Study of the Stability of Aluminophosphate Glasses–Matrices for Immobilization of Radioactive Waste

Doklady Earth Sciences - Liquid radioactive wastes of the reprocessing of spent nuclear fuel are included in a glassy Na–Al–P matrix for subsequent placement in underground storage....     

Rock Mass Characteristics in Beishan, A Preselected Area for China’s High-Level Radioactive Waste Disposal

Geological and hydrological characteristics, joint geometric features, rock physical and mechanical properties and rock mass quality are studied in the Beishan area, preselected for China’s high-level radioactive waste (HLW) disposal engineering. A comprehensive survey method is developed to study joint geometric features in the outcrop and samples from borehole BS06 into the Xinchang rock mass were tested. The optimal joint sets are determined by rose diagrams and equal-area lower hemisphere plots of joint poles. Results show that: 1) the distribution of joint occurrence obeys a normal distribution, while the distribution of joint spacing obeys a negative exponential distribution; 2) concentric circular and tangent circular sampling windows are applied to study the trace length and the trace midpoint density. Results indicate that tangent circular sampling window is more stable and reasonable; 3) Beishan granite shows high density, low porosity and high strength based on many laboratory tests and the physical properties and mechanical properties are closely related; and 4) a synthesis index, Joint Structure Rating (JSR), is applied to evaluate the quality of rock mass. Through the research results of rock mass characteristics, the Xinchang rock mass in the Beishan preselected area has the favorable conditions for China’s HLW disposal repository site.     

Rare-Earth Elements from Modern Mineral–Organic Associations in the Zone of Sulfide Ore Hypergenesis

The REE composition of modern mineral–organic associations in the sulfide ore hypergenesis zone of the Berezitovoe deposit in the Russian Far East was studied for the first time. It is shown that the mineral–organic associations widely abundant in the valley of Konstantinovskii Creek and represented by bright brown crusts on the surface of deluvial deposits were formed at the expense of the influence of acid highly mineralized mine waters from the Berezitovoe deposit. The mineral–organic associations found in the Creek valley may be considered as a new indicator for evaluation of the geoecological state of modern technogenic landscapes.     

Estimation of Sill Matrices in the Linear Model of Coregionalization

When using least squares to fit the linear model of coregionalization to multivariate geostatistical data, the sill matrices for the different regions must be estimated, subject to the constraint that they be non-negative definite. In 1992, Goulard and Voltz proposed and empirically examined an iterative algorithm for doing this. Although no proof was given for its convergence or for the uniqueness of the solution to the problem, the algorithm has subsequently been extensively and successfully used. In this paper, we prove that the minimization problem, in fact, has a unique solution and that the algorithm is guaranteed to converge to it from any starting point. We also discuss the effect of the starting point on the speed of convergence.     

Role of Elisional Water Exchange in the Hydrodynamic Field Formation in the Yamal–Kara Depression

Lithology and Mineral Resources - Unique material pertaining to the hydrodynamics of petroliferous rocks in the Yamal–Kara Depression has been summarized for the first time in the last 30...     

Exploration of Water Resource and Multiple Model for Water Resource Development in Karst Areas with the Preferred Plane Theory

According to the theory of preferred plane, preferred planes (faults) always control the distribution of bedrock fissure water and hold abundant groundwater. Thus, the exploration of fissure or karst water can be converted into searching for the watery preferred plane (WPP). In the paper, the characteristic of watery preferred planes is analyzed and a series of superior indices has been set up. It is introduced that WPPs are determined by the methods of geological analysis, superior index and complex geophysical analysis. Meanwhile, new multiple model for water resource development in the water-scarce areas of karst mountainous regions are advanced.     

Silica Distribution in the System Quartz–Water–Vapor Depending on the Temperature Gradient

Careful measurements of temperature on the surface of autoclaves indicate that small temperature gradients (TG) occur in the standard electric furnaces. These gradients can affect the results of long-lasting (up to 775 days) experiments in the system quartz–water–vapor at 300°C. From the bottom of the autoclave to its top, the temperature decreased in the upper parts of the electric furnaces and increased in their lower parts (TG =–0.08 and 0.15°C/cm, respectively). In the upper parts of the electric furnaces, the concentration of dissolved silica (m) was close to the quartz solubility (10 mmol/kg), and no other changes took place, which is consistent with the currently conventionally admitted notion that quartz is stable under these conditions. In the lower parts of the electric furnaces, m decreased to 0.03 mmol/kg, and opal was precipitated on the walls of the capsules above the solution (the opal was transformed into secondary quartz with time). These data suggest that no equilibrium silica distribution between liquid and vapor water phases was reached. We have suggested and analyzed as wide as possible circle of hypotheses conceivably able to explain this unequilibrated state. The most realistic explanation of the phenomenon seems to be that distillation is initiated by preferable evaporation of the solution in its thin (<100 nm) layer at the meniscus edge. A mathematic model of the process is suggested. The model is consistent with experimental data. The phenomenon in question can be detected in various experimental and technological systems and hampers the attainment of complete equilibrium. In natural systems, this phenomenon can lead to the migration of cavities partly filled with solution at an inversion of the geothermal gradient (beneath sills and lava flows).     

Mathematical Model of the Geothermal Water Resources in the South Hot Spring System in Chongqing

INTRODUCTION Southhotspring,smallhotspringandQiaokou barepresent,betweenthem,thegeothermalwaters ofthesouthhotspringsysteminthesouthhotspring anticlineinChongqing.Thesouthhotspringanti clineisageothermalwaterstoragesystem.Itex tendsfromnorthtosouthinthecentralpartof Chongqing.Itis45kmlongfromsouthtonorthand2kmwide.Thesouthhotspringandsmallhot spring,inthemiddleoftheanticline,arewell known touristattractionsfortheirgeothermalwaters.Ex cessiveexploitationledtoagradualdeclineinthewa terlev…     

Formation of Water-Bearing Defects in Olivine in the Presence of Water–Hydrocarbon Fluid at 6.3 GPa and 1200°C

The main trends of water dissolution in Fe-bearing olivine have been investigated in the olivine–H₂O–hydrocarbon fluid system in experiments at a pressure of 6.3 GPa, a temperature of 1200°C, and hydrogen fugacity ( fH₂) buffered by the Mo–MoO₂ equilibrium. The content and contribution of ОH defects of different types in Fe-bearing olivines depend on the composition of reduced fluids in the system. As the fraction of hydrocarbons in the fluid increases, the H₂O content in olivine crystals decreases from 900 to 160–180 ppm, while the ОН absorption peaks become lower at high frequencies and occupy a larger part of the infrared spectrum in the low-frequency region. According to the experimental results, even the deepest seated mantle olivines with OH defects were not equilibrated with a fluid rich in light alkanes or oxygenated hydrocarbons.     

Daily Course of CO2 Fluxes in the Atmosphere–Water System and Variable Fluorescence of Phytoplankton during the Open-Water Period for Lake Baikal according to Long-Term Measurements

The process of gas exchange of CO₂ in the atmosphere–water system and its relation to the daily course of variable fluorescence of phytoplankton is studied on the basis of long-term (2004–2014) measurements during the open water period for Lake Baikal. It is found that the decrease in photosynthetic activity of plankton is almost synchronous to the increase in the CO₂ flux from atmosphere to water. It follows from comparison of the spring and summer data with December measurements that the daily decrease in variable fluorescence of phytoplankton is caused by the internal daily rhythm of the photosynthetic activity of plankton.

     

A Thermodynamic Model of the Water–Rock Interaction under Hydrothermal Exposure of the Bazhenov Formation

Thermodynamic modeling of the hydrothermal exposure of the rocks of the Bazhenov Formation resulted in revealing the equilibrium mineral associations at 50–350°C and the pressure of saturated water vapor. The calculation results show that mineral parageneses varied slightly with the increase of temperature. Thus, zeolites were characterized by the stilbite–laumontite–wairakite series; kaolinite, pyrite, dolomite, and brannerite were replaced by montmorillonite and/or albite, pyrrhotite, calcite, and uraninite, respectively. The modeling results were confirmed in experiments.     

Stereological Method for Reducing Probability of Earthquake-Induced Damage in a Nuclear Waste Repository

In Sweden, spent nuclear fuel is planned to be placed in copper/iron canisters and deposited at a depth of approximately 500 m in granitic rock. Earthquakes may induce secondary shear movements in fractures intersecting canister deposition holes, thereby threatening the integrity of the canisters. The extent of a secondary movement is related to earthquake distance and magnitude and to the size of the intersecting fracture. A probability of a canister being intersected by a critically large fracture can be calculated for given fracture size and orientation distributions, assuming that no measures are taken to identify and avoid such fractures. This paper analyses a stereological method of reducing this probability through observations of fractures fully intersecting the drift tunnels overlying the deposition holes. Deposition positions located in the planar extension of such full intersections are rejected. Both exact, numerical solutions and approximate solutions to this stereological problem are derived and the correctness of the solutions is verified by simulations. Also, the cost in terms of unutilised deposition positions is calculated. The probability of critical canister/fracture intersections is a few percent for typical fracture populations determined from field observations at a candidate site for a spent nuclear fuel repository in Sweden. By applying the suggested method, it is demonstrated that this probability can be reduced by a factor of about 35 in a typical case. The expense in terms of unutilised tunnel length is around 10 percent, which is seen as reasonable.     

A Leaching Model for “Aged” Sodium–Aluminophosphate Vitreous Waste Forms of Radionuclides

Doklady Earth Sciences - High-level radioactive wastes of nuclear power engineering are vitrified for removal to deep underground repositories. Radionuclide decay leads to heating and...     

Contribution of Hydrothermal Processes to the Enrichment of Lithium in Brines: Evidence from Water–Rock Interacting Experiments

Aquatic Geochemistry - Over the world, the available lithium (Li) resources are reserved mainly in closed-basin brines, with high Li concentration (&gt;?150&nbsp;mg/L) and low Mg/Li...     

Durability assessment of the Ala?at? tuff (Izmir) in western Turkey

Ala?at? tuff has been used extensively as a source of building stone for outdoor and indoor decorations since the historical times in and around the tourist town of Ala?at? (western Turkey). The use of the Alacati tuff in buildings has been made compulsory by the Ala?at? municipality, for preserving the historical appearance of the buildings, after 2005 in Ala?at?. It has been noticed that, evident deteriorations developed in tuff surfaces of the stone buildings and garden walls within 5?C6?years of their emplacement. Durability properties of the Ala?at? tuff are evaluated by determining the mineralogical, chemical, and physico-mechanical properties of the fresh tuff samples obtained from the only operative quarry in the area. Ageing tests such as Na₂SO₄ and MgSO₄ salt crystallization, freezing?Cthawing, and wetting?Cdrying were conducted on the fresh tuff samples to assess their durability. Additionally, the durability of the tuff is also evaluated by determining its average pore diameter, saturation coefficient, wet-to-dry strength ratio, static rock and slake-durability indices. Fresh Ala?at? tuff has high porosity and low unit weight and strengths and are classified to be very poor to moderately durable stone based on the test results of different durability assessment methods. Mineralogical and geochemical analyses have also been carried out on the deteriorated tuff samples collected from the surfaces of the stone buildings to determine the effect of weathering on tuff and the test results have been compared with those of the fresh tuff samples. There is no major difference observed between the mineralogy and chemistry of the fresh and weathered tuff samples thus, it has been concluded that physical weathering has been dominant in the area in deterioration of tuff.