Deposition holes

The nature of a BMT study is well demonstrated with BMT3 of the DECOVALEX I project. It was a problem associated with a near-field repository model, set up as a two-dimensional plane-strain problem in which a tunnel with a deposition hole was located in a fractured rock mass. The model is 50 X 50 m in size, and situated at 500 m below the ground level (Figure 1). The fracture network is a two-dimensional realization of 6,580 fractures from a realistic three-dimensional fracture network model of the Stripa Mine, Sweden (Figure 2). The problem is set up as a fully coupled THM near-field repository problem, with thermal effects caused by heat release from radioactive waste in the deposition hole (the heater). Heat output decreases... 

Displacement results agreed reasonably well among the research teams and between discrete and continuum approaches. Large discrepancies occurred only when monitoring points are located on loose blocks with large movements, close to the boundary of the tunnel and the deposition hole. 

This paper focuses on a repository located in sparsely fractured rock with a hydraulic conducting horizontal fracture intersecting the vertical deposition hole (Figure lb). The analysis for the case of a homogenous intact rock (Figure la) is presented in Millard et al., (2003). This paper... 

The repository geometry is based on the Japanese H12 project (JNC, 2000). Because of repetitive symmetry, the simulations were conducted on a one-quarter symmetric model containing one deposition hole (Figure 2). The upper and lower boundaries are placed at vertical distances of 50 m from the drift floor according to the BMTl definition (Nguyen et al., 2003). 

The test site is a 65 m long TBM-bored tunnel including six 1.75 m diameter deposition holes of m depth. The outer 25 m long part has two holes and it is separated from the inner 40 m section including 4 holes by means of a tight plug. Details of the work plan may be found in Dahlstrbm (1998), Svemar Pusch (2000) and Persson Broman (2000). 

The canisters were cylinders of 1.05 m diameter and 4.83 m height, installed in the deposition holes and surrounded by compacted bentonite rings 0.5 m height and 1.65 m of outer diameter. The gap between blocks and the rock was filled up with bentonite pellets. A small 1 cm gap was left between canister and bentonite blocks as a tolerance for installation purposes. The initial density of the bentonite blocks was 1.78 g/cm ... 

Figures 3 and 4 present the results of the simulation for the mid plane of the deposition hole 1, regarding temperature and saturation degree. These results correspond to the location of some sensors for which some measurements are already available. Degree of saturation measurements have been obtained from relative humidity transducers by means of the psychrometric law.

In Sweden, a repository design of KBS-3 system has been develop (SKB, 1999). The KBS-3 is a multibarrier system to isolate the spent nuclear fuel. The spent nuclear fuel is placed in corrosion-resistant 5-m long copper canisters. Each of the canisters is surrounded by an engineered barrier system (EBS) of bentonite clay in separate deposition holes excavated along tunnels in... 

The Swedish Nuclear Fuel and Waste Management Company (SKB) is investigating the stability of a pillar between two closely located deposition holes at Aspo Hard Rock Laboratory (AHRL). This in-situ experiment is called Aspb Pillar Stability Experiment (APSE) and it is described more detailed elsewhere in this proceeding see APSE by Andersson et al. (2(X).1). 

The preparation of buffer clay is made by compaction of dry clay powder to blocks with a high density. The blocks are then placed in the deposition holes to surround the containers. Very dense blocks of highly compacted smectitic clay powder are placed around the containers, embedding them tightly. The required tightness is attained when the clay material swells after taking up water from the surrounding rock. 

Vertica.1 Axia.1 Deposition. The vertical axial deposition (VAD) process (18) was developed by a consortium of Japanese cable manufacturers and Nippon Telephone and Telegraph (NTT). This process also forms a cylindrical soot form. However, deposition is achieved end-on without use of a mandrel and subsequent formation of a central hole. Both the core and cladding are deposited simultaneously using more than one torch (Fig. 12). 

There are, however, a variety of other sources of methane that have been considered for fuel supply. Eor example, methane present in coal (qv) deposits and formed during mining operations can form explosive mixtures known as fire damp. In Western Europe, some methane has been recovered by suction from bore holes drilled in coal beds and the U.S. Bureau of Mines has tested the economic practicaUty of such a system. Removal of methane prior to mining the coal would reduce explosion ha2ards associated with coal removal. As much as 11.3 x 10 (400 trillion (10 ) cubic feet or 400 TCE) of... 

Aluminum, the most common material used for contacts, is easy to use, has low resistivity, and reduces surface Si02 to form interfacial metal-oxide bonds that promote adhesion to the substrate. However, as designs reach submicrometer dimensions, aluminum, Al, has been found to be a poor choice for metallization of contacts and via holes. Al has relatively poor step coverage, which is nonuniform layer thickness when deposited over right-angled geometric features. This leads to keyhole void formation when spaces between features are smaller than 0.7 p.m. New collimated sputtering techniques can extend the lower limit of Al use to 0.5-p.m appHcations. 

Diameters of the holes vary from 5—25.4 cm. Drilling perpendicularly to the deposit is preferable but ia folding or tilted beds inclined drilling is often practiced. Spaciag of the holes and borehole diameters depend on the hardness and fracturiag characteristics of the stone, and desired top size for the primary cmsher. 

The homogeneous reactor experiment-2 (HRE-2) was tested as a power-breeder in the late 1950s. The core contained highly enriched uranyl sulfate in heavy water and the reflector contained a slurry of thorium oxide [1314-20-1J, Th02, in D2O. The reactor thus produced fissile uranium-233 by absorption of neutrons in thorium-232 [7440-29-1J, the essentially stable single isotope of thorium. Local deposits of uranium caused reactivity excursions and intense sources of heat that melted holes in the container (18), and the project was terrninated. 

A typical setting of equipment for a sulfur well and the principles of mining are illustrated schematically in Eigure 1. Eirst, a hole is drilled to the bottom layer of the salt-dome cap rock with equipment of the same type as that used in oil fields. Three concentric pipes within a protective casing are placed in the hole. A 20-cm pipe inside an outer casing is sunk through the cap rock to the bottom of the sulfur deposit. Its lower end is perforated with small holes. Then, a 10-cm pipe is lowered to within a short distance of the bottom. Last and innermost is a 2.5-cm pipe, which is lowered more than halfway to the bottom of the well. 

CVD processing can be used to provide selective deposition on certain areas of a surface. Selective tungsten CVD is used to fill vias or holes selectively through siUcon oxide layers in siUcon-device technology. In this case, the siUcon from the substrate catalyzes the reduction of tungsten hexafluoride, whereas the siUcon oxide does not. Selective CVD deposition can also be accompHshed using lasers or focused electron beams for local heating. 

A special case of air atomization is high volume low pressure (hvlp) spray. In this case the air pressure at the spray gun is less than 70 kPa (10 psig) and there are relatively large (up to 0.32 cm) holes in the air cap to easily pass the low pressure air. This type of atomizer produces a soft or slow moving spray and is generally considered to be rather efficient in depositing the material on the workpiece. However, the use of low pressure air for atomization usually limits the viscosity and/or flow rate of the material that can be atomized. 

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