Simulations of THM processes in buffer-rock barriers of high-level waste disposal in an argillaceous formation

The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical (THM) coupling phenomena and their influences on the repository safety. In this paper, the high-level waste (HLW) disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE_BRIGHT developed by the Technical University of Catalonia in Barcelona. The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments. The calculation results are presented to show the hydro-mechanical (HM) processes during the operation phase and the THM processes in the after-closure phase. According to the simulation results, the most probable critical processes for the disposal project have been represented and analyzed. The work also provides an input for additional development regarding the design, assessment and validation of the HLW disposal concept.     

The MITC9 <Emphasis Type="Italic">shell</Emphasis> element in <Emphasis Type="Italic">plate</Emphasis> bending: mathematical analysis of a simplified case

We consider the 9-node shell element referred to as the MITC9 shell element in plate bending solutions and present a simplified mathematical analysis. The element uses bi-quadratic interpolations of the rotations and transverse displacement, and the “rotated Raviart-Thomas” interpolations for the transverse shear stresses. A rigorous mathematical analysis of the element is still lacking, even for the simplified case of plate solutions (that is, flat shells), although the numerical evidence suggests a good and reliable behavior. Here we start such an analysis by considering a very simple particular case; namely, a rectangular plate, clamped all around the boundary, and solved with a uniform decomposition. Moreover, we consider only the so-called limit case, corresponding to the limit equations that are obtained for the thickness t going to zero. While the mathematical analysis of the limit case is simpler, such analysis, in general, gives an excellent indication of whether shear locking is present in the real case t > 0. We detail that the element in the setting considered shows indeed optimal behavior.     

Sensitivity of photon-counting based K-edge imaging in X-ray computed tomography

The feasibility of K-edge imaging using energy-resolved, photon-counting transmission measurements in X-ray computed tomography (CT) has been demonstrated by simulations and experiments. The method is based on probing the discontinuities of the attenuation coefficient of heavy elements above and below the K-edge energy by using energy-sensitive, photon counting X-ray detectors. In this paper, we investigate the dependence of the sensitivity of K-edge imaging on the atomic number Z of the contrast material, on the object diameter D , on the spectral response of the X-ray detector and on the X-ray tube voltage. We assume a photon-counting detector equipped with six adjustable energy thresholds. Physical effects leading to a degradation of the energy resolution of the detector are taken into account using the concept of a spectral response function R(E,U) for which we assume four different models. As a validation of our analytical considerations and in order to investigate the influence of elliptically shaped phantoms, we provide CT simulations of an anthropomorphic Forbild-Abdomen phantom containing a gold-contrast agent. The dependence on the values of the energy thresholds is taken into account by optimizing the achievable signal-to-noise ratios (SNR) with respect to the threshold values. We find that for a given X-ray spectrum and object size the SNR in the heavy element's basis material image peaks for a certain atomic number Z. The dependence of the SNR in the high- Z basis-material image on the object diameter is the natural, exponential decrease with particularly deteriorating effects in the case where the attenuation from the object itself causes a total signal loss below the K-edge. The influence of the energy-response of the detector is very important. We observed that the optimal SNR values obtained with an ideal detector and with a CdTe pixel detector whose response, showing significant tailing, has been determined at a synchrotron differ by factors of about two to three. The potentially very important impact of scattered X-ray radiation and pulse pile-up occurring at high photon rates on the sensitivity of the technique is qualitatively discussed.     

Impacts on decision making of executives: Probabilities versus outcomes.

The determinants of decision making of executives are of special interest for companies. For a long time choices have been investigated based on theories that assume an equal impact of expected outcomes and expected probabilities (Von Neumann and Morgenstern 1953, Savage 1954, Kahneman and Tversky 1979). The influence of probabilities in decision processes is, however, questioned by a growing body of research (Rottenstreich and Kivetz 2006, Shapira 1995, March and Shapira 1987, 1992). To monitor the information acquisition process of board members and high-ranking executives in the German insurance industry we conducted 51 personal interviews, which included computer-aided simulations. These simulations clearly and objectively support former statements of executives (Shapira 1995) that they focus more on the amount of decision outcomes than on the corresponding probabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hochdruckreaktionen von oxometallaten,III Hochdruck-hochtemperatur-zersetzung von KVO3

The high pressure - high temperature behaviour of KVO₃ was investigated in a modified belt-type apparatus at different pressures (3–40 kbar), temperatures (500–1100°C), using reducing (BN, graphite) or inert (Cu, Ag, Au) capsule materials. Hollandites K_2?xV₈O₁₆, modified Hollandites K_2?xV_8+2xO_16+x, and V₂O₃ were synthesized as quenchable, crystalline materials. A sequence of reactions is proposed for the high pressure decomposition of KVO₃ in inert capsules which involves the formation of potassium peroxovanadates.     

Direct solution of large systems of linear equations

A very efficient computer subroutine for the direct solution of large numbers of simultaneous linear equations is presented. Basically the program uses Gauss elimination on positive-definite symmetrical systems. The specific features are that systems of very large size and bandwidth can be solved and that all operations on zero elements are eliminated. Also, the program is very simple and can be incorporated into existing programs with a minimum of effort. The amount of backup storage available on the computer used will govern the maximum size of the system which can be solved. A FORTRAN IV listing of the subroutine is given.     

Homogene,abschreckbare hochdruckphasen in den systemen AgSbSe2 - AgInSe2 und AgBiSe2 - AgInSe2

Quenchable, homogenous high pressure phases in the systems AgSbSe₂ - AgInSe₂ and AgBiSe₂ - AgInSe₂ could be synthesized from appropriate mixtures of the ternary compounds in a belt-type high-pressure apparatus. The phases AgSb_1?xIn_xSe₂ crystallize with the rocksalt structure at the Sb-rich side and with the α-NaFeO₂ structure at the In-rich side of the phase diagram. All AgBi_1?xIn_xSe₂ samples have α-NaFeO₂-structure. The high temperature B1-type modification of AgBiSe₂ is quenchable to room temperature at high pressures. Annealing of the high pressure phases at 1 bar and 300°C yielded the starting mixtures of AgInSe₂ with chalcopyrite structure and AgSbSe₂ or AgBiSe₂, rsp. At 1 bar, 25°C the high pressure phases could be stored for at least 8 months.     

杂砂岩碱集料反应特征

杂砂岩集料所含的石英组分是引起碱集料反应的主要活性来源,研究该集料中的石英溶出及其在碱溶液中的行为特征,结果发现:石英颗粒尺寸和相应的硅溶出速度之间存在着一定的相关性,即:石英颗粒尺寸越小,其比表面积越大,同等条件下相应的硅溶出速度越大;石英颗粒的结构特征变化规律与杂砂岩试样本身的碱活性大小之间不存在相关性.集料中的铝主要来源于γ-Al2O3纳米相、黑云母和白云母,其对溶液中硅溶出的影响机理不同.集料中的铝溶出生成铝硅酸盐从而引起溶液中溶出硅含量的降低,砂浆或混凝土碱集料反应膨胀率的大小与溶液中所谓的"自由硅"含量有关,即"自由硅"含量越大,同等条件下的碱集料反应膨胀越大.这些相关性对于实际工程应用非常重要,由此可望建立评价杂砂岩碱活性敏感性的直接测试方法.研究还发现通过添加高铝粉可抑制碱集料反应产生的膨胀.