follow points computed
by the MCNP Monte Carlo coders and the associated cross section set.* Critical data
for uranyl fluoride-water mixtures at the four smaller enrichments are reproduced by this
means within 0.01 keff and the method is used for conversion to U(2.00) and U(3.00)
solutions.** It may be noted that the use of Hansen-Roach cross sections leads to 3% to
4% overestimates of U(2.00)F4-paraffin critical sphere radii."
Figures 16 and 17 give estimated nfinite cylinder diameters and infinite slab thicknesses for
U(93), 1(30.3), U(4.89). U(3.00), and U(2.00). Values for the latter four U35t enrichments
were obtained from sphere radii by means of extrapolation distances consistent with the
sphere radii, infinite cylinder diameters, and infinite slab thicknesses tabulated in Ref. 14.
Robert C. Little, Los Ma-os National Laboratory. Los Alamnos, NM 87545, 1980.
N. L. Provost, Los Alai),, National Laboratory. Los Alamos. N\M 87545 (1986).
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Paxton, H.C. & Pruvost, N.L. Critical dimensions of systems containing /sup 235/U, /sup 239/Pu, and /sup 233/U: 1986 Revision, report, July 1, 1987; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1109879/m1/35/: accessed March 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.