The Modeling Research Of Convetional Island's Thermodynamic System In Nuclear Power Unit Based On RELAP5

Compared with thermal power unit, nuclear power unit is special in aspect of safety. So any nuclear power unit must have nuclear security verification using simulation analysis and calculation software before it obtains the production license. Nuclear safety analysis has become a necessary link before a nuclear power unit generates the power. RELAP5 thermal hydraulic calculation program is one of the developed softwares based on nuclear safety analysis. It has a wide applicability. RELAP5 does well in primary circuit calculation analysis, the relevant application for secondary circuit is less. Therefore, the core content of this article is to establish a model of CI thermodynamic system in nuclear power unit based on RELAP5.In this paper, we modified the steam turbine model in RELAP5 calculation program first. Since the existing RELAP5 turbine model has a big deflection in calculation when the unit is on the dynamic process, it is hard to achieve the dynamic response of the unit. Therefore, this paper do some modification in RELAP5 turbine model's source program based on pressure and flow's relationship. Then we replace some formula of RELAP5 turbine model. Compared with the stability and transient calculation results of advanced turbine model and the original RELAP5 model and designed parameters, the model is verified to be correct. The result shows that the modified turbine model has ability of certain dynamic response and higher accuracy.Secondly, the heat exchange equipment models of CI are established, including steam generator, MSR, condenser, feed water heater and deaerator. Otherwise, the supercooling phenomenon of condensate is simulated which is caused by noncondensable gas in condenser, the results prove that the condenser model has a high degree of simulation.Finally, the CI thermal system model and the related control system is established. To test the accuracy of model in the condition of steady state, the experiments of steady state have been done in 50%n 70% and 100% load, the result shows that the model can meet the static characteristic of the unit. Then to test the stability of model in the condition of dynamic state, the experiments of linear load changes and step load changes have been done. The result shows that the dynamic change of model is consistent with the trends of nuclear power unit's actual process, the model can satisfy the basic dynamic characteristics of the unit.