Dynamics of periphytic Bacillariophyta at different stages of operation of the Chornobyl Nuclear Power Plant cooling pond (Ukraine)

The paper deals with the long-term dynamics of taxonomic composition of diatom periphyton in the Chornobyl nuclear power plant cooling pond (ChNPP cooling pond) at different stages of its operation: before the accident, after the accident and during the present period. The dominant complex of diatoms was marked by the highest diversity in the period after the accident, due to water temperature decreasing and new habitats appearing. The large-scale water-level drawdown in the present period caused the water table to reduce, and the habitats became less diverse. Owing to this, the number of dominant species decreased. Studying the present-day taxonomic composition of periphytic algae in the ChNPP cooling pond by way of light microscopy and scanning electron microscopy made it possible to identify 141 diatom species, represented by 143 infraspecific taxa, from 45 genera, 20 families, 12 orders and 3 classes. 14 species and infraspecific taxa of diatoms from genera Amphora, Cocconeis, Gomphonema, Hippodonta, Karayevia, Navicula, Placoneis, Planothidium, Psammothidium, Sellaphora are new for Ukrainian flora. High contamination of the ChNPP cooling pond with man-made radionuclides 90Sr, 137Cs and the large-scale water-level drawdown did not cause a significant degradation of diatom periphyton, which, in new ecological conditions, is distinguished by high taxonomic diversity and spatial heterogeneity.

Using CO2 as a Cooling Fluid for Power Plants: A Novel Approach for CO2 Storage and Utilization

To our knowledge, the potential use of CO2 as a heat-transmitting fluid for cooling applications in power plants has not been explored very extensively. In this paper, we conduct a theoretical analysis to explore the use of CO2 as the heat transmission fluid. We evaluate and compare the thermophysical properties of both dry air and CO2 and perform a simple analysis on a steam-condensing device where steam flows through one of the flow paths and the cooling fluid (CO2 or air) is expanded from a high-pressure container and flows through the other. Sample calculations are carried out for a saturated-vapor steam at 0.008 MPa and 41.5 °C with the mass flow rate of 0.01 kg/s. The pressure of the storage container ranges from 1 to 5 MPa, and its temperature is kept at 35 °C. The pressure of the cooling fluid (CO2 or dry air) is set at 0.1 MPa. With air as the heat-removing fluid, the steam exits the condensing device as a vapor-liquid steam of 53% to 10% vapor for the container pressure of 1 to 5 MPa. With CO2 as the heat-removing fluid, the steam exits the device still containing 44% and 7% vapor for the container pressure of 1 MPa and 2 MPa, respectively. For the container pressure of 3 MPa and higher, the steam exits the device as a single-phase saturated liquid. Thus, due to its excellent Joule–Thomson cooling effect and heat capacity, CO2 is a better fluid for power plant cooling applications. The condensing surface area is also estimated, and the results show that when CO2 is used, the condensing surface is 50% to 60% less than that when dry air is used. This leads to significant reductions in the condenser size and the capital costs. A rough estimate of the amount of CO2 that can be stored and utilized is also carried out for a steam power plant which operates with steam with a temperature of 540 °C (813 K) and a pressure of 10 MPa at the turbine inlet and saturated-vapor steam at 0.008 MPa at the turbine outlet. The results indicate that if CO2 is used as a cooling fluid, CO2 emitted from a 1000 MW power plant during a period of 250 days could be stored and utilized.

WAYS OF REDUCING INTAKE WATER RECEPTION BY THE COOLING SYSTEM OF A SHIP POWER PLANT

The issues of the possibility of reducing the intake of seawater by the power plant cooling system are considered. This will ensure a reduction in the negative anthropogenic impact of the system. Throttle control, thermal control with bypass and variable pump speed are analyzing. It has been founding that the latter method is the most optimal.