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The paper focuses on the fact that nuclear failures and incidents can lead to radioactive contamination of NPP premises. Nuclear and radiation hazard may be caused by malefactors in technological processes when applying computers or inadequate control in case of insufficient level of information security. The researchers performed analysis of factors for reducing risks of nuclear and radiation accidents at NPPs considering specific conditions related to information security of NPP physical protection systems. The paper considers connection of heterogeneous factors that may increase the risk of NPP accidents, possibilities and ways to improve adequate modelling of security of information with limited access directly related to the functioning of automated set of engineering and technical means for NPP physical protection. Within the overall Hutchinson formalization, it is proposed to include additional functional dependencies on indicators specific for NPPs into analysis algorithms.

Relevance. The research discusses the actual risks that can arise from the formation of the radioisotope cobalt 60Co from the stable isotope 59Co during radiation neutron capture, which is specific to repair work at a nuclear power plant, but these risks are poorly understood. Aim. The research aims to analyse the possibility of additional exposure to ionising radiation for the repair personnel of a nuclear power plant due to the use of a repair tool that may contain cobalt. Methodology. The physical-theoretical and analytical approaches are used in the study. Results. A certain risk has been identified as a result of the use of drills or other tools for cutting metal containing cobalt among the repair tools. The calculation (analysis) of the activation of a cobalt-containing drill bit showed that a drill bit weighing 500 g containing 8% of 59Co in the tool steel acquires a partial activity (i.e., only cobalt activity) of 5.397 × 10-8 Ci, which leads to gamma radiation with an exposure dose rate of 0.024 mSv/year. The calculations of dose rates did not consider gamma radiation from the nuclear isomeric transition 60mCo→60Co, which could only worsen the radiation risk picture (when considering other examples). Conclusions. The use of a drill bit with the cobalt content specified in the calculations (or the location of the drill bit in the vicinity of the personnel), one way or another, contributes to the personnel exposure. It is proved that the calculation was not conservative, but rather liberal, because gamma radiation from the 60mCo isomer was not considered, otherwise, the obtained numerical values would have been higher. A practical recommendation to prohibit or reduce the use of tools containing cobalt during repairs on nuclear power plant equipment was made, theoretically, given that the analytically justified need to study the issue of radiation safety is relevant and vital for the safety of NPP maintenance personnel

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Issues related to the introduction of new control technologies and temperature monitoring at NPPs are being considered, since NPP longterm operation depends on the reliability of process control means. It is promising to build instrumentation and control complexes using one-wire technologies, since the operation information removal and transmission means should be carried out under the conditions of spatial constraints on the location of cabling. One-wire technologies make it easy to build a measurement network of the most complex topology. It is proposed to use DS18B20 universal digital primary measuring transducers as NPP testing equipment. In this regard, scientific and technical interest is a new approach to the measurement of temperature fields based on 1-Wire technology. It was proposed to use UR-1 demagnetizer as a source of a variable electromagnetic field imitating NPP equipment operating conditions. The paper also presents a study for visualization of the generated electromagnetic fields. A Hall sensor is used for measuring the fields under consideration. The proposed method can be used to conduct other similar studies to assess the response of temperature sensors (or other digital sensors) to an external magnetic field. A visualization method is used to evaluate the informational function and a conclusion is made about the applicability of such sensors in the systems of metrological control and monitoring of NPP auxiliary equipment.