Session: 07-02: Experiments and Analyses - I

Paper Number: 130962

130962 - Experimental Investigation of the Effect of Pcs on Hydrogen Stratification Behaviour in Large Enclosed Spaces 

Abstract: 

Under severe accident conditions, the migration and stratification of hydrogen within the containment vessel have consistently posed a significant risk to the integrity of the containment structure. Passive Containment Cooling System (PCS) is used as the localized cooler in the containment to export decay heat after severe accidents. Localized steam condensation will result in different temperature distribution, gas distribution, and hydrogen transport in the containment, affecting the gas distribution in the enclosed space. The large test facility "PANGU" is used to study the effect of PCS on gas mixing and stratification characteristics. The test facility is a steel pressure vessel with a total volume of 1010 m3， the outer surface is covered with a heat-insulating material to ensure it is adiabatic to the environment. The arrangement of the temperature measurement mainly considers the adequate coverage of the temperature field of the whole plant to reflect the temperature distribution accurately and comprehensively. In addition, anemometers are installed in the straight section space and near the heat exchanger to obtain real-time flow field information. A mass spectrometer measures the composition and concentration of the gas mixture. A thermal conductivity meter measures the relative concentration of helium among the non-condensable gases. This paper presents the impact of PCS on the distribution of gas mixture in experimental and analytical investigations during a postulated severe accident. Helium is used to simulate hydrogen released by cladding metal water reaction. The experiments are characterized by a 4-phase injection scenario. In Phase I, pure steam is injected, in Phase II PCS is activated, while in Phase III, pure helium is injected. Finally, in Phase Ⅳ, pure steam is injected again. Results depicting the helium stratification and temperature stratification in the facility are presented regarding helium concentration profiles and temperature contour maps. The results show that the operation of PCS resulted in temperature stratification in the vertical direction in Phase II, located near the upper edge of the heat exchanger. The gas flow in the vicinity of the heat exchanger tubes, in the area below the heat exchanger and the annular corridor in the lower part of the facility, is pronounced under the effect of condensation. In contrast, the gas flow in the space above the heat exchanger, in the upper header, and between the compartments is relatively stagnant. Additionally, most injected helium is trapped near the heat exchanger tubes and does not diffuse into the space above the heat exchanger or the upper head.

Presenting Author: Zhang Jiahui Harbin Engineering University

Presenting Author Biography: Harbin Engineering University

Authors:

Jiahui Zhang Harbin Engineering University
Gao Li China Nuclear Power Engineering Co., Ltd.
Hu Yangxing Harbin Engineering University
Hu Zongwen China Nuclear Power Engineering Co., Ltd.
Hua Yongzhen China Nuclear Power Engineering Co., Ltd.
Sun Zhongning Harbin Engineering University
Zhang Nan Harbin Engineering University