Earthquake-induced rock shear through a bentonite-filled deposition hole in a repository for spent nuclear fuel is an important scenario for the safety analysis because it may cause substantial damage to the canister hosting the spent fuel. Appropriate tools to investigate the effects on the buffer and the canister are required.

The study described here explored the laboratory tests conducted to develop a material model of the bentonite buffer to be used in the simulations, the material models that these tests have provided and finite element (FE) simulations of three scale tests of a rock shear for comparison between modelled and measured results. The results were used for validation of the material models and the calculation technique that was used for modelling different rock-shear cases.

The laboratory study consisted of swelling-pressure tests and tests to determine shear strength and stress-strain properties. The material model is elastic-plastic with a nonlinear stress-strain relation which depends on the density of the bentonite buffer and is a function of the strain rate. The three scale tests were modelled using the Abaqus finite element code. Good agreement between modelled and measured results was observed, in spite of the complexity of the models and the difficulties associated with measuring stresses and strains under the very fast shear.

The modelling results thus validate the modelling of the SR-Site. The modelling technique, the element mesh and the material models used in these analyses are well fitted and useful for this type of modelling.

To reveal the factors that determine the different ranges of compositional variations in high- and low-temperature Al-rich K-dioctahedral micas, relationships between structural parameters and cation composition were analysed for: (1) a series of synthetic 2M1 muscovite–phengite–aluminoceladonite samples; and (2) Al-rich, K-dioctahedral 2M1 micas with previously published refined structural data. The dependences of the unit-cell parameters on cation composition and the variations in tetrahedral and octahedral lateral dimensions and sheet thicknesses, interlayer distances and tetrahedral rotation angles were analysed and compared with those found previously for the series 1M trans-vacant (tv) illite–1M aluminoceladonite. The similarities in the variations of unit-cell parameters with cation composition observed in 2M1 and 1M natural and synthetic K-dioctahedral micas imply that these variations are controlled by similar – albeit not identical – structural factors. A major structural factor is the readjustment of the differently sized tetrahedral and octahedral sheets, which is realized in a different manner in micas formed under different pressure and temperature conditions.

The effects of chemical treatment on the radiation-shielding properties of Philippine natural zeolites were investigated using EpiXS following the EPICS2017 library. The zeolites were studied using X-ray diffraction and energy-dispersive X-ray spectroscopy. The acid treatment eliminated Fe and Ca, having a negative impact on the cross-section of the HCl-modified zeolite. The mass attenuation coefficients of the raw, NaOH- and HCl-modified zeolites at 1332 keV were 0.0545, 0.0544 and 0.0548 cm2 g–1, respectively. At 100–10,000 keV, the linear attenuation coefficient depends on the density and increases in the order HCl-modified > NaOH-modified > raw zeolite. In the energy range of 100–16,000 keV, the mean free path and half-value layer values are in the order of HCl-modified < NaOH-modified < raw zeolite. The raw and NaOH-modified zeolites have comparable effective atomic numbers, whereas the HCl-treated zeolite has significantly lower such values.

Samples from the pyrophyllite reserves in the Malatya–Pütürge region, used in the production of the whitest cement in Europe, were beneficiated using flotation. The mineralogical composition of the natural pyrophyllite, as determined using X-ray diffraction, includes pyrophyllite, kaolinite, quartz, illite–mica and feldspar. The chemical composition of pyrophyllite contains 69.75% SiO2 and 23.04% Al2O3. The pyrophyllite percentage (40–45 wt.%) of the natural sample increased to 60–80 wt.% after flotation. In flotation experiments, the effects of reagent amounts, types and their mixtures were investigated. Methyl isobutyl carbinol (MIBC) and pine oil as frothers and kerosene as a collector were used in the flotation studies. The use of reagents as mixtures has a positive effect on the beneficiation compared to use on their own. The best result was obtained for a mixture of MIBC with kerosene, which is a non-ionic hydrocarbon oil, yielding a concentrate containing 26.63% Al2O3. Improved results were also observed for kerosene plus frother mixtures after flotation cleaning circuits. The bubbles formed during flotation were photographed and the bubble diameters were measured using the ImageJ program. The Al2O3 content was evaluated by correlating the bubble diameters. In general, selectivity decreased during experiments in which bubble diameters were reduced.

Acid activation was carried out by heating muds prepared from Ca-rich bentonite (CaB), sulfuric acid (H2SO4) and distilled water, yielding various bleaching earths (BEs). The roles of each of the process variables, namely mass fraction of H2SO4 (x) in the dried CaB and pure H2SO4 mixture, heating temperature (T) and contact time (t), in the activation were tested. The raw CaB and each BE were examined with X-ray diffraction, chemical analyses, N2 adsorption/desorption, pH-metry and tintometry. The BE contents in both the aqueous and oily suspensions were set to 2% by mass in order to measure the pH value and the bleaching power, respectively. The optimum conditions for the activation to obtain a BE having the same bleaching power (0.60) as Tonsil® Optimum Bleaching Earth for soybean oil were determined as x = 0.35, T = 100°C and t = 2 h. The bleaching power increased only marginally upon increasing the activation time from 2 h up to 10 h at a given x and T. After 10 h, significant changes did not take place in the bleaching power of the BE. The mass fraction of total structural metal oxide (y), pH value, specific pore volume (V), specific surface area (S) and mean internal diameter (D) of the mesopores for the optimized BE are y = 0.10, pH = 3.0, V = 0.31 cm3 g–1, S = 225 m2 g–1 and D = 7 nm. The pH and D values were more important for bleaching the alkaline refined soybean oil compared to the other parameters tested.

X-ray analyses indicate that chlorite, illite and mixed-layer chloritesmectite are present in the < 2μ fraction of the Precambrian Gowganda Formation near Bruce Mines, Ontario. The mixed-layer material is restricted to the porous graywacke sandstones and is epigenetic in origin. The chlorite and illite are ubiquitous and may reflect high-grade diagenesis, low-grade metamorphism or a source rich in these minerals.

The investigations on clays progressing at the Macaulay Institute are fundamentally connected with pedological studies. The general aim of these investigations is to provide evidence which we believe will give us a better insight into the fundamental differences between the soil types as mapped in the field and provide us with an explanation of certain of their characteristics and properties. Within the last year a systematic investigation has been commenced into the clay minerals associated with each different soil type in Aberdeenshire. The methods being used are X-ray examination and differential thermal analysis. A brief account of the X-ray work has been given by Mr G. F. Walker.

Selected samples of large cavity filling and vein-type fibrous zeolites from Eocene volcanic rocks in the Kahrizak region, northern Iran, have been studied for their mineralogical and chemical characteristics. X-ray powder diffraction and electron microprobe analyses confirmed the presence of natrolite, mesolite and scolecite with compositions of [Na14.922Ca0.202K0.015Ba0.002] [Al15.697Si24.267O80]·nH2O, [Ca15.714Na14.224][Al46.431Si73.398O240]·nH2O and [Ca7.804Na0.142K0.024 Ba0.012Mg0.006][Al15.320Si24.437O80]·nH2O, respectively. In addition, examination of textural relationships in thin sections and back-scattered electron images reveals a paragenetic order in which the Ca-rich zeolites crystallized first. It is most probable that the fibrous zeolites of Kahrizak were formed during two pulses of hydrothermal activity in the area. Scolecite and mesolite were precipitated from Ca-rich solution, whereas the second stage Na-rich, low-temperature fluid crystallized natrolite and reacted with Ca-species.

Plate-like α-Al2O3 particles are used to reinforce metal or ceramics to improve their mechanical properties. Here, we have demonstrated the production of alumina platelets using kaolin as a raw material in a sodium sulphate flux. When kaolin was sintered using Na2SO4 flux, the main phase formed in samples sintered at 900ºC was mullite, but alumina was produced at 1000ºC. Sintering at 1200ºC led to alumina and sodium aluminosilicate, with little of the mullite phase present. Plate-like α-Al2O3 particles were observed in samples sintered at 1200ºC, with diameters ranging from 1.5 to 4.5 µm and thicknesses from 0.05 to 0.1 µm. This production method is economically feasible because the raw materials have a low cost and the sintering temperature is low.

The study of M and Mg ion exchange (M = Co, Ni, Cu, Zn), between silicate gels SiO2.q(M, Mg)O.nH2O and amino acid (glycine) saline aqueous solutions (M, Mg)SO4, shows that the introduction of the complexing agent completely upsets the original distribution equilibria of M and Mg between the two types of phases. The values of the measured bulk distribution coefficient

are lowered considerably relative to the inorganic reference distribution coefficients. The lowering of D may be accounted for by calculating the contents of the different species, MA, MA+, M2+, under which the metallic element M is present in the solutions. The values of

resulting from the calculated M2+ contents are identical to the values of Dref, determined in systems without a complexing agent.

Clay minerals possess the peculiar characteristic that they normally occur as very small crystals. We cannot, therefore, afford to ignore the contribution that colloid science can make to the study of clay minerals. Many colloidal systems are stable because the particles are electrically charged. There is, of course, electrical neutrality of the system as a whole, but there is an electric separation within the system whereby electricity of one kind (it may be a positive or negative, depending on the system) is anchored for the time being to the particles while the complementary charge exists as ions (counter ions they are often called). Some of the counter ions must be regarded as in solution in the suspending medium (normally water) for it is their mobility relative to the particles which gives rise to electrical conductivity and to electrophoresis, electro-endosmosis and streaming potential.

Two clays of the kaolinite type, one from Bihar and the other from Kerala, were each separated into particle-size fractions greater than and smaller than 1·4 µ.e.s.d. X-ray diffraction, differential thermal analysis, cation-exchange capacity and moisture absorption determinations and chemical analysis of the fractions showed that the micaceous mineral was concentrated in the fine fraction of one whereas it was mostly in the coarse fraction of the other. The evidence suggests that the mineral in the former belongs to the illite group and in the latter to the mica group.

Exchangeable cation associations in physical mixtures of bentonite and laponite have been examined using X-ray diffraction and a combination of electron microprobe analysis and multivariate statistical methods. The results suggest that cation exchange can occur in air-dry mixtures when pressure (∼64 kbar) is applied. Although no attempt is made to describe the mechanism of the reaction it appears to require the presence of adsorbed water.

The term colloid is now generally applied to any system which contains a large area of phase boundary per unit volume. There can be no doubt that clay minerals rank as colloids and it is very desirable that clay mineralogists and colloid chemists should be brought together as in the present meeting.

The skill displayed by clay mineralogists in overcoming the technical difficulties with which they were confronted has been remarkable, and the benefits derived from their painstaking investigations are already being felt outside the immediate field of their studies and particularly in other branches of colloid science. To have precise information about the dimensions and crystal structure of the particles in a colloidal system can make all the difference between success and failure in distinguishing between alternative explanations of colloidal phenomena.