Testing and Performance Criteria for Stabilized/Solidified Waste Forms - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 303

In addition to leachability and UCS (discussed in 11.5.2 and 11.5.3), the tests to
demonstrate stability of cement-solidified Class B and C wastes include resistance to
thermal cycling, 134 resistance to 100 Mrads dose, resistance to biodegradation, 104 resis-
tance to immersion for 90 days, and generation of < 0.5 vol% free-standing liquid. 135

11.6 INTEGRATED EVALUATION PROTOCOLS

11.6.1 I NTRODUCTION

The purpose of S/S is to maximize the containment of environmental contaminants
by both physical and chemical means and to convert the hazardous waste into an
environmentally acceptable waste form. Whenever possible, utilization of stabi-
lized/solidified hazardous wastes should be preferred over disposal in order to
decrease the burden of land disposal. 15 If a waste does require landfilling, however,
the degree of environmental protection provided by S/S should allow for disposal
in less costly landfilling facilities, by reducing or eliminating the need for engineered
barriers or liner systems.
S/S radioactive and mixed waste forms usually cannot be utilized, and are also
disposed of differently from S/S hazardous waste forms. Thus, the evaluation of S/S
radioactive and mixed waste forms is different from that of S/S hazardous waste
forms. This section introduces two integrated evaluation protocols for S/S waste
forms.

11.6.2 I NTEGRATED E VALUATION F RAMEWORK

Recently, Kosson et al. 136 proposed an alternative framework for evaluation of inor-
ganic constituent leaching from wastes and secondary materials, as shown in Figure
11.1. The framework is based on the measurement of intrinsic leaching properties
of the material in conjunction with mathematical modeling to estimate release under
field management scenarios. To achieve the desired framework \ , a three-tiered testing
program is proposed:

• Tier 1: Screening-based assessment (availability)

• Tier 2: Equilibrium-based assessment (over a range of pH and liquid-to-

solid ratio conditions)

• Tier 3: Mass transfer-based assessment

It is suggested that waste management or utilization scenarios should be used
to link laboratory assessment results to impact assessment. A series of laboratory
tests will be conducted based on the leaching mode that controls release (equilibrium
or mass transfer), the site-specific liquid-to-solid ratio, the field pH, and a time frame
for assessment. Using the laboratory measurements, a release model is established
to estimate the cumulative mass of the constituent released over the time frame for
a percolation/equilibrium scenario.