Session: 01-04: Nuclear Plant Operation, Modification, Life Extension, Maintenance and Life Cycle - IV

Paper Number: 134766

134766 - Analysis of Water Hammer in the Reactor Coolant System Based on Wave Tracking Method 

Abstract: 

Reactor coolant system is an important part of nuclear power plant, and its operation process involves complex hydraulic phenomena. Among them, the water hammer phenomenon is a common hydrodynamic phenomenon, which will produce strong impact and vibration on pipelines and equipment, thus affecting the stability and safety of the system. Therefore, it is very important to simulate and analyze the water hammer phenomenon.

Compared with the method of characteristic (MOC), we use the Wave Tracking Method (WTM) to simulate the water hammer phenomenon, which can quickly and accurately calculate the propagation process of the water hammer wave. By introducing a simplified convolutional unsteady flow friction model, a new water hammer wave tracking equation is established to improve the computational efficiency and accuracy. We verify the accuracy of the wave tracking method and model by water hammer experiments with initial Reynolds numbers of 52250, 15040 and 8400, respectively, and compare them with FlowMaster calculations. The results show that the wave tracking method has the same accuracy as the method of characteristic adopted by FlowMaster. The calculation accuracy of the convolutional unsteady flow friction model is higher, which can better simulate the peak and phase of the water hammer wave.

Next, we used the WTM to establish the mathematical and physical models of the three loops of the main coolant system of the 900MW PWR. The pressure fluctuation of reactor coolant system was simulated under four working conditions: the main pumps stopped after power outage, the pumps started, the single pump started after power outage and the single pump shaft stuck. The simulation results show that due to the significant inertia effect of the main pump and the short length of the loop pipeline, the rotational speed stability time of the three main pumps after power off is about 220 seconds, and the simultaneous start-up time of the three main pumps is 8 seconds, which is consistent with the actual unit operation time. In the process of single pump power outage and pump shutdown, the stop time of the accident pump is 25s, and the reverse flow of the accident loop does not occur under the action of the ratchet type anti-reversal device. In the case of a single pump shaft stuck, the system produced a water hammer phenomenon, resulting in a maximum pressure of 16.66MPa and a minimum pressure of 14.97MPa. According to the simulation results, when the main pump has a large inertia, the normal transient operation will not produce destructive water hammer phenomenon. However, when the shaft of the main pump is stuck, there will be a large pressure impact on the pipeline, which endangers the safety of the reactor main coolant system..

The results of this paper are of great significance for evaluating the impact of water hammer on the reactor coolant system, and provide new water hammer solution method and ideas for the simulation of water hammer in other similar pipeline systems.

Presenting Author: Qianping Zhang China Nuclear Power Operation Technology Corporation, Wuhan

Presenting Author Biography: Master, Engineer, Research direction: fluid network simulation software development

Authors:

Qianping Zhang China Nuclear Power Operation Technology Corporation, Wuhan
Shubiao Dong China Nuclear Power Operation Technology Corporation, Wuhan
Xiaoyu Zhang China Nuclear Power Operation Technology Corporation, Wuhan