CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION

OF CEMENTITIOUS WASTE PRODUCTS – AN INDIAN SCENARIO

byR.G. Yeotikar*, R.R. Rakesh, Biplob Paul,

T.P. Valsala, Ajay Shirole and Dilip Kumar Chaudhari

Bhabha Atomic Research Centre,INDIA

*E mail- yeotikar@barc.gov.in

2

Layout of presentation

• Aims and objectives of CRP

• Works planning in details & future works to be carried out for CRP

• Practices followed for cementation

• Some of the results of cementation work

• Expected result / outcome of CRP

3

Aim & objectives of CRP-1

• Preparation of cement waste products (CWP) on laboratory and plant scale with different cement formulation from :

• Sluges from treatment of LLW• Intermediate level liquid waste• Ion exchange resins• Miscellaneous wastes

• Improvement of CWP

4

• Cement Waste Products (CWPs) for • Chemical durability• Compressive strength• Homogeneity• Micro structure• Biological interaction

• Back fill material

• Site specific material / parameter

• Engineering barriers

Aim & objectives of CRP-2 Long term evaluation

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• Study of cementation and hardening of CWP in presence of

• Various wastes • Different cement compositions • Role of additives during cementation

Aim & objectives of CRP-3

6

Work planning

• Development of CWP having better leaching characteristics and which can have more activity loading.

• Preparation of CWP• Laboratory scale• Plant scale

• Characterization of CWP• Laboratory • Field

• Evaluation of backfill material

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Preparation of CWP on Lab. Scale

Variable• Waste, cement and admixtures• Waste to cement ratio • Admixture to cement ratio• Water / waste to cement ratio

Method• Preparation of number of blocks for each variable at a

time• Casting in moulds • Curing : 28 days • Leaching for 6 to 12 months as per ANSI 16.1 in DM

Water• Leachant vol. /block vol.= 10

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• CWP on 20 liter scale

• CWP on 200 liter scale

• Taking the sample of CWP during in-situ cementation

• Core drilling of few samples from in-situ cementation

Preparation of CWP on Plant Scale

9

TYPES OF CEMENTS

• Ordinary Portland cement (opc) • ASTM type 1. OPC

• Slag based cement (SBC)

• Fly ash cement

• High alumina cement

• Blended cements

OPC clinker + gypsum + admixtures

- ground together

Component Weight % in

OPC TYPE I

SLAG BASED

CEMENT

BLENDED CEMENT

SiO2 20-24 34.10 27.8

Al2O3 3-8 14.15 13.3

CaO 60-65 36.04 47.6

MgO 0-2 11.21 5.2

Fe2O3 3-8 0.56 2.3

SO3 1-4 1.20 1.2

Sulphide - 0.22 -

General composition of the different cements

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ADMIXTURES• Inorganic admixtures

– Backfill material– Bentonite– Vermiculite– Silica fumes– Precipitated silica

– Clay – Rock powder

• Organic admixtures- water reducing chemicals such as – Platilcisers– Super plasticisers

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Characterization of CWP

• Leaching characterization• Mechanical properties

• Compressive strength

• Homogeneity • XRD analysis• Pore size distribution• Microscopy –optical & SEM

• Others • Hydraulic conductivity• Accelerated diffusion test

• Instrumental methods

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Instrumental methods of characterisation of CWPS

Aim • To correlate the compressive strength, porosity, diffusion coefficient, permeability and leaching characteristics with respect to composition

• To shortlist CWP for leaching test

• To track the mineralogical changes with time after simulated disposal in NSDF

• To identify mechanisms of hardening, strength development/ deterioration etc.

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Field test characterization • Disposal of CWPs in earth trench in NSDF• Removal of CWPs periodically (once in two

years) and examination for :– Surface for cracks, chip off, color change etc.– Rebound hammer test – Homogeneity – Compressive strength– Hydraulic conductivity – Porosity – Mineralogical changes– Chloride penetration– Depth of carbonation – Change in diffusion coefficient

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Long term Leaching characterization of CWP

• Laboratory scale CWP blocks in DM water

• Leaching of 200 lit CWP block

• Dynamic leaching of CWP

• Simulation of radiolysis of water - leaching

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400 LITRE STEEL CONTAINER

200 LITRE CWP

LEACHANT 200 L;ITRES

WITH AND WITHOUT DECAYING WOO

LIFTING HOOKS

LID

SUPPORTS

LONG TERM LEACH TEST OF 200 LITRE CWP

PROPOSED SET UP

collector

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• At one such location – Trombay

• Simulated CWPs of different sizes have been disposed in 2001.

• The location is having sandy silt with appreciable content of montmorillonite clay

• Similar experiments have been planned in other locations having different strata such as black cotton soil and sandy soil.

Field test characterization-disposal CWP in NSDF

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Field test characterization-disposal CWP in NSDF

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20

20 litre blocks

0.2 litre blocks

basalt

degraded basalt

Clay

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Characterization of CWPs after excavation

• Compressive strength,• MIP, XRD, SEM, • Analysis of soil adhering to CWP • Rebound hammer tests• Ultrasonic tests

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Depth (m) Type of soil/rock

0 - 2.0 Black cotton plastic soil

2.0 - 10.0 Weathered basalt

below 10.0 Hard igneous basalt

Geological Succession of the area

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A typical geological section of the RSMS area

Ref. : Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.

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Parameters Values

Bulk density (g/cc) 1.7

Porosity (%) 30.0

Radionuclides Kd (ml/g)

137Cs 600 – 1000

90Sr 140 – 300

PHYSICAL AND GEO-CHEMICAL PROPERTIES OF THE SITE

The representative physical properties such as density and porosity has been presented in Table 1.

The distribution coefficient values of soil samples obtained from RSMS site[2] were analysed and are presented in Table 2.

Table 2: Distribution coefficient of the soil

Table 1: Physical Properties of the soil

Ref: Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.

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Property Soil sample

T1(at 1 m depth)

T2(at 2 m depth)

(g/cc) 1.60 1.88

w (%) 26.6 29.0

d (g/cc) 1.26 1.46

G 2.82 2.70

e 1.24 0.85

Sr (%) 60.5 92.1

Particle size distribution characteristics:

Coarse sand (4.75-2.0 mm.) 15 23

Medium sand (2.0-0.420 mm.) 29 25

Fine sand (0.420-0.074 mm.) 17 15

Silt size (0.074-0.002mm.) 21 16

Clay size (<0.002mm.) 18 21

Consistency limits:

L.L. (%) 41 49

P.L. (%) 17 35

P.I. (%) 24 14

S.L. (%) 30 26

Specific surface area (m2/g) 41 52

Soil classification SM SC

Ref: Rakesh R.R. 2005. Simulation of radioactive contaminant transport in unsaturated soils, Ph. D. Thesis. Dept. of Civil Engineering, Indian Institute of Technology, Bombay, India.

Properties of soil of RSMS, Trombay

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LONG TERM EVALUATION OF CWPs- Non-Destructive Test (NDT) Procedures

•Ultrasonic Tests• Ultrasonic pulse velocity can be used to determine homogeneity, presence of voids, cracks of CWP • Basic data correlating ultra sonic pulse velocity with density,

porosity and strength will be generated by preparing and testing number of blocks.

•Rebound Hammer Test• Simple and quick method of obtaining correlation between compressive strength and rebound number • The force and pulse duration are critical parameters & will be used on various CWPs of 20 and 200 litre CWPs as quality control measure

•Will be used for disposed CWPs after their removal

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Evaluation of admixture and clay

• Distribution coefficient

• Composition

• Physical properties,

• Chemical properties

TYPICAL SPECIFICATIONS OF VERMICULITE AND BENTONITE

Item Vermiculite Bentonite

Size -30 + 70 Mesh 90 % should pass through 200 mesh

True density (gm/cc) 2.6 – 2.7 2.4 – 2.6

Cation Exchange Capacity (meq/100gm)

40-50 70-100

Chemical Composition

SiO2 (%) 35-40 45-55

Al2O3 (%) 10-12 15-20

Fe2O3 (%) 6-8 3-6

MgO (%) 20-25 3-4

Na2O (%) --- 1-2

H2O (%) 10-15 10-15

Swelling (%) 20-50 100-250

Porosity (%) 50-60 40-60

Evaluations of admixtures for their sorption characteristics

Mineral Kd (ml/g) in Synthetic Granitic water

137Cs 85+89Sr

Bentonite 1460 665

Apatite 117 215

Calcite 111 237

Galena 7.6 420

Red mud 141 320

Pyrite 82 185

Vermiculite 4250 365

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Evaluation of bentonite for particle size distribution

Majority of particles are in the range of 100- 500 microns

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Evaluation of bentonite for swelling behavior

Bentonite

Type

Equilibrating media

Initial

Volume

(ml)

Final

Volume

(ml)

Swelling

%

Sodium Tap

water

10 30 200

Sodium Dist.Water 10 35 250

Calcium Tap

water

10 30 200

Calcium Dist.Water 10 38 280

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• Swelling is complete in 8-10hrs.• The swelling is of the order of 200-280 %.• The swelling is more in distilled water than in

service water : due to replacement of Ca ions from bentonite in the distilled by water molecule

• The swelling is more in case of calcium bentonite than sodium bentonite : Replcement of bigger Ca ions by water molecule

• Swelling gets enhanced due to exchange of Ca and Na ions with water molecule

Evaluation of bentonite for swelling behavior

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Evaluation of bentonite for thermal stability

•The heat treated and un-heat treated bentonites in the range 300-500 oC show comparable swelling.

•In DTA run there are two major endo peaks at 100 and 450oC corresponding to free and bound water loss.

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Evaluation of bentonite for water equilibration

Shaking time, hrs

pH Conductivity, microS/cm

Hardness as CaCO3 ppm

Sodium, ppm

Chloride

ppm

Silica,

ppm

4.5 7.55 4562 837 NA 310 NA

10 7.47 5750 962 NA 350 NA

15.5 7.48 6325 1075 NA 250 NA

22 7.7 6525 1185 NA 225 NA

27 7.78 7050 1500 NA 385 NA

37 7.66 6100 1400 700 300 25

49 7.46 6400 1380 720 300 35

61 7.16 6300 1390 790 305 35

73 7.7 7000 1620 730 300 37

85.5 7.8 6500 1350 720 350 35

87.5 7.85 6400 1370 750 300 35

Water gets saturated very fast and thereafter no marked change

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Evaluation of vermiculite for particle size distribution

About 90 % of the particle size distribution is in the range of -16 to +80 ASTM mesh.

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Evaluation of vermiculite for Cs loading

There is structural change in the vermiculite due to Cs loading.

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Evaluation of vermiculite for thermal stability

DTA runs of as such and heat treated vermiculite indicate that the vermiculite is thermally quite stable.

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Micro organisms of interest for degradation Study on cement waste products

Micro organism Reactivity Effect on cement matrix

Nuclear waste matrix

Thiobacillus concretivorus, T. Thiooxidans and t. Ferrooxidan

Oxidation of sulphur compound to sulphuric acid

Calcium sulphate formation leads to increased volume and cracking

Cationic resin waste (R-SO3H)

incorporated into SBC

Pseudomonas cepacoa Heterotropic

Produce organic acid from decaying organic matter

Complex calcium in pore water

All CWPs disposed in NSDF in humid environment

Nitrosomonas and nitrobactor

Oxidise inorganic nitrogen compounds to nitric acid

Neutralise Ca(OH)2

in pore water

Anionic resin (R-CH2-N(CH3)3OH)

wastes incorporated in SBC

Bio-degradation of CWP

1. Identification of cement degrading bacteria in NSDF soils

2. Flow test on 60 ml size CWP &

3. Characterization of degraded CWP

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Practices followed for Cementation of various types of Radioactive Waste in India

• Cementation is carried out at various locations for immobilization of – Sludge generated due to LLW treatment– Intermediate level wastes– Ion exchange resins– Miscellaneous wastes

• Techniques of Cementation at plant scale – In drum mixing – Conical Mixture Equipment and pouring the CWP in

200 lit drum.– In-situ cementation in 4000 lit capacity in CS tank in

RCC trenches.• Admixtures used - Vermiculite

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In-situ Conditioning of ILW and Sludge of LLW in Cement Matrix at Tarapur

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CONE MIXER ASSEMBLY USED FOR CEMENTATION

CURRENT CWPs FOR IMMOBILISATION OF NUCLEAR WASTES

WASTECEMENT TYPE WASTE TO

CEMENT RATIO

COMP. STRENGTH

( kg/cm2)

137Cs LEACH RATE

(g/cm2/d)

LLW SLUDGES/ ASHES/MOL. SIEVES

OPC 1.2 TO 10.4 TO 1

70 TO 100 Cs 10-4 Cs 10-6

HIGH Na ILW OPC/SBC BLENDED

1 ~ 1.2 TO 1 1.1 TO 1

45 TO 7095 TO 100

Cs 10-5

Cs 10-6

Na FORMATE ILW OPC/SBC 0.65 TO 1 95 TO 105 Cs- 10-5

IX RESINS* SBC 0.35 ~ 0.8 TO 1 50 TO 63 Cs- 10-4

IX RESIN PYROLYSIS RESIDUE*

OPC 0.6 TO 1 70 TO 75 Cs- 10-5

LUBRICATING OILS (ΑLPHA)

OPC 0.55 TO 1 30 TO 60 Cs- 10-5

α 10-7

TBP HYDROLYSIS PRODUCTS

OPC 0.6 TO 1 60 TO 70 β 10-6

α 10-7

ΑLPHA SLUDGES OPC 1.2 TO 1 50 TO 70 β 10-5

AVAILABLE FACILITIES

Cementation techniques Near surface disposal facility (NSDF)Radiological lab. Compressive strength testing unitAccelerated diffusion test unitXRD & XRF Optical microscope & SEM-EDXIon chromatograph & AASMercury intrusion porosity (MIP) unitPore water analysisFTIRImpedance spectroscopyGas chromatograph

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Some of the results of cementation

• Evaluation of cement composition

• Optimization of waste to cement ratio

• Sampling of CWP during plant scale

• Evaluation of CWP from plant scale and comparison of result with laboratory

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Block details OPC + 20 % Vermiculite

SBC Sample from conditioning tank

Core drilled sample from conditioning tank after 60 days

Cured for 14 days

Cured for 28 days

Leaching in DW

Leaching in GW

Waste to cement proportion 1:1.3 1:2 1:1.3 1:1.3 1:1.3 1:1.3

Diameter, cm 2.9 2.9 5.2 5.3 5.15 5.15

Height, cm 2.0 2.4 7.3 6.7 2.43 2.57

Surface area, cm2 31.20 35.06 156.75 155.7 80.93 83.2

Weight, g 24.1 28.99 264.0 257.0 80.0 83

Total βγ activity in the block, MBq

12.787 12.787 99.26 91.21 30.08 37.84

Contact dose rate, mSv/hr 1.0 1.0 2.82 3.0 1.0 1.1

Volume of block, cm3 13.2 15.8 154.95 147.74 50.59 53.5

Volume of leachant, cm3 315 350 1500 780 810 830

Compressive strength, kg/cm2 40-45 4.-45 20-25 35-40 35-40 35-40

Leach Rate, g/cm2/d x 10-5 1.25 2.01 1.9 0.94 1.25 1.0

Ref : A.S. Pente, U.S. Singh, C. P. Kaushik, R.G. Yeotikar, A. Mishra and S.S. Ali., “Cementation study of Intermediate Level radioactive liquid waste stored at Tarapur”, Proc.: Nuclear and Radiochemistry Symposium (NUCAR-2001), Department of Chemistry, University of Pune, Pune, India, Feb. 7-10, 2001, pp 540-541 .

Cement composition evaluation for immobilization of ILW*

* Specific activity of ILW : 1000 MBq/l

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Properties of CWPs of immobilisation of various types of nuclear waste

WASTECEMENT TYPE WASTE TO

CEMENT RATIO

COMP. STRENGTH

( kg/cm2)

137Cs LEACH RATE

(g/cm2/d)

LLW SLUDGES/ ASHES/MOL. SIEVES

OPC 1.2 TO 10.4 TO 1

70 TO 100 Cs 10-4 Cs 10-6

HIGH Na ILW OPC/SBC BLENDED

1 ~ 1.2 TO 1 1.1 TO 1

45 TO 7095 TO 100

Cs 10-5

Cs 10-6

Na FORMATE ILW OPC/SBC 0.65 TO 1 95 TO 105 Cs- 10-5

IX RESINS* SBC 0.35 ~ 0.8 TO 1 50 TO 63 Cs- 10-4

IX RESIN PYROLYSIS RESIDUE*

OPC 0.6 TO 1 70 TO 75 Cs- 10-5

LUBRICATING OILS (ΑLPHA)

OPC 0.55 TO 1 30 TO 60 Cs- 10-5

α 10-7

TBP HYDROLYSIS PRODUCTS

OPC 0.6 TO 1 60 TO 70 β 10-6

α 10-7

ΑLPHA SLUDGES OPC 1.2 TO 1 50 TO 70 β 10-5

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Cementation of IX resins

• Different Waste to cement ratio

• Properties of cement matrix• Homogeneity • Pore size distribution• Diffusion phenomenon• Leaching evaluation• Mineralogical examination

Mineral phases detected by XRD analyses of CWP using SBC incorporating IX resins

IX Resins Waste

Mineral phases detected

Cationic Calcium silicate hydrate, calcite, phosphate, silicate, sulphide

Anionic Calcium silicate hydrate, calcite, silicate,

Mixed Calcium silicate hydrate, calcite, phosphate, silicate,

PORE SIZE DISTRIBUTION OF CWP

ab

(a) IX RESINS IN SBC(b) ILW IN BLENDED CEMENT

1E-3 0.01 0.1 1 10 100

0

20

40

60

80

100

Per

cen

t T

ota

l

Pore Diameter (Micron)

Cationic Resin Aninic Resin Mixed Resins

1E-3 0.01 0.1 1 10

0

20

40

60

80

100

Blended Cement-ILW Matrix OPC-ILW Matrix

Per

cent

Tot

alPore Diameter (micron)

Void*

OPTICAL MICROSCOPY

CWPs incorporating IX resin

* FORMED DUE TO SHRINKING OF RESIN CAUSED BY LOSS OF WATER TO CEMENT HYDRATION

COMPARION OF 137CESIUM LEACHING WITH PHYSICAL CHARACTERISATION OF

CWPs INCORPORATING IX RESINS

IX Resins

137Cs Leach rate (g/cm2/d)

Diffusion Coeff. by 137Cs leaching (cm2/s)

Diffusion Coeff. by Ώ measure-ment (cm2/s)

Hydraulic condu-ctivity(cm/s)

Pore vol. by MIP (ml/g)

Comp. stren-gth(kg/cm2)

Mixed Resins

6.5x 10-4 5 x 10-9 3.12 x 10-8 3.21 X 10-9 0.20 56

K+ Resins

5 x 10-4 6 x 10-9 2.06 x 10-8 4.98 X 10-9 0.24 50

Borated Anionic Resins

3.6 x10-4 4 x 10-9 4.57 x 10-8 2.3 X 10-9 0.16 60

CHARACTARISATION OF FULL SIZE INACTIVE CWP INCORPORATING IX RESINS USING SBC

CORE DRILLED CWP

CORE SAMPLES

EXPECTED OUTCOME OF CRP WORK-1

• Development of improved cementitious waste products (CWP)

• Addition of admixtures• Modification of technique

• Complete characterisation of CWP• Understanding the mechanism of static and dynamic

leaching in presence of various components.• Finalisation of composition of cement for

immobilisation of various wastes e.g.• ILW• Sludge from treatment of LLW• Miscellaneous wastes• IX resins

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EXPECTED OUTCOME OF CRP WORK-2

• Development of Instrumental techniques of characterisation of CWP

• Development and calibration of NDT Techniques for evaluation of CWP

• Ultrasonic tests• Rebound hammer tests

• Carry out field tests at different locations and co-relation of various results.

• Long term study of CWP with respects to following which can provide information for further improvement

• Bio degradation in various environment• Radiation stability

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EXPECTED OUTCOME OF CRP WORK-3

• Understanding of behaviour of container material in presence of backfill and other geological material, e.g

• Soil • Ground water• Interaction with backfill, CWP and others

• Evaluation of various candidate container material• Evaluation of CWP source term for migration study• Understanding hardening and other physico-chemical

aspects of cementation which will be helpful for improvement

THANKS