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99Tc is a key radionuclide in the safety case of deep geological disposal of high-level radioactive waste (HLW) due to its long half-life of 2.13×105 years and high yield in nuclear reactors. The formation of technetium colloid in groundwater was believed to play a potential important role on its migration and transport with ground-water to biosphere under deep geological disposal conditions. In this paper, the membrane filtration experimental method was established firstly for the study of the colloidal behavior of technetium in aqueous solutions. All experiments were performed in an argon glove box to maintain the anaerobic conditions (O2 concentrations lower than 5 ppm) which will be expected in the HLW repository and initial technetium concentrations in the range from 10-9 mol/L to 10-5 mol/L, and liquid scintillation spectrophotometry was used to determine 99Tc. It is found that pH value and ionic strength have no significant effect on the liquid scintillation determination of 99Tc, and the filter has no obvious adsorption behavior for different oxidation states of technetium (Tc(Ⅳ) and Tc(Ⅶ)). The experimental studies of technetium colloidal behavior in deionized water system were conducted by using this experimental method. The results indicate that Tc(Ⅶ) has no significantly colloidal behavior even under anaerobic conditions due to its low hydrolysis ability, and can exist stably in the system for a long time, therefore it is a potentially higher mobile species. As Tc(Ⅳ) is trend to hydrolyze to form oxic polymers easily, which then aggregate immediately to form the intrinsic colloids over a wide ranging of pH values from 4 to 11 under the anaerobic conditions. Moreover, it is found that the Tc(Ⅶ) intrinsic colloid would exist stably during the experimental period of 398 days in the pH range of 4-11, and its concentrations may be several times or even one order of magnitude higher than the Tc(Ⅳ) presented as the ionic form. These results seem mean that the formation of Tc(Ⅶ) colloid may enhance the migration capacity of Tc(Ⅳ) which is considered to be relatively immobile, then potentially facilitating transport of Tc(Ⅳ) under geological disposal conditions. But the next experimental results demonstrate that with the increasing of the ionic strength, the Tc(Ⅳ) colloid would aggregate into large particles even continue to form precipitation. This experimental results illustrate that higher ionic strength in aqueous systems may eliminate the dangerous of Tc(Ⅳ) transfer to biosphere with groundwater in the form of intrinsic colloid. The effect of technetium colloidal on its migration behavior needs to be take into account, and some important formation mechanism of technetium colloidal also needs to be clarified and confirmed. Therefore, it is necessary to carry out more researches on radionuclide colloids in the research and development projects of geological disposal of HLW in China.

As a prospective alternative liquid propellant, 1,4,4-tetramethyl-2-tetrazene (TMTZ) possesses high enthalpy of formation and environment friendly decomposition products, and shows a promising application prospect in aerospace, munitions manufacturing, etc. An environment friendly and convenient synthesis of TMTZ through electrochemical oxidative coupling of undimethylhydrazine (UDMH) on commercially procured electrodes was carried out under mild conditions, in which the purity is up to 98.5% with a yield of over 45%. It is a simple, clean and suitable method for industrial production in contrast with the previously reported conventional chemical oxidation syntheses. [ABSTRACT FROM AUTHOR]

Most of the existing studies on crystal density prediction focus on CHON energetic materials. Due to the different application ranges of the formulas, large prediction errors appear in predicting the crystal density of CHONF highly energetic explosophoric material. In order to improve the performance evaluation accuracy, at the B3PW91/6-31g(d, p) evel, the performances of the Rice and Politzer formulas in predicting the crystal density of 56 such materials screened from the Cambridge Crystal Data Center were first systematically studied. In addition, on the basis of the typical parameters related to the molecular surface electrostatic potential, the density prediction formula suitable for this system was constructed by using symbolic regression method and four operators of "addition, subtraction, multiplication, and division". The results showed that the root-mean-square error of the symbolic regression formula was reduced from 0. 106g/cm³ of the Rice formula to 0. 045g/ cm³, and the predicted error of over 50% of materials were less than 0.030g/cm³. The symbolic regression method greatly improved the crystal density prediction accuracy of fluorine-containing highly energetic explosophoric materials. [ABSTRACT FROM AUTHOR]

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H-Trifurazano[3,4-b:3',4'-f:3",4"-d]azepine (HTFAZ) was synthesized via the reactions of nucleophilic substitution, cyclization and reduction using 3,4-bis(3'-nitrofurazano-4'-yl)furoxan (DNTF) as starting material. Based on the reactivity of HTFAZ, the two novel energetic compounds 7-(2,4,6-trinitrophenyl)-trifurazano[3,4-b:3',4'-f:3",4"-d]azepine (compound 1) and 7-(2,4,6-trinitro-3,5-diaminophenyl)-trifurazano[3,4-b:3',4'-f:3",4"-d]azepine (compound 2) were self-designed and synthesized. The structures of the target compounds were characterized by IR, H NMR, C NMR and elemental analysis. The thermal behaviors of compounds 1 and compound 2 were investigated by DSC and the detonation performances of the two compounds were predicted by Kamlet-Jacobs equations. The results show that the yield of HTFAZ reaches 63.2% after improving synthetic route. The thermal decomposition temperatures of compound 1 and compound 2 are 371.7'and 296.3', respectively, showing good thermal stability. The density of compound 1 is 1.90g/cm, the peak temperature of thermal decomposition is 371.7', the theoretical detonation velocity is 8033m/s and theoretical detonation pressure is 30.11GPa, The detonation performance of compound 1 is better than that of TNT, and the density and thermal stability are greater than those of TNT and RDX. [ABSTRACT FROM AUTHOR]