Cernavoda NPP's performance and its availability to supply steam for district heating

The paper presents the results of the warranty/ performance tests carried-out at Unit 1 of Cernavoda NPP (Romania), during 1997, and the availability of the unit, confirmed at the tests, to supply steam for the district heating, without reducing the electrical output. Among the tests' results, extremely good seems the Gross Heat Rate which allowed the turbogenerator - 706,5 MWe design capacity - to actually generate 7 18,4 MWe, while the reactor was loaded at 99,1 percent Based on this result, an assessment was initiated of the possibility to increase the rated electrical output of the Unit the analysis being now in progress. The tests demonstrated the availability of an additional steam flow, in comparison with the flow required for the rated electrical output. Based on this result, a decision was taken, in order to provide heat for district heating: to extract the steam directly from the Unit's steam header, fed by the Steam Generators, maintaining the design rated electrical output. Thus, the modifications required for the operation of the turbine in co- generation were postponed. A comparative analysis is presented in the paper for two alternatives: No.I -steam taken directly from the Unit's steam header, and No.II - turbogenerator operated in co-generation, with the extraction of the steam from the exit of the High Pressure (HP) cylinder of the turbine. The basic assumption in this analysis - acceptable for a limited heat demand - is that the electrical power and the thermal power for heating are equal in both alternatives. The calculation proves that the higher thermal efficiency of the operation in co-generation (alternative No.II) leads to insignificant savings in the consumption of nuclear fuel. The operation of the turbine in co-generation (alternative No.II) becomes really efficient, from economical point of view, only when the heat load will be so large that the additional steam flow mentioned above, will be not sufficient to cover all the heat demand; hence, for getting more steam it will be necessary to reduce the electrical output. Such threshold of heat demand for Cernavoda NPP Unit 1 is at 30-33 Gcal/h. The drop in electrical output will be smaller in alternative No.II than in alternative No.I; from this difference, will rise the main advantage of co-generation at Cernavoda NPP Unit 1. (author)