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Waste heat recovery from flue gas based on water vapor condensation is an important issue as the waste heat recovery significantly increases the efficiency of the thermal power units. General principles for designing of this type of heat exchangers are known rather well; however, investigations of the local characteristics necessary for the optimization of those heat exchangers are very limited. Investigations of water vapor condensation from biofuel flue gas in the model of a vertical condensing heat exchanger were performed without and with water injection into a calorimetric tube. During the base-case investigations, no water was injected into the calorimetric tube. The results showed that the humidity and the temperature of inlet flue gas have a significant effect on the local and average heat transfer. For some regimes, the initial part of the condensing heat exchanger was not effective in terms of heat transfer because there the flue gas was cooled by convection until its temperature reached the dew point temperature. The results also showed that, at higher Reynolds numbers, there was an increase in the length of the convection prevailing region. After that region, a sudden increase was observed in heat transfer due to water vapor condensation.

During 2002–2005 the assessment of possibilities for disposal of spent nuclear fuel (SNF) in Lithuania was performed with support of Swedish experts. Potential geological formations for disposal of SNF were selected, disposal concept was developed, reference disposal site was defined and preliminary generic safety assessment was performed. Performing safety assessment the analysis of radionuclides migration from the repository as well as their impact to human and environment were also very important issues. In this paper results on the analysis of the radionuclide releases from the reference geological repository site for RBMK-1500 SNF in crystalline rocks in Lithuania are presented. For radionuclide migration in the near field region of the repository integrated finite difference method and the concept of compartments were used. For radionuclide migration in the far field the discrete channel network concept was used. The assessment of radionuclide migration in the near and far field region was performed using computer codes AMRER4.5 [1] and CHAN3D [2]. The results of analysis show that most of safety relevant radionuclides of RBMK-1500 SNF are effectively retarded in the near field region. The exposure due to possible release of the radionuclides from the crystalline rocks would be dominated by 129I firstly while after app. 250 thousand years 226Ra is dominating already.

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