• Calcination — heating at elevated temperature to convert all cations to the oxide form (removes waters of hydration, hydroxides, nitrates in the presence or absence of air, i. e. rotary pyrolytic calciners). May be coupled with other high temperature processes.

• Drying — heating at 110°C to remove bound water in preparation for solidification, embedding or other high temperature processes.

• Vitrification — the process of solidifying a liquid, sludge, solid, thermal residue, granular waste form, or calcine in a glass (borosilicate, iron phosphate, aluminosilicate).

• Metal formation — melting a metallic waste with or without other metal additives.

Table 6.2 Waste form processing technologies

Processing Process technology mode

Treatment and waste stream scale

Thermal Joule Heated Continuous technologies Melter (JHM)

Large

Advanced Joule Continuous Heater Melter (AJHM)

Large

Cold Crucible Continuous Induction Melter (ССІМ)

Large

Waste forms produced

Disadvantages

Proven technology; typically operates with a ‘cold cap’ to minimize volatility of species of concern

Increased capacity, throughput, and melt rate

compared to JFIM

Allows processing of corrosive glasses; no refractories; no electrodes; water cooled; can be stirred if needed; increased capacity compared to JFIM and AJFIM; can operate at higher temperatures than JHM and AJHM; operates with a ‘cold cap’ to minimize volatility

Electrode and refractory erosion may be a problem; solubility control of certain species (Cr, Mo, and S04) critical

Operates with minimal or no ‘cold cap’ with associated increases in volatility of species of concern

Higher temperature operation can increase volatilization of species of concern but ‘cold cap’ coverage minimizes these impacts

Thermal In-Container Batch Depends on technologies Vitrification (ICV); also known as ‘Bulk Vitrification’ container size (could be mediurr to large) Self-Sustaining Vitrification (SSV) Batch Small Cold Press and Sinter (Cold Uniaxial Pressing, CUP: Cold Isostatic Pressing, CIP) Batch Small Hot Isostatic Pressing (HIP) Batch Small

Inexpensive and simple for low activity wastes or contaminated soils; not

applicable to HLW

Inexpensive; can be used to process small amounts of wastes at remote locations Higher waste loadings;

Minimum disposal volume

Zero off-gas emissions; higher waste loadings; minimum disposal volume; mature flexible

technology; no major secondary wastes; mature industrial process

Inhomogeneous waste forms produced; no temperature control so radionuclide vaporization is high; little or no convection in melt

May require some pre-processing, i. e. grinding of the waste and pre­mixing

Usually small scale; may require pre-calcining or pre-treating waste to an oxide to avoid shrinkage of form

Processes small quantities; can overpressurize if large amounts of volatiles (e. g. nitrates/ hydrates) are present; may require pre­calcining or pre-treating waste to an oxide (shrinkage handled by bellows like canisters)

Processing Process Treatment and technology mode waste stream scale Thermal technologies Hot Uniaxial Batch Small Press (HUP)

Cyclone Furnaces Continuous Large

Waste forms Advantages Disadvantages

produced

Borosilicate glass (lab scale only); GCM’s, crystalline ceramic, simple oxides, metal matrix, zeolites, hydroceramic Borosilicate glass, GCM’s, other glasses (LaB’s, FeP, AIP, chalcognide, etc.), crystalline ceramics, simple oxides, metal matrix

Higher waste loadings;

minimum disposal volume, mature flexible technology; mature industrial process

Suitable for soils containing low volatility radionuclides

Usually small scale; may require pre calcining or pre-treating waste to an oxide for shrinkage control

Secondary recovery process needed to treat off gases

Fluidized Bed Continuous

Steam Reforming (FBSR)

Electric Arc Batch Furnaces
Thermal technologies	Medium/Large
Plasma Furnaces Batch	Small

Pyrolysis (not incineration); immobilizes halides, sulfates,"Tc sequestered in sodalite; moderate temperature; >85% volatile species contained; wastes processed without neutralization; destroys organics and nitrates; industrially proven technology; no secondary liquid waste stream Established Industrial Practice; Similar technology is used for ICV

Plasma generating electrode erosion; efficient for the destruction of organics

Product is granular and requires a high integrity container (НІС) or

encapsulation in a binder to make a glass ceramic material, a geopolymer, or a hydroceramic; Radionuclide partitioning amongst the phases needs to be further studied

No large-scale radioactive practice; high temperatures; volatilization of radionuclides

Large-scale practice in Belgium

(Belgoprocess; high temperatures; volatilization of radionuclides [206-208])

Processing Process technology mode	Treatment and waste stream scale Small
Microwave Batch Heating
Cement Continuous or Batch
Non-thermal technologies	Large

Waste forms Advantages Disadvantages

produced

Suitable for mixed wastes; Can be used as a heat source in other equipment (e. g fluidized bed)

Simple technology; design formulation for best waste retention; fly ash and slag additives keep ssTc and Cr in reduced oxidation state to prevent leaching

Limited to small scale; process scale up; inhomogeneous heating (need a susceptor material); no large-scale practice

Formulations waste specific; some sequestering of radionuclides in hydration products vs. grain boundaries needs more study; radiolytic

production of H2 in high radiation; pH of pore water alkaline and promotes leaching

Non-thermal Geopolymer Batch

technologies

Hydroceramics Batch	Small
Ceramicrete Batch	Small
Continuous or batch
Bitumen	Large to small

Minimal water so radiolytic H2 generation is limited, fire resistant, pore water less alkaline than cements

High capacity for high sodium or calcium containing wastes; stabilize halides and sulfates.

Very dense; room temperature curing; high waste loading

Simple; low operating cost; leach-resistant characteristics

Formulations waste specific; distribution of radionuclides among the phases needs more study; batches are thick and require extrusion

Require hydrothermal set; requires more water than geopolymers so radiolytic H2 generation; batches are thick and require extrusion; wastes with >25wt% nitrate must be pre-treated

High heat of hydration; bubble formation which can be vibrated out of mixture during set

Flammable; requires heat to make bitumen molten; poor performance with salts; thick even when molten; requires extrusion

184 Radioactive waste management and contaminated site clean-up

• Pyrolysis — process of destroying organics in the absence of air (more environmentally compliant than incineration which destroys organics in the presence of air). Pyrolysis can be carried out in calciners, drums, or by fluidized bed steam reforming (FBSR).

• Hot isostatic pressing (HIP) — a manufacturing process used to reduce the porosity of metals and increase the density of many ceramic materials by subjecting the waste/additive mixture to both elevated temperature and isostatic gas pressure in a high pressure containment vessel.

• Cold isostatic pressing (CIP) and sintering — a manufacturing process used to reduce the porosity of metals and increase the density of many ceramic materials by subjecting the waste/additive mixture to isostatic liquid pressure in a flexible but impervious form such as a balloon before sintering at high temperature.

• Hot uniaxial pressing (HUP) — a manufacturing process used to reduce the porosity of metals and increase the density of many ceramic materi­als by subjecting the waste/additive mixture to uniaxial mechanical pres­sure from above and below in containment form while simultaneously subjecting the form to elevated temperature.

• Cold uniaxial pressing (CUP) and sintering — a manufacturing process used to reduce the porosity of metals and increase the density of many ceramic materials by subjecting the waste/additive mixture to uniaxial mechanical pressure from above and below in containment form before sintering at high temperature either with or without the containment form.