Solution of the international benchmark with trip of one of four reactor coolant pumps for VVER-1000 reactor plants using the computer code package KORSAR/GP and complex reactor nodalization

The International OECD/NEA test benchmark for the trip of one of four operating reactor coolant pumps (RCPs) was solved using thermohydraulic code package KORSAR/GP. KORSAR/GP applies 1D calculational units. This benchmark was based on experimental results obtained during commissioning of Kalinin NPP, Unit 3. During the experiments a large amount of experimental data was obtained that enabled us to supplement the validation of the computer codes and nodalizations of 1D thermohydraulic codes. In the given transient there was a difference between coolant temperatures in different loops that resulted in the necessity of numerical simulation of the coolant mixing in the reactor plenums. To solve this problem, complex branched nodalization (i.e. the set of code calculational units) was used. The analysis results matched closely with the experimental data. Thus it was shown that the nodalization developed with the use of KORSAR/GP and the code itself can be applied for the simulation of VVER-1000 transients with one ore more RCPs in operation and sharp difference between coolant temperature in loops. (author)