Intracoin - An International Nuclide Transport Code Intercomparison Study

1981 ◽  
Vol 11 ◽  
Author(s):  
K. Andersson ◽  
B. Grundfelt ◽  
J. Hadermann
Keyword(s):  
Extreme Environments ◽  
Poor Quality ◽  
Wide Range ◽  
Radioactive Waste Repositories ◽  
High Level ◽  
Intercomparison Study ◽  
Micro Organisms ◽  
Hostile Environments ◽  
Waste Repositories ◽  
Geological Formations

Much effort is currently centred on the construction of elaborate computer programs to model the release to the biosphere of radionuclides from proposed high level radioactive waste repositories in deep geological formations. Although the lack or poor quality of background data is often emphasised, it is generally considered that by examining a wide range of possible values of the important parameters involved, likely processes are assessed or their omission and possible relevence is acknowledged. However, one factor that has been almost totally ignored is the presence of micro-organisms in deep geological formations. The common assumption is that the biosphere is limited to the earth's surface, and soil to a depth of a few metres. Recent research has shown, however, that viable micro-organisms can inhabit deep groundwaters and that the biosphere can extend to depths of at least 5 km. Examples of organisms tolerant to extreme environments are given in Table 1 although ranges are likely to be conservative due to the difficulties of culturing these organisms, which tend to have exotic nutritional requirements, and sampling them in extremely hostile environments.

The Effect of Microbial Activity on the Containment of Radioactive Waste in a Deep Geological Repository

1981 ◽  
Vol 11 ◽  
Author(s):  
Julia M. West ◽  
Ian G. Mckinley ◽  
Neil A. Chapman
Keyword(s):  
Radioactive Waste ◽  
Poor Quality ◽  
Wide Range ◽  
Geological Repository ◽  
Background Data ◽  
Radioactive Waste Repositories ◽  
High Level ◽  
Waste Repositories ◽  
Geological Formations

Much effort is currently centred on the construction of elaborate computer programs to model the release to the biosphere of radionuclides from proposed high level radioactive waste repositories in deep geological formations. Although the lack or poor quality of background data is often emphasised, it is generally considered that by examining a wide range of possible values of the important parameters involved, likely processes are assessed or their omission and possible relevence is acknowledged.

Brazilian research on extremophiles in the context of astrobiology

2012 ◽  
Vol 11 (4) ◽  
pp. 325-333 ◽  
Author(s):  
Rubens T. D. Duarte ◽  
Felipe Nóbrega ◽  
Cristina R. Nakayama ◽  
Vivian H. Pellizari
Keyword(s):  
Hydrothermal Vents ◽  
High Pressures ◽  
Human Life ◽  
Extreme Environments ◽  
Brazilian Coast ◽  
Polar Regions ◽  
Oceanic Sediments ◽  
Wide Range ◽  
Antarctic Continent ◽  
Micro Organisms

AbstractExtremophiles are organisms adapted to grow at extreme ranges of environmental variables, such as high or low temperatures, acid or alkaline medium, high salt concentration, high pressures and so forth. Most extremophiles are micro-organisms that belong to the Archaea and Bacteria domains, and are widely spread across the world, which include the polar regions, volcanoes, deserts, deep oceanic sediments, hydrothermal vents, hypersaline lakes, acid and alkaline water bodies, and other extreme environments considered hostile to human life. Despite the tropical climate, Brazil has a wide range of ecosystems which include some permanent or seasonally extreme environments. For example, the Cerrado is a biome with very low soil pH with high Al+3concentration, the mangroves in the Brazilian coast are anaerobic and saline, Pantanal has thousands of alkaline–saline lakes, the Caatinga arid and hot soils and the deep sea sediments in the Brazilian ocean shelf. These environments harbour extremophilic organisms that, coupled with the high natural biodiversity in Brazil, could be explored for different purposes. However, only a few projects in Brazil intended to study the extremophiles. In the frame of astrobiology, for example, these organisms could provide important models for defining the limits of life and hypothesize about life outside Earth. Brazilian microbiologists have, however, studied the extremophilic micro-organisms inhabiting non-Brazilian environments, such as the Antarctic continent. The experience and previous results obtained from the Brazilian Antarctic Program (PROANTAR) provide important results that are directly related to astrobiology. This article is a brief synopsis of the Brazilian experience in researching extremophiles, indicating the most important results related to astrobiology and some future perspectives in this area.

Appraisal of waveform repeatability for crosshole and hole-to-tunnel seismic monitoring of radioactive waste repositories

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. Q21-Q34 ◽  
Author(s):  
Stefano Marelli ◽  
Edgar Manukyan ◽  
Hansruedi Maurer ◽  
Stewart A. Greenhalgh ◽  
Alan G. Green
Keyword(s):  
Radioactive Waste ◽  
Damage Zone ◽  
P Wave ◽  
Frequency Noise ◽  
Coherent Noise ◽  
High Level Radioactive Waste ◽  
Seismic Waveform ◽  
Radioactive Waste Repositories ◽  
High Level ◽  
Waste Repositories

Countries worldwide are seeking solutions for the permanent removal of high-level radioactive waste from the environment. Surrounding the waste with multiple engineered barriers and emplacement in deep geological repositories is widely accepted as a safe means of isolating it from the biosphere for the necessary [Formula: see text]. As a precautionary measure, society demands that repositories be monitored for [Formula: see text] after they are backfilled and sealed. Effective monitoring that does not compromise the engineered and natural barriers is challenging. To address this issue, we investigate the viability of crosshole and hole-to-tunnel seismic methods for remotely monitoring high level radioactive waste repositories. Measurements are made at two underground rock laboratories in Switzerland, one within granitic rock and one within clay-rich sediments. Numerical simulations demonstrate that temporal changes of the monitored features (i.e., bentonite plug, excavation damage zone, sand-filled microtunnel) should produce significant changes in the seismicwaveforms. Nevertheless, inversion for medium-property changes requires that true seismic waveform changes are not overwhelmed by recording variations. We find that a P-wave sparker source is highly repeatable up to frequencies of [Formula: see text] for propagation distances out to tens of meters involved in repository-scale monitoring. Hydrophone repeatability is limited by incoherent high frequency noise and variable hydrophone-borehole coupling conditions, but firmly grouted geophones within the tunnels yield consistent recordings. Three kinds of coherent noise contaminate the data: (1) mechanically induced electrical effects in the hydrophone chains; (2) high currents in the sparker cable, which cause it to oscillate radially as a line source; and (3) tube waves. Our investigations outline a quantitative methodology to assess data-quality requirements for successful monitoring. We suggest that full waveform seismic tomography can be used to monitor radioactive waste emplacement tunnels, provided that careful attention is paid to instrument fidelity and noise suppression.

scholarly journals Thermally Induced Bentonite Alterations in the SKB ABM5 Hot Bentonite Experiment

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1017
Author(s):  
Ritwick Sudheer Kumar ◽  
Carolin Podlech ◽  
Georg Grathoff ◽  
Laurence N. Warr ◽  
Daniel Svensson
Keyword(s):  
Thermal Conditions ◽  
Maximum Temperature ◽  
Thermally Induced ◽  
Calcite Dissolution ◽  
Mineral Stability ◽  
Radioactive Waste Repositories ◽  
High Level ◽  
Waste Repositories ◽  
Tetrahedral Substitution ◽  
Measuring Ph

Pilot sites are currently used to test the performance of bentonite barriers for sealing high-level radioactive waste repositories, but the degree of mineral stability under enhanced thermal conditions remains a topic of debate. This study focuses on the SKB ABM5 experiment, which ran for 5 years (2012 to 2017) and locally reached a maximum temperature of 250 °C. Five bentonites were investigated using XRD with Rietveld refinement, SEM-EDX and by measuring pH, CEC and EC. Samples extracted from bentonite blocks at 0.1, 1, 4 and 7 cm away from the heating pipe showed various stages of alteration related to the horizontal thermal gradient. Bentonites close to the contact with lower CEC values showed smectite alterations in the form of tetrahedral substitution of Si4+ by Al3+ and some octahedral metal substitutions, probably related to ferric/ferrous iron derived from corrosion of the heater during oxidative boiling, with pyrite dissolution and acidity occurring in some bentonite layers. This alteration was furthermore associated with higher amounts of hematite and minor calcite dissolution. However, as none of the bentonites showed any smectite loss and only displayed stronger alterations at the heater–bentonite contact, the sealants are considered to have remained largely intact.

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