This document presents the issues of cooperation between a high temperature nuclear reactor and a coal-fired boiler in a hybrid system, where the main goal is to reduce the cumulative emission of carbon dioxide. Both devices can run on a common steam turbine and electricity generator. The meaning of the cooperation of these two sources is such as to obtain the final financial results, to achieve the level of CO2 emissions and thus the valley, that such a hybrid solution rewards comparison in the energy market and apply for different financial support schemes. Coal-nuclear hybrid system, as a unit generating electricity in cogeneration with heat, could apply for a share in the capacity market, where the entry gate is the indicated maximum level of CO2 emissions, e.g. 450 kg/MWh, which is unattainable for coal technologies. Based on the data on the actual amounts of coal fuel and the characteristic data of the OP-380 coal boiler, calculations were made of the actual CO2 emissions from such a source. The reported amount of emissions disqualifies such a source from further electricity production due to the fact that the current EU emission standards are twice exceeded. The results of the calculations confirm the assumptions regarding the connection of the two sources into a hybrid system that meets environmental standards in terms of carbon dioxide emissions. High temperature reactor may produce steam of parameters consistent with the parameters of steam from a coal boiler (temperature, pressure). The paper presents very preliminary, simplified analysis of such system. Results seems to be quite optimistic while considering emission issue, however important problems related to the elasticity of operation have been also identified.