Evaluation of Standard Durability Tests Towards the
Qualification Process for the Glass-Zeolite Ceramic Waste
Form
Authors: Simpson L. J. , Wronkiewicz D. J. 
Published: September 2012

ABSTRACTGlass-bonded zeolite is being developed as a potential ceramic waste form
for the disposition of radionuclides associated with the U.S. Department of
Energy's (DOE's) spent nuclear fuel conditioning activities. The utility of
several standard durability tests [e.g., Materials Characterization Center
Test #1 (MCC-1), Product Consistency Test-B (PCT-B), and Vapor Hydration
Test (VHT)] was evaluated as a first step in developing methods and criteria
that can be applied towards the process of qualifying this material for
acceptance into the DOE Civilian Radioactive Waste Management System. The
effects of pH, leachant composition, and sample
surface-area-to-leachant-volume ratios on the durability test results are
discussed, in an attempt to investigate the release mechanisms and other
physical and chemical parameters that are important for the acceptance
criteria, including the establishment of appropriate test methodologies
required for product consistency measurements.Results from PCT-Bs conducted with 4 μm diameter salt-loaded zeolite powder
indicate that a good correlation exists between release rate and ionic size
and/or charge for the release behavior of the simulated fission products in
deionized water (DRV), EJ-13 groundwater, and brine solutions. Simulated
divalent and trivalent fission products [Sr, Ba, and rare earth (RE) ions]
were preferentially retained in the zeolite (relative to the singly ionized
cations) after tests with the salt-loaded zeolite in DIW. In general, the
preferential cation release order for salt-loaded zeolite A in DrW is Li
> Na ≥ K > Cs > Al > Si > RE > Sr > Ba. Results from
PCT-Bs with the salt-loaded zeolite A immersed in high-ionic-strength brines
at 90°C indicate a significant increase, relative to DIW tests, in the
release rates of the Sr, Ba, and RE ions despite a decrease in the release
of the Si and Al ions that make up the framework matrix of the zeolite. An
increase in the Mg and Ca concentrations in the reacted zeolites suggests
that an ion exchange process may be responsible for this increase.Vapor hydration and MCC-1 tests were performed with ceramic waste form
monoliths of glass-bonded zeolite. The VHTs (temperatures at 120,150, and
200°C) provided useful information about the effect of glass composition on
corrosion rates and alteration phase formation, and about the overall
toughness and structural integrity of the ceramic waste form. The MCC-1 test
was investigated as an alternative to the PCT for acceptance criteria
measurements. The MCC-1 results indicate that corrosion testing with both
DIW and high-ionic-strength leachants (that specifically affect the ion
exchange behavior of the fission products) are required to fully assess the
durability of the ceramic waste form. These preliminary results establish
the utility of the MCC-1 test for providing possible acceptance criteria
measurements, including elemental release comparisons between the
environmental assessment benchmark and the ceramic waste form.