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The ionization chamber tritium monitor is the most important online monitoring equipment for monitoring the concentration of tritium in the air. In order to solve the problem of quantity value transmission, the calibration technology of ionization chamber tritium monitor was studied. The laboratory calibration device of tritium monitor is established according to the mass flow method. The reference tritium gas for calibration is diluted and prepared by controlling the volume of standard tritium gas filled into the calibration device. The prepared reference tritium gas is used to calibrate the ionization chamber tritium monitor. At the same time, the influence factors of the calibration process on the calibration results are studied on the developed laboratory calibration device; the expanded uncertainty of reference tritium gas concentration prepared by laboratory calibration device is 3.2%-3.6%(k=2); when tritium activity concentration is 3.10×103-1.98×105 Bq/L, the response linearity of SP1400 tritium monitor to tritium gas activity is good(r2=0.999 3), the calibration factor is 0.97, and the standard synthetic uncertainty is 4.3%-5.0%. The laboratory calibration device of tritium monitor can prepare tritium gas with different activity concentrations. The calibration method is simple to operate and easy to popularize, which can meet the needs of tritium monitor calibration.

Filling methods in the mining industry can maximize the recovery of mineral resources and protect the underground and surface environments. In recent years, such methods have been widely used in metal mines where pipeline transportation typically plays a decisive role in the safety and stability of the entire filling system. Because the filling slurry contains a large percentage of solid coarse particles, the involved pipeline is typically eroded and often damaged during such a process. A possible solution is the so-called nesting repair technology. In the present study, nesting a 127 mm outer diameter pipeline in 151 mm inner diameter borehole is considered to meet the repair objective. First, by using the rheological theory, the pipeline transmission resistance and self-flow conveying range are calculated under different working conditions. It is shown that the pipeline transmission resistance is larger when the inner diameter of casing is 80 mm, and the limit flow rate of vertical pipeline self-flow is 120 m3/h; moreover, when the pipeline diameter is 100 mm and the flow rate is 140 m3/h, the self-flow conveying can be satisfied in most of the underground −455 m stage. Accordingly, a plan is presented for the nesting repair strategy, based on the installation of a drill bit under the casing and lowering the casing into the borehole as if it were a drill pipe. Finally, the outcomes of such a strategy are verified. The filling flow rate range using the new pipelines is found to be in the range from 188.60 to 224.39 m3/h, and its average filling flow rate reaches 209.83 m3/h when conveying 2319.6 m long-distance quarry. [ABSTRACT FROM AUTHOR]

Pre-existing concealed goafs underneath open-pit slopes (PCO-goafs) pose a serious threat to the stability of open-pit slopes (OP-slopes), which is a common problem worldwide. In this paper, the variable weight-target approaching method, equilibrium beam theory, Pratt's arch theory, and numerical simulation are used to analyze the management solutions and stability of five PCO-goaf groups in the Nannihu molybdenum mine located in Luoyang City, Henan Province, China. The five PCO-goaf groups, numbered 1#, 2#, 3#, 4#, and 5#, are divided into four hazard classes, ranging from extremely poor to good stability. The stability of 1#, 2#, and 4# is poor and must be managed by filling, and the design strength of backfill is 1.2 MPa; caving is used to treat 3# and 5#, and the safe thickness of the overlying roof is calculated to be 10.5–41 m. After treatment, the safety coefficient of the slope is greater than 1.2, indicating that the slope is stable. This study provides insight and guidance for the safe operation of open-pit mines threatened by the existence of PCO-goafs. [ABSTRACT FROM AUTHOR]

A CdSnO3• 3H2O hollow-nanocuboid photocatalyst was successfully synthesized via a facile template-free microwave hydrothermal method for the first time. The as-prepared samples were characterized by x-ray diffraction, UV-vis diffuse reflectance spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and x-ray photoelectron spectroscopy. Moreover, samples prepared under different reaction times were analyzed by transmission electron microscopy to investigate the formation process of the CdSnO3• 3H2O hollow-nanocuboids. Based on this result, a possible mechanism for the formation process was proposed. The sample prepared at 160 °C for 2 h at pH 11 exhibited the best photocatalytic activity and stability for the degradation of gaseous benzene under UV irradiation (λ = 254 nm) as compared with the other samples. The conversion and mineralization rates of benzene were about 12.5% and 67%, respectively. The mineralization rate was twice as high as that of commercial TiO2 (Degussa Co.). Furthermore, the excellent stability for the benzene decomposition was attributed to the positive charge on the catalyst surface, which was analyzed both by electron spin resonance and Zeta-potentials. [ABSTRACT FROM AUTHOR]