The immobilization of technetium-99 ((99)Tc) in a suitable host matrix has proven to be a challenging task for researchers in the nuclear waste community around the world. In this context, the present work reports on the solubility and retention of rhenium, a nonradioactive surrogate for (99)Tc, in a sodium borosilicate glass. Glasses containing target Re concentrations from 0 to 10,000 ppm [by mass, added as KReO(4) (Re(7+))] were synthesized in vacuum-sealed quartz ampules to minimize the loss of Re from volatilization during melting at 1000 °C. The rhenium was found as Re(7+) in all of the glasses as observed by X-ray absorption near-edge structure. The solubility of Re in borosilicate glasses was determined to be ~3000 ppm (by mass) using inductively coupled plasma optical emission spectroscopy. At higher rhenium concentrations, additional rhenium was retained in the glasses as crystalline inclusions of alkali perrhenates detected with X-ray diffraction. Since (99)Tc concentrations in a glass waste form are predicted to be <10 ppm (by mass), these Re results implied that the solubility should not be a limiting factor in processing radioactive wastes, assuming Tc as Tc(7+) and similarities between Re(7+) and Tc(7+) behavior in this glass system.

Rhenium Solubility In Borosilicate Nuclear Waste Glass Implications For The Processing And Immobilization Of Technetium-99 (And Supporting Information With Graphical Abstract)

https://link.springer.com/content/pdf/10.1186/s42834-020-00054-8.pdf

Evaluation and future framework of green mine construction in China based on the DPSIR model

Graph theory belongs to the discrete mathematics in subject,there-fore it manifests many characteristics of the discrete mathematics.The information and development of many concepts and theories in graph theory are mutually independent,thus they are divided into a lot of mutually independent special subjects.The algorithm of graph theory is the collection of a series of measures to solve problems and the important component part of discrete mathematics.This paper will first introduce some theories and relevant concepts of graph theory,then it will study and discuss the algorithm which is often used in graph theory,at last it advices everyone to solve practical problems by founding the graph theory model with discoursing on a specific graph theory model.

Study on the Olgorithm and Applications in Graph Theory

A novel Sr2Nd8(SiO4)6O2 glass-ceramics for rapid immobilization of FP and An3+ co-doped uranium tailings by microwave sintering: mechanism and performance

Uranium-containing wastewater poses a major threat to human health because of its toxicity and radioactivity. To address this issue, tea waste-derived porous biochar supporting the Fe–Mn bimetallic composite (FMBC) was fabricated using impregnation-pyrolysis and applied for U(VI) removal from aqueous solution. Batch experiments and characterization analysis were performed to investigate the adsorption properties and interaction mechanisms. Results showed that FMBC exhibit a maximum U(VI) removal capacity of 510.8 mg/g at pH = 5, T = 303 k, and t = 25 min. The kinetic and isotherm date fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively, indicating that uranium adsorption is dominated by chemical adsorption on FMBC. FTIR and XPS analyses further confirmed that the U(VI) adsorption mechanism by FMBC was attributed to surface complexation, π–π bonding, and reduction processes. In addition, the Cationic competitive adsorption experiment further highlighted the excellent selective performance of FMBC for U(VI) removal from aqueous solutions, which is important in radionuclides' pollution treatment.

Highly efficient removal of U(VI) in aqueous solutions by tea waste-derived biochar-supported iron-manganese oxide composite

Based on the importance of having an evaluation index system, a new method that combines PCA with graph distance classification is presented to make up the deficiencies of principal component analysis in the process of index screening, and this method is applied in the construction of an evaluation index system for the environmental quality of decommissioning uranium tailing. The seepage indexes were classified into six classes using graph distance classification, which selects the representative elements, including pH, , 210Pb, 210Po, F−, and . All of the representative elements were analyzed by PCA while determining the seepage indexes, including pH, U, Ra, , NH4-N, and F−, and establishing an index system for environmental quality evaluation that consists of two primary indexes (seepage and radiation environment) and 12 secondary indexes. The results showed that the model had ensured that the sifted indexes had a significant effect on the evaluation result and avoided the deletion of some important indexes and that it had stronger applicability and maneuverability.

/pdf/constructing-a-method-for-an-evaluation-index-system-based-2cpnl61yaz.pdf

Constructing a Method for an Evaluation Index System Based on Graph Distance Classification and Principal Component Analysis

In this work, the dense glass matrix of uranium tailings was successfully fabricated via microwave sintering process with Na2CO3 as a sintering aid. The effects of Na2CO3 additive and sintering temperature on the microstructure and mechanical properties of as-prepared solids were systematically investigated. XRD results confirmed the vitrified forms can be achieved at 1200°C within 30 min with 20 wt.% Na2CO3 addition. Importantly, the Na2CO3 additive significantly reduced the firing temperature from 1500°C to 1200°C and promoted densification. FT-IR analysis demonstrated that the main characteristic peaks of the sintered samples were attributed to the vibration of Si-O-Si. Microstructural studies presented the homogeneous distribution of glass phases. The results of mechanical properties of the sintered forms show that bulk density and Vickers hardness increased with increasing Na2CO3 content as well as sintering temperature, and the highest bulk density (2.45 ± 0.01 g/cm3) and Vickers hardness (823 ± 25 HV) were obtained at the temperature of 1300°C with 20 wt.% Na2CO3 addition, the heating rate of 20°C/min, and the soaking time of 30 min. It implied that the combination of microwave sintering with the appropriate addition of Na2CO3 would provide an efficient method for the immobilization of radionuclides in uranium tailings.

/pdf/microwave-vitrification-of-uranium-tailings-microstructure-4d42evlozs.pdf

Microwave Vitrification of Uranium Tailings: Microstructure and Mechanical Property

https://iopscience.iop.org/article/10.1088/1755-1315/349/1/012048/pdf

Preparation of Hawaii nut shell biochar/graphene sponge and study on uranium adsorption properties

The invention discloses a uranium tailings pond beach face microwave solidification method. The uranium tailings pond beach face microwave solidification method includes: performing layer and direction separation microwave solidification treatment on a uranium tailings pond beach face through a longitudinal-deep microwave heating system and a surface microwave heating system so as to finally realize sintering for the whole beach face, and obtaining volume reduction effect through the sintering. When the uranium tailings pond beach face microwave solidification method performs the longitudinal-deep microwave solidification treatment on the uranium tailings pond beach face, perforation and point distribution are first performed on the whole beach face, and then round horn feed mouths sequentially penetrate into holes so as to perform the deep sintering on the uranium tailings pond beach face, and when the surface microwave solidification treatment is performed on the uranium tailings pond beach face, the large area sintering is realized through square horn feed mouths. The uranium tailings pond beach face microwave solidification method finally realizes the sintering for the whole beach face through the longitudinal-deep microwave solidification and the surface microwave solidification, and is good in treating effect, and additionally the uranium tailings pond beach face microwave solidification method further has the characteristics of being high in temperature rising speed, short in sintering time, timely in control, sensitive in reaction, strong in penetrability, high in energy utilization rate, low in generation amount of secondary waste and the like.

Uranium tailings pond beach face microwave solidification method

The invention discloses microwave curing equipment for a beach surface of a uranium tailing pond. The microwave curing equipment comprises a microwave heating system, a lifting device, an exhaust gastreatment system, a power supply system and a moving device, the microwave heating system moves to the beach surface of the uranium tailing pond needing to be treated through the lifting device and the moving device, microwaves output by the microwave generator can directly act on the beach surface, and the purposes of high-temperature sintering and solidification of the beach surface of the uranium tailing pond are achieved. According to the invention, during microwave treatment of the beach surface of the uranium tailing pond, the microwave heating system is used for carrying out layering, direction dividing and solidification treatment on the beach surface of the uranium tailing pond, and finally sintering treatment of the whole beach surface is achieved. In addition, the volume reduction effect is achieved through sintering treatment, sintering is conducted in a microwave heating mode, the interior and the exterior of the material can be heated at the same time and warmed at the same time without any heat conduction process, the heating speed is high and uniform, and the equipment has characteristic of being high in temperature increasing speed, short in sintering time, high inpenetrability, high in energy utilization rate, less in generated secondary waste and the like.

Zhang Qiucai

Papers

Constructing a Method for an Evaluation Index System Based on Graph Distance Classification and Principal Component Analysis

Microwave Vitrification of Uranium Tailings: Microstructure and Mechanical Property

Preparation of Hawaii nut shell biochar/graphene sponge and study on uranium adsorption properties

Uranium tailings pond beach face microwave solidification method

Microwave curing equipment for beach surface of uranium tailing pond