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AECL-9891 ^|^ ATOMIC ENERGY WSM ENERGIE ATOMIQUE OF CANADA LIMITED ^fi9 DU CANADA LIMITEE Research Company ^^B^^ Societe de Recherche

ELEMENTAL, MINERALOGICAL, AND PORE-SOLUTION COMPOSITIONS OF SELECTED CANADIAN CLAYS

COMPOSITIONS ELEMENTAIRES, MINERALOGIQUES ET DE SOLUTION INTERSTITIELLE D'ARGILES CANADIENNES SELECTIONNEES

D. W. Oscarson, D. A. Dixon

Whiteshell Nuclear Research Etablissement de recherches Establishment nucltfaires de Whiteshell Pinawa, Manitoba ROE 1LO March 1989 mars Copyright

ELEMENTAL, MINERALOGICAL, AND PORE-SOLUTION COMPOSITIONS OF SELECTED CANADIAN CLAYS

D.V. Oscarson and D.A. Dixon

Vhiteshell Nuclear Research Establishment Pinava, Manitoba ROE 1LO 1989 AECL-9891 COMPOSITIONS ÉLÉMENTAIRES, MINÉRALOGIQUES ET DE SOLUTION INTERSTITIELLE D'ARGILES CANADIENNES SÉLECTIONNÉES

par

D.W. Oscarson et D.A. Dixon

RÉSUMÉ

Les argiles constitueront un élément important de la barrière et du système de scellement d'étanchéité d'une enceinte d'évacuation de déchets nucléaires au Canada. Dans le présent rapport, on présente les compositions élémentaires, minéralogiques et de solution interstitielle d'argiles candidates de scellement d'étanchéité à utiliser dans le cadre du Programme canadien de gestion des déchets de combustible nucléaire.

Énergie atomique du Canada limitée Établissement de recherches nucléaires de Vhiteshell Pinava, Manitoba ROE 1L0 1989

AECL-9891 ELEMENTAL, NINERALOGICAL, AND PORE-SOLUTION COMPOSITIONS OF SELECTED CANADIAN CLAYS

D.V. Oscarson and D.A. Dixon

ABSTRACT

Clay materials will be an important component of a barrier and sealing system in a nuclear fuel waste disposal vault in Canada. In this report the elemental, mineralogical, and pore-solution compositions of candidate clay sealing materials for the Canadian Nuclear Fuel Waste Management Program are presented.

Atomic Energy of Canada Limited Vhiteshell Nuclear Research Establishment Pinava, Manitoba ROE 1L0 1989

AECL-9891 CONTENTS

Page 1. INTRODUCTION

2. MATERIALS AND METHODS 1 2.1 ELEMENTAL ANALYSIS 1 2.2 MINERALOGICAL COMPOSITION 2 2.3 PORE-SOLUTION CHEMISTRY 2 2.3.1 Static Experiment 2 2.3.2 Dynamic Experiment 5

3. RESULTS AND DISCUSSION 5 3.1 ELEMENTAL COMPOSITION 5 3.2 MINERALOGICAL COMPOSITION 5 3.2.1 Avonlea Bentonite 5 3.2.2 Sealbond Illite 5 3.2.3 Lake Agassiz Clay 9 3.3 PORE-SOLUTION CHEMISTRY 11 3.3.1 Static Experiment 11 3.3.2 Dynamic Experiment 13

4. SUMMARY 16

REFERENCES 17 1. INTRODUCTION

In Canada, clay-based materials will be used in a nuclear fuel waste disposal vault to surround containers holding used nuclear fuel waste in boreholes, and to fill and seal much of the remainder of the vault (Hancox, 1986). To evaluate the effectiveness of these clay-based seal- ants, and to determine their compatibility with other disposal vault components such as the waste containers, it is necessary to fully char- acterize the clay material. In this report the elemental, mineralogical, and pore-solution compositions of three candidate clays for use as sealing materials in a nuclear fuel waste disposal vault are presented.

2. MATERIALS AND METHODS

The clays examined here are referred to as Avonlea bentonite, Sealbond illite, and Lake Agassiz clay. The following descriptions of these clays are taken largely from Quigley (1984).

Avonlea bentonite; This clay is a commercial product mined by Avonlea Mineral Industries Ltd., Regina, Saskatchewan. It is from the Bearpaw Formation of Upper Cretaceous age, in southern Saskatchewan; the formation is sedimentary and derived from volcanic ash. Sodium is the predominant exchangeable cation.

Sealbond illite; This clay is mined by Domtar Inc. Construction Materials Group, Mississauga, Ontario. It is from the Dundas Shale Member of the Georgian Bay Formation of Ordovician age in southern Ontario. The rocks are sedimentary marine in origin. The mined formation is a soft, grey, illite-bearing shale containing thin discontinuous interlayers of carbonate and/or sand- stone. Sealbond is the pulverized shale with no additives.

Lake Agassiz clay; This material is mined by Kildonan Concrete Products Ltd., Winnipeg, Manitoba. It is from freshwater lake sediments of glacial Lake Agassiz of Pleistocene age, in southern Manitoba. The material consists of a lower clay layer deposited in deep water and an upper silt, clay and sand unit deposited in shallow water. The mined soil is described as the "gumbo" layer of the glacial lake sediments.

2.1 ELEMENTAL ANALYSIS

The clays were analyzed as received from the suppliers, without further treatment. It is this clay that will likely be used in a nuclear fuel waste disposal vault.

Three samples of each of the clays were dissolved by heating for one hour at 1000°C in a Li-metaborate/Li-tetraborate flux (Shapiro, 1975) in graphite crucibles. The cooled beads were then dissolved in 8Z (wt./vol.) HNOj. The solutions were analyzed for Na, K, and Cs by flaae emission spectrometry; for U by high-performance liquid chromatography; for - 2 -

Ft Cl, Br and I by ion chromatography; and all other elements given in Tables 1 and 2 (except those noted below) were determined by inductively coupled plasma spectrometry (ICPS). The total Fe and Fe(II) contents given in Tables 1 and 2 were determined by the method given by Stucki (1981) and are from Oscarson (1985). The N, S, P, and organic and inorganic C contents given in Table 2 are from Oscarson et al. (1986). The following methods were used: N - semi-micro Kjeldahl method in conjunction with an ammonium ion-selective electrode (Bremner and Mulvaney, 1982); S - combustion using an induction furnace followed by the iodometric measurement of the evolved S02; P - colorimetrically using molybdivanado-phosphoric acid (Jackson, 1958); organic C - wet oxidation using K2Cr207 (Nelson and Sommers, 1982); inorganic C - measurement of C02 evolved upon igniting a sample in an inert atmosphere at 750°C using an open-tube resistance furnace (Bach and Deane, 1979).

The moisture content of the clays was determined gravimetrically after heating at 110°C for 24 h. All values in Tables 1 and 2 are reported on an oven-dry basis. 2.2 MIWERALOGICAL COMPOSITION

The mineralogical composition of the clays was determined by X-ray diffraction (XRD) using Ni-filtered, Cu-Koc radiation generated at 50 kV and 150 mA. Both powder and parallel-oriented samples of the whole clays were examined. After the clays were saturated with Mg2+, parallel- oriented samples were prepared on glass slides using the filter-membrane peel technique given by Drever (1973). These samples were examined by XRD after the following treatments (Jackson, 1975): (a) air-drying, (b) solvation with ethylene glycol, (c) heating at 350°C for 2 h, or (d) heating at 550°C for 2 h. The XRD patterns were obtained with the samples in a dry-air environment to limit the rehydration of the heated samples during the XRO analysis (Oscarson, 1988). Samples of the Sealbond clay were also saturated with K+ and heated at 350 and 550°C for 2 h before XRD analysis. 2.3 PORE-SOLUTION CHEMISTRY

2.3.1 Static Experiment Samples of the Avonlea clay and deionized-distilled water (DV) were placed in polyethylene zip-lock bags at the following water-to-clay ratios: 1.5, 2 and 3 L/kg. The moist clays were then thoroughly kneaded to ensure a uniform moisture distribution. After a three-week reaction period at room temperature, a fraction of the solution was separated froa the clay by ultracentrifugation and then filtered (0.45-um pore size). The solution was analyzed for Na and K by atomic absorption; Ca, Mg, and S04 by ICPS; Cl and F by ion chromatography; HC03 by acidimetric titration; and the pH was measured with a glass electrode. - 3 -

TABLE 1

COMPOSITION OF THE CLAYS ON AN OXIDE BASIS (vt.%)

Oxide Avonlea Sealbond Lake Agassiz Bentonite Illite Clay

SiO2 64.7 ± 0.3* 57.1 ± o.3 53.3 + 0.6 A12O3 16.3 ± 0.2 15.6 + o.1 16.8 ± 0.2 Fe,O3** 4.46 6.74 6.15 CaO 1.79 + 0 3.19 + 0.02 4.06 ± 0 MgO 2.26 ± 0.04 3.44 + 0.02 3.39 + 0.02 Na2O 2.23 ± 0.01 0.88 ± o 0.61 ± 0.01 K2O 0.56 ± 0.01 4.58 ± o.07 2.64 + 0.02 0.14 ± 0.02 0.28 ± o.01 0.34 + 0.02 SO3 0,.68 0.04 0.30 ± o.03 0.20 ± 0.03 .52 3.74 5,.63 co2*** 1. BaO 0,.47 ± 0.02 0.06 + 0 0..10 + 0 TiO2 0,.25 ± 0.01 0.90 ± o.02 0..67 + 0.02 MnO 0,.073 ± 0.004 0.109 ± o.001 0..073 + 0.001 Cr2O3 < 0.,010 0.012 ± o.001 0.,016 + 0.001 ZnO 0.,009 + 0.001 0.014 + 0.002 0.,017 + 0.001 SrO 0.024 ± 0.001 0.014 ± o,.001 0.,018 ± o Cs2O < 0.010 < 0.010 < 0.010 As2O3 < 0.05 < 0.05 < 0.05 CuO < 0.033 < 0.033 < 0.033 NiO < 0.017 < 0.017 < 0.017 CoO < 0.010 < 0.010 < 0.010 U02 < 0.0006 < 0.0006 < 0.0006 H2O**** 6.9 ± 0.1 0.6 ± o.1 4.0 ± 0.2 Mean ± one standard deviation, n = 3. Single determination; from Oscarson (1985). Sum of the inorganic and organic C (Table 2); single determinations. Depends on the relative humidity. - 4 -

TABLE 2

ELEMENTAL COMPOSITION OF THE CLAYS (vt.% unless otherwise noted)

Element Avonlea Sealbond Lake Agassiz Bentonite Illite Clay

Si 30.2 26.7 24.9 Al 8.65 8.25 8.56 Fe (total) 3.12 4.71 4.30 Fe(II) 0.27 3.1 0.73 Metallic Fe (mg/kg) 0.3 0.9 - C (organic) 0.12 0.33 0.57 C (inorganic) 0.29 0.68 0.95 S (total) 0.27 0.12 0.08 N (total) <£ 0.01 0.03 0.04 Ca 1.28 2.28 2.91 Mg 1.36 2.07 2.04 Na 1.65 0.64 0.46 K 0.46 3.80 2.19 P 0.06 0.12 0.15 Ba 0.42 0.05 0.09 Ti 0.15 0.53 0.40 Mn 0.057 0.085 0.056 Cr <: 0.007 0.008 0.010 Zn 0.006 0.011 0.014 Sr 0.020 0.012 0.015 Cs < 0.009 < 0.009 < 0.009 As < 0.04 < 0.04 < 0.04 Cu < 0.026 < 0.026 < 0.026 Ni < 0,013 < 0.013 < 0.013 Co < 0.008 < 0.008 < 0.008 F 0.0139 ± 0.0011* 0.0169 + 0.0014 0.0218 ± 0.0007 Cl 0.0394 + 0.0035 0.0382 + 0.0010 0.0060 ± 0.0008 Br < 0.0050 C 0.0050 < 0.0050 I < 0.0014 ( 0.0014 < 0.0014 U < 0.0005 ( 0.0005 < 0.0005

Mean ± one standard deviation, n = 3. - 5 -

2.3.2 Dynamic Experiment

Block samples of unprocessed Avonlea clay, having a field dry bulk density of about 1.1 to 1.3 Mg/m3, were collected and then carefully trimmed to snugly fit in a cylindrical chamber with a diameter of 50 mm and a height of 25 to 50 mm. A description of the sampling procedure and the test apparatus is given by Oscarson et al. (1989). Five samples vere per- meated with DW and the effluent was collected periodically for at least six months. The hydraulic gradient across the samples ranged from 1500 to 3000. The effluent was analyzed for all the elements listed above except HC03. From the density and the volume occupied by the clay samples, and the volume of the solution passing through the clay, the number of pore volumes of effluent vere calculated.

3. RESULTS AND DISCUSSION

3.1 ELEMENTAL COMPOSITION

The composition of the three clays is given on an oxide and an elemental basis in Tables 1 and 2, respectively. For simplicity, the error associated with the results and given in Table 1 is not repeated in Table 2.

3.2 MINERALOGICAL COMPOSITION

3.2.1 Avonlea Bentonite

The XRD patterns for Avonlea bentonite indicate that the predominant phyllosilicate present in this clay is a dioctahedral smectite (montmorillonite) (Figures 1 and 2). Other layer silicates present in minor amounts are illite (hydrous mica) and kaolinite (Figures 1 and 2, Table 3). Illites contain approximately 8 vt.X K20 (van Olpen and Fripiat, 1979). Based on the K20 content of this clay (Table 1) and the XRD results, the illite content is about 5 vt.%. The presence of kaolinite (< 5 wt.%) is indicated by the small peak at 0.715 nm (Figures 1 and 2) that disappears upon heating to 550°C (Figure 2D) (Jackson, 1975). The clay also contains 5 to 10 vt.X quartz and minor amounts (< 5 vt.X) of feldspar, gypsum, and calcite. The presence of a peak at 0.271 nm (Figure 1) suggests that there may also be a trace of apatite in this clay. However, if all the phosphorus in this clay (Table 1) is assumed to be present in the form of hydroxyapatite [Ca5(P04)30H], its content in the clay would be approximately 0.3%; this amount is probably not enough to be detected by XRD. The clay also contains minor amounts (below the detection limit of XRD) of Fe minerals such as magnetite, hematite, and goethite (Oscarson et al., 1984; Oscarson and Heimann, unpublished data). Vith the exception of the presence of kaolinite reported here, the composition of this clay is in agreement with that given by Quigley (1984).

3.2.2 Sealbond Illite

Illite (35 to 50 vt.Z), kaolinite (15 to 25 vt.Z), and vermiculite (< 5 vt.X) are the phyllosilicates detected by XRD in the Sealbond illite - 6 - d -spacing (nm) 2.95 0.885 0.444 0.298 0.225

10 20 30 40 50 60 65

Degrees 20 (CuKa) FIGURE 1: X-ray Powder Diffraction Pattern of the Avonlea Bentonite

d -spocing {nm) 2.95 0.885 0.444 0.298 0.225 0.182 0.154 s i

o o

C. heated, 35O°C

B. glycoloted

!.. .. 10 20 30 40 50 60 Degrees 2 0 (CuKa)

FIGURE 2: X-ray Diffraction Patterns of Oriented Samples of the Avonlea Bentonite After the Indicated Treatments. Nunbers in the patterns by some peaks are the d-spacings in na. - 7 -

TABLE 3 X-RAY POWDER DIFFRACTION DATA FOR THE AVONLEA BENTONITE FROM FIGURE 1

Peak Number d-spacing Mineral (from Figure 1) (nm)

1 1.58 100 smectite (001) 2 1.47 65 smectite (001) 3 1.01 15 mica (illite) 4 0.901 5 5 0.799 5 6 0.715 5 kaolinite 7 0.641 5 feldspar 8 0.518 5 smectite (003) 9 0.449 20 layer silicates (110) 10 0.426 15 quartz 11 0.405 15 K-Na-feldspars and/or cristobalite 12 0.376 15 feldspar 13 0.366 10 Na-Ca-feldspars 14 0.335 35 quartz 15 0.321 25 Na-Ca-feldspars 16 0.319 25 Na-Ca-feldspars 17 0.314 10 gypsum 18 0.302 10 calcite 19 0.271 5 apatite? 20 0.256 10 Fe minerals and/or olivine 21 0.253 10 Fe minerals and/or olivine 22 0.246 10 quartz 23 0.228 5 quartz and/or calcite 24 0.183 20 quartz 25 0.177 5 26 0.154 5 quartz 27 0.150 10 2:1 dioctahedral silicates (060)

(Figures 3 and 4, Table 4). The relatively large amount of K in this clay (Table 1) is further support for a significant illite component. Quigley (1984) reported the presence of chlorite in this clay, but the clay examined here contains no detectable chlorite as indicated by the absence of an XRD peak at 1.43 nm [the d(001) peak of chlorite] after heating to 350 and 550°C (Figures 4C and D) [chlorite is not destroyed by heating at 550°C (Jackson, 1975; Brown and Brindley, 1984)]. The peak at 1.43 nm in Figures 3 and 4A is attributed to vermiculite. At temperatures > 300°C this mineral dehydrates and collapses to approximately 1 nm and reinforces the illite (and other 1-nm phyllosilicates that may be present) peak at 1.0 nm (Jackson, 1975) (Figures 4C and D). The presence of vermiculite in this clay is in agreement with the results of Czurda et al. (1973). The presence of kaolinite is indicated by the peak at 0.712 nm (Figures 3 and 4A, B, and C) that disappears on heating to 550°C (Figure 4D) (Jackson, 1975; Brown and Brindley, 1984). Saturating this clay with K+ and heating - 8 -

d - spacing (nm) .95 0.885 0.444 0.298 0.225 0.I82 0.I54 1 1 1 1 1

12 21 10 13 17 IB 19 22 . 20 23 w J I I 1 UMWf »AV JUAA 10 20 30 40 50 60 65 Degrees 29 (CuKa)

FIGURE 3: X-ray Powder Diffraction Pattern of the Sealbond Illite

d- spacing (nm) 1.77 0.885 0.59I 0.444 0.356 0.298 0.256 0.225 1 1 1 1 I 1 1

D. heoted, 550°C 8

C. heated, 350°C 1 AJ1 A B. glycolated

A. air-dried 5. I ^ T ' 1 J 3 5 10 15 20 25 30 35 40 Degrees 26 (CuKa)

FIGURE 4: X-ray Diffraction Patterns of Oriented Samples of the Sealbond Illite After the Indicated Treatments. Numbeis in the patterns by some peaks are the d-spacings in nm. - 9 -

TABLE 4 X-RAY POVDER DIFFRACTION DATA FOR THE SEALBOND ILLITE FROM FIGURE 3

Peak Number d-spacing I/I. Mineral (from Figure 3) (nm)

1 1.43 10 veimiculite (001) 2 1.01 15 mica (illite) (001) 3 0.712 20 kaolinite (001) and vermiculite (002) 4 0.500 5 mica (002) 5 0.478 5 vermiculite (003) 6 0.450 10 layer silicates (110) 7 0.427 20 quartz 8 0.404 5 K-Na-feldspars and/or cristobalite 9 0.373 5 feldspar 10 0.^55 10 kaolinite (002) and vermiculite (004) 11 0.335 100 i,jartz 12 0.320 10 Na-Ca-feldspars 13 0.304 10 calcite 14 0.292 5 K-feldspars 15 0.260 5 Fe minerals and/or olivine 16 0.258 10 Fe minerals and/or olivine 17 0.246 10 quartz 18 0.229 10 quartz and/or calcite 19 0.213 10 cristobalite 20 0.198 5 21 0.182 10 quartz 22 0.154 10 quartz 23 0.150 5 2:1 dioctahedral silicates (060) at 350 and 550°C gave essentially the same result as shown for the Mg2+-saturated clay (data not shown). [The K-saturated clay was examined because K+ is more effective than Mg2+ in facilitating the collapse of vermiculite from 1.4 to 1.0 nm (Brown and Brindley, 1984; Whittig and Allardice, 1986)]. This clay also contains a significant amount of quartz (20 to 30 vt.X), and minor amounts (< 5 wt.%) of calcite and feldspar (Figure 3, Table 4). With the exception of the kaolinite and vermiculite reported here as opposed to the chlorite reported by Quigley (1984), the results of the two studies are in agreement.

3.2.3 Lake Agassiz Clay The predominant clay mineral present in the Lake Agassiz clay is dioctahedral smectite (montmorillonite) (30 to 40 wt.%) (Figures 5 and 6, Table 5). Other phyllosilicates present in lesser amounts are illite (15 to 25 vt.X) and kaolinite (5 to 15 vt.X). The clay also contains quartz (10 to 20 vt.X), calcite (5 to 10 vt.X), and minor amounts (< 5 vt.X) of - 10 -

d -spocing (nm) 2.95 0.885 0.444 0.298 0.225 0.182 0.154

3 10 20 30 40 50 60 65 Degrees 29 (CuKa)

FIGURE 5: X-ray Powder Diffraction Pattern of the Lake Agassiz Clay

d -spacing (nm)

2.95 0.885 0.444 0.298 0.225 0.182 O.t54 1 1

30 40 50 60 Degrees 29 (CuKa)

FIGURE 6: X-ray Diffraction Patterns of Oriented Samples of the Lake Agassiz Clay after the Indicated Treatments. Numbers in the patterns by some peaks are the d-spacings in nm. - 11 -

TABLE 5 X-RAY POWDER DIFFRACTION DATA FOR THE LAKE AGASSIZ CLAY FROH FIGURE 5

Peak Number d-spacing Mineral (from Figure 5) (nm)

1 1.56 60 smectite (001) 2 1.01 15 mica (illite) (001) 3 0.718 10 kaolinite (001) 4 0.500 5 mica (002) 5 0.450 20 layer silicates (110) 6 0.426 25 quartz 7 0.404 10 Na-Ca-feldspars 8 0.335 100 quartz 9 0.319 15 Na-Ca-feldspars 10 0.304 20 calcite 11 0.289 25 dolomite 12 0.257 15 Fe minerals and/or olivine 13 0.246 15 quartz 14 0.228 10 quartz and/or calcite 15 0.182 15 quartz 16 0.154 10 quartz 17 0.150 5 2:1 dioctahedral silicates (060)

feldspar and dolomite (Figure 5 and Table 5). The composition is in agreement with that reported by Quigley (1984).

The differences in the mineralogical composition of some of the clays noted in this study and that of Quigley (1984) for clays from the same deposit can probably be attributed to the heterogeneity of the clay deposits. This highlights the need for quality control during the mining of the clay sealing materials to ensure that a clay with an acceptable composition is used in a disposal vault.

3.3 PORE-SOLUTION CHEMISTRY

3.3.1 Static Experiment

The solution composition at the various solution/clay ratios for the Avonlea clay are given in Table 6. The values obtained at the solution/clay ratio of three are in good agreement with those reported by Robin et al. (1988). The predominant ions in solution are Na+ and SOj". It is postulated that upon vetting the clay, the gypsum present (Figure 1, Table 3) partially dissolves, some of the Ca2+ in solution then displaces Na+ on the exchange complex of the clay, resulting in high Na* and S0|~ concentrations in solution. In Figure 7 the calculated ionic strength of the various solutions is plotted as a function of the solution/clay ratio. A saturated sealing material composed of a 1:1 mixture (by dry mass) of Avonlea clay and sand compacted to a dry bulk density of approximately 1.6 Mg/m3 (Gray and Cheung, 1986) will have a - 12 -

TABLE 6

PORE-SOLUTION COMPOSITION (mg/L) OF THE AVONLEA BENTONITE AT VARIOUS SOLUTION/CLAY RATIOS

Species Solution/Clay Ratio (L/kg)

1.5 2 3

Na 2700 2100 1400 K 31 26 18 Ca 344 213 113 Mg 46 30 14 Cl 365 254 165 F 11.2 8.58 5.76 SO4 6320 4620 3110 HCO3 116 106 144 pH 7.6 7.5 7.6 ionic strength (mol/L) 0.219 0.159 0.105

O.I

o ~ 0.2

a* c a> £0.3 u = -0.073 (s/c)+ 0.319 C a 1 1 1 1 1 I 0.40 12 3 Solution/clay ratio, s/c (L/kg)

FIGURE 7: Ionic Strength of the Pore Solution of the Avonlea Bentonite Versus the Solution/Clay Ratio - 13 -

solution/clay ratio of approximately 0.5 L/kg. If a linear relationship is assumed and the regression line in Figure 7 is extrapolated to this solution/clay ratio, the ionic strength of the pore solution would be approximately 0.3 mol/L. 3.3.2 Dynamic Experiment The composition of the effluent collected from the dense clays is given in Table 7; the same data are presented on a cumulative basis and also normalized to the dry veight of clay in Table 8. Generally, the results are similar to those reported in Table 6. The effluent contains high concentrations of Na+, Cl~, and S0^~. (The concentration of S was measured in this experiment. It was assumed that the S was present largely as S0|~; an analysis of selected samples for both S and S0|~ confirmed this assumption). The concentrations decreased as the volume of solution passing through the clay increased; Cl and S are, therefore, relatively quickly washed out of the clay. This can be explained by the high solubility of gypsum and Cl-bearing salts. From the data in Tables 2 and 8, the amounts of these ions removed from the clay (Sample 1, Table 8) as a function of the volume of solution passing through the clay was calculated and is shown in Figure 8. Over 80% of the Cl was removed from the clay within four pore volumes. The removal of S was somewhat slower: six pore volumes were required to wash out 80%. Essentially all of the S was removed from the clay within 10 pore volumes.

The F~ concentrations ranged from about 0.2 to 0.7 mg/L (except for the relatively high levels in Sample 2), and the levels were relatively constant over the reaction periods (Table 7). This suggests that a spar- ingly soluble F-containing mineral—CaF2 (fluorite) or Ca5(P04)3F (fluorapatite), for example—was controlling the level of F~ in solution. The amounts of F-containing minerals in the clay are, however, far too small to be detected by XRD. In contrast to Cl and S, < 1% of the total F is removed from the clay even after 11 pore volumes (Tables 2 and 8). The Si concentrations also remained fairly constant at 15 to 4 3 30 mg/L (5.4 x 10~ to 1.1 x 10" mol H4Si0,/L) throughout the reaction periods (Table 7). These solutions were supersaturated with respect to quartz (log K° = -4.00) and cristobalite (log K° = -3.94), and undersatu- rated with respect to amorphous silica (log K° = -2.74) (Lindsay, 1979).

From the limited data, the pH of the pore solution ranged from 7.4 to 8.9 (Tables 6 and 7). During the initial part of the experiment, when the concentrations of most of the ions were highest, the ionic strength ranged from about 0.1 to 0.2 mol/L (Table 7); these results are in fair agreement with those found in the static experiments (Table 6 and Figure 7). The differences in the concentrations of the ions among the various clay samples (Tables 7 and 8) are attributed to the heterogeneity of the samples. The samples were collected from different locations in the Avonlea bentonite deposit. TABLE 7

COMPOSITION OF THE EFFLUENT FROM THE AVONLEA BENTONITE (ag/L)

Pore Ca Mg Na K S Cl F Si pH Volumes

Sample 1 1.2 44 12 1000 6 520 250 0.13 12 1.4 71 13 1400 9 770 260 0.23 16 1.2 120 17 1900 13 1280 58 0.25 23 1.2 69 12 1400 10 970 20 0.22 21 1.3 27 3.5 690 5.6 470 6 0.31 18 1.6 35 4.0 760 7.4 520 7 0.32 19 1.7 35 3.9 700 6.9 480 3 0.32 18 7.9 2.0 39 4.5 780 5.9 530 7 0.40 21 7.7

Sample 2 0.45 42 15 1900 12 970 630 0.36 14 0.54 36 14 2100 13 1100 670 0.56 17 7.4 0.26 27 5.8 2100 15 630 610 0.91 13 0.32 12 2.7 980 7.3 400 260 1.4 18 0.36 3.5 0.9 630 6.0 130 110 1.4 21

Sample 3 0.47 42 21 2500 16 1100 640 0.60 21 0.48 22 12 2000 12 480 440 0.36 24 0.62 11 6.5 1800 11 44 270 0.42 27 0.39 8.1 4.0 1100 8.9 5.5 120 0.32 22 0.48 7.8 2.6 1200 5.0 4.6 76 0.32 23

Sample 4 0.95 5.1 2.0 480 16 220 590 0.28 16 0.51 21 28 3100 20 1400 940 0.40 28 0.75 15 5.2 980 6.5 290 250 0.40 21 0.18 8.5 5.7 1400 9.1 360 320 0.60 29 0.43 4.9 5.9 1500 9.5 330 250 0.60 34 0.41 4.0 4.5 1400 9.1 67 100 0.72 35 0.42 3.6 3.1 1200 8.6 6 37 0.32 30 0.39 2.2 1.9 1100 6.8 5 13 0.64 26 0.36 9.0 1.8 930 7.0 6 9 0.72 27

Sample 5 0.20 92 33 3300 20 1800 920 0.40 22 0.57 31 21 2600 31 1300 760 0.40 23 0.34 7.0 7.4 1600 7.0 570 370 0.48 28 0.51 4.4 4.0 1300 9.8 72 160 0.44 27 8.9 0.45 3.8 3.4 1300 8.9 3 64 0.32 29 0.44 4.4 2.3 1100 7.6 4 31 0.44 30 8.8 - 15 -

TABLE 8 CUMULATIVE COMPOSITION OF THE EFFLUENT FROM THE AVONLEA BENTONITE

(mg/kg of oven-dry clay)

Cumulative Ca Mg Na K S Cl F Si Pore Volumes

Sample 1 1.2 22 6.1 550 3.9 280 135 0.071 7.0 2.6 66 15 1100 12 750 290 0.21 22 3.8 130 23 2000 27 1400 320 0.32 27 4.9 160 29 2700 47 1900 330 0.43 36 6.3 180 30 3100 70 2100 340 0.61 46 7.8 200 34 3700 98 2500 340 0.83 59 9.5 220 35 4200 130 2800 340 1.1 71 11 260 40 4800 170 3300 350 1.4 90

Sample 2 0.45 8.0 2.4 380 20 190 120 0.069 2.8 0.99 14 4.8 790 20 400 250 0.18 5.6 1.3 18 6.1 1000 23 480 320 0.28 7.0 1.6 20 6.1 1200 23 530 360 0.47 11 1.9 20 6.1 1300 23 550 370 0.68 13

Sample 3 0.47 8.0 4.8 520 3.9 230 130 0.13 4.2 0.95 12 7.3 1100 7.8 330 220 0.21 8.4 1.6 16 8.5 1600 7.8 340 300 0.33 17 2.0 16 9.7 1700 12 340 320 0.39 20 2.4 18 9.7 2000 12 340 330 0.46 25

Sample 4 0.95 2.0 3.2 200 6.6 91 250 0.12 5.6 1.5 4.0 7.3 890 11 400 450 0.21 13 2.2 12 8.5 1200 12 490 540 0.55 20 2.4 12 9.7 1300 14 520 560 0.60 21 2.8 14 9.7 1600 16 580 610 0.71 28 3.2 14 11 1800 17 590 620 0.80 32 3.7 14 11 2000 20 590 630 0.86 38 4.0 14 12 2200 20 590 630 0.97 43 4.4 16 12 2300 20 590 630 1.1 46

Sample 5 0.20 8.0 2.4 480 9.4 220 140 0.04 32 0.77 12 9.7 1100 13 550 330 0.14 38 1.1 16 9.7 1400 15 640 380 0.21 42 1.6 18 12 1700 16 650 420 0.31 49 2.1 18 12 1900 20 650 430 0.37 55 2.5 20 12 2100 20 650 430 0.45 60 - 16 -

4 6 8 10 !2 Pore volumes

FIGURE 8: Percentage of Cl and S Removed from the Avonlea Bentonite Versus the Number of Pore Volumes

4. SUMMARY

The elemental, mineralogical, and pore-solution compositions of candidate clays for use as barrier and sealing materials in a nuclear fuel waste disposal vault have been determined. Some 30 elements in the clays vere measured. Dioctahedral smectite is the predominant mineral in the Avonlea bentonite and the Lake Agassiz clay, whereas illite is the major component of the Sealbond clay. The predominant ions in the pore solution of the Avonlea bentonite were Na+, SOj~, and Cl". The concentrations of S0£~ and Cl~ in the effluent solution decreased rapidly as the amount of solution passing through the clay increased. - 17 -

REFERENCES

Bach, B.B. and P.G. Deane. 1979. An open tube resistance furnace method for determining water and carbon dioxide in cements, and water in clay-like materials. Lab. Pract. 28, 843-844. Bremner, J.M. and C.S. Mulvaney. 1982. Nitrogen—total. In Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, 2nd ed. A.L. Page, R.H. Miller, and D.R. Keeney, Eds. American Society of Agronomy, Inc., Madison, Visconsin. pp. 595-624. Brown, G. and G.V. Brindley. 1984. X-ray diffraction procedures for clay mineral identification. In Crystal Structures of Clay Minerals and Their X-ray Identification. G.V. Brindley and G. Brown, Eds. Mineralogical Society, London, pp. 305-360. Czurda, K., C.G. Winder, and R.M. Quigley. 1973. Sedimentology, mineral facies and petrofabric of the Meaford-Dundas formation (upper Ordovician) in southern Ontario. Can. J. Earth Sci. 10, 1790-1804. Drever, J.I. 1973. The preparation of oriented clay mineral specimens for X-ray diffraction analysis by a filter-membrane peel technique. Am. Miner. 58, 553-554. Gray, M.N and S.C.H. Cheung. 1986. Disposal vault sealing. In Proceedings of the Twentieth Information Meeting of the Canadian Nuclear Fuel Vaste Management Program. Atomic Energy of Canada Limited Technical Record, TR-375*, pp. 253-259. Hancox, W.T. 1986. Progress in the Canadian Nuclear Fuel Vaste Management Program. In Proc. 2nd Int. Conf. Radioactive Vaste Management. Winnipeg, Manitoba, pp. 1-9. Jackson, M.L. 1975. Soil Chemical Analysis—Advanced Course. 2nd ed. Published by the author, University of Wisconsin, Madison, Wisconsin. Jackson, M.L. 1958. Soil Chemical Analysis. Prentice Hall, Inc., Englewood Cliffs, New Jersey. Lindsay, W.L. 1979. Chemical Equilibrium in Soils. John Wiley and Sons, New York. Nelson, D.W. and L.E. Sommers. 1982. Total carbon, organic carbon, and organic matter. In Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, 2nd ed. A.L. Page, R.H. Miller, and D.R. Keeney, Eds. American Society of Agronomy, Inc., Madison, Wisconsin, pp. 539-579. Oscarson, D.W. 1985. Clay chemistry studies. In Proc. 19th Information Meeting of the Canadian Nuclear Fuel Waste Management Program: Engineered Barriers and Waste Forms. Toronto, Ontario. Atonic Energy of Canada Limited Technical Record, TR-350*, pp. 412-424. - 18 -

Oscarson, D.W. 1988. A method for preventing the rehydration of heated smectites during X-ray diffraction analysis. Comm. Soil Sci. Plant Anal. 19(15), 1667-1680. Oscarson, D.V., D.A. Dixon and M.N. Gray. 1989. Swelling pressure and permeability of an unprocessed and processed bentonitic clay. Eng. Geol. (in press). Oscarson, D.W., R.B. Heimann and R.L. Watson. 1984. Metallic iron content of candidate clays and silica sand for use in the Canadian Nuclear Fuel Waste Management Program. Atomic Energy of Canada Limited Technical Record, TR-281*. Oscarson, D.W., S. Stroes-Gascoyne, and S.C.H. Cheung. 1986. The effect of organic matter in clay sealing materials on the performance of a nuclear fuel waste disposal vault. Atomic Energy of Canada Limited Report, AECL-9078. Quigley, R.M. 1984. Quantitative mineralogy and preliminary pore-water chemistry of candidate buffer and backfill materials for a nuclear fuel waste disposal vault. Atomic Energy of Canada Limited Report, AECL-7827.

Robin, M.J.L., R.V. Gillham, and O.V. Oscarson. 1988. The effect of temperature and pore solution composition on the diffusion of strontium in a 1:1 mixture of bentonite and sand. Atomic Energy of Canada Limited Technical Record, TR-424*.

Shapiro, L. 1975. Rapid analysis of silicate, carbonate, and phosphate rocks—Revised edition. U.S. Geol. Surv. Bull. 1401, 76. Stucki, J.W. 1981. The quantitative assay of minerals for Fe2+ and Fe3+ using 1,10-phenanthroline: II. A photochemical method. Soil Sci. Soc. Am. J. 45, 638-641. van Olphen, H. and J.J. Fripiat, Eds. 1979. Data Handbook for Clay Minerals and other Non-Metallic Minerals. Pergamon Press, Oxford, England. Vhittig, L.D. and W.R. Allardice. 1986. X-ray diffraction techniques. In Methods of Soil Analysis, Part 1, Physical and Mineralogical Methods, 2nd ed. A. Klute, Ed. American Society of Agronomy, Inc., Madison, Wisconsin, pp. 331-362.

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