Study of water hammer characteristics for integral reactor primary circuit of 900 MW PWR

In light of the hydraulic transition process, the complete mathematic model and boundary conditions for water hammer in primary circuit system of three-loop 900 MW PWR were established. The FORTRAN simulation program of water hammer was developed based on the method of characteristic line. And the numerical study on the water hammer characteristics of three pumps paralleled system was carried out under the conditions of startup and switching. The results indicate that two flow mutation and flow reversal occur on the closed branch of valve with a trend of attenuation of shock wave, and the maximum back flow is 1370 m³/h. The results also show that two pressure mutation and oscillation occur on the later startup branch, and the maximum value of pressure mutation is up to 40 kPa. The starting way of paralleled pumps decides the value of back flow and pressure mutation. (authors)