Multi-physical Processes Coupling Calculation Study For PWR

The nuclear power plant includes many different systems, and each of them has theirparticular functions and complicated physical processes. At the both normal and accidentstatus, these complicated physical processes are strongly coupling with each other. If weconsider these physical processes separately, for design calculating, the results would be tooconservative, and it hinders the economic development of nuclear power plant. On the otherhand, the lack of full understanding of complex mechanisms related to the interaction betweenthese physical processes limits the reliability of safety analysis. So, according to the researchpurpose, coupling the programs with different physical processes could be a method to solvethe problems above.The primary coolant system of QINSHAN-II nuclear power plant was selected as studyproject in this paper. The lattice physics code CASMO4E was used to calculate thehomogeneous parameters of different kinds of assemblies in the reactor core. And, accordingthe operation status, the calculation points were determined, and the cross-section library wasgenerated. The sub-channel thermal-hydraulic program TISKTH-3and the Green’s functionnodal expansion code NGFM were used to calculate the thermal-hydraulic and neutroniccharacteristic in the reactor core respectively. The methods of coupling thermal-hydraulic andneutronic kinetic (TH/NK) programs were discussed. Finally, the multi-physical processescode package was established, and its calculation flow was controlled with batch file.Through the study, the following conclusions were received:The reflector should not be just simplified as water layer, because it would greatly affectthe accuracy of radial power distribution; before the TH/NK coupling calculation, thesensitivity study of feedback parameters is necessary, it would reduce the error ofcross-section library; because of the non-linear characteristic, this paper selected Lagrangeinterpolation method to calculation the cross-section from library, and it gives a good result;the multi-physical processes coupling calculation would greatly reduce the peak value at theaxial direction, so the results become more efficient than before.