Research Coordination Meeting on CRP

“Behaviour of Cementitious Materials in Long-TermStorage and Disposal of Radioactive Waste”

(Romania, November 24-28, 2008)

CEMENTATION OF CERTAN TYPES OF LIQUID RADIOACTIVE WASTE OF

RADIOCHEMICAL PLANT

L. Sukhanov. P. Poluektov, K. Zakharova, O. Khimtchenko, Yu.Matyunin

A.A. Bochvar Research Institute of Inorganic Materials, Moscow

Research Coordination Meeting on CRP

“Behaviour of Cementitious Materials in Long-TermStorage and Disposal of Radioactive Waste”

(Romania, November 24-28, 2008)

CEMENTATION OF CERTAN TYPES OF LIQUID RADIOACTIVE WASTE OF

RADIOCHEMICAL PLANT

L. Sukhanov. P. Poluektov, K. Zakharova, O. Khimtchenko, Yu.Matyunin

A.A. Bochvar Research Institute of Inorganic Materials, Moscow

Individual project of Leonid Sukhanov

(A.A.Bochvar Research Institute) 

  Subject: Cementation of certain types of liquid ILW

generated from SNF reprocessing at radiochemical combine PA Mayak, Urals

Cementation of pulps from storage tanks of the radiochemical combine MCC (Mining and Chemical Combine), Siberia

 

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MAIN OBJECTIVES AND SCOPE OF INDIVIDUAL PROJECT

Studying processes that occur during production of the cement compounds generated during solidification of some kinds of liquid RW of radiochemical combines - PA Mayak, Urals and MCC, Siberia

Determining of cement compound characteristics (mechanical strength, water resistance, frost resistance, flowability, heat release, loading capacity of waste and others)

Giving recommendations for operation of a commercial facility for production of cement compounds satisfying waste acceptance criteria and national requirements

Assessing behaviour of the produced cement compounds during their storage 3

PLANNED INVESTIGATIONS FOR THE FIRST YEAR -

- cementation of evaporator concentrates and

pulps of PA Mayak

Under this work, special emphasis will be given to: cementation of salt solutions containing hydroxide

sludge production of high-flowable cement compounds cementation of spent filter materials pulps

The researches were carried out using the equipment,

instruments, personnel and materials

of A. A. Bochvar Research Institute.

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Evaporation, Rectification

Ammonia solution

Acidic decontamination solutionAcidic rafinate from extraction

Concentrate from membrane-sorption LLW treatment

Evaporation bottom

Re-evaporation

CondensateNitric acid

Ammonia solution

Purification Evaporator concentrate

Cement compound

Cementation

Long-term storage (disposal)

Tritium containing waste

Ion-exchange resin pulpsFilter perlite pulpsManganese dioxide pulps

PA Mayak’s liquid RW planning to send to cementation

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SPECIFIC FEATURES OF PA MAYAK’S LIQUID ILW THAT HAVE EFFECT ON CEMENTATION PROCESS

PARAMETERS A variety of different types of liquid wastes,

specifically:- salt alkaline waste (3 types) and acid waste (2 types) - liquid tritium waste

- pulps of filter materials and hydroxides (4 types)

Certain components present in LRW can significantly influence the liquid ILW treatment scheme and, specifically, the cementation process and properties of a produced cement compound (iron hydrooxide, ammonia, nitric acid, tritium, etc.)

The cement compound will be stored not in drums or other containers, but in concrete compartments of a storage facility (the volume of each compartment is about 380 m3)

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REQUIREMENTS FOR CEMENT COMPOUNDS AT PA MAYAK REMENTATION COMPLEX

The produced cement compound quality must satisfy:

The National Standards: – GOST R 51883-2002 “Cementitious Radioactive

Waste. General Requirements“ – NP-019-2000 “Reguirements to liquid RW

Management”

Additional requirements: sufficient flowability to ensure uniform filling of

storage facility compartments low heat release during the compound solidification

in storage facility compartments

maximum loading capacity of a cement compound

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NATIONAL STANDARD REQUIREMENTS FOR CEMENT COMPOUNDS

Quality index Permitted value

Specific activity of compound: Beta-activity

Alpha-activity

<3.7·1010 Bq/kg (1·10-3 Ci/g)<3.7·107 Bq/kg (1·10-6 Ci/g)

Leaching rate of radionuclides(Cs-137 and Sr-90)

<1·10-3 g/cm2·day

Mechanical strength (compressing strength) >50 kg/cm2

Radiation resistance

Mechanical strength should be not less than 50 kg/cm2 at a radiation dose of 1 mln Gy *

Thermal cycle resistance

Mechanical strength should be not less than 50 kg/cm2 after 30 freezing-thawing cycles *

Water resistance Mechanical strength should be not less than 50 kg/cm2 after 90 days of being in water *

* but not less than 75% of initial strength8

RESEARCH METHODOLOGY Sample Preparation

The cement paste made through mixing the components by using the laboratory-scale equipment is placed into the device designed for preparation of cement compound samples. The device represents a dismountable cartridge (cassette) consisting of several cells (molds) to allow making cement cubes 2×2×2 cm in size.

The device is placed in a humid-air atmosphere in an exsiccator with water at the bottom to prevent desiccation (drying).

When held for 28 days, the samples were taken from the cells for further analyses.

Radionuclides used for RW simulation are Sr-90, Cs-137 and tritium. 9

RESEARCH METHODOLOGY

Matrix Materials 

In most experiments a mixture of Portland cement (Grade

PC500-D0) and bentonit was used as a matrix material.

The content of bentonit in the matrix material in all the

experiments was 10 wt %. Bentonit, which was introduced

from a cement compound being in contact with water, acted

as a sorbent to reduce leachability of radionuclides,

primarily Cs-137.

The Slag Portland cement, a mixture of Portland cement

and metallurgical slag, was used in a number of

experiments. 10

RESEARCH METHODOLOGY Determination of Ultimate Compressive Strength

Ultimate compressive strength is determined by means of a hydraulic press using the standard procedure.

Cement Paste Plasticity TestPlasticity of a cement paste is characterized by degree of

its flowability (spreadability) measured by the viscosimeter using the standard procedure.

Frost resistance Frost resistance is determined by the procedure, which

included 30 freezing/thawing cycles.

Immersion Tests Water resistance is determined by comparison of the

strength of the samples held in water for 90 days to the strength of the reference samples held in the air under room conditions.

Long-Term Leaching Tests of Cement CompoundsA degree of radionuclide fixation in a cement compound is

determined by the rate of radionuclide leaching and by the activity that passed into a solution from a cement compound. 11

Measurement of Cement-Paste Flowability Molds for Preparation of Cement by Suttard’s Viscosimeter

Measurement of Cement-Paste Flowability Molds for Preparation of Cement by Suttard’s Viscosimeter

EXPERIMENTAL TECHNIQUES AND EQUIPMENT

Compound Samples12

Hydraulic Press for Testing of Cement-Compound Sample Strength Hydraulic Press for Testing of Cement-Compound Sample Strength

EXPERIMENTAL TECHNIQUES AND EQUIPMENT

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Apparatus for Determination

of Cement Hydration Heat

EXPERIMENTAL TECHNIQUES AND EQUIPMENT

-,-Radiometer UMF-200014

EXPERIMENTAL TECHNIQUES AND EQUIPMENT

Exiccator for Damp Curing of Cement Compound Samples

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RESEARCH SUBJECT

The following solutions and pulps simulating

different liquid RW of PA Mayak were under

consideration:

• salt solutions with iron hydrate sludge

• filter-material pulps

• mixture of hydrated-salt sludge and filter-material pulps

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CEMENTATION OF HYDRATED-SALT SLUDGEAssessment of the effect of a compound composition on

flowability of cement-paste and mechanical strength of a solid product

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Composition of hydrated-salt sludge,

g/l

Composition of

compound, % by mass

Waste/

Cement

Water/

Cement

Loading

capacity

of compou

nd,% by mass

Flowabi-lity

of compou

nd,mm

Mechanical strength

of cement compound

[comp]

Fe(OH)3

Na2SO

4

NaNO3

Sludg

e

Cement

Time,days

[comp],kg/cm2

30 30 240 59.5 40.5 1.47 1.1 15.0 1202851360

353245

30 30 240 57.1 42.9 1.33 1.0 14.1 1102851360

344055

30 30 240 54.5 45.5 1.2 0.9 13.6 9028330

5295

15 15 270 54.5 45.5 1.2 0.9 13.6 1403263159

324973

15 15 270 40 60.0 0.67 0.5 10.0 702856

155169

CEMENTATION OF HYDRATED-SALT SLUDGEAssessment of the effect of a compound composition on

flowability of cement-paste and mechanical strength of a solid product

Findings of the experiments: The waste/cement ratio is the key factor that influences the flowability of the cement paste and mechanical strength of obtained compound

If waste/cement ratio decreased, the cement-paste flowability drops considerably and the mechanical strength increases.

When the waste/cement ratio was ~1.5 (water/cement ratio equals 1.1), the mechanical strength does not reach required standardized even within a year. With smaller values of waste/cement ratio (water/cement ratio), the samples develop necessary strength, but very slowly

Reduction of the iron hydroxide content in a cement compound, other conditions being equal, results in increase of the cement-paste flowability, but is of little influence on mechanical strength of a compound

Decrease of the water/cement ratio to 0.5 results in notable increase of strength, but in this case the cement paste practically loses flowability.18

CEMENTATION OF HYDRATED-SALT SLUDGE

Assessment of the effect of sludge age on cement compound quality

• Sludge composition: Fe(OH)3 – 30 g/l, Na2SO4 – 30g/l, NaNO3 – 240 g/l • Waste/cement ratio – 0.67, water/cement ratio – 0.5, • Loading capacity of cement compound – 19 wt %.

Age of sludge,

days

Flowability of

cement compoun

d,mm

Mechanical strengthof cement compound

Holding time, days

[comp],kg/cm2

No holding

157 120 275

5 130 250 35010 70 235 28816 40 235 350

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CEMENTATION OF HYDRATED-SALT SLUDGE

Continuation

Assessment of the effect of sludge age on quality of a cement compound

Findings of the experiments: With increasing age of the hydrated-salt sludge, the cement-paste flowability drops, and the mechanical strength variation does not show a clearly defined tendency. Furthermore, in all cases the mechanical strength is much higher than the standardized required value.

During preparation of a cement compound, the false setting effect was observed. On further mixing, this effect disappears. The false-setting start time varies depending on composition of solution, its age and the mixing conditions.

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CEMENTATION OF FILTER MATERIAL PULPS

Filter material pulps contents: • spent ion-exchange resins (IER) •spent filter perlite (FP)• manganese dioxide sludge.

IER is the mixture of cation and anion exchange resins in the ratio of 1:1 by weight

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Assessment of loading capacity of cement compounds

Content of components in

pulp, wt %Waste

/CWater

/C

Loading capacity of

cement compound,

wt %

Mechanical strengthof cement compound

IER FP MnO2Holding time,

days[comp],kg/cm2

13.2 7.3 - 0.83 0.66 9.442

112129122

13.2 7.3 - 1.13 0.90 10.942

11265

102

13.2 7.3 - 1.70 1.35 13.028

6802540

7.8 4.3 0.65 0.58 0.50 4.631

540250285

6.8 3.8 0.60 0.65 0.58 4.429

525240300

6.8 3.8 0.60 0.78 0.65 6.929

520240235

CEMENTATION OF FILTER MATERIAL PULPS

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CEMENTATION OF FILTER MATERIAL PULPSAssessment of optimal loading capacity of cement

compounds Continuation

Findings of the experiments:

During cementation of filter-material pulps (water/cement ratio – 0.9), the loading capacity of a cement compound should not exceed 10 wt % of the solid pulp components to prevent significant reduction of mechanical strength of cement compounds. With smaller cement-compound loading capacity and water/cement ratio, the samples are developing the strength that exceeds the required standardized value even within a month.

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CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

 Assessment of the effect of the superplasticizer and the method of its introduction on cement-paste flowability

Sample composition:

• Fe(OH)3-15 g/l

• Na2SO4-19 g/l

• NaNO3-18.5 g/l • IER -66 g/l• FP - 36 g/l

Pulp/cement ratio - 1.0

Loading capacity - 7 wt %24

CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS 

Continuation Assessment of the effect of the superplasticizer and the method

of its introduction on cement-paste flowability

Findings of the experiments: Presence of the plasticizer in the pulp and the plasticizer-introduction method have no significant effect on flowability.

Method of С-3 Introduction

without С-3Introduction

of С-3 into PulpIntroduction

of С-3 into Cement Paste

рН 7 8 10 12 7 8 10 12 7 8 10 12

Flowability,

mm

103

103

190

190

180

180

224

205 164 220

178

176 -

175

175 200

175

175 -

MechanicalStrength

comp, kg/cm2 120 110 -

113

113 - - 125 - 130 127 113 130

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CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

Assessment of the effect of pulp age and pH on cement-paste flowability and cement-

compound strength

Pulp composition:• Fe(OH)3-28.6 g/l

• Na2SO4- 24.2 g/l

• NaNO3 - 24.6 g/l• IER - 66 g/l • FP - 36.3 g/l Pulp/cement ratio - 0.85 (equivalent of the water/cement ratio of 0.72)

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CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

Continuation Assessment of the effect of pulp age and рН on cement-paste flowability and cement-compound strength

Pulp рН

Pulp Age, days

Flow-ability,

mm

Mechanical Strength

comp in 35 days, kg/cm2

7 1 75 1857 3 93 1957 10 88 1257 21 133 1187 31 138 1457 3 145 1677 10 105 1857 21 128 1367 31 129 128

12 1 116 155 27

Continuation Assessment of the effect of pulp age and рН on cement-paste

flowability and cement-compound strength

Findings of the experiments:

The pulps with рН =7:-the mechanical strength does not practically depend

on the pulp age when cementing.-the flowability of the cement paste with the pulp

aged 10 and less days is somewhat less than that of the cemented pulps aged 21 and 31 days.

With high alkalinity of the pulp (рН =12), increased time of its holding up to one month prior to cementation does not lead to a noticeable change in the cement-paste flowability and the mechanical strength of the cement compound.

CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

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CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

Assessment of the effect of the binder type on characteristics of cement compounds

Pulp composition:•Fe(OH)3-20 g/l

• Na2SO4 -20 g/l

• NaNO3-260 g/l • IER - 66 g/l • FP - 36 g/l

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Binder Type S/BPulp рН

Cement Paste

Flowability, mm

Mechanical Strength

comp in 28 days, kg/cm2

Portland Cement

0.9 10 165 -

Portland Cement

0.9 12 150 225

Slag Portland Cement

0.9 12 145 125

Portland Cement

1.0 12 158 -

Slag Portland Cement

1.0 12 140 130

Portland Cement

1.1 10 195 190

Slag Portland Cement

1.1 10 145 125

CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

Continuation

Assessment of the effect of the binder type on characteristics of cement compounds

Findings of the experiments: Using both Portland cement and Slag Portland cement as a matrix, flowability and mechanical strength of cement compounds meet the requirements 30

CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

Frost Resistance and Water Resistance of Cement Compounds with ILW of PA Mayak

Cement compound composition, wt %Frost

ResistanceWater

Resistance

Fe (OH) 3

Na2SO4 NaNO3 IER FP Н2ОBinde

r

comp

frost,kg/cm2

compwater,kg/cm2

comp

frost,kg/cm2

compwater,kg/cm2

Portland cement ( Grade 500-DO)0.34 0.25 18.6 - - 20.6 60.2 250 280 215 2200.50 0.50 9.0 - - 30.0 60.0 220 210 220 2500.60 0.60 10.8 - - 36.5 51.5 120 120 105 80

- - - 6.0 3.4 36.0 54.6 155 162 120 154

- - - 7.0 3.9 42.1 46.0 75 72 102 950.80 0.80 10.8 2.7 1.5 33.4 50.0 154 178 - -

0.90 0.90 11.3 2.9 1.6 34.8 47.6 138 152 157 160

Slag Portland cement0.80 0.80 10.3 2.6 1.4 31.5 52.6 225 238 170 205

0.80 0.80 10.8 2.7 1.5 33.4 50.0 196 191 120 158

0.90 0.90 11.3 2.9 1.6 34.8 47.6 103 132 146 162

0.80 0.80 10.3 2.6 1.4 31.5 52.6 162 140 168 195

* compfrost, compwater - mechanical compressive strength of the samples tested for frost resistance and water resistance, and mechanical compressive strength of the reference samples

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CEMENTATION OF MIXTURE OF HYDRATED-SALT SLUDGE AND FILTER-MATERIAL PULPS

ContinuationFrost resistance and water resistance of cement compounds

with ILW of PA MayakFindings of the experiments

The all solidified samples have the required frost resistance and water resistance

The investigations on the frost resistance and water resistance of the cemented ILW of PA Mayak showed that the ability of the samples to withstand multiple freezing/thawing cycles was sharply dropped if the test samples failed to reach not less than 75 % of the final strength value

Therefore, testing of the samples with 28 days holding (as provided for by the National Standard), often leads to negative findings (important for methodology of cement compound testing)

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CEMENTATION OF TRITIUM-CONTAINING LRW

 

Sample Composition,

wt %

Tritium fraction of (… ×10-3 %) washed out from the sample within one day after different periods of cement compound hardering0-1 days 1-2

days2-3 days

3-7 days

7-14 days

SPC – 66.5, water – 33.5

2.4 1.4 0.8 0.5 0.4

PC – 28.5, clinoptilolite – 51.5, water – 20.0

4.7 2.4 1.4 0.5 0.4

MgO – 43.0, MgSO4 –14.0, H2O – 43.0

5.0 3.2 1.8 1.6 1.7

Amount of Tritium Transferred to Contact Water from Cement Compounds with Waterproof Coat within One Day

33

CEMENTATION OF TRITIUM-CONTAINING LRW

 

Findings of the experiments:

Within the first days of the contact, as revealed by all the experiments, the tritium leaching rate was equal to 1×10-4 g/cm2 day. In three days the tritium losses are reducing

The degree of tritium retention in the magnesia-compound-based samples is somewhat less than that when using SPC and PC

ContinuationAmount of Tritium Transferred to Contact Water from

Cement Compounds with Waterproof Coat within One Day

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CONCLUSION AND RECOMMENDATIONS:

A set of the experimental data has been obtained on characterization of the process of cementation of liquid ILW resulting from the reprocessing of PA Mayak’s SNF (hydrated-salt sludge, filter-material pulps and their mixtures0. Using the simulated LRW, it has been shown that the quality of the produced cement compound meets the national standard requirements if the Portland cement and Slug Portland cement are used as the matrix materials.

Next steps in period 2009-2010 to be taken: using the pilot facility, the technological process conditions will be developed and tested for a commercial cementation facility to provide the large-scale production of cement compounds with required quality and flowability to ensure uniform filling of storage facility compartments

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Thank You for Your Attention

Leonid Sukhanov

Deputy director of SNF and RW Management Centre

A.A.Bochvar Research Institute of Inorganic Materials

123060, Russia, Moscow, P.O. Box-369, Rogov Street, 5aFax: 007-499-730-6427, E-mail: lpsoukh@bochvar.ru

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