Posiva Oy is a Finnish company with headquarters in the municipality of Eurajoki, Finland. It was founded in 1995 by Teollisuuden Voima (60% of stock) and Fortum (40% of stock), two Finnish nuclear plant operators, for researching and creating a method of final disposal of spent nuclear fuel from their plants.For this purpose, Posiva is currently constructing the Onkalo spent nuclear fuel repository, the world's first deep geological repository, at the Olkiluoto Nuclear Power Plant site..
In this paper, 114 uniaxial compressive strength tests were carried out on specimens of veined gneiss with diameters ranging from 14 mm to 100 mm. The main objective of the study was to investigate the influence of the specimen size on the strength behavior of this metamorphic, heterogeneous rock. This size effect results in an increase in strength from small 14-mm diameter specimens up to 50-mm diameter specimens. Thereafter, a mild decrease in results is observed from 50-mm to 100-mm diameter specimens, in line with traditionally considered size-effect approaches. The findings generally agree with previous studies on size effects in sedimentary and igneous rocks, suggesting that metamorphic rocks may also tend to follow the Unified Size-Effect Law (USEL), accounting for general and reverse size-effects in strength. Nevertheless, some variability observed in the results, mainly attributed to inherent heterogeneity of the studied rock could influence how clearly this ascending-descending trend is captured by the model.
The Full-Scale In-Situ System Test (FISST) constitutes one of the most comprehensive and large-scale experimental investigation s to date, aimed at advancing the design and understanding of engineered barrier systems (EBS) within the framework of nuclear waste repository development. Initiated in 2018, the FISST involves the placement of two test canisters within designated deposition holes in the ONKALO® underground research facility's demonstration area, located in a tunnel approximately 50 meters in length. FISST represents a full-scale implementation of the KBS-3V disposal design concept, the reference methodology adopted in Finland and Sweden for the final disposal of nuclear waste. A laboratory testing campaign was undertaken to calibrate the thermo-hydro-mechanical (THM) model parameters for the deposition hole buffer and tunnel backfill materials used in FISST. These materials consisted of Wyoming-type bentonite utilized for blocks and pellets within the deposition hole, along with Italian and Bulgarian bentonites employed in the form of blocks and pellets as tunnel backfill materials. Blocks and pellets were produced with these three types of bentonites. This study focuses on the calibration of key material properties associated with the components of FISST, including thermal conductivity, water retention characteristics, permeability, and mechanical parameters. The Barcelona Basic Model (BBM) was used to represent the block materials, while model with double porosities was employed for the pellets. Additionally, a methodology was developed to linearize the BBM for improving computational efficiency in the simulations that followed. Subsequently, the linearized Barcelona Basic Model (BBM) was employed in thermo-hydro-mechanical (THM) calculations. Following the calibration of the material models, a large-scale 3D thermo-hydraulic (TH) simulation, was performed to define TH boundary conditions for a 3D THM model on a reduced scale. This approach validated the feasibility of 3D modeling under defined TH boundary conditions with accurately calibrated THM parameters. All simulations were conducted using CODE_BRIGHT, a finite element method (FEM) program specifically tailored for advanced THM modeling of complex systems.
O presente artigo, fruto de uma Tese de Doutorado e de diálogos entre professoras da Educação Básica e do Ensino Superior, da cidade de Porto Alegre/RS, apresenta reflexões sobre o conceito de branquitude e como este se reflete no cotidiano da escola. A partir do diálogo com a literatura sobre o tema e das respostas de professores e professoras a um questionário, refletimos acerca do conceito de branquitude e do porquê silenciamos a discussão a o respeito dessa identidade racial na escola. O artigo discute como operam os privilégios raciais, simbólicos e materiais que os sujeitos brancos detém no interior das dinâmicas da escola e como isso vai perpetuando as hierarquias na sociedade.
Hydraulic, overcoring and LVDT stress measurements have been conducted for characterizing the in situ stress state at the spent nuclear fuel repository at Olkiluoto site, located in Western Finland. The effect of foliation on the stress measurement data was investigated. The analysis of the hydraulic data conducted in foliated rock types shows that the hydraulically-induced fracture propagates along a foliation plane rather than developing along the true maximum horizontal stress direction as dictated by the theory of hydraulic fracturing. An integration of the stress measurement data considered to be reliable was conducted for establishing the most likely stress field and confidence intervals for the large (site) and small scales. At the depth of the planned repository, the stress magnitudes obtained for the two scales were found to be similar, thus concluding that the confidence in the derived stresses is high. The mean magnitudes of the major, intermediate and minor principal stresses are 22, 18, and 11 MPa, respectively. The estimated orientation of the major principal stress (WNW-ESE) agrees with the regional stress state.
