Critical dimensions of systems containing /sup 235/U, /sup 239/Pu, and /sup 233/U: 1986 Revision Page: 92 of 205
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Experiments at OR NI resulted in defiit ive measures of t he effectiveness of borosilicate-
glass Raschig rings as ftxed poisons in U(93)02(N3 ) solution and
233U02(N03)2 solutions. "3 All mieasireients were iade in cylindrical geometry, with
the amount of boron in the rings, the cylinder diameter, the ring dimensions, and the
solution concept ration as variables. The nat rural borou cont ent of the rings varied from 0.5
to 5.7 wt %, and the portion of t he ves-el bohuic occupied by the glass ranged from 20.9
to 30 percent . Solut ions cont aining bet ween 415 and 63.3 g U / L were used. Results from
exponential experiments, with the use of a critical layer of solution above the column of
solution-ring mixture as a neutron source, provided estimates of the material buckling of
the subcrit ical mixt ure as funct ions of solution coiceitrat ion, boron content of the glass,
and the glass volume present. These Il(93) sohition experiments indicated that k," 1 if
the rings were uniformly (list ribut ed under the condit ions of Table 24.
TABLE 24. EXPERIMENTALLY DETERMINED CONDITIONS FOR k" < 1
WHEN RASCHIG RINGS ARE UNIFORMLY DISTRIBUTED IN
U(93)02(NO3)2 OR IN 233U02(N03)2 SOLUTIONS
.ininum Volume Mininuni Boron Maximumn Solution
Fraction Occupied Content of Glass Concentration
Isotope by Glass (%) (wt%) (g U /L)
ii(93) 24 3.3 415
22 4.0 415
24 0.5 72
2331 38 3.9 333
33 3.9 204
Two series of subcrit ical measurements were conducted at Rocky Flats for hydrogen-
moderated U(93)O2 (NO3)2 systems that contained randomly packed borosilicate-glass
Raschig rings. In one case the glass displaced 17.8 vol% of solution ini a 107-cm-dianieter
tank that was surrounded by a close-fit ting square concrete vault with open top.'25 The
rings, 3.8 cm-long and 3.8-cm-o.d. with 0.20-cm-thick walls, contained 0.090 g B/cn'.
results indicate that such a tank, if filled to infinite height, would not be critical with i a
solut ion cont airing -325 g 2"U/ L. Transformat ion of dimensions gave 70 cm as the radius
of the corresponding sphere and 67 ci as the thickness of a corresponding infinite slab.
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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/m1/92/: accessed March 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.