Simulation of a control rod ejection accident in a VVER-1000/V446 using RELAP5/Mod3.2

In this study, the RELAP5 Mod3.2 code has been used to analyze the REA in a VVER-1000 reactor. For a conservative simulation, a 58 mm break is considered in the upper head of the reactor pressure vessel due to the impact of an ejected rod.Four cases, 104% of nominal power and 0.45$ of inserted reactivity, 71% of nominal power and 0.47$ of inserted reactivity, 54% of nominal power and 0.6$ of inserted reactivity, and 1% of nominal power and 0.9$ of inserted reactivity are the initial conditions. The relative power, pressure in the pressurizer, mass flow rate via break point, BRU-A performance, and fuel surface temperature are the investigated parameters. The results of the RELAP5 code are consistent with VVER-1000 FSAR data.

► RELAP5 Code is used to analyze the REA in a VVER-1000.
► A 58 mm break is considered in the upper head of the reactor pressure vessel.
► Reactor shut-down occurred in 1.7–5.4 s.
► The studied accident is not categorized among level 1 accidents.
► Results are consistent with VVER-1000 FSAR data.