Modeling of the Radiation Doses during Dismantling of RBMK-1500 Reactor Pressurized Tanks from Emergency Core Cooling System

Decommissioning of the Ignalina Nuclear Power Plant involves multiple problems. One of them is personnel radiation safety during the performance of dismantling activities. In this paper, modeling results of radiation doses during the dismantling of the pressurized tank from the emergency core cooling system (ECCS PT) of RBMK-1500 reactor are presented. The radiological surveys indicate that the inner surface of the ECCS PT is contaminated with radioactive products of corrosion and sediments due to the radioactive water. The effective doses to the workers have been modeled for different strategies of ECCS PT dismantling. In order to select the optimal personnel radiation safety, the modeling has been performed by the means of computer code “VISIPLAN 3D ALARA Planning tool” developed by SCK CEN (Belgium). The impacts of dismantling tools, shielding types, and extract ventilation flow rate on effective doses during the dismantling of ECCS PT have been analyzed. The total effective personnel doses have been obtained by summarizing the effective personnel doses from various sources of exposure, that is, direct radiation from radioactive equipment, internal radiation due to inhalation of radioactive aerosols, and direct radiation from radioactive aerosols arising during hot cutting in premises. The uncertainty of the collective doses is also presented in this paper

Experimental investigation of water vapor condensation from hot humidified air in serpentine heat exchanger

Data availability: Data will be made available on request.Copyright © 2023 The Authors. Condensing economizers are used in industry and power plants for waste heat recovery. Despite widespread use, their thermal design is still not optimized due to the complexity of the condensation process especially when non-condensing gasses are prevalent. This paper presents an experimental study of water vapor condensation on the vertical tubes of a serpentine bundle in a humidified air crossflow at water vapor mass fractions of 10% and 20%. The analysis showed a clear dependence of the efficiency of the condensation process on the humidified air inlet temperature and Reynolds number, and the efficiency increases as these parameters decrease. Condensation efficiency also depends highly on flow humidity especially in the region of higher Reynolds numbers. A comparison of the average Nusselt number in the case of dry air with the experimentally determined average Nusselt number is also presented, and showed a uniform increase in the Nusselt number as the inlet temperature of the humidified air decreased.This work was partly funded by the European Union H2020 program project iWAYS under grant agreement number 958274

An experimental investigation of water vapor condensation from biofuel flue gas in a model of condenser, (2) local heat transfer in a calorimetric tube with water injection

Data Availability Statement: Not applicable.Copyright © 2021 by the authors. In order for the operation of the condensing heat exchanger to be efficient, the flue gas temperature at the inlet to the heat exchanger should be reduced so that condensation can start from the very beginning of the exchanger. A possible way to reduce the flue gas temperature is the injection of water into the flue gas flow. Injected water additionally moistens the flue gas and increases its level of humidity. Therefore, more favorable conditions are created for condensation and heat transfer. The results presented in the second paper of the series on condensation heat transfer indicate that water injection into the flue gas flow drastically changes the distribution of temperatures along the heat exchanger and enhances local total heat transfer. The injected water causes an increase in the local total heat transfer by at least two times in comparison with the case when no water is injected. Different temperatures of injected water mainly have a major impact on the local total heat transfer until almost the middle of the model of the condensing heat exchanger. From the middle part until the end, the heat transfer is almost the same at different injected water temperatures.Research Council of Lithuania (LMTLT), grant number S-MIP-20-30

Flue Gas Condensation in a Model of the Heat Exchanger: The Effect of the Cooling Water Flow Rate and Its Temperature on Local Heat Transfer

In boiler houses, the biggest heat energy losses are caused by flue gas being released into the atmosphere. Installation of condensing heat exchangers allows reducing the temperature of the flue gas being released, condensation of water vapor, and, thus, efficient use of the waste heat. There are many investigations of average heat transfer in different types of condensing heat exchangers. They indicate also that the cooling water flow rate and its temperature are important parameters defining water vapor condensation efficiency. Investigations of local condensation heat transfer in condensing heat exchangers are very limited. Only recently experimental investigations of the flue gas temperature and Re number effect on local condensation heat transfer in the model of the condensing heat exchanger at a constant cooling water flow rate and its temperature have started being published. In this paper, for the first time, detailed experimental investigations of the cooling water flow rate and its temperature effect on local condensation heat transfer of the water vapor from the flue gas in the model of the condensing heat exchanger (long vertical tube) are presented. The results revealed that at higher flue gas Rein, the effect of the cooling water flow rate and its temperature has a stronger impact on local heat transfer distribution along the test section.Research Council of Lithuania (LMTLT), grant number S-MIP-20-30

Investigation of characteristics of solid particles from a mixture of sewage sludge and wood pellets synthetic gas and their clean-up

The most reasonable way to utilise sewage sludge in Europe is in energy production. In the process of thermochemical conversion of sewage sludge, combustible gas is produced. Studies of synthetic gas composition show that this gas contains various impurities, which must be cleaned before gas supply to the final user. Although there are many ways to clean toxic materials existing in the synthetic gas, the application of plasma treatment seems the most promising. Exposure to the high temperature of plasma changes the structure and the chemical composition of solid particulates existing in the gas. In this study on the synthetic gas, ESP cleaning efficiency, size and elemental analysis of solid particles collected from different parts of the experimental setup with a gasifier operating on a mixture of sludge and wood pellets were analysed. The results showed the difference in particle sizes and changes in elemental composition of particles collected from different parts of the experimental setup. It was determined that the synthetic gas obtained by gasification of a mixture of sludge and wood pellets contains a great concentration of solid particles, which leads to the total collection efficiency of an electrostatic precipitator being only about 60 %

Investigation of effect of cooling water characteristics on flue gas condensation along vertical tube heat exchanger

Data availability: Data will be made available on request.Flue gas condensing heat exchangers obtain the highest thermal efficiency of power boilers through the recovery of sensible and latent heat of condensation from flue gases containing certain amount of water vapor. Many parameters influence the operation of economizers, among them the amount of water vapor in the flue gas and cooling water parameters. This paper presents experimental results obtained for various local parameters of vertical tube bundle economizer when the flue gas water vapor mass fraction is 6 % and 14 % and when different cooling water inlet flow rates and temperatures are applied. The results showed that the change in the water flow rate had negligible effect on variation of the local flue gas and cooling water temperature along heat exchanger. However, its effect on the condensate flux and the local Nusselt number was significant. The cooling water temperature and, especially, water vapor mass fraction had a great impact on the average Nu number, but the effect of the flue gas Re number was less evident. It was determined that there exists a ratio of cooling water to flue gas mass flow rate, where the operation of the economizer is optimal in terms heat transfer and condensation efficiency.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors

Experimental investigation of water vapor condensation from flue gas in different rows of a heat exchanger model

Data availability: Data will be made available on request.Condensing heat exchangers (HE) are used in many applications because of their usability with different fluids and a wide operating range in terms of pressure, temperature and power. Despite that, the thermal design of condensing heat exchangers is still not optimized, due to the complexity of the condensation process and lack of related research. This paper presents results of experimental investigations of biofuel flue gas water vapor condensation on vertical tubes in different rows of a tube bundle in a crossflow. The effects of water vapor mass fraction, inlet flue gas temperature and the Reynolds number on heat transfer when the inlet cooling water temperature and flow rate are constant were analyzed. The results obtained showed that the main parameters which had the most influence on the condensation process were the water vapor mass fraction in the flue gas and its temperature at the inlet to the test section. In the range of inlet flue gas Reynolds numbers investigated, the Re effect on heat transfer was not as significant as the effect of the parameters indicated above. However, the Re number had some influence on the heat transfer variation along the inline tube bundle. A comparison of the average Nu number in the case of dry air with the experimentally determined average Nu number, even with low condensable gas mass fraction (6 %), showed that it increased considerably. A correlation was proposed, which helps to determine the average Nu number for the heat exchanger in the range of experiments performed.partly funded from the European Union’s H2020 programme iWAYS project under grant agreement number 958274