The thermal stability of 1,3,5,5-tetranitrohexahydropyrimidine (TNDA) in liquid phase under isothermal conditions was studied. It was established that the TNDA decomposition (k liq = 3.1 • 10 21 •exp(À 26865/T), E a = 223.4 kJ mol À 1) is accompanied by strong autocatalysis (k cat = 9.8 • 10 14 •exp(-18056/T), E a = 150.2 kJ mol À 1). The mechanism of autocatalysis was proposed. The essence of autocatalysis is the oxidation of TNDA by decomposition products, followed by the destruction of the molecule. An unusual feature of this autocatalysis is that, in contrast to autocatalysis of nitroesters, the process does not disappear at high temperatures, but rather determines the kinetics of heat release in the combustion wave. The surface temperature and combustion mechanism of TNDA were established through thermocouple studies. It was shown that the autocatalysis reaction at the surface temperature controls the burning rate.
The combustion behavior and thermal stability of 4,6,8-trinitro-4,5,7,8-tetrahydro-6H-furazano[3,4-f]-1,3,5-triazepine (FRDX) and 1,4,5,8-tetranitrodifurazano[3,4-c][3,4-h]tetraazadecaline (FTNAD) were investigated and compared with analogs, where the furazan ring is substituted with CH 2 or C=O units. It has been shown that the furazan-fused unit reduces the thermal stability of azacyclic nitramines, probably due to the weakening of the NÀ NO 2 bond. The burning rates of FRDX and FTNAD are determined by the kinetics of heat release in the melt. There is the peculiar effect of the furazan unit on the burning rate: according to thermocouple measurements, the unit increases the volatility of cyclic nitramines and reduces the temperature of the burning surface, which should lead to a decrease in the burning rate, but on the other hand, it simultaneously increases the rate of heat release in the melt, and as a result, the burning rate increases rather than falls.
A convenient method to access the above perchlorates has been developed, based on the cyclocondensation of 3-aminofurazans with 1,3-diketones in the presence of HClO4. All compounds were fully characterized by multinuclear NMR spectroscopy and X-ray crystal structure determinations. Initial safety testing (impact and friction sensitivity) and thermal stability measurements (DSC/DTA) were also carried out. Energetic performance was calculated by using the PILEM code based on calculated enthalpies of formation and experimental densities at r.t. These salts exhibit excellent burn rates and combustion behavior and are promising ingredients for energetic materials.
The article represents the results of calculations of the influence factors of fuel assemblies on the current of ionizing chambers (IC) in the simulation of a reaktimetr of reactor VVER. Two independent approaches and two programs were used to solve the neutron transport equation. The influence factors of the extreme series of fuel assemblies nearest to the reflection shield and IC on the IC readings are calculated. According to the known software "MCNP-4C" factors are obtained from the solution of forward and adjoint problems. Software "TDMCC", developed in RFNC-VNIIEF, the influence factors obtained from the solution of the forward problem. Both of programs implement the Monte Carlo method to solve the transport equation. The obtained coefficients were used in the calculations of measurements that were carried out at the physical start-up of unit 1 of Novovoronezh-2 NPP, including the simulation of measurement of scram-system efficiency. The article represents the dependence of the relative current on time in the logarithmic scale, as well as the dependence of reactivity on time, built on the results of numerical simulation using three sets of the influence factors in the process of resetting the scram-system. As an illustration, the dependencies are not different from each other.
The article represents the results of calculations of the influence factors of fuel assemblies on the current of ionizing chambers (IC) in the simulation of a reaktimetr of reactor VVER. Two independent approaches and two programs were used to solve the neutron transport equation. The influence factors of the extreme series of fuel assemblies nearest to the reflection shield and IC on the IC readings are calculated. According to the known software "MCNP-4C" factors are obtained from the solution of forward and adjoint problems. Software "TDMCC", developed in RFNC-VNIIEF, the influence factors obtained from the solution of the forward problem. Both of programs implement the Monte Carlo method to solve the transport equation. The obtained coefficients were used in the calculations of measurements that were carried out at the physical start-up of unit 1 of Novovoronezh-2 NPP, including the simulation of measurement of scram-system efficiency. The article represents the dependence of the relative current on time in the logarithmic scale, as well as the dependence of reactivity on time, built on the results of numerical simulation using three sets of the influence factors in the process of resetting the scram-system. As an illustration, the dependencies are not different from each other.
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