Development of circuit model with natural circulation of coolant under conditions of ship motion

Safety is the key requirement to any nuclear power installation. Various factors affect safety during operation of the nuclear power installation. These factors are difficult to study due to the high economic costs. This problem can be solved by developing prototype models to conduct the research of many complex processes. Dynamic impact on the ship installation is one of these processes. The most significant impact is the impact on the natural circulation of the coolant, that is one of the basic emergency safety systems. Also, it is a promising way to ensure movement in the main circulation circuit. The purpose of this paper is to assess the influence of external dynamic forces on the processes of natural circulation. For the study a testing bench has been developed that simulates one of the circulation loops of the reactor unit. The basic method to obtain experimental data is temperature sounding of the specific sections of the circulation route. A mathematical model has been developed that describes this process. The model is based on the equations of momentum conservation and heat balance. In accordance with the experimental data, the calculation of natural circulation for static and dynamic modes has been carried out. A mathematical model to describe this process has been developed. A comparative analysis of the results of calculating the static and dynamic modes has been carried out. It is founded out that the decrease of mass flow rate is about 10 % as compared with the static regime. It confirms the qualitative effect of ship motion on natural circulation. The practical significance of the research is the development of a model under conditions of ship motion, as well as verification of the model at the testing bench. The results show a significant effect of ship motion on the mass flow rate of the coolant in the case of natural circulation. Thus, to ensure the required safety of ship installations, it is recommended to conduct a study of natural circulation in accordance with the developed model under conditions of maximum possible ship motion.

Influence of pipeline geometry on hydrodynamics and heat transfer processes by an example of a ship steam generator

The theoretical and computational analysis proposed in this work is aimed at identifying the features of thermal and hydrodynamic processes carried out in the steam-generating channels of the ship type water-moderated nuclear power installations. It is shown that the complex geometry of the thermohydraulic tract curvilinear channels of the steam generating system has a significant effect on the efficiency of the transport nuclear power installation. In addition to the formation of large-scale vortex structures and swirling flow in the pipeline, the phenomenon of the swirling flow crisis is revealed, under which the low-frequency component of the acoustic spectrum is enhanced. The scientific and applied significance of the proposed research is associated with the need to ensure a wide range of operational changes in efficient and safe operation power modes of icebreaker nuclear power installations. The research, aimed at developing the principles of physical and mathematical modeling of complex vortex flows, is necessary to optimize the design parameters of the thermal power equipment elements of new generation ship nuclear power installations in order to ensure increased safety and reliability of their operation.

Assessment of the Radiation and Health Physics Situation in the Area of Ship Repair Enterprises in Kamchatka Krai

The objectives of the study are to examine the radiation and health physics situation in the area of ship repair enterprises servicing ships with nuclear power installation; to assess its possible impact on the environment and the population. Materials and research methods. The study of radiation and health physics situation on the territory was conducted by walking gamma survey using portable gamma spectrometric complexes MKS-01A "Multirad-gamma" and MKS-AT6101C. Gamma-spectrometric and radiochemical methods of analysis were used to determine the specific activity of man-made and natural radionuclides in environmental samples. Results of the study and their analysis. Practical medical and hygienic measures to study the radiation and health physics situation were carried out in 2019. It was found that the ambient equivalent dose rate in the areas of ship repair enterprises is at the level of regional values and does not exceed 0.12 μSv/h. Radionuclide specific activity in the soil of the surveyed areas does not exceed 4.5 Bq/kg — for 90Sr and 12 Bq/kg — for 137Cs, which does not exceed the established norms for unrestricted use of solid materials. Radionuclide content in the sea water samples taken in the area of closed administrative territorial unit Krasheninnikov Bay does not exceed on average: for 137Cs — 7 mBq/L, for 90Sr — 2.1 mBq/L. When comparing the results obtained with the official data on the radionuclide content in the water of Avacha Bay (90Sr up to 2.08 mBq/L at the annual average of 1.14 mBq/L), we may state that they are at the same level as the regional ones. Radionuclide content in bottom sediment samples varies within the following limits: for 137Cs — from 0.14 to 3 Bq/kg, for 90Sr — from 0.11 to 1.5 Bq/kg and is similar to the general values for soil samples. Thus, the radiation and health physics characteristics of the study area vary little and remain practically at the level of the results of studies conducted in 2014-2015. The content of man-made radionuclides in the samples of environmental objects is at the level of average values typical for the region. Potentially radiation-hazardous works carried out in 2019 at enterprises of closed administrative territorial unit Vilyuchinsk had no reliable radiation impact on the environment and population.