properties, volumes and current disposal and re-use of ...very wide areas of solid solution. forms...

NUCLEAR ENERGY AGENCYCOMMITTEE FOR TECHNICAL AND ECONOMIC STUDIES ON NUCLEAR ENERGY DEVELOPMENT AND FUEL CYCLE2nd Meeting of the Ad hoc Expert Group on "Radioactive Waste in Perspective" 6-7 November 2007

Properties, volumes and current disposaland re-use of residues from thermo-chemical energy productionRolf Sjöblom

DISPOSITION

ConclusionsTesting and acceptance

Waste disposalUtilization in concreteand as a binding agent

Building blocks and radiation exposure

Properties of coalcombustion residues

Destinations in UK, EU, USA and Japan

Coal combustion & residue generation

Remediation of heaps and lagoons

Historical background

RADIOACTIVE WASTE IN PERSPECTIVE

• It has been said that – the introduction of nuclear power has been

like having invented an airplane and trying to figure out how to land it whilst in the air

• Let us therefore - very briefly and for the sake of perspective -– first recapitulate our own legacy

• Published in 1996 & in usein Sweden 1997

• Great benefits in medicine (diagonsis & cancer treatment)

• Severe delayed cancer effects (e g luminous paint)

=> When nuclear fission & chain reactions had been discoveredaround 1940

• Relatively good handle on radiation protection• Little awareness regarding implications of induced radioactivity

Birth of the atomic age.Oil painting by Gary Sheahanshowing first chain reaction.

ATOMIC PILES & NUCLEAR LEGACY

• Graphite being one of a few materials that slowdown neutrons without absorbing them

• Enables chain reaction in U-235, naturalabundancy, by thermal neutrons

• Enables production of plutonium through activationof U-238

• 2nd atomic bomb (at Nagasaki) made of Pu-239• Present estimate of costs for nuclear legacy in the

US: 250 E**9 USD (> Swedish GNP)• Estimated to take decades (but figures are

uncertain ...)• Much more in Russia ...• More also elsewhere ...

PRESENT SITUATION(a number of countries)

• Large and adequate resources are beingallocated in a timely manner to the RD&D required (and the corresponding research is being conducted)

• Funds are accumulated from those benefittingfrom the nuclear power to cover all future costsfor decommissioning and waste management

• Implementation is either being carried outalready or is at a late and concrete stage of planning

• All of the above is carried out under strict public control

HOW DOES THIS COMPARE WITH COAL?

• Coal has been around for centuries• Ample time for feedback of experience• => no legacy – OR? • Let us recapitulate

COAL The preception of coal from old works of art – black smoke –- same as on old photographs – High Tech of the time

Why is it that smoke from coal is black while that of wood is white?

Clean fumes and ashes, in comparison

Fuel and oxygen in air in good contact

Ash content of trunk ≈ 0,5 %

WOOD

High content of sootwith PAH e t c

Protective ash layeraround burning particles

Ash content≈ 15 %

COAL

QUESTION:

HEALTH ISSUE OF IMMEDIATE CONCERN

EXAMPLE OF A STEAM EXPLOSIONThey were eventually

avoided by the following

• Safe pressure vessels• Safety valves• Proper composition of

feed water• Proper instructions for

the operation• E t c

COAL – A CENTURY AGO• Pressure 10 – 20 bar• Efficiency of a condensation plant ≈ 10 %

• High frequency of fatalities due to steamexplosions

• High emissions of dust PAH, heavy metalssulphur dioxide and natural radionuclidesleading to:– Impact on human health through inhalation– Impact on environment through e g acid rain

• Ash in heaps or lagoons

COAL – A CENTURY AGO

COAL TODAY

MODERN COAL FIRED PLANT DESIGN

DISPOSITION









EFFICIENT COMBUSTION

EFFICIENT AIR POLLUTION CONTROL

Various methodologies and types of equipment for modern air pollution control

COAL BASED THERMO-CHEMICAL ENERGY PRODUCTION – OECD TODAY

• Water supercritical• Efficiency of a condensation plant ≈ 40 - 50 % (>

100 % for cogeneration with biofuels <= condensation of water from flue gases)

• Heat and pressure related fraction of injuries insignificant

• Emissions to air and water low, and relatedimpact on health and environment insignificant

• Restoration of ash heaps or lagoons• Recycling of ash• Impact on climate and landscape

(important but will not be mentioned further here)

COAL BASED THERMO-CHEMICAL ENERGY PRODUCTION TODAY, CONTINUED

• ≈ 40 – 50 % of all electric power generation based on coal (it boomed as a result of the oil crisis in the seventies)

• Total coal used in the world for electricpower generation ≈ 3 229 Mton per year

• (Total coal for all purposes in the world ≈ 5 425 Mton per year)

• About 15 % by weight is ash• Total coal ash from electric power

generation ≈ 484 Mton per year

Coal used for electricity generation coal ash from electricity generation

Asia excl China, Japan & India

China

India

Japan

Former USSR

North America OECD

EU - 25 countries

Other

SOURCE: OECD/NEA:s DATABASE

VARYING STATUS INTERNATIONALLY

• Most of the information available refers to OECD countries, primarily USA/Canada, EU and Japan

• They will constitute the reference in the following• These countries generally

– have implemented APC (Air Pollution Control)– carry our remediation of ash heaps and lagoons– recycle ashes– dispose of ashes in proper landfills

• Other countries may have facilities at most of the various stages of development described above

• It is likely that the types of coal that are mostdifficult to manage from health and environmentpoints of view are used primarily in developingcountries

DISPOSITION









THE RESIDUES GENERATED• Variation with respect to

– Quality of the coal– Operating conditions of the furnace (e g load)– Point of exit– Method of exit (bottom ashes may be taken out dry or

wet)– Method of removal (dry or pumped as a slurry, e g for

fly ash)– Storage before use (with or without weather

protection)• Most of the ash is fly ash, and it will be the focus

for the following

EXAMPEL OF FRACTIONATION

Table 6 Coal combustion products (CCP) production in EU 15 in 1999 (kt)

[ECOBA,2002]

FlyAsh

BottomAsh

BoilerSlag

FBCAshes

Other SDA-Product

FGD-Gypsum

Total Total%

CCPProduction

37 144 5 622 2 417 985 240 520 7 574 54 502 na

Utilization 18 169 2 500 2 417 445 240 471 6 622 30 864 55.6Landfill,ReclamationRestoration

15 425 2 070 0 393 0 37 424 18 349 33

TemporaryStockpile

717 31 0 0 0 0 445 1 193 2.1

Disposal 3 806 1 057 0 147 0 12 94 5 116 9.2

IS COAL ASH WASTE?DIRECTIVE 2006/12/EC OF THE EUROPEAN PARLIAMENT AND OF THE

COUNCIL of 5 April 2006 on waste, Annex 1: CATEGORIES OF WASTE

Q1 Production or consumption residues not otherwise specified below

Q2 Off-specification products. . .

Q15 Contaminated materials, substances or products resulting from remedial action with respect to land

Q16 Any materials, substances or products whichare not contained in the abovementionedcategories.

EVERYTHING IS WASTE?

Annex II – a decision tree for waste versus by-product decisions

Brussels, 21.2.2007, COM(2007) 59 final

COMMUNICATION FROM THE COMMISSION TO THE

COUNCILAND THE EUROPEAN

PARLIAMENTon the Interpretative

Communication on wasteand by-products

From Joshi R C and Lothia R P: Fly ash in concrete. Production, Properties and use.

About 11 –30 % of the

ash is crystallineand forms

phasesvisible by

XRD.

The rest is silicateglass.

Table 5 Arithmetic average of concentr ations of radionuclides in certain ash(Bq kg -1)

[UNSCEAR, 1992, Annex C [1]; Leenhouts, 1996 [2]; Hedvall, 1997 [3]]

238U 232Th 228Th 228Ra 226Ra 210Pb 210Po 40KEscapingfly ash(coal) [1]

200 70 110 130 240 930 1700 265

Bottomash/ flyash (coal)[2]

240/200 240/200 240/200 151/220 138/220 653/670

Peat flyash [3]

268-1048

<215 <1480

ASH PARTICLES ARE MOSTLY SPHERICAL AND < 45 MICRON

DISPOSITION









PROPERTIES TO UTILIZE

• Ability to cure / harden– Self hardening– Pozzolana (hardens when lime or equivalents

are added)• Ability to bind / stabilize

– Spinels with Fe– Silicates with Mg and Mn

• Ability to fill space

PORTLAND CEMENT• ≈ 150 years old when people had learned to fire at

temperatures much higher than what was required for lime and mortar (which is ≈ 800 – 900 °C)

• Comprises mainly C2S and C3S whereC = Ca, Mg, Fe-II e t cS = Si, Al, Fe-III e t c

• Portland cement reacts readily with water to form silicategel together with needle shaped Ca(OH) 2

• Portland cement concrete remains strongly alkaline(pH>>10) until carbonated by air

• Carbonation by air is a slow process in ordinaryconstructions and anticipated times of use

• Portland cement concrete is strong but brittle and requires reenforcement by steel

• The steel will corrode (& expand) unless pH is high

POZZOLANIC FLY ASHES• Reactive form

– Chemically active high temperature form– Small particle size– Often initially a high pH in contact with water

• Reacts readily with calcium hydroxide from– portland cement– lime

• Particle properties advantageous to give good flow and packing properties– Particles smaller than those of portland cement– Round shape

• Improves chemical resistance and durability• Slower curing but higher quality of end product• Lower heat of reaction – less thermal fracturing for large

constructions

SELF HARDENING ASHES• Generally have higher content of Ca and Mg

compared to pozzolanic ashes• The following types of fly ashes are typically self

hardening– Ashes from lignite– Ashes from wood based fuels

• Ca might not be in a hydrolysed form expansion and associated disintegration

• Might be counteracted by gradual addition of water

• High Al and S might give rise to expansion and (partial) disintegration by ettringite formation

Solubility(log scale) of aluminaand silicaversus pH

Silicate glass with high

surface area + Ca-rich

material with high pH

high reactivity

LONG PROCESS• Initial resistance from Portland Cement

manufacturers• Initial quality variations and other problems• Initial problems with Authorities on

permissiveness• Now established in many OECD countries

that regulations must not discriminateagainst the use of coal ash

• Still a very steep uphill battle for bioashes– at least in Sweden

A DAM BUILT WITH COAL ASH CONCRETE

PANTHEON IN ROME ≈ 2 000 YEARS OLDIt was constructed by the romans using so-called

roman cement. It was made from a mixture of pozzolana and lime. The pozzolana was either ashfrom natural volcanoes (e g Pozzolan) or crushed

fired bricks, or both.

ANOTHER EXAMPLE - COLLOSSEUM

ABILITY TO BIND / STABILIZE• ≠ Make hard or cure• Means binding hazardous substances (&

elements) in a stable manner low availabilityto living organisms

• Microelements in ash do not form phases of theirown incorporated in ”solid solution” in phasesof major elements

• Certain phases act as sinks for heavy metals:– Spinells with iron. Very wide areas of solid solution.

Forms nodules with heavy metals at bottom of sea. – Certain micas (sheet silicates) high in Mn and Mg

• Frequently aged ash may have higher content of heavy metals than ordinary soil material but a lower availability. (I e heavy metals may migrate from surrounding soil and become trapped in ash)

Long term performance for different processes

0,001 1 1000

Sulphide formation

Carbonate formation

Clay formation

Secondary reactions

Hydration

Combustion processes

years

Main changeStill in effect

POSSIBLE CHANGES IN ASH IN THE LONG TERM

DISPOSITION









TESTING FOR ACCEPTANCE

• 24 hour leach test in deionized water

• Can only be used for inert material - according to the test itself

• Is actually mainly used (at least in Sweden) on freshvery reactive material

• Ash cures and ages over long times – years and more

• Results from fresh ash:– Most elements one or more

orders of magnitude toohigh

– But Cr, As, Sb, Mo, V e t c potentially too low

EU COUNCIL DECISION of 19 December 2002 establishing criteria

and procedures for the acceptance of waste at landfills pursuant to Article

16 of and Annex II to Directive1999/31/EC

Prescribed use of test methodEN 12457/1-4

ACCUMULATED EXPERIENCE FROM NUCLEAR WASTE RESEARCH TYPICALLY

CONDUCTED ≈ 30 YEARS AGO

Leach testing: Readers may come across many references to 'leach-testing' of all types of solid radioactive waste destined for geological disposal and it is worth pointing out that there are basically two types of experiment which should not be confused.

The first is essentially a standard sorting technique, used to compare the overall quality of waste forms, for example batches of a vitrified waste with slightly different compositions. These are tests only, and give information on the bulk 'leachability' of a product. …

ACCUMULATED EXPERIENCE FROM NUCLEAR WASTE RESEARCH TYPICALLY CONDUCTED ≈ 30

YEARS AGO, CONTINUED, (MY UNDERLINING)

The second type of leach testing is an experimental method which attempts to replicate realistic disposal conditions. As discussed later, the disposal environment will be characterized by virtually zero groundwater flow, so these experiments are generally closed-system, static leaching tests. Data are produced in the form of individual element concentrations in solution as a function of time, temperature, solid to fluid ratio, and so on. This second type of experiment is the only reliable means of providing data for release modelling and, as many authors have pointed out (e.g. Ogard and Bryant, 1982; Savage and Chapman, 1982), data on bulk leach rates from flow-through tests should not be applied to realistic safety assessments. The leaching of various waste forms has been very intensively studied and is now quite well understood.

ENVIRONMENTAL IMPACT FROM GEOTECHNICAL CONSTRUCTIONS

• Based on site specifics– Actual availabilities including variations– Hydrogeologic characteristics– Design of the construction in question

• Based on generics– WHO criteria for drinking water– Limits for oral intake– ICRP e t c statements on external radiation

DISPOSITION









HEAPS AND LAGOONS –- REMEDIATION

RECLAMATION• Mixing with other

material (e g sewage sludge) usually requiredto avoid dust and promotevegetation

• Balance of nutrients

• Excess of certainelements, e g boron

DISPOSITION









DESTINATIONS FOR COAL ASH – UKSource: Woolley G R, Simpson D T Quick W and Graham J: Ashes to Assets

Fly Ash Bottom Ash Boiler Slag FBC-Ash Other1) SDA-Product FGD-Gypsum1 2 3 4 5 6 7

CCP Production 42.751 6.130 1.980 955 51 505 11.541

Subtotal 1 - 5 51.867Subtotal 6 - 7 12.046Total 1 - 7 63.913

CCP Utilisation Total %Cement raw materia l 1 1082266.5 Cement raw material 5.943 9,2Blended cemen t 2 220004.2 Blended cement 2.422 3,8Concrete additio n 3 5.893 77 197 Concrete addition 6.167 9,6Aerated concrete block s 4 801 14 Aerated concrete blocks 815 1,3Non-aerated concrete block s 5 64681.1603 Non-aerated concrete blocks 1.538 2,4Lightweight aggregat e 6 0 0 Lightweight aggregate 0 0,0Bricks + ceramic s 7 34278 Bricks + ceramics 114 0,2

8gnituorG 36624968 Grouting 1.358 2,19relliftlahpsA 110 Asphalt filler 110 0,2

Subgrade stabilisatio n 10 22601631 Subgrade stabilisation 264 0,4Pavement base cours e 11 469 441 802 46 Pavement base course 1.758 2,7General engineering fil l 12 111193914.1 General engineering fill 1.921 3,0

31lliflarutcurtS 85651746.1 Structural fill 1.861 2,9Soil amendmen t 14 86226 Soil amendment 96 0,1

51llifnI 3479241978 Infill 1.233 1,961tirggnitsalB 330240 Blasting grit 453 0,771noitirtuntnalP 6 Plant nutrition 6 0,0

Set retarder for cemen t 18 625 Set retarder for cement 625 1,0Projection plaste r 19 701 Projection plaster 701 1,1

02sdraobretsalP 4.656 Plaster boards 4.656 7,2Gypsum block s 21 249 Gypsum blocks 249 0,4Self levelling floor screed s 22 1.342 Self levelling floor screeds 1.342 2,1

32sesurehtO 191 21 135 21 2 48 4 Other uses 422 0,7Reclamation, Restoration 24 312.26016030424.2763.81 Reclamation, Restoration 23.416 36,3Temporary stockpil e 25 147.12410634303.3 Temporary stockpile 5.622 8,7

62lasopsiD 0179630935977 Disposal 1.461 2,3Total utilisation 1 - 23 27 20.937 2.736 1.980 471 51 302 7.577 Total utilisation 1 - 23 34.054 52,8Utilisation rate in % 28 48 45 100 49 100 60 66 Utilisation rate in %Average utilisation rate in % 29 53 Average utilisation rate in %Total utilisation 1 - 24 30 39.304 5.160 1.980 777 51 408 9.790 Total utilisation 1 - 24 57.470 89,0Utilisation rate in % 31 91 84 100 81 100 81 85 Utilisation rate in %Average utilisation rate in % 32 89 Average utilisation rate in %Reuse of stockpiled CCP s 33 635 5 0 0 0 0 0 Reuse of stockpiled CCPs 640 1,0

Total production 1-26 incl. reuse 34 43.386 6.135 1.980 955 51 505 11.541 Total production 1-26 incl. reuse 64.553 100,01) cenospheres, fly ash and slag from coal gasification

gro.aboce@ofni:liam-egro.aboce.www:etisbew

ECOBA e.V. Postfach 103932 D-45039 Essen Phone: +49-201-8128 274 Fax: +49-201-8128 364

ECOBA - European Coal Combustion Products Association

Production and Utilisation of CCPs in 2005 in Europe (EU 15) [kilo tonnes (metric)]Source: ECOBA

DESTINATIONS FOR COAL ASH – USTotal generation of coal combustion residues in 2003:

122 Mtons, of which 46 Mtons were utilizeded

Source: US Federal HighwayAdministration and US EPA

DESTINATIONS FOR COAL ASH – US

Source: US Federal HighwayAdministration and US EPA

Effective coal ash utilization by sector in fiscal 2005)snotdnasuoht:tinU(

ltem Electric powerutilities

Generalindustries Total

Sector Contents Amount Ratio (%) Amount Ratio(%) Amount Ratio

(%)5,66890784,8777123,261294lairetamwaRtnemeC33,1241008,1241erutximdA79,030141,0452,199deximydaeR8,86343726,87181253,562615latoT

7,35936,300137,3592tnemtaertlioSskrowcilbuP1,313345,0514613skrowcilbuP42,293242,637148,066rofskrowcilbuP

rewopcirtceleSubgrade stabilization 116 1,47 0 0 116 1,09

80,090011,09relliftlahpsABackfiliing in coal mines 160 2,03 0 0 160 1,5

17,11052183,0188281,21269latoT42,364391,544165,2202draobnoitcurtsnoCnoitcurtsnoC

works Lightweight aggregate 1 0,01 0 0 1 0,013,02370,0283,003tcudorpetercnoC55,397362,564159,2332latoT

Agriculture, Fertilizer & Thawing material 62 0,78 24 0,87 86 0,8177,198128,360150,138tnemevorpmilioS&yrtserof85,257296,403148,1541latoTseirehsif20,0240,0110,01egaweSsrehtO

1,01140,0131,001erutcafunamnorI42,31314179,07255,716831srehtO63,31624150,19296,717931latoT

0013760100147720019987sisehtnyslatoT

ASH utilization in Japan. Source: JCOAL

IMPORTANT PREREQUISITES FOR UTILIZATION

• Suitable health and environment relatedproperties

• Suitable technical properties– puzzolanic properties for concrete, e t c

• Sufficiently sofisticated use to warrantcosts for transportation

• Manageable quality assurance– E g with regard to variations

DISPOSITION









EXAMPLE OF DOSE FROM BUILDING BLOCKS

European Commission, Radiation protection 112, Radiological Protection Principles concerning the NaturalRadioactivity of Building Materials. 1999 Directorate-General Environment, Nuclear Safety and Civil Protection

• For example: a content of 40 Bq kg-1, 30 Bq kg-1 and 400 Bq kg-1 for radium, thorium and potassium, respectively in domestic buildingmaterials gives rise to an annual effective doseby external radiation of about 0,25 mSv

• Enhanced or elevated levels of naturalradionuclides in building materials may causedoses in the order of several mSv/year

• The dose from inhalation of radon, thoron and their short lived decay products is usually not dominating

European Commission, Radiation protection 112, Radiological Protection Principles concerning the NaturalRadioactivity of Building Materials. 1999 Directorate-General Environment, Nuclear Safety and Civil Protection. Continued. Proposed dose criterion.

European Commission, Radiation protection 112, Radiological Protection Principles concerning the NaturalRadioactivity of Building Materials. 1999 Directorate-General Environment, Nuclear Safety and Civil Protection. Continued. Proposed dose criterion.

Where

Swedish Radiation ProtectionAuthority (SSI) requirements

• Total impact from one nuclear site shall not exceed a total of 0,1 MSv/year to person in critical group

• Actual doses are much lower• Total impact from one geotechnical application

of ash from wood contaminated by Cs-137 from Tjernobyl must not exceed 0,01 MSv/year to person in critical group

• Ash at levels > 0,5 kBq/kg of Cs-137 is ”contaminated” and falls under special control

COMPARISON BETWEEN THERMOCHEMICAL ENERGY GENERATION FROM COAL AND WOOD

COAL ASH (EU)• Deliberate use in

building blocks for domestic houses

• Dose 100 % sure• Level of protection

around 1 mSv/year• Added dose from

similar other sourcesnot applicable

WOOD ASH (SSI Sweden)• Inadvertant leakage to

well or uptake in fish• Dose unlikely but difficult

to prove in advance• Level of protection 0,01

mSv/year• Added dose from similar

other sources unlikely butcannot be excluded

ICRP BASIC PRINCIPLES OF RADIATION PROTECTION

(ICRP = International Commission on Radiation Protection)

• JUSTIFICATION: ”Any decision that alters the radiation exposure situation should do more good than harm”

• OPTIMISATION: ”the likelihood of incurring exposures, the number of people exposed and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factors”

Clear violation of both principles

ICRP RECOMMENDATIONS VALID THROUGH OCTOBER 2007

• ”Some human activities increase the overall exposure to radiation. The Commission calls these human activities’practices’.

• Other human activities can decrease the overall exposure by influencing the existing causes of exposure. The Commission describes these activities as ’intervention’.”

NEW RECOMMENDATIONS (DRAFT)• “Planned exposure situations are situations

involving the planned introduction and operation of sources. …

• Emergency exposure situations are unexpected situations that occur during the operation of a planned situation, or from a malicious act, requiring urgent action.

• Existing exposure situations are exposure situations that already exist when a decision on control has to be taken, including natural background radiation and residues from past practices that have been operated outside the Commission's recommendations, or long-term exposure situations.”

Corresponds to ”dose constraints”

Corresponds to ”reference level”

NEW ICRP RECOMMENDATIONS - DRAFT(National regulations may become stricter)

To be selected between 1 and 20 mSv/year according to the situation

From 0,1 mSv/yearunless the benefit to society is minor (dose to the public)

reference leveldose constraints

Existing exposure situations (e g coal ash utilization)

Planned exposure situations (e g nuclear power plant operation)

DISPOSITION









DISPOSAL OF NON-RADIOACTIVE WASTE• Focus on the acute problems of today:

– Gas generation– Leach water management

• Present methodologies for covering landfillsinadequate or unproven for long term– Plastic sheets – rupture during differential settlements– Bentonite mats - rupture during differential

settlements– Natural clay material – locally available only in certain

areas (large volumes are required)– Biofuel and coal ash – few international studies

Example of Tveta Landfill Cover Project

Use of ashes from wood-based fuel

PROPERTIES OF INTEREST

• Curing to a moderately strong but ductilematerial

• Fairly low permeability – meets standards for landfills for non-hazardous waste

• Fair absorption of heavy metals• Properties improve with time• High pH in pore water initially• pH in pore water around 9 after a few

years

NUCLEAR WASTE MANAGEMENT. Source SKB

COMPARISON PORTLAND CEMENT – ASH CEMENT

PORTLAND CEMENT• High pH in porewater,

high buffer capacity• Distorts groundwater

chemistry in surrounding rock

• Converts bentonite to non-swelling minerals

• Consumtion of new resources

ASH CEMENT• Moderately high pH in

pore water• Compatible with

groundwater chemistryin surrounding rock

• Compatible with bentonite

• Use of recycledmaterial

DISPOSITION









SOME (TENTATIVE) CONCLUSIONSThermochemical energy generation using coal

• Affects climate• Changes the face of the earth• Generates volumes of ash ≈ 15 % of

coal used• Coal ash may contain various substances

of health and environmental concern• There are reasons to suspect that the

cleanest ashes appear where the awareness and resources are the highest

SOME (TENTATIVE) CONCLUSIONSThermochemical energy generation using coal

• Health and environment standards appearto be more lenient for coal and coal ash as compared to nuclear power

• Coal ash has positive properties in that it can form impervious structures and bind many hazardous substances

• There is room for improvement on – Knowledge on mechanisms for change in the

long term– Use of natural and anthropogenic analogues

properties, volumes and current disposal and re-use of ...very wide areas of solid solution. forms...

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