Vol 123, No 3 (2018)

A diagnostic model for managing the risk of NPP incidents attending different irregularities of equipment operation is examined for the example of the oil delivery system of the main circulation pump. The model includes the construction of a graph of the operation of the oil system and ranking in order to obtain indices of priority for monitoring information flow that reflect the actuation probability of each form of protection. The results of the analysis can used as input data for predicting the duration of a stable state of a technological system in the course of operation on the basis of stochastic extrapolation of the parameters by means of single-channel queuing systems with finite storage – technological protection and blocking.

The intensification of steam generation in combination with improvement of the temperature regime, specifically, with the elimination of temperature fluctuations of the loaded components of the apparatus (heat-exchange tubes, warming-medium headers) increases the steam-generation capacity and eliminates the factors causing damage to the structural elements of steam generators. The possibility of intensifying heat-and-mass transfer on the basis of the experience gained in operating steam generators in NPP with VVER (horizontal) and NPP in foreign countries (vertical) is examined. It is concluded on the basis of the analysis that it is expedient to develop a domestically produced apparatus of the vertical type, which will make possible well-founded production of steam generators for NPP with VVER in the future.

Corrosion processes, specifically, erosion-corrosion, are one of the causes of damage occurring in NPP equipment during operation. Measures are taken to prevent erosion-corrosion wear of thermal-power equipment and pipelines. One such measure is the development and adoption of water chemistry regimes that are capable of forming a protective fi lm on a metal surface. Octadecylamine is one such reagent. The results of laboratory tests and industrial experiments studying the effect of octadecylamine on the development of erosion-corrosion wear of NPP equipment are presented. The octadecylamine-hydrazine water chemistry regime at octadecylamine concentration 0.5 mg/dm³ reduces the rate of erosion-corrosion wear by about 15-fold. The positive effect of micro-additions of octadecylamine is confirmed by direct erosion-corrosion studies performed at the Kola NPP.

The chemical stability of vitrified high-level nuclear industry wastes in contact with water was studied experimentally in application to underground disposal of the wastes. The experiments were performed on samples of sodium aluminophosphate glass used in industrial solidification of wastes. Stable isotopes of strontium, cesium, uranium, and rare-earth elements as geochemical analogs of actinides were introduced into the glass to simulate radionuclides. It was observed that water vapor affects the degradation of the glass when vitrified wastes are placed in temporary repositories. It is shown that as a result of the degradation the rate of leaching of the glass in water increases significantly. In addition, a substantial portion of radionuclide simulators in colloidal form goes into the water medium.

A method of calculating the optimal operating parameters of a centrifuge cascade for separating multicomponent mixtures of isotopes is developed. A computational scheme is proposed for calculating the parameters of a cascade and the distribution of the centrifuges over the stages with a prescribed total number of centrifuges in different variants of optimization. Calculations showing the particulars of optimization and the efficacy of the developed method are presented.

An approach to the comparative assessment of the impact of accidental radioactive emissions on the biota and radioecological validation of nuclear fuel cycle objects is presented. It is shown that the dose loads on woody tier in a coniferous forest as a result of severe accidents in NPPs with PWR-890, BWR-1412, and EPR-1600 significantly exceed the limit recommended by the ICRP. The impact of the radiation factor can result in serious disturbances in forest ecosystems in the immediate vicinity of NPPs.