Introduction. The patterns of hydrogen-air mixtures formation during the flow of hydrogen into the upper part of a large volume room in the initial moments of time are insufficiently studied. Therefore, the determination of regularities of formation of local explosive and fire-hazardous hydrogen-air mixtures when hydrogen flows into the lower part of the dome space of the reactor building is important.

Goals and objectives. The purpose of the article is a theoretical study of occurrence of local fire and explosive zones of the hydrogen-air mixture generated during hydrogen leakage in the containment area of the reactor building in order to substantiate parameters of concentration sensors of the hydrogen concentration control system.
To achieve it, a zone mathematical model of hydrogen concentration calculation in a pressurized room has been developed. Numerical experiments on regularities of hydrogen-air mixtures formation have been carried out.

Theoretical basis. The generalized three-dimensional non-stationary differential equation of the laws of conservation of mass, momentum and energy is used to calculate local hydrogen concentration fields. The developed zone model makes it possible to determine hydrogen concentrations in the convective column and in the ceiling layer.

Results and discussion. The characteristic fields of hydrogen mass concentrations in the volume of the dome space are obtained. It has been shown that at the initial stage of hydrogen leakage, a zone of the ceiling layer is formed under the ceiling of the dome space, which confirms the validity of the usage of the zone model. The hydrogen concentrations obtained by the field and zone models are compared. The distributions of hydrogen mass concentration along the convective column height at different Reynolds numbers in the hydrogen leakage hole have been obtained. It has been shown that hydrogen concentration sensors can detect a hydrogen leakage mode in the dome space only in a narrow area of Reynolds Re = 900–5,000. There is a leakage mode (Re = 3,358), in which the maximum hydrogen volume concentration is generated at the location of the concentration sensors at the maximum size of the fire and explosive hydrogen-air mixture zones in the room.

Conclusions. The hydrogen concentration sensors used in the dome space of the NPP reactor building with water-­water reactors may not detect hydrogen at the top point of the dome at a sensitivity threshold of 2 % vol. In this case, in terms of the height of the convective column, hydrogen-air mixtures are formed within the fire and explosive concentration limits.

Introduction. The data given in the article show that the problem of increase of fire safety at operation of vehicles is actual. The main purpose of the article is to develop a scientifically based method of examination of contact connections of pole terminals of starter batteries, which have signs of high transient resistance or change in geometrical shape in order to find out the reason of damage in the course of fire-technical expertise.

Materials and methods. The researches were carried out with the use of a scanning-electron microscope JSM-6390LV with an attachment for energy-dispersive microanalysis. The objects of research were pole terminals of a lead-acid storage battery of European type and their tips. Contact surfaces of the tips were analyzed without preliminary sample preparation.

Theoretical background (theory and calculations). A physical and mathematical model of ultimate load-bearing capacity of lead battery terminal, which corresponds to real design, has been developed. On this basis, there is formulated a computational and practical algorithm for expert analysis of its mechanical and geometrical characteristics. The solution has been simplified to short calculating formulas, allowing to estimate the contact load-bearing capacity. The applicability of the developed mathematical model to carrying out fire-technical exami­nations is shown by a concrete example.

Results and discussion. Examples are given of car fires, which were caused by loss of load-bearing capacity in the contact of battery terminals with wire-end terminals during in the process of operation. Pictures of the result of high transient resistance on the contact surface and its elemental composition are given. Experimental data confirmed that the transfer of the material of the pole leads to the tips of wires in the form of drops of lead and its layers is a significant forensic feature in determining the cause of the fire.

Conclusions. The method of determination of load-bearing capacity of contact of a lead battery pole to the wire end, on the basis of which it is possible to draw a conclusion about participation of great transient resistance in the contact to the subsequent fire, is offered. The data given in the article may be used by specialists during an expert examination of lead battery terminals, seized from places of fires, in order to establish the mechanism of their damage and, finally, the cause of a fire.

Introduction. Nuclear power plants in the Russian Federation produce about 20 % of the total electricity.
On the basis of fast neutron reactors using sodium as a coolant, Rosatom State Corporation is implementing the “Breakthrough” project aimed at the implementation of a nuclear fuel cycle using the energy potential of natural uranium. Study and generalization of information about fire and radiation hazards of sodium coolant is an urgent task to ensure safety in the operation of this type of reactors.

Goals and objectives. The purpose of the article is an analytical study of information about sodium coolant radiation and fire hazard, published in domestic and foreign scientific literature. To achieve it, an analysis of fast neutron reactors operating in the world was carried out, the coolants used in fast reactors were considered. System analysis of radionuclides present in sodium coolant has been carried out, comparative diagrams according to radionuclide radiation properties are presented, the most dangerous radionuclides for humans present in the sodium coolant have been identified. The fire hazard of sodium metal and peculiarities of extinguishing fires associated with the leakage of sodium coolant in the primary and secondary circuits of the reactor plant are analyzed.

Results and its discussion. At the present time, there is 1 experimental-industrial fast neutron reactor in operation in the world, located in Russia, and 1 experimental reactor in India and China. Sodium is used as a coolant in these reactors. As a result of the literature analysis from open sources, it was found that the main sources of impurities in the metal coolant are protective gas, structural and technological materials of the installation, and products of nuclear reactions. A systematic analysis of the properties of radionuclides present in the metal coolant made it possible to determine the most dangerous of them for human life and health. The fire hazard of sodium coolant is mainly due to its chemical activity. The main ways of extinguishing spilled sodium is isolation from oxygen by covering the puddle of metallic sodium with powdered fire-extinguishing MHS, powdered aluminum oxide or reduction of oxygen concentration in the air below 4 % by volume gas extinguishing with nitrogen, carbon dioxide or inert gases.

Conclusions. As a result of the analysis of radionuclides present in the sodium coolant of a fast neutron reactor, it was found that the most dangerous for people are 24Na, 137Cs, 125Sb, 22Na, 239Pu, 54Mn, 110mAg, 131I. Based on the results of the analysis of the fire hazard of radioactive sodium, the most common fire extinguishing agents are established and the features of extinguishing fires that occur when a sodium coolant ignites are described.

Introduction. The usage of intumescent coating (hereinafter referred to as IC) is justified by the development of a fire protection project, taking into account the data on its fire protection efficiency, estimated under the influence of standard temperature conditions, the usage of which can lead to overestimating the fire resistance margin in the project or underestimating the thermal impact on the steel building structures with IC fire protection in conditions of a real fire.

Aims and purposes. The purpose of the study is to evaluate the effect of fire temperature conditions on the effectiveness of IC. To achieve this goal, the following tasks were carried out: a temperature mode of fire in a building under different fire loads by the example of a warehouse building was estimated; experiments to estimate the influence of different heat fluxes, reduced thickness of metal and IC thickness on its effectiveness by the full factor experiment of the type 2 were conducted.

Methods. To mathematically simulate real temperature fires, the Fire Dynamics Simulator (FDS) software package, which implements a field (differential) mathematical model, was used. To study the effect of the obtained fire temperature regimes on the effectiveness of IC, experiments were carried out according to the plan of a complete factor experiment type 2. The test specimens were carbon steel metal plates with dimensions of 100 × 100 mm with reduced thickness of 3 and 4.5 mm and painted with 0.25 and 0.5 mm organic-based single-component IC. A radiant heat flux panel with a radiant heat flux density of 10 to 50 kW/m2 was used to assess the effects of heat flux.

Results and discussion. In the course of numerical experiments in the FDS software package, it was found that the thermal impact on steel building structures during a fire can differ significantly from the standard temperature regime, both upwards and downwards. The results of the experiment showed that the heating time of the test samples had the greatest influence of the actors under consideration (the value of the heat flux, the reduced thickness of the metal, the thickness of IC) had the value of the heat flux, as the largest absolute value of the regression equation was obtained.

Conclusion. The assumption of possible underestimation of the thermal effect under “standard” temperature conditions on the fire resistance of steel building structures with IC fire protection was confirmed by the tests.

Introduction. Fire protection of stairwells plays a key role in ensuring human safety in residential buildings of sectional type, since a single stairwell blocked by fire makes it impossible to safely evacuate people from all apartments in a section and complicates the possibility of their rescue. Modern regulations exclude the possibility of gas-dynamic connection of apartments directly to stairwells by prohibiting evacuation from apartments directly to the stairwell in buildings higher than 3 floors. Since a considerable part of the existing housing stock in the country has such architectural solutions, in which apartments have access to stairwells directly, there is a need for a scientific analysis of the effectiveness of engineering solutions to ensure the necessary level of protection of usual stairwells during the reconstruction of buildings.

The purpose of this article is to develop criteria and mathematical relationships for evaluating the effectiveness of engineering solutions for the protection of stairwells.

Methods. Analytical and mathematical methods are used to assess the combined effect of the dynamics of changes in fire hazards in the stairwell and in apartments with the location of a rescued person, depending on the engineering solutions for the stairwell protection.

Results. Theoretical provisions have been developed to estimate the influence of different engineering solutions to limit the spread of fire from a burning apartment to a stairwell and apartments on the other floors, taking into account the ventilation of the stairwell and the fire resistance of structures in relation to the problem of ensuring evacuation and saving people. The developed provisions have been approbated.

Conclusions. On the basis of the researches criteria and mathematical relations have been worked out to estimate the efficiency of different engineering solutions to protect stairwells, based on the forecasts of dynamics of spread of fire hazards from a fire origin to the stairwell and apartments, taking into account window openings, fire resistance of constructions in comparison with the time intervals of evacuation and rescuing people.

Introduction. The purpose of this study is to determine the minimum cost of a path to a standstill forest fire and its localization. To achieve this goal, it is necessary to perform the tasks of analyzing the selected method for calculating the minimum costs for the process of unloading a fire landing and the process of localization of a low forest fire accordingly; identifying and characterizing the necessary equipment used in localizing a low forest fire; on definition of the optimal way and the number of employees of the Ministry of Emergency Situations as part of a fire landing force using an algorithm in the form of a pseudocode.

The analytical part. The models, methods and algorithms of search of shortest way, optimization, circulation routing of transport are reviewed. Some problem of extinguishing of forest fire is set. The application of the modi­fied Clarke and Wright algorithm, which considers a possibility of variation of depth of route splice and definition of optimal value of probability of realization of the worsening step, makes it possible to find the minimum time spent by aviation forest protection for localization of a low forest fire. A solution to the problem of fire troop deli­very thanks to pseudocode implementing the basic Clarke and Wright algorithm is given.

Conclusions. The solution based on the modified Clarke and Wright algorithm provides circular air routes that will be assigned to a helicopter, so that the delivery of firefighting troops will become economically feasible. The results of the research will be useful to analysts and software developers for the implementation of aerial firefighting activities.

The analysis of existing methods of extinguishing lithium-ion accumulators (LIA) in electric energy storage (accumulation) systems (ESS) is provided. The classification, fields of application and normative documents regulating the selection and design of ESS are presented. The description of the structure and ways to ensure fire safety of ESS are provided. The possible technical solutions with the use of sprinkler and other systems for extinguishing and detecting fires in energy storage modules are summarized. The recommendations of extinguishing agent manufacturers on extinguishing fires involving LIA are considered.