Critical dimensions of systems containing /sup 235/U, /sup 239/Pu, and /sup 233/U: 1986 Revision Page: 78 of 205
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Three reports front Hanford"' "" describe critical experiments with homogeneous PuO-
polystyrene rmixt ores at H/ Pu ratios of 5, 15 and 50. Each set of experiments applies to bare
and Plexiglas-reflected parallelepipeds ranging from elongated to squat shapes. For each
composition, critical dimensions are extrapolated to the infinite cylinder and infinite slab
and converted to the equivalent sphere. Calculations based on these dimensions also give
corresponding dimensions for plut oninn-water and PuO -water mixt ures. Reported sphere
radii, infinite cylinder diameters, and infinite slab thicknesses for the reflected systems are
given in Table 15.
The PuO2- polystyrene experiments were supplemented by similar rmeasurenents with
slightly moderated compressed PuO2 compacts."" The deduced critical dimensions of
reflected spheres, infinite cylinders, and ifinuite slabs which were reported appear in Table
HOMOGENEOUS PLUTONIUM-URANIUM SYSTEMS
Liquid Metal Fast. Breeder Reactor (LMFBR) fuel cycle operations have led to crit-
ical experiments with moderated plutonium-uranium mixtures at Hanford and Alder-
muaston. Haford measurements with bare and Plexiglas-reflected PuO2-UO2-polystyrene
compacts, which were readily interpretable,103'o5 were supplemented by others with par-
tially reflected plutoniumn-uranium nitrate solutions.0' Aldermaston reported criticality of
polyethylene-reflected Pu2-11 02-polyethylene compacts of various shapes."i and water-
reflected plutonimruu--uranniurrr nitrate solutions at various concentrations of plutonium. 108
Table 18 gives critical dimensions derived from the above experiments for various reflected
shapes. The Hanford reports also give critical sphere, cylinder, and slab dimensions for
idealized 239PuO2-U(0.72)02- water mixtures.
Calculations'l" based on the Hanford and Aldermaston data led to subcritical limits for
plutonium-uranium mixtures that appear in the American National Standard for Nuclear
Criticality Control and Safety of Plnt.onium-Uranium Fuel Mixtures Outside Reactors.'"0
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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/m1/78/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.