To examine the proliferation resistance of borosilicate glass, a process to
extract and recover a plutonium analog (thorium) from borosilicate glass was
developed and examined. The glass matrix examined was a modified standard
frit consisting of the ARM-1 frit (with simulated fission products) loaded
with 2 wt. % thorium (as an analog for plutonium) and 2 wt. % each of three
rare earth elements (Gd, Sm, Eu), which were added for criticality control
and to possibly increase the proliferation resistance of the glass matrix.
The plutonium analog was extracted from the crushed glass with a nitric acid
dissolution process, and subsequently decontaminated using a solvent
extraction process. The acid dissolution process was able to extract 88.4 ±
6.8 % of the plutonium surrogate from the glass host form. The bench top
solvent extraction process was 30.2 ± 10.9 % efficient in recovering the
plutonium analog as a purified product. Overall, this process was able to
extract 26.7 ± 9.9 % of the plutonium analog from the glass as a purified
product. To quantify the proliferation resistance of borosilicate glass as a
host form for weapons-grade plutonium, MCNP was used to determine the
compressed critical mass of a plutonium alloy with the same composition as
the product of the extraction process. For the average product composition,
the compressed critical mass was 4.7 kg of material. On average, one
compressed critical mass could be recovered from 613 kg of borosilicate
glass (2 wt. % Pu loading).