Reducing the risk of human-made disasters is directly related to the trouble-free operation of nuclear power plants. Analysts name the human factor like a one of the causes of accidents at the nuclear power plants, which mainly determines both the probability of their occurrence and the consequences. Minimizing of the human factor impact suggests a number of actions, including automation and digitalization, the applying of which on the plant is impossible without of mathematical models of technological processes. A simulation model of a digital automatic control system (SAR) of pressure in a pressure compensator used to maintain pressure in the first circuit of the nuclear power plant is presented in this article. As a result of modeling are the charts of transition process which are used for calculating of the digital ACS quality indicators. The ACS simulation model is implemented in a classical way, but in practice such classical regulators do not provide the predefined quality indicators. In this connection, a model of adaptive ACS with a neuroregulator is proposed to improve the qualitative characteristics of the system.

Keywords: nuclear power plant, reactor, compensator, pressure, temperature, perturbation, regulator, valve, gate valve, turbine, model, circuit, neural network, optimization.

Computational and analytical studies of the influence of the duration of operation of nuclear power plants during the extension of their operation on the radiation changes in the concrete of the shaft of water-water power reactors (VVER) on various aggregates have been carried out. The studies were carried out using the existing experimentally tested methods for the analytical determination of radiation changes in concrete and their components. It has been established that during the extension of the operation of nuclear power plants with VVER reactors, the radiation changes in the concrete of the reactor shaft can be commensurate with the allowable changes in concrete or exceed them. It is shown that the radiation changes in the concrete of the reactor shaft increase with an increase in the duration of operation and depend on the power of the reactor (440 or 1000 MW), the thickness of the "dry" shield around the reactor, and the material of the concrete filler used. Radiation changes in all concrete of the NPP shaft with VVER-440 reactors will be more significant than in the concrete of the NPP shaft with VVER-1000 reactors. It has been established that the radiation changes in the concrete of the reactor shaft and the maximum duration of operation when using aggregates from various rocks differ significantly. It is noted which concretes (on which aggregates) have the smallest, largest and intermediate radiation changes. It is shown that with an increase in the operating temperature, the radiation changes in concrete will decrease, and the allowable operating time of the NPP will increase.

Keywords: radiation changes, reactor shaft concretes, concrete aggregates, rocks, water-water power reactors VVER-440 and VVER-1000, extension of NPP operation

The water-chemical condition of the steam generators (SG) within the established limits are supporting by a purge. The purge is two kinds they are permanent and periodic. The main idea of the purge consists in taking part of the boiler water from the places of the most likely accumulation of sludge, corrosion products, salts, as well as water purification and its subsequent return to the circuit. The further way of boiler water which is taken from SG is the purge expander. The thermal-hydraulic sketch which is shown in the article and considered to be a mathematic model of the purge expander illustrated level changes in dynamic. Also the mathematic model of automatic control system for purge expander level control which includes a fuzzy governor is presented in the article. Both models are realized with use of software for technique system modelling called SimInTech. The technique implementation of level governor in the SG purge expander realized on the base of the standard software and hardware TPTS-EM which is used as grassroots automation for automatic control system in the technological process of NPP having water-water power reactor which power is 1000 megawatt.

Keywords: reactor, purge, steam generator, corrosion, erosion abrasion, heat carrier, purge expander, governor, model, fuzzy logic, level, pressure, consumption