Feasibility Of Radioactive Waste Disposal Research Articles

Main outcomes from in situ thermo-hydro-mechanical experiments programme to demonstrate feasibility of radioactive high-level waste disposal in the Callovo-Oxfordian claystone

In the context of radioactive waste disposal, an underground research laboratory (URL) is a facility in which experiments are conducted to demonstrate the feasibility of constructing and operating a radioactive waste disposal facility within a geological formation. The Meuse/Haute-Marne URL is a site-specific facility planned to study the feasibility of a radioactive waste disposal in the Callovo-Oxfordian (COx) claystone. The thermo-hydro-mechanical (THM) behaviour of the host rock is significant for the design of the underground nuclear waste disposal facility and for its long-term safety. The French National Radioactive Waste Management Agency (Andra) has begun a research programme aiming to demonstrate the relevancy of the French high-level waste (HLW) concept. This paper presents the programme implemented from small-scale (small diameter) boreholes to full-scale demonstration experiments to study the THM effects of the thermal transient on the COx claystone and the strategy implemented in this new programme to demonstrate and optimise current disposal facility components for HLW. It shows that the French high-level waste concept is feasible and working in the COx claystone. It also exhibits that, as for other plastic clay or claystone, heating-induced pore pressure increases and that the THM behaviour is anisotropic.

Imprinting chemical remanent magnetization in claystones at 95 °C

Thermal effects related to burial and hydrothermal alteration leads to chemical remanent magnetization (CRM). We present an experimental study of CRM production by heating claystones at 95 °C. A vertical magnetic field of 2 mT was applied to the claystones during heating and the evolution of the remanence during heating in air is monitored intermittently for up to four months. Solid fragments (9 to 26 g) of claystones are included in a Teflon holder that is placed in the oven under a controlled atmosphere. Newly formed grains acquire a CRM and a thermoviscous magnetization (TVRM), both being parallel to the applied magnetic field. CRM is related to the amount of newly formed grains that pass the critical volume during the reaction. To measure the acquired remanence, the claystones are first cooled in a zero magnetic field and then measured using a 2G SQUID magnetometer. In the frame of the research programme on the feasibility of radioactive waste disposal in a deep geological formation, we investigate the magnetic transformation of Mont Terri Lower Dogger claystones (Switzerland) due to thermal imprinting at 95 °C. We simulate the dehydration that occurs in the walls of galleries after excavation when interstitial water evaporates and rehydration when the galleries are refilled allowing water to move towards dehydrated zones. During dehydration, the remanence gains one order of magnitude at the beginning of the experiment and then it follows a linear rate of 0.23 ± 0.07 mA m − 1 /day between 3 and 14 days. The magnetic susceptibility increases by a few percent. The increase of the remanence and of the magnetic susceptibility stops after 15 days. Mass monitoring indicates that interstitial water evaporates when remanence and magnetic susceptibility stabilizes. During rehydration, the remanence increases again whilst magnetic susceptibility drops by a few percent. After 20 days, the remanence during rehydration follows a rate of 0.42 ± 0.15 mA m − 1 /day. By contrast, when rehydration takes place later, after 66 days, the rate is much lower (0.09 ± 0.04 mA m − 1 /day). Low temperature investigation of magnetic properties indicates an initial magnetic assemblage of magnetite and pyrrhotite. Newly formed magnetite and hematite carry the remanence. We propose that magnetite is formed at the expense of pyrite. Hematite results from the progressive oxidation of newly formed magnetite. Our results suggest the possibility that any claystones that pass the oil window can be remagnetized due to the unique action of temperature.

Disposal of radioactive wastes by hydraulic fracturing: Part I. General concept and first field experiments

Editorial note. This is the first of a series of articles on the development of radioactive waste disposal by hydraulic fracturing at Oak Ridge National Laboratory. Five papers, including this one, are planned to describe fully the advance from the initial concept to a practical method for radioactive waste disposal: • Part I, General concept and first field experiments; • Part II, Mechanics of fracture formation and design of observation and monitoring wells; • Part III, Chemical development waste-cement mixes; • Part IV, Design of ORNL's shale-fracturing plant; • Part V, First injections of actual wastes. The series will provide a detailed account of all aspects associated with the development of this unique and promising method of waste disposal. Readers will recognize, at the end of the series, that the individual articles are not reports of discrete investigations, separated from each other and conducted in logical sequence, but rather are parts of the whole picture emerging as the investigation continues. Although the work relates specifically to the natural conditions at Oak Ridge and to the disposal needs of ORNL, the results of this investigation will suggest possible adaptations of the method at other sites, as well as to other types of wastes. The feasibility of radioactive waste disposal by hydraulic fracturing has been demonstrated at Oak Ridge National Laboratory. This disposal method is an adaptation of hydraulic fracturing techniques used in the petroleum industry and is aimed at replacing current methods of shallow ground disposal. A number of problems had to be solved in the development of this method. First, it had to be shown that the fractures formed in shales at Oak Ridge would follow the bedding planes, and not break up vertically toward the surface. This has been done, as is described in this paper.

Feasibility of Radioactive Waste Disposal in Shallow Sedimentary Formations

One of the pressing problems of the potential nuclear-power industry is the necessity for disposing of radioactive wastes incident to operating reactors and recovering fissionable material from exp...