A comparison of the net present value, the payback period, and the levelized cost of electricity for three different projects of construction and exploitation of plants for electricity production with the aim of decarbonizing the energy sector is conducted. The first project is the building of a large-scale nuclear power plant with a light-water reactor, the second one is the deployment of several identical small modular reactors, and the third project is based on solar and wind power plants. Given that the sun and wind are intermittent renewable energy sources, it is inevitable to take into account the construction of an energy storage facility in the last project. The results show that the most profitable are the small modular reactors, while the investment into solar and wind power plants is burdened with the necessary electricity storage plant costs. Another drawback of an investment in solar and wind power plants is their shorter exploitation lifetime of 25 years compared to the long-term operation of nuclear power plants of 60 years or even more.

Horizontal Steam Generators (HSGs) are crucial components in nuclear power plants with the pressurized water reactors of the Water-Water Energetic Reactor (WWER) type, facilitating the efficient transfer of heat from the primary reactor coolant to the secondary working fluid. Within the HSG, the reactor coolant (primary fluid) flows inside tubes of horizontal tube bundles, while the secondary fluid, a two-phase mixture of water and steam, flows on the shell side. The generated steam flows from the HSG towards the steam turbine. The working fluid is returned to the HSG from the steam turbine plant as the preheated feedwater. Аn improved HSG design incorporates an extension of the already existing perforated plate above the tube bundles towards the HSG shell wall on the hot side and a removal of protection plate that existed on the HSG wall in the area of the steam dome on the hot side. Additionally, a new perforated plate at the steam outlet replaces the traditional steam dryer. This study presents a comprehensive three-dimensional thermohydraulic model of a WWER-1000 HSG. The mathematical model consists of mass, momentum, and energy conservation equations, written separately for the liquid and vapor phases of the secondary fluid in three orthogonal spatial directions. The primary fluid is modeled by a one-dimensional energy equation. The system of differential equations is numerically solved using the control volume method and the SIMPLE algorithm, which has been modified for two-phase flow. As a result of the simulations, fields of velocity for both liquid and vapor phases, pressure fields, and void fraction fields in the secondary fluid were obtained. The calculation was initially performed for an existing steam generator implemented in the Novovoronezh nuclear power plant in Russia, and the obtained results were compared with measured values for model verification. After successful validation, the model was applied to calculate the improved HSG design. The thermohydraulic images of both the existing and improved generators were then compared in detail, providing valuable insight into the impact of the proposed modifications on system performance. The obtained results contribute to the optimization of HSG design and operational parameters, aiming to upgrade economy of its design with preserving the efficiency and safety of the nuclear power plant.

A comparison of the net present value, the payback period and the levelized cost of electricity for three different projects of construction and exploitation of plants for electricity production with the aim of decarbonizing the energy sector is conducted. The first project is building of a large-scale nuclear power plant with a light-water reactor, the second one is a deployment of several identical small modular reactors and the third project is based on solar and wind power plants. Given that the sun and wind are intermittent renewable energy sources, it is inevitable to take into account the construction of an energy storage facility in the last project. The results show that the most profitable are the small modular reactors, while the investment into solar and wind power plants are burdened with the necessary electricity storage plants costs. Another drawback of an investment in solar and wind power plant is their shorter exploitation lifetime of 25 years, compared to the long-term operation of nuclear power plants of 60 years or even more.