Thermochemical processing using powder metal fuels of ...isl.group.shef.ac.uk/papers/MIOIMEThermomechanical2004paper.pdf · Thermochemical processing using powder metal ... wastes

Thermochemical processing using powder metalfuels of radioactive and hazardous waste

M I Ojovan1�, W E Lee1, I A Sobolev2, S A Dmitriev2, O K Karlina2, V L Klimov2, G A Petrov2

and C N Semenov2

1Immobilization Science Laboratory, Department of Engineering Materials, University of Sheffield, Sheffield, UK2Moscow SIA ‘Radon’, Moscow, Russia

Abstract: An overview of thermochemical treatment technologies (TTTs) for radioactive and toxic wastes

is given. TTTs have been developed for pretreatment (e.g. decontamination), treatment and conditioning of

specific wastes such as mixed, organic or chlorine-containing radioactive waste and contaminated soils.

TTTs use powder metal fuels (PMFs) specifically formulated for the waste composition, which react with

some of the waste components. Thermochemical processing can be carried out in a self-sustaining

regime and enables ecologically safe processing of wastes without complex and expensive equipment. It

leads to almost total confinement of contaminants in a mineral or glass composite end-product with minimal

release of hazardous components and radionuclides in the off-gas.

Keywords: thermochemical processes, waste processing, radioactive waste, toxic waste

NOTATION

IER ion-exchange resin

PMF powder metal fuel

PVC polyvinyl chloride

SHS self-sustaining high-temperature synthesis

SIA Scientific and Industrial Association

TTT thermochemical treatment technology

VRC volume reduction factor

1 INTRODUCTION

Thermochemical processing has been developed predomi-

nantly in Russia to immobilize toxic and radioactive

wastes and utilizes selective combustion of powder metal

fuel (PMF) constituents with the most hazardous waste

components in a heterogeneous system ensuring complete

decomposition of organics and retention of toxic and radio-

active elements in the condensed combustion products.

These are in the form of mineral-like or glass composite

materials suitable for subsequent safe storage, transpor-

tation and eventual reuse of non-radioactive materials or

disposal of radioactive waste.

Thermochemical treatment technologies (TTTs) are

intended for pretreatment (e.g. decontamination), treatment

and conditioning of specific types of radioactive and toxic

waste such as spent ion-exchange resins, inorganic absor-

bents, wastes from research nuclear reactors, irradiated

graphite, mixed, organic or chlorine-containing radioactive

waste, contaminated soils and unburnable heavily surface-

contaminated materials. Table 1 compares TTTs with

other thermal methods for processing of wastes.

Thermochemical processing uses the energy of exothermic

reactions in a mixture of radioactive or hazardous waste with

PMF. The PMF composition is designed to minimize the

release of hazardous substances and radionuclides in the

off-gas and to confine the contaminants in the solid products.

Generally, the PMF consists of combustible powder

metals, oxygen-containing components and some additives

(pore-formingmaterials, stabilizers, surface-active substances

and others), with a predominance of metal powders. Thermo-

dynamic simulation is applied widely during designing of the

PMF, followed by experimental performance and operational

safety assessment tests of TTTs.

2 TTT DEVELOPMENT AND APPLICATIONS

A number of applications of thermochemical processing

methods have been demonstrated, including:

(a) pretreatment: surface decontamination of metals,

asphalt and concrete;

The MS was received on 18 November 2003 and was accepted after revisionfor publication on 14 June 2004.�Corresponding author: Department of Engineering Materials, Universityof Sheffield, Sir Robert Hadfield Building, Mappin Street, SheffieldS1 3JD, UK.

1

E04503 # IMechE 2004 Proc. Instn Mech. Engrs Vol. 218 Part E: J. Process Mechanical Engineering

(b) treatment: processing of organic wastes, namely spent

ion-exchange resins, plastics, polymers and medical

and biological waste;

(c) treatment and immobilization: processing irradiated

reactor graphite with almost total 14C retention;

(d) immobilization: self-sustaining vitrification ash resi-

dues, calcined bottom residues, spent inorganic sor-

bents, contaminated soils.

Potential applications of TTTs have also been investigated,

including:

(a) self-sustaining processing of zirconium-containing radio-

active waste with synthesis of Synroc-type waste forms;

(b) self-sustaining immobilization of U- and Pu-containing

wastes in mineral-like and glass composite materials;

(c) remelting and decontamination of metallic wastes, e.g.

stainless steel.

Initial studies ofwaste thermochemical processingwere carried

out at the end of the 1980s andwere intended to study the feasi-

bility of self-sustaining high-temperature synthesis (SHS). A

novel, highly efficient, ecologically safe and cheap calcination

method evolved from this was with SHS being supplied by

PMF components selectively interacting with nitrogen oxides

[1]. This method, however, has not been used on an industrial

scale, since the Russian vitrification processes used a one-stage

calcination–melting approach utilizing non-calcined wastes.

Nonetheless, TTT was developed to produce ceramic waste

forms immobilizing liquid wastes (bottom residues) using a

clay base to absorb toxicants and SHS to sustain sintering of

the ceramics [2]. In the mid-1990s a thermochemical deconta-

mination method was developed to remove radioactive spots

from asphalt coatings [3]. These studies were followed by

development of a new PMF composition enabling decontami-

nation of metals and concrete surfaces [4, 5]. Moreover, the

possibility was demonstrated of removing deep penetrating

contaminants from up to 100 mm depth of stainless steel

using certain PMF [6].

Incineration of biological waste was a tremendous chal-

lenge in the 1990s, particularly with respect to cattle dis-

eases such as spongiform encephalitis, and led to

development of a new PMF able to incinerate large numbers

of animal cadavers in field conditions [7, 8]. Self-sustaining

vitrification was used to immobilize ash residues, contami-

nated clays and spent inorganic sorbents [9]. A TTT process

was invented to combust organic ion exchangers and

immobilize ash residues [10]. Almost full retention of

radioactive contaminants including the most dangerous con-

stituent of irradiated reactor graphite 14C in a corundum–

carbide waste form via a specially designed SHS process

was demonstrated in a number of studies [11].

TTTs were show to be feasible for synthesizing Synroc-

type waste forms [12]. Mineral-like waste forms were pro-

duced via TTTs to retain long-lived radionuclides, e.g. U

and Pu [13], and this process is currently being tailored for

in situ application in borehole repositories [14]. TTTs were

also demonstrated to be useful for remelting metallic wastes

including stainless steel [15]. Table 2 gives a brief overview

of the most important milestones in developing TTT.

Table 1 Comparison of thermal treatment methods

Method ThermolysisSelf-sustaining high-temperaturesynthesis (SHS) Thermochemical processing (TTTs)

Characteristics Thermal processing withdecomposition of chemicalcompounds on heating

Chemical process that occurs withrelease of heat in autowave regimeof combustion and resulting information of solid products

Thermochemical process that useswaste specific fuels and utilizesconstituents in both synthesis anddecomposition chemical reactions.May involve liquid phase

Area of application Toxic, low- and intermediate-levelradioactive wastes, mixed wastes

Toxic, low-, intermediate- and high-level radioactive wastes, mixedwastes

Toxic, low-, intermediate- and high-level radioactive wastes, mixedwastes

Main targets Decomposition of organics, volumereduction

Synthesis of waste forms Decomposition of organics, volumereduction; synthesis of wasteforms; immobilization throughmelting; decontamination;selective recovery

Stage of implementation Industrial application Laboratory experiments Pilot industrial application

Advantages Universal High efficiency High efficiency and selectivity

Table 2 Thermochemical treatment methods for toxic and radio-

active wastes

Method Reference

Calcination of wastes [1]Sintering of ceramics [2]Decontamination of asphalt [3]Decontamination of concrete [4]Decontamination of metals [5]Deep decontamination of metals [6]Treatment of mixed wastes [7]Incineration of biological wastes [8]Vitrification of ash residues [9]Incineration of ion exchangers [10]Processing of reactor graphite [11]Synthesis of Synroc-type ceramics [12]Synthesis of mineral-like matrices [13]Immobilisation of U- and Pu-containing wastes [14]Remelting of metals [15]

2 M I OJOVAN, W E LEE, I A SOBOLEV, S A DMITRIEV, et al.

Proc. Instn Mech. Engrs Vol. 218 Part E: J. Process Mechanical Engineering E04503 # IMechE 2004

3 THERMOCHEMICAL DECONTAMINATION

The thermochemical decontamination technique can be

used to decontaminate surfaces of materials including

asphalt, concrete and metals. This technology is particularly

suitable when the radioactive contamination is strongly

bonded in the near-surface layers where conventional

decontamination methods cannot efficiently remove the

radionuclides [16]. Thermochemical decontamination is

based on thermal treatment of a superficial layer of contami-

nated material by the heat generated from combustion of a

layer of PMF covering the surface (Fig. 1) [3–6].

The PMF layer on the surface is burning flameless and

continuously within a few minutes. The heat volatilizes

most of the radionuclides, which are then trapped by

the resulting slag layer, which is formed as a result of

PMF combustion. Thermochemical interaction between

the slag layer and decontaminated material may also result

in removal of a near-surface layer along with the

contaminants.

Thermochemical decontamination technology is rather

simple and comprises few operations [3–6]. The first oper-

ation is to determine the extent of and then to cover the con-

taminated region of the surface with a thin (0.8–1 cm) layer

of PMF. This layer is then ignited, combustion lasting

for several to a few tens of minutes, depending on the

PMF type. The last stage following the extinction of the

PMF involves collecting the resulting slag from the surface.

Decontamination efficiency is calculated by the formula

K ¼A0 � Af

A0

100% (1)

where A0 is the radioactivity of the material surface before

decontamination and Af is the radioactivity of the material

surface after decontamination. The decontamination effi-

ciency depends mainly on temperature and duration of sur-

face heating. These variables are determined by the PMF

composition and its consumption per unit of treated area.

Process optimization for various materials includes select-

ing the mixture composition and ensuring the necessary

combustion temperature.

Decontamination of metal surfaces is achieved as a result

of radionuclide volatilization and their fixation in a slag

layer that forms as a result of PMF combustion. To

remove well-bonded radioactive contamination typically

requires removal of a thin layer (�1 mm) of the metal sur-

face. Relatively deep penetration of radioactive contami-

nants into metals may occur owing to corrosive and

mechanical destruction of the near-surface metal structure.

A special thermochemical technique has been developed

for deep (�100 m) decontamination, which combines both

thermal volatilization and chemical surface oxidation of

the metal [6, 15–17].

Thermochemical decontamination of concrete (Fig. 2) is

achieved via thermal shock spallation caused by PMF. The

PMF is coated on the contaminated concrete plate and

ignited. After PMF combustion, the concrete upper layers

crack and spall. These spalled concrete fragments are

embedded in the slag and both are removed after cooling.

Decontamination efficiency for concrete is as high as

90–95 per cent for each decontamination procedure.

The depth of radioactive contamination removed is up to

5–8 mm, and these procedures can be repeated if necessary

to remove several layers of contaminated concrete.

Fig. 1 Schematic of a thermochemical decontamination

technique

Fig. 2 Thermochemical decontamination of a concrete slab: PMF layer covers the contaminated region (left)

and spalled fragments ready for collection (right)

THERMOCHEMICAL PROCESSING USING POWDER METAL FUELS OF RADIOACTIVE AND HAZARDOUS WASTE 3


For asphalt decontamination transfer, of the contaminated

layer to the softened state of asphalt is achieved at

130–180 8C. The glass fibre backed PMF filling is applied

to the contaminated asphalt surface. After PMF combustion,

the softened asphalt is removed mechanically to the neces-

sary depth. The deeper the radionuclide contamination of

asphalt, the longer is the PMF combustion and consequently

the thicker the PMF layer needed.

The main characteristics of the thermochemical deconta-

mination method are given in Table 3. Thermochemical

decontamination was successfully used in many cases

when conventional methods were inefficient [3–6, 16, 17].

4 PROCESSING OF ORGANIC WASTES

Some organic radioactive wastes require special treatment

technologies. These include spent ion-exchange resins

(IERs), mixed, polymer and chlorine-containing (for

example PVC) wastes and biological objects. The thermo-

chemical processing of radioactive organic waste is based

on application of a specifically formulated PMF. The com-

position of this PMF is designed using thermodynamic cal-

culations and takes into account the chemical composition

of waste and the need to decompose certain organics but

retain the toxic and radioactive elements. The goal of the

thermodynamic simulation is to achieve simultaneous

decomposition of organic matter in the waste and retention

of hazardous radionuclides and chemical species in the final

ash–slag product.

IERs most generally used in water purification systems at

nuclear power stations and nuclear research centres are

copolymers of styrene and divinylbenzene. The thermo-

chemical technology for spent IERs was developed to

treat resins in a wet state [18, 19]. Spent IERs usually con-

tain a large amount of water, often more than 50 wt %. The

major radioactive contaminants of spent IERs are 137Cs,90Sr, 60Co, 106Ru and 54Mn. In addition, spent IERs are fre-

quently contaminated with heavy and toxic metals. The

metal powders in the PMF (including Al, Mg, Ca and Si)

react with water from the IERs, producing enough heat to

sustain its thermal destruction and interaction with the

PMF-generated slag. As a result, the waste volume is

decreased significantly and contaminants combine with

the PMF slag to form chemically stable compounds. A

number of PMFs have been developed for this purpose

(Table 4).

The process of incineration of IERs mixed with PMFs is

illustrated schematically in Fig. 3. A wet IER and PMF,

previously mixed in the appropriate ratio, are fed into the

furnace where reaction is initiated and combustion occurs,

resulting in the release of a great quantity of heat, evapor-

ation and gasification of the IER. Air is supplied to the

combustion chamber to burn out the products of IER gasifi-

cation and hydrogen resulting from the reaction of the metal

with water.

The process in the furnace is controlled so that radio-

nuclides contained in the wet resin are converted into low-

volatile compounds of ash residue. Figure 4 shows an

actual thermochemical facility (capacity up to 20 kg/h).

Table 3 Main features of thermochemical decontamination process

Material

Maximumtemperatureachieved(8C)

Duration ofPMFcombustionprocess(min)

Efficiency ofdecontamination(%)

Radionuclidecarryover(137Cs) (%)

Metal 1100 20 95–99 0.1–0.5Asphalt 400 15 99.9 0.1–0.5Concrete 1300 20 95–99 0.1–0.5

Table 4 Main characteristics of PMFs for the thermochemical

processing of IERs

PMFMajorcombustible

Heatvalue Hu

(kJ/kg)

Stoichiometriccoefficient L0(kg air/kg PMF)

Bulkdensity(kg/m3)

MTKD-45 Mg, Al 27 000 3.35 680–710SKTKD-50 Mg, Ca, Al,

Si26 000 3.46 900–1000

SKTKD-51 Mg, Al, Si 25 900 3.95 800–900

Fig. 3 Schematic of thermochemical treatment of IER: 1, wet

IER; 2, PMF; 3, mixer; 4, mixture; 5, air supply;

6, reactor; 7, off-gases; 8, ash–slag residue

Fig. 4 View of thermochemical reactor for incineration of

spent ion-exchange resins



Thermochemical treatment of organic polymer materials

is performed in much the same way. In the case of chlorine-

bearing polymers, chlorine from the polymer and the metal

in the PMF combine to form chemical compounds, which

are retained in the slag [19].

Table 5 shows the NOx, SOx and CO content in the

gaseous combustion product of a mixture of wet IER

(KU-2-8) and PMF type MTKD-45 at the furnace outlet.

Note that these gases are directed to the gas purification

system before being discharged into the atmosphere so

that the concentrations of these contaminants are further

diminished by several orders of magnitude.

The volume reduction coefficients (VRCs) depend on the

PMF type used. These were 9.5, 10 and 14 in the case of

PMF types SKTKD-50, MTKD-45 and SKTKD-51 respect-

ively. Analysis of the ash residue shows that the slag con-

fines radionuclides in fixed form at levels of 90 per cent

or more for 137Cs and more than 95 per cent for 90Sr and60Co [18, 19].

The problem of neutralization of hazardous biological

objects, for example, cadavers of animals affected by var-

ious virus and bacteriological diseases, is of great current

interest. Conventional burial of such cadavers may generate

sources of epidemics so that incineration has become

accepted as the best method of rendering harmless this

toxic waste. High temperatures above 1000 8C ensure

destruction of organics and guarantee an absence of viruses

in the resulting ash. However, incineration of animal cada-

vers using hydrocarbon fuels requires complicated and

expensive equipment. It consumes large amounts of conven-

tional fuel because of its two-step nature: drying of the

cadaver, and incineration proper of its constituents, e.g.

proteins, fats and bones. In contrast to this, the application

of a PMF permits practically apparatus-free incineration

of large animal cadavers in field conditions (Fig. 5).

The consumption of the PMF is rather small owing to the

use of the water from a biological object in reactions, thus

ensuring a one-step incineration process. Apparatus-free,

highly efficient technology for incineration of animal cada-

vers in field conditions has been demonstrated using PMF,

including an international demonstration in Brno, Czech

Republic [8, 20]. The performance of the method developed

is governed by the active chemical interaction of the PMF

with water of the biological tissue. Figure 6 shows three

photographs taken during the incineration of a cow in

field conditions.

Chemical analysis of aerosols and gases released from the

reaction zone did not show excessive concentrations of

nitrogen, carbon and sulphur oxides. Analysis of ash and

slag showed an absence of hazardous metals, chemical com-

pounds and any organic substances (Table 6).

The remnant ash–slag residue after cadaver/PMF incin-

eration can also be used as a fertilizer. It should be pointed

that this technology can be applied to the incineration of bio-

logical residues of different origins, including vegetation.

Table 5 Chemical contaminants in off-gases from IER combus-

tion by a PMF

Contaminant

Average/maximumcontent in thecombustion products(mg/m3)

Typical maximumpermittedconcentrations [16](mg/m3)

NO and NO2 20/50 300–500SO2 and SO3 220/430 100–2000CO ,1.25 50–200

Fig. 5 Schematic of PMF field incineration of biological

waste: 1, cadaver of animal; 2, trench; 3, fire grate;

4, air supply; 5, vertical supports; 6, metal hood; 7,

layer of PMF with coke

Fig. 6 PMF field incineration of biological waste: left, before; centre, process under way; right, final ash–slag

residue



5 PROCESSING OF IRRADIATED REACTORGRAPHITE

Graphite waste containing fragments of fuel and activation

and fission products mainly arise during operation of

uranium–graphite reactors. The 14C content in reactor

graphite may be as much as 1 wt %. For safe disposal and

long-term storage, such waste must be properly processed

into chemically stable materials. Other carbon-containing

(including 14C radionuclide) wastes are also the subject of

special attention. Incineration of irradiated carbon is not

permitted because of discharge into the atmosphere of bio-

logically significant 14C in 14CO2 and14CO. To treat 14C-

containing waste, a thermochemical treatment technology

has been developed based on self-sustaining exothermic

reactions in a mixture of carbon (graphite), aluminium and

titanium dioxide [11, 21]

3C (graphite)þ 4Alþ 3TiO2 ! 3TiCþ 2Al2O3

As a result, 14C and other radionuclides become immobi-

lized in a stable carbide–corundum ceramic matrix.

Figure 7 demonstrates the SHS process of formation of

carbide–corundum waste from a mixture of graphite

with PMF.

Thermochemical processing of graphite is carried out in

an inert atmosphere, e.g. in an argon atmosphere. A mixture

of PMF with powdered graphite is placed into a crucible

container where the self-sustaining synthesis reaction

is ignited (Fig. 7, left photo). The self-sustaining process

occurs with substantial release of heat; temperatures

higher than 1700 8C are achieved. Nevertheless, the relative

carryover of carbon is minimized to values of 1024/1027 for

CO and CO2 respectively. The self-sustaining reactions

result in a chemically stable titanium carbide–corundum

matrix acceptable for long-term storage and disposal.

Special additions such as zircon, barium and calcium

metatitanites have also been used to improve radionuclide

retention [22–24].

6 SELF-SUSTAINING IMMOBILIZATION

While vitrification is the best current solution for immobi-

lizing hazardous waste, its use is limited to large-volume

waste streams such as high- and intermediate-level nuclear

waste. This is due to the relative complexity of the vitrifica-

tion technology and the high initial cost of equipment. How-

ever, in addition, a range of accumulated wastes of different

composition and properties from the bulk streams have been

generated during various activities of both industrial facili-

ties and research institutions, usually in relatively small

amounts. Examples include spent ion exchangers, wastes

from research centres, contaminated soils and incinerator

ashes. Owing to the relatively small volumes of such

wastes, the use of conventional vitrification technologies

cannot be justified. A viable alternative is the application

of a self-sustaining immobilization process that utilizes

the energy released during exothermic chemical reactions

Table 6 Results of the analysis of ash–slag residue

Parameter

From the results ofLABTECH Brno,Czech Republic(mg/l)

From the resultsof SIA ‘Radon’(wt %)

Sum of polycyclicaromatichydrocarbons

,0.0006 Not measured

Al 195 4Sb ,0.001 Not measuredPb ,0.05 Not measuredCd ,0.005 Not measuredHg ,0.0008 Not measuredFe ,0.1 Not measuredAmmonia ions 175 Not measuredNitrides 0.22 Not measuredPhosphates 0.6 Not measuredSulphates ,0.6 Not measuredK2O Not measured 3MgO Not measured 49Al2O3 Not measured 20MgAl2O3 Not measured 24

Fig. 7 Thermochemical processing of graphite: left, ignition: centre, downward motion of reactive zone;

right, final product



in a mixture of radioactive waste with specially designed

PMFs [9, 25–28]. PMFs are used to melt the waste and

form a glass-like material without requiring an external

power supply. This process is controlled by the composition

of the initial mixture of waste and PMF. The composition of

the PMF is designed to release sufficient heat to sustain

waste melting and to produce a mineral or glass-like end-

product. Suitable PMF compositions and PMF/waste

ratios are determined through computer simulation, mini-

mizing carryover of hazardous components and ensuring

retention of contaminants in the final waste form. Self-

sustaining immobilization does not require expensive

equipment and is economically justified, particularly for

small-volume hazardous wastes. The possibility of such

processes has been demonstrated for a number of waste

streams including calcined radioactive waste, contaminated

clay soils, ashes and spent inorganic ion exchangers, zirco-

nium alloys and irradiated graphite. New schemes are

designed to be applied in situ, ensuring waste immobiliz-

ation in the final disposal environment [28].

Thermodynamic simulation has been applied to the design

of appropriate PMF formulations [29, 30]. Ash residues

from radioactive waste incineration as well as contaminated

clay soil were used. The b,g-emitting radionuclides of cae-

sium, strontium and cobalt and the a-emitting radionuclides

of heavy metals (actinides, radium, and polonium) were the

main carriers of radioactivity in the ash residue. The radio-

nuclide content in the soil was represented mainly by137Cs. For U- and Pu-containing wastes, natural zircon was

added to the PMF to aid radionuclide retention [31].Table 7 illustrates the properties of the glass composites

obtained through a thermochemical solidification process

such as self-sustaining immobilization. The retention of

radionuclides by glass composite materials is due to high

leaching rates similar to those obtained by conventional

vitrification.

A significant advantage of the thermochemical immobil-

ization process is its autonomy: self-sustaining immobiliz-

ation can be carried out remotely without the need for a

processing area. This method has been proposed recently

for in situ immobilization of waste in borehole-type reposi-

tories [14, 27]. Figure 8 demonstrates the process occurring

in a double-walled container in field tests of in situ

immobilization.

Self-sustaining immobilization has been proven as a

feasible scheme to vitrify ashes produced as a result of

Table 7 Characteristics of self-sustaining immobilization processes and the glass composites obtained

Wastecontent

Processtemperature Density

Compressivestrength

Leach rate� (g/cm2 day)

(wt %) (8C) (g/cm3) (MPa) 137Cs 239Pu

Ash 50 1530 2.8 20 9.0 � 1026 5.4 � 1026

56 1356 2.8 17 4.9 � 1026 2.8 � 1026

60 1245 3.0 16 7.9 � 1025 7.0 � 1025

Soil 45 1905 2.4 10 1.0 � 1025 —50 1627 2.0 10 8.1 � 1026 —56 1530 1.5 8 2.1 � 1026 —

Clinoptilolite 55 1476 1.74 9 4.0 � 1025 —

�Normalized leach rates were measured according to IAEA test protocol ISO 6961-1982.

Fig. 8 Self-sustaining immobilization: (a) process within double-wall container crucible; (b) borehole in situ

testing experiment; (c) monolith block produced in situ



incineration of solid radioactive waste, contaminated soils

and spent ion exchangers, e.g. clinoptilolite. An experimen-

tal ash vitrification plant has been under operation at

Moscow SIA ‘Radon’ for a number of years, and a modular

mobile facility is currently under development. The mobile

facility aims to immobilize ashes, soils and spent sorbents at

their point of generation [26].

7 CONCLUSIONS

Highly efficient thermochemical processes have been devel-

oped to process specific types of toxic and radioactive

waste. These are used for pretreatment (e.g. decontamina-

tion), treatment and conditioning of spent ion-exchange

resins, inorganic absorbents, irradiated graphite, organic

and biological wastes and contaminated soils. Thermo-

chemical processing is based on utilization of powder

metal fuels that can be specifically formulated for each indi-

vidual waste composition. Powder metal fuels selectively

react with the most hazardous constituents of the wastes

to minimize the release of toxic substances. The application

of thermochemical processing results in almost total con-

finement of contaminants in a mineral or glass-like end-

product. Technologies based on thermochemical processing

are simple in implementation and can be realized without

complex production equipment and energy supply.

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Proceedings of the Institution of Mechanical Engineers

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