Factors analysis of water hammer in FLOWMASTER for main feedwater systems of PWR nuclear power plants

WANG Xin¹, HAN Wei-shi²

1. College of Nuclear Science and Technology, Harbin Engineering University, 145 Nantong Street, Harbin 15001, People’s Republic of China (wxhaijun@yahoo.com.cn)

2. College of Nuclear Science and Technology, Harbin Engineering University, 145 Nantong Street, Harbin 150001, People’s Republic of China (hanws2007@163.com)

Abstract: The main feedwater system of a nuclear power plant (NPP) is an important part in ensuring the cooling of a steam generator. It is the main pipe section where water hammers frequently occur. Studying the regular patterns of water hammers in the main feedwater systems is significant to the stable operation of the system. This article focuses on a parametric study to avoid the consequences of water hammer effect in PWR by employing a general purpose fluid dynamic simulation software-FLOWMASTER. Through FLOWMASTER's transient calculating functions, a mathematical model is established with boundary conditions such as feedwater pumps, control valves, etc., calculations of water hammer pressure when feedwater pumps and control valves shut down, and simulations during instantaneous changes in water hammer pressure. Combining a plethora of engineering practical examples, this research verified the viability of calculating water hammer pressure through FLOWMASTER's transient functions and we found out that, increasing the periods of closure of control valves and feedwater pumps control water hammers effectively. We also found out that changing the intervals of closing signals to feedwater pumps and control valves aid to relieve hydraulic impact. This could be a guideline for practical engineering design and system optimization.

Keywords: water hammers,main; feedwater system; nuclear power plant; simulation