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3-30
The high alpha activity of uranium containing 232U will present two problems:
1. In the UF, there will be a strong (u,n) reaction. A crude estimate of the neutron
emission from a 16-kg UF, product cylinder containing 0.6 wt% 23% is 5.7 x io7
2.
neutrons/sec at 10 days decay, 2.5 x lo8 at 30 days decay, and 8.7 x lo8 at 90 days
decay.
The 232U will provide a strong heat source in the UF, and the metal products. A
crude estimate of the heat generation rate from pure 232U as a function of time after
purification is: 0.03 W/g at 10 days, 0.13 W/g at 30 days, and 0.46 W/g at 90 days.
The degree to which these properties will affect weapon manufacture or delivery is
unknown.
Alternative Enrichment Arrangements to Reduce 232U Content in the Product. In considering
the complications introduced to the final uranium metal product, i.e., the radiation
level and heat generation resulting from 232U, it is apparent that removal of the 232U
would be beneficial. Enrichment cascades can be designed to accomplish this. The most efficient
arrangement would be to first design a cascade to strip 232U from all other uranium
isotopes and then to feed the tails from
the first cascade to a second cascade where
the fissile isotopes can be enriched. This
Pmduct Containin
Nearly All the 23%
is illustrated in Fig. 3.3-2.
c
Uaste
Fig. 3.3-2. Illustration of Enrichment
Arrangement to Produce Low 232U Content
Urani urn.
Such an enrichment arrangement can be
independent of the specific enriching device.
Based on the discussion of the gas centrifuge
process in Appendix A and at the beginning
of this section, a small, low separative work
capacity machine may be within the technical
capabilities of a would-be diverter (see
Appendix A).
A1 though no information exists on the
separative work capacity of a Zippe machine
in a cascade, a reasonable estimate of its
separative capacity is about 0.3 kg SWU/yr
when separating 235U from 238U.