Analysis of Nuclear Reactor Parameters in the VVER-1200 during a Loss of Coolant Accident and Steam Generator Tube Rupture with Emergency Core Cooling System Failure

Abstract

Nuclear energy is widely recognized as a clean energy source and has gained popularity for its role in electricity production. It currently accounts for around 10% of global electricity production, with nuclear reactors being a key element in the operation of nuclear power plants. Numerous reactor types have been developed over the years but the VVER-1200, a Generation III+ PWR, is implemented worldwide due to its advanced safety features. In this work, PCTRAN, a thermal-hydraulic modeling software has been utilized to simulate fault circumstances on the VVER-1200 reactor with or without the emergency core cooling system (ECCS) in operation. As this software encompasses several built-in malfunctions, steam generator tube rupture (SGTR) with 100 cm2 break at B, and break loss of coolant accident (LOCA) at cold leg with 856 cm2 failure have been introduced into the software to analyze the impact of the faults on the nuclear plant parameters such as pressure, temperature, reactivity, water level, and so on. Following the SGTR and LOCA, pressure, temperature, power, and coolant flow dropped drastically within the first 200 seconds after the reactor got tripped at 13 secs. With ECCS in operation, the accumulator valve provides water from the emergency water storage tank (EWST), stabilizing power, fuel temperature, reactor coolant flow, and pressure, thereby preventing core damage. However, ECCS failure results in core exposure, fuel melting, radioactive leakage, and core collapse from molten core concrete interaction.