Operations producing a stable waste form and suitable package, for example immobilisation in cement, glass or ceramic. Treatment residues and secondary wastes must be included in the waste inventory.
A waste form together with its container and any associated internal barriers prepared for handling, storage or disposal.
Immobilisation of radioactive waste in a glass matrix. glass composition, durability, secondary phases and the complete package affect performance.
Interaction of waste glass with water through ion exchange, network dissolution and alteration-product formation. Dissolved-element release need not equal the total extent of glass alteration.
Formation of new solids during glass alteration. Such phases can retain selected elements or consume dissolved network constituents, changing the apparent release and reaction rate.
A glass-durability test with a finite initially specified leachant inventory. Dissolved products, pH and alteration layers evolve, so the test does not maintain the same conditions as continuous fresh-water flow.
Element release departing from bulk glass proportions. Selective ion exchange, retention in an alteration layer, sorption and secondary precipitation can all produce noncoincident normalised solution releases.
A low continuing rate after alteration products or solution chemistry have slowed the initial reaction. It need not be zero or represent thermodynamic equilibrium of the original glass.
A hydrated, compositionally modified interfacial layer formed during glass corrosion. Its porosity, transport properties and continuing reactions can affect the residual alteration rate.
The dilute-solution dissolution rate at specified temperature, pH and composition, before dissolved reaction products suppress the chemical driving force. It is not a maximum across all temperatures and pH values.
A single-pass flow-through leach test measures the dissolution of a solid while fresh solution continuously enters a reaction cell and the outlet solution is collected for analysis. Unlike a closed vessel, the cell continually exports dissolved constituents. A reported implementation uses a pump, a solution reservoir, a reaction cell and controlled temperature.[ref]
At steady state, an elemental mass balance gives the normalized release ratewhere is the volumetric volumetric flow rate, is the mass concentration of element , is its initial mass fraction in the solid, and is the exposed surface area. For example, using litres per day, grams per litre and square metres gives grams of equivalent solid per square metre per day. This expression follows by dividing the exported elemental mass per day by .
Changing changes the accumulation of dissolved material and therefore the chemical affinity for dissolution. A rate independent of further increases in can help identify a dilute-solution regime. Different elemental release rates can also reveal incongruent dissolution or retention in secondary phases, so interpreting a release rate as whole-solid loss requires an explicit material model.
Dissolution releasing glass constituents in their bulk proportions. Element-normalised releases then coincide if precipitation, sorption and analytical losses do not selectively remove released constituents.
The solution-released mass of an element divided by its initial glass mass fraction and the exposed glass area: . It has units of glass-equivalent mass per area; it does not alone establish congruent dissolution.
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