• CN: 11-2187/TH
  • ISSN: 0577-6686

Journal of Mechanical Engineering ›› 2024, Vol. 60 ›› Issue (24): 199-210.doi: 10.3901/JME.2024.24.199

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Effect of Nucleate Boiling on Corrosion Behavior of Zirconium Alloy in Oxygen-enriched High Temperature Water

ZENG Qifeng1,2, LIU Yanjie3, ZHANG Lefu1, SI Shengyi4, LI Cong2, LU Junqiang2, LIU Qingdong3   

  1. 1. Institute of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240;
    2. Shanghai Nuclear Engineering Research & Design Institute Co., Ltd., Shanghai 200233;
    3. School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240;
    4. Nuclear Power Operations Research Institute, Shanghai 200120
  • Received:2024-03-15 Revised:2024-09-16 Online:2024-12-20 Published:2025-02-01

Abstract: In order to understand the effect of void fraction on CRUD deposition and corrosion behavior of zirconium alloy in high temperature water with dissolved oxygen, a 42-days corrosion test was carried out on Zr-4 and SZA-4 alloy cladding tubes in high temperature and high pressure water loop system. The microstructures of oxide and CRUD were analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The hydrogen absorbed by Zr metal substrate was examined by a hydrogen analyzer. The results show that, with the increase of temperature and void fraction along the cladding tube, the oxide film thickness of the two Zr alloys generally grow, the oxide-metal interface become uneven and hydrogen absorption increase accordingly. After corrosion for 42 days, both Zr-4 and SZA-4 alloys are still in the early corrosion stage before transition. The oxide consists of outer equiaxed grains and inner columnar grains, which is dense and totally protectable. There are several second phase particles (SPPs) without full oxidization distributing across the whole oxide, and a transition layer was observed at the oxide and α-Zr matrix (O/M) interface. The CRUD is mainly composed of iron oxide crystals with different grain sizes, and can be divided into loose and dense region, and there are a lot of holes in the loose region with small grain size. The oxide thickness for Nb-containing SZA-4 alloy is greater than that of Zr-4 alloy without Nb, indicating the inferior corrosion resistance of SZA-4 alloy in oxygen-enriched high temperature water. The phenomena confirm that Nb element increases the corrosion rate of Zr alloy when some dissolved oxygen is present in water, which is contrary to the corrosion behavior in conventional pressurized water reactor environment.

Key words: zirconium alloys, corrosion, oxide, dissolved oxygen, void fraction, CRUD

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