Abstract
Mitigation of hazardous and radioactive waste can be improved through conversion of existing waste to a
more chemically stable and physically robust waste form. One option for waste conversion is the
fluidized bed steam reforming (FBSR) process. The resulting FBSR granular material was encapsulated
in a geopolymer matrix referred to here as Geo-7. This provides mechanical strength for ease in transport
and disposal. However, it is necessary to understand the phase assemblage evolution as a result of
geopolymer encapsulation. In this study, we examine the mineral assemblages formed during the
synthesis of the multiphase ceramic waste form. The FBSR granular samples were created from waste
simulant that was chemically adjusted to resemble Hanford tank waste. Another set of samples was
created using Savannah River Site Tank 50 waste simulant in order to mimic a blend of waste collected
from 68 Hanford tank. Waste form performance tests were conducted using the product consistency test
(PCT), the Toxicity Characteristic Leaching Procedure (TCLP), and the single-pass flow-through (SPFT)
test. X-ray diffraction analyses revealed the structure of a previously unreported NAS phase and indicate
that monolith creation may lead to a reduction in crystallinity as compared to the primary FBSR granular
product.
