Curium-doped stannate pyrochlore: Durability under radiation and leaching in water

The radiation resistance of the phase (Gd,Cm)₂Sn₂O₇ with a pyrochlore-type structure containing 3.0 wt % ²⁴⁴Cm was studied. It was established that amorphization occurs at a dose of 10¹⁹ α-decay/g (1.52 displacements per atom), which is 2–5 times higher than that needed for amorphization of titanate and titanate–zirconate pyrochlore phases with a similar structure. The heating of the amorphous ceramics restores the structure of the pyrochlore. The restoration process begins in the temperature interval of 600–700°C. This allows us to estimate the critical amorphization temperature as 650°C. On the 14th day, the rate of Cm leaching from the initial sample in water at 90°C is 10^–1; Gd, 10^–2; and Sn, 10^–3 g/(m2 day). After amorphization the leaching rate increases by an order of magnitude (Cm) and two orders of magnitude (Gd), but it does not change for Sn. Compared to the zirconate and titanate–zirconate phases, stannate pyrochlore is markedly less resistant in water and cannot be regarded as a matrix for the immobilization of REE-actinide fraction wastes.     

Synthesis and Study of Neodyme–Titanate Ceramic with Curium

Doklady Earth Sciences - The properties of the potential matrix of the REE–actinide fraction of high-level radioactive waste have been studied. A sample containing 2 wt % of curium was...     

A two-stage model of fracture of rocks

In this paper we propose a two-stage model of rock fracture. In the first stage, cracks or local regions of failure are uncorrelated and occur randomly throughout the rock in response to loading of pre-existing flaws. As damage accumulates in the rock, there is a gradual increase in the probability that large clusters of closely spaced cracks or local failure sites will develop. Based on statistical arguments, a critical density of damage will occur where clusters of flaws become large enough to lead to larger-scale failure of the rock (stage two). While crack interaction and cooperative failure is expected to occur within clusters of closely spaced cracks, the initial development of clusters is predicted based on the random variation in pre-existing flaw populations. Thus the onset of the unstable second stage in the model can be computed from the generation of random, uncorrelated damage. The proposed model incorporates notions of the kinetic (and therefore time-dependent) nature of the strength of solids as well as the discrete hierarchic structure of rocks and the flaw populations that lead to damage accumulation. The advantage offered by this model is that its salient features are valid for fracture processes occurring over a wide range of scales including earthquake processes. A notion of the rank of fracture (fracture size) is introduced, and criteria are presented for both fracture nucleation and the transition of the failure process from one scale to another.     

The rock fracture experiment with a drive control: A spatial aspect

The statistical analysis of the space–time distributions of acoustical signals emitted from the compressed samples of Westerly granite is presented. The samples were uniaxially loaded in two regimes, one of which included a feedback loop controlled by the current acoustical emission (AE) activity. The distribution of distances between newly-appeared hypocenters follows the power law with the exponent that does not depend on the mode of loading. In both regimes, a transient period of the decorrelated accumulation of damaged sites was revealed between the initial and focal stages of the fracture process. The Hurst analysis indicates a more pronounced trend to planar organization of final damage structure in the case of AE-controlled loading.     

Pairs of earthquakes in the Kuriles

The areas of strong paired earthquakes, including the Simushir ones, have been defined on the basis of the kinetic concepts of the strength of the solids, the multilevel rock structure, and the related hierarchical model of the rock fracture. The analysis of the spatiotemporal kinetics of these areas did not show any physical difference as compared to the preparation for the single events.     

Mass Rock Fall Prediction in Zhezkazgan Mines at the Basis of Seismic Regime Analyzing.

Zhezkazgan copper deposit is strongly exploited since 1942. Its typical feature is multilevelmineralization. Mine's thickness of sedimentary rock. Primary copper supply is from 150 to 450meters in depth. Capacity of ore body is 1,5-30 m, suddenly 30 - 60 moters. High capacity partsof deposit is mined out by room - pillar system. Stress state of rock mass of the deposit is characterized by that, what horizontal stresses is higher in 4-10 times than vertical stresses, which iscaused by weight o…