Assessment of coupled effect of steam pipe on seismic analysis of reactor coolant system

Reactor coolant system is connected with auxiliary pipes. surge pipes and steam pipes. In order to facilitate the dynamic analysis of reactor coolant system, it is necessary to decouple the pipes connected with the reactor coolant system according to certain decoupling criteria. There are some international standards, which stipulate two requirements for the decoupling of subsystems from the master system, i.e. quality and frequency. When the relevant conditions are satisfied, the subsystem can be decoupled from the main system during seismic simulation. According to the above decoupling criterion, it can be preliminarily determined that the first condition of the decoupling criterion is satisfied for the decoupling surge pipes, and the second condition is satisfied for the decoupling the steam pipes. In order to further explore the influence of decoupling steam pipes on the seismic analysis results of reactor coolant system, the seismic response of reactor coolant system with or without steam pipes is selected as the research object in this study, and the ANSYS program is used for simulation analysis. Firstly, the modal analysis of reactor coolant system before and after decoupling steam pipes is carried out, and the modal and resonant frequency are extracted, and the influence of steam pipes on the resonant frequency of reactor coolant system is analyzed. Furthermore, the standardized seismic dynamic analysis of reactor coolant system with or without steam pipes is carried out, and the load of nozzles (reactor pressure vessel inlet and outlet nozzles, steam generator inlet and outlet nozzles, main pump inlet and outlet nozzles) and the load of main equipment support (reactor pressure vessel support, steam generator support, main pump support) are output and compared. Through the analysis of nozzle load and support load, it can be seen that the steam pipes have little influence on the seismic analysis of reactor coolant system, i.e. it can be decoupled in the seismic analysis of reactor coolant system. (authors)