Modeling of NEK Steam Line Break Analysis in Computer Code Apros 6

Models of Nuclear power plant Krsko (NEK) Reactor Building (RB) was developed in computer code Apros 6. Simulation results of RB model built in Apros 6 were compared to Krsko NPP RELAP and GOTHIC code models developed by University of Zagreb - Faculty of Electrical Engineering and Computing (FER). Best estimate Apros 6 analysis of double-ended Main Steam Line Break (MSLB) transient was simulated. MSLB transient between Steam Generator (SG) outlet and Main Steam Isolation Valve (MSIV), so the blowdown of affected SG could not be prevented, was assumed. When the break occurs, the rapid steam flow to Containment building occurs from affected SG, causing rapid cooling and pressure drop of Reactor Coolant System (RCS). Containment absolute pressure, temperature and selected heat structure temperatures from Apros 6 simulation were compared to results of GOTHIC code.