Microbial processes relevant for the long-term performance of high-level radioactive waste repositories in clays

2014 ◽  
Vol 400 (1) ◽  
pp. 179-194 ◽  
Author(s):  
Artur Meleshyn
Keyword(s):  
Radioactive Waste ◽  
Microbial Processes ◽  
High Level Radioactive Waste ◽  
Radioactive Waste Repositories ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance ◽  
Waste Repositories

scholarly journals Preliminary Performance Assessment for Deep Borehole Disposal of High-Level Radioactive Waste

2012 ◽  
Vol 1475 ◽  
Author(s):  
Peter N. Swift ◽  
Bill W. Arnold ◽  
Patrick V. Brady ◽  
Geoff Freeze ◽  
Teklu Hadgu ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
High Level Radioactive Waste ◽  
Deep Boreholes ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTDeep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.

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.

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