Holmehus clay — A Tertiary smectitic clay of potential use for isolation of hazardous waste

Abstract

The Danish Tertiary Holmehus clay belongs to the series of illite-smectite mixed-layer clays in northern Europe and has a potential to serve as an effective engineered barrier for isolating hazardous waste. Mineralogical specification was made of the components illite/smectite mixed-layer and dioctahedral vermiculite/smectite mixedlayer structures. The lower content of expandable phase than of smectiterich clays like MX-80 gives somewhat higher hydraulic conductivity and somewhat lower swelling pressure but both are deemed suitable for isolating canisters with high-level radioactive waste in deep repositories for densities at water saturation of at least 1900 kg/m3. The lower swelling pressure, the potential of being chemically more stable, and the high buffer capacity by providing dissolved Si makes Holmehus clay a candidate for use in both deep and near-surface repositories. dioctahedral vermiculite. The acronyms "IS-ml" and "diVS-ml" refer to illite/smectite mixed-85 layer and dioctahedral vermiculite/smectite mixed-layer, respectively. 86Samples were milled to < 63 μm and dried at 40 °C before XRF measurement. Analysis 87 was carried out on KBr-pressed pellets using a wavelength dispersive Phillips PW 2404 X-ray Geotechnical experiments 111The geotechnical properties were determined by conducting oedometer tests for 112 evaluation of the hydraulic conductivity and swelling pressure for two types of porewater 113(distilled water and 3.5% CaCl 2 solution) and typical densities. (Table 1). Small amounts of chlorite and feldspars were also found as well as 121 traces of anatase, pyrite, gypsum and jarosite. 122The IS-ml phases were fully expandable to 17 Å spacing by ethylene glycol saturation 001/002-and 002/003-interferences, showed that the smectite layer-fraction of the IS-ml was 127 60 % and that the diVS-ml was 20-25%. Transmission electron microscopy (TEM) 131The two mixed layer phases in fraction < 2 µm were r characterized by two morphological forms: 132(i) xenomorphic flakes, probably products of diagenetic alteration; and (ii) laths with idiomorphic 133 ends (probably detrital material originating from weathered crust). Lath-like particles are 134 enriched in fraction <0.5 μm. 135The TEM-EDX analyses showed that the IS-ml structures make up 45 frequency-% and 136 the diVS-ml phases make up 15 frequency-% in Holmehus clay. The rest was found to consist of 137 quartz (18 frequency-%) and Fe-as well as Ti-phases. The content of smectite layers (S%) in IS-138 ml was 60% and for the diVS-ml was 30% ( (Table 2).

Interaction of clay and concrete relevant to the deep disposal of high-level radioactive waste

“…A Danish mixed-layer I/S clay "Holmehus clay" of Tertiary age used in this study was sedimented in nature under marine to brackish conditions. It also contains smectite, glauconite, quartz, feldspars, calcite, glass, kaolinite, Ti oxide and pyrite (Pusch et al 2014).…”

Removal of radioactive cesium from contaminated water by whey protein amyloids–carbon hybrid filters

“…Currently, the storage and/or disposal of large volumes of lowand intermediate-level radioactive liquid waste represents an issue of high concern. [1][2][3] The compaction of these large volumes, that comprise thousands of cubic meters, is highly desirable from both an environmental and an economical point of view. Among the different ssion products in nuclear power reactors, cesium-137 ( 137 Cs) is of particular importance.…”

Influence of smectite content on the deformation behaviour of clay

“…The Danish deposits of Palaeogene clay, which have a significant content of smectite minerals (Pusch et al 2015;Heilmann-Clausen 1995;Nielsen and Heilmann-Clausen 1988), are formed from weathering of volcanic ash, deposited from volcanic eruptions in present-day Norway (Heilmann-Clausen 1995). The weathering may have been completed onshore or in the sea as the fine particles may have been carried over large distances by the currents.…”