Based on IR spectroscopy data, it was established that nonstoichiometry defects in the structure of aluminum oxides were components of the Wannier-Mott exciton states and included the Al-O, Al-Al, O 2 , O 2 + , O 2 − , O 2 2− , O 3 , and O 2 n isolated oscillators in the ground and electronically excited states. It was shown that their presence manifested itself by thermoemission of molecular oxygen singlet forms, excess heat capacity, and anomalous diamagnetism at elevated temperatures.

High-resolution IR spectroscopic study has shown that stepwise heating of samples of silicon oxides in the temperature range from 50 to 1000°C is accompanied by accumulation of electronically excited states in the skeletal Si-O bond system, as well as by formation of associates in the cationic and anionic sublattices. Stationary association process and cooperative interaction of the excited states give rise to IR luminescence and diamagnetic response which increases as the temperature rises. Accumulation of the excited states in the chemical structure and their relaxation, including that occurring due to thermal desorption of singlet oxygen, are characterized by nonmonotonic temperature dependence of the heat capacity.

A comparative analysis of structural features of SiO2 polymorphic modifications was made by Raman, and high-resolution electronic spectroscopy. It was found that the presence of isolated Si-O, Si-Si, and O-O oscillators in the ground and electronically excited states is a characteristic feature of all the structures involving silicon atoms in oxygen tetrahedral coordination surrounding. It was shown that the increase in the silicon coordination number to six (stishovite) leads to a decrease in the extent of formation of electronically excited states due to removal of barriers to the relaxation of excitation energies. This conclusion is confirmed by the low-frequency shift of the fundamental absorption and by the disappearance of the high-frequency anomaly (Si-O) and characteristic lines of Si-Si oscillators.

Юрий Александрович Изюмов (к семидесятилетию со дня рождения), Александров К.А., Гуляев Ю.В., Каган Ю.М., Камилов И.К., Копаев Ю.В., Месяц Г.А., Румянцев А.Ю., Садовский М.В., Устинов В.В., Черешнев В.А., Черноплеков Н.А., Шавров В.Г.

In our estimates we use the results of experiments on a BOR-60 reactor [2] in which sodium boiling was effected throughout the entire volume of the fuel assembly (FA) as the result of T-ray heating of tungsten rods. The neutron flux fluctuations were measured with an ionization chamber set up 2.5 m from the core; the acoustic signals were measured with an inserted piezoelectric transducer at a distance of ~ 30 cm from the place where bubbles collapsed. For correlation with the noise of the neutron flux we formed the envelope of the acoustic signal with a rectifier and a filter with a time constant of ~ 30 msec. Figure 1 shows the statistical characteristics of the noise in the frequency range; these characteristics were obtained by Fourier transformation of the estimates of the correlation functions. The duration of the procedure {T = 10 rain) and the frequency resolution selected (~ 0.1 Hz) ensure measurement of the spectral densities to within 10-15%. A distinctive feature of the spectra are peaks at a frequency of about 1 Hz which are absent under Conditions without boiling. Experiments on stands and calculations showed [3, 4] that the existence of resonances is characteristic of the process of sodium boiling. This is due to either the periodic formation and collapse of a vapor bubble during local boiling under the conditions of partial blockage or oscillations of the vapor volume when vapor covers the entire cross section of the FA; the boiling mode in the BOR-60 experiments in analogous to the latter. The possibility of detecting boiling from the periodic component of the neutron noise was considered in [3] but the problem of correlation differences between the signals was not considered there.

These first experiments on the BOR-60 reactor have shown that in principle it is possible to detect the boiling of sodium from the acoustic and neutron fluctuations; useful information has been obtained on the character of the signals and the scope for using various processing methods. However, further measurements and calculations are needed before we can design a reliable real-time system for monitoring for sodium boiling in the core of a fast reactor.