Understanding Uranium Migration in Hard Rocks

2008 ◽  
pp. 19-26 ◽  
Author(s):  
W. Eberhard Falck ◽  
David Read ◽  
S. Black ◽  
D. Thornley ◽  
M. Markovaara-Koivisto ◽  
...  
Keyword(s):  
Hard Rocks ◽  
Uranium Migration

Uranium migration through intact sandstone: effect of pollutant concentration and the reversibility of uptake

1996 ◽  
Vol 21 (1-4) ◽  
pp. 215-228 ◽  
Author(s):  
R. Sims ◽  
T.A. Lawless ◽  
J.L. Alexander ◽  
D.G. Bennett ◽  
D. Read
Keyword(s):  
Pollutant Concentration ◽  
Uranium Migration

scholarly journals Rockslides on limestone cliffs with subhorizontal bedding in the southwestern calcareous area of China

2014 ◽  
Vol 14 (9) ◽  
pp. 2627-2635 ◽  
Author(s):  
Z. Feng ◽  
B. Li ◽  
Y. P. Yin ◽  
K. He
Keyword(s):  
Numerical Modeling ◽  
Rock Mass ◽  
Hard Rock ◽  
Compression Fracture ◽  
Field Observations ◽  
Mountainous Areas ◽  
Hard Rocks ◽  
Rupture Plane ◽  
Rock Collapse ◽  
Cliff Retreat

Abstract. Calcareous mountainous areas are highly prone to geohazards, and rockslides play an important role in cliff retreat. This study presents three examples of failures of limestone cliffs with subhorizontal bedding in the southwestern calcareous area of China. Field observations and numerical modeling of Yudong Escarpment, Zengzi Cliff, and Wangxia Cliff showed that pre-existing vertical joints passing through thick limestone and the alternation of competent and incompetent layers are the most significant features for rockslides. A "hard-on-soft" cliff made of hard rocks superimposed on soft rocks is prone to rock slump, characterized by shearing through the underlying weak strata along a curved surface and backward tilting. When a slope contains weak interlayers rather than a soft basal, a rock collapse could occur from the compression fracture and tensile split of the rock mass near the interfaces. A rockslide might shear through a hard rock mass if no discontinuities are exposed in the cliff slope, and sliding may occur along a moderately inclined rupture plane. The "toe breakout" mechanism mainly depends on the strength characteristics of the rock mass.

The cutting resistance of hard rocks during working by a rotor excavator

1974 ◽  
Vol 10 (4) ◽  
pp. 472-475
Author(s):  
M. G. Moiseenko ◽  
P. V. Ostapenko
Keyword(s):  
Cutting Resistance ◽  
Rotor Excavator ◽  
Hard Rocks

Phosphate biogeochemical barrier for uranium in situ immobilization in an aquifer nearby sludge repository

2021 ◽  
Author(s):  
Grigory Artemiev ◽  
Alexey Safonov ◽  
Nadezhda Popova
Keyword(s):  
Essential Elements ◽  
Ion Concentration ◽  
Soluble Form ◽  
High Concentration ◽  
Rapid Reduction ◽  
Near Surface ◽  
Nitrate Ions ◽  
Uranium Migration ◽  
Storage Facilities

<p>Uranium migration in the oxidized environment of near-surface groundwater is a typical problem of many radiochemical, ore mining and ore processing enterprises that have sludge storage facilities on their territory. Uranium migration, as a rule, occurs against a high salt background due to the composition of the sludge: primarily, nitrate and sulfate anions and calcium cations. One of the ways to prevent the uranium pollution is geochemical or engineering barriers. For uranium immobilization, it is necessary to create conditions for its reduction to a slightly soluble form of uraninite and further mineralization, for example, in the phosphate form. An important factor contributing to the rapid reduction of uranium is a in the redox potential decreasing and the removal of nitrate ions, which can be achieved through the activation of microflora. It should be added that phosphate itself is one of the essential elements for the development of microflora. This work was carried out in relation to the upper aquifer (7-12 m) near the sludge storage facilities of ChMZ, which is engaged in uranium processing and enrichment. One of the problems of this aquifer, in addition to the high concentration of nitrate ions (up to 15 g / l), is the high velocity of formation waters.<br>In laboratory conditions, the compositions of injection solutions were selected containing sources of organic matter to stimulate the microbiota development and phosphates for uranium mineralization. When developing the injection composition, special attention was paid to assessing the formation of calcite deposits in aquifer conditions to partially reduce the filtration parameters of the horizon and reduce the rate of movement of formation waters. This must be achieved to ensure the possibility of long-term deposition of uranium and removal of nitrate. The composition of the optimal solution was selected and in a series of model experiments the mineral phases containing the lowest hydrated form of the uranium-containing phosphate mineral meta-otenite were obtained.<br>In situ mineral phosphate barrier Formation field tests were carried out in water horizon conditions in a volume of 100m3 by injection of an organic and phosphates mixture. As a result, at the first stage of field work, a significant decreasing nitrate ion concentration, and reducing conditions formation coupled with the dissolved uranium concentration of decreasing were noted.</p>

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