A laser system was developed for real-time detection of the global radionuclide 129 I and NO 2 during spent nuclear fuel reprocessing. This system was used for determining the concentrations of these substances in a gas stream under actual conditions of nitric acid dissolution of spent nuclear fuel at the Khlopin Radium Institute, Research and Production Association. The tests showed that the laser system is suitable for measuring both the 129 I and NO 2 concentrations directly in the gas phase during spent nuclear fuel reprocessing (this is essential for monitoring this process and controlling the dissolution cycle safety) and in the gases emitted by radiochemical enterprises. The sensitivity with respect to 129 I, achieved with the laser system developed, also makes it suitable for real-time monitoring of 129 I and NO 2 at the maximum permissible concentration (MAC) level. This will allow evaluation of the environmental condition of air in the working areas of radiochemical enterprises, as well as in residential areas.

Various information transmission systems, based on two-mode lasers with controlled emission frequencies, are proposed. It is suggested that these systems can be implemented by modulation of the intermode spacing of a two-mode laser. An experimental investigation is reported of frequency control methods. It is shown that these methods should make it possible to construct information transmission systems with high transmission rates subject to weak nonlinear distortions of the information-carrying signal.

An investigation was made of the influence of temperature and of the frequency of the exciting radiation on the fluorescence of molecular 129I vapour excited by 633 nm He—Ne laser radiation. Heating of the iodine vapour and a shift of the exciting radiation frequency by 2 GHz toward shorter wavelengths, relative to the centre of the 20Ne gain profile, enhanced by almost an order of magnitude the sensitivity of detection of 129I by the laser-induced fluorescence method. The main contribution to the fluorescence signal came from the 6–3 P(33) absorption line.

Theoretical and experimental investigations were made of the reaction of the laser power to an external radiation signal. The laser with an injected signal (LIS) was an He—Ne laser emitting radiation at the wavelength of 3.39 μm in the form of two orthogonally polarised modes. A study was made of the influence of the frequency detuning of the external signal from the LIS radiation, and also of the intensities of both radiations on the laser power response.

A laser-fluorescence system is developed that uses a He-Ne (633 nm) laser for continuous monitoring of I-129 during HNO3 dissolution of irradiated nuclear fuel. Tests at Khlopin Radium Institute indicated that the sensitivity of the I-129 detection (at worst 8.10(-5) g/m(3)) ensures reliable monitoring of this isotope both directly in the working gas during industrial reprocessing of irradiated nuclear fuel and following gas-purification systems at radiochemical plants.

A three-mode method for the separation of frequency resonances in a laser with a nonlinear absorbing medium is proposed. The results are reported of a study of frequency resonances in an He–Ne/I2 laser emitting the wavelength of 0.63μ. It was found that the three-mode method ensures considerable enhancement of the frequency resonance gain compared with the two-mode method, which is desirable in spectroscopic applications of lasers and in the stabilization of the laser emission frequency.

The first results are given of investigations of frequency resonances of a 3He–20Ne/127I2 laser (0.63 μ wavelength) emitting two modes with parallel polarizations. Investigations were made of the resolution, of the amplitudes of the frequency resonances and their shifts, and of the influence of the temperature on the frequency pedestal. It is shown that the high signal-to-noise ratio makes frequency resonances promising for use in laser spectroscopy.

The first report is given of the attainment of high-contrast resonances in a linear two-mode 3He–22Ne laser {λ = 0.63 μ) with an internal 129I2 absorption cell. The maximum contrast ratio of these resonances was 25% and their width was the same as that of similar resonances in the single-mode regime within the measurement error.