Nuclear Techniques ›› 2017, Vol. 40 ›› Issue (12): 120605-120605.doi: 10.11889/j.0253-3219.2017.hjs.40.120605

• NUCLEAR ENERGY SCIENCE AND ENGINEERING • Previous Articles    

Porosity properties and molten salt impregnation characteristics of nuclear graphites

ZHANG Baoliang1,2,3, QI Wei2, XIA Huihao2, SUN Libin1, WU Xinxin1   

  1. 1 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;
    2 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China;
    3 China Institute of Atomic Energy, Beijing 102413, China
  • Received:2017-06-21 Revised:2017-07-18 Online:2017-12-10 Published:2017-12-08
  • Supported by:
    Supported by Strategic Priority Research Program of Chinese Academy of Sciences (No.XDA02040200)

Abstract: Background: Nuclear graphite is a porous material and its pores can be easily impregnated with the molten fuel salt in a high pressure environment in the molten salt reactor (MSR). A seepage of the fuel salt into the graphite leads to the formation of local hot spots, which significantly damage the graphite, thereby reducing the service life of the graphite components. Purpose: This study aims to investigate the relationship between porosity property and molten salt impregnation of nuclear graphite. Methods: The porosity properties were examined by optical microscopy (OM), mercury porosimetry, and helium gas pycnometry. The impregnation tests were performed by impregnating graphites with molten fluoride salt at a temperature of 650° centigrade and a pressure of 0.1 MPa and 0.5 MPa respectively. Results: The porosity results indicated that the IG-110/IG-430 showed uniformly-distributed gas-evolved pores, small entrance pore diameter 2-4 μm, and a high open porosity; NBG-17/NBG-18 showed a big gas-evolved pores, wide range entrance pore diameter, and a high closed porosity (numerous calcination cracks in filler). Conclusion: The impregnation results showed that the impregnation mechanism of molten salt was similar to mercury. Only the applied pressure is greater than threshold pressure, the impregnation starts. With the increase of pressure, the small pores will also be filled with salt. The distribution of molten salt indicated that most of the cracks (calcination cracks and Mrozowski cracks) were closed.

Key words: Nuclear graphite, Pore structure, Molten salt impregnation, Entrance-pore diameter

CLC Number: 

  • TL342