Nuclear Techniques ›› 2017, Vol. 40 ›› Issue (3): 30602-030602.doi: 10.11889/j.0253-3219.2017.hjs.40.030602

• NUCLEAR ENERGY SCIENCE AND ENGINEERING • Previous Articles     Next Articles

Study on new zirconium alloys for CAP1400 fuel assembly

ZENG Qifeng1, ZHU Libing1, YUAN Gaihuan2, WANG Lian2, LIU Jiazheng1, GAO Bo2   

  1. 1. Shanghai Nuclear Engineering Research & Design Institute, Shanghai 200233, China;
    2. State Nuclear Baoti Zirconium Industry Company, Baoji 721013, China
  • Received:2016-08-25 Revised:2016-12-13 Online:2017-03-10 Published:2017-03-11
  • Supported by:

    Supported by Development and Application of Domestic New Zirconium Alloys Project (No.2011ZX06004-023)

Abstract:

Background: Zirconium alloys are widely used as cladding tube and structural materials in pressurized water reactors because of their low thermal neutron cross section, good mechanical properties and corrosion resistance. At present, the main problem in the development of domestic zirconium alloys is the development of new zirconium alloys with independent intellectual property rights, and improving the corrosion resistance and hydrogen pick-up behaviors of zirconium alloys, making them significantly better than Zr-4 alloy, at the same time, keeping comparable mechanical properties, radiation growth and creep resistance with Zr-4 alloy. Purpose: Therefore, a series of various model zirconium alloys were prepared by vacuum arc smelting based on Zr-Sn-Nb alloy with minor alloying elements such as Ge and Si, in order to select the most promising candidate alloys to meet these requirements, via comparative studies on the corrosion resistance, hydrogen pick-up behaviors and mechanical properties. Methods: Transmission electron microscopy (TEM) was used to characterize the detail microstructure of base alloys. Corrosion resistance was examined by the weight gain in static autoclave with different water chemistry environments. Hydrogen pick-up behaviors were directly reflected by the hydrogen contents across the oxidation layers and underneath matrix measured by hydrogen determinator. The mechanical properties were evaluated by conventional tensile testing. Results: It was found that SZA-6 and SZA-4 alloys consisted of fully recrystallized grain structures with uniformly distributed fine second phase particles located within grain interior and at grain boundaries. Both SZA-4 and SZA-6 alloys exhibited excellent corrosion resistance in all three water chemistry conditions. The corrosion resistance of SZA-6 was better than the reference commercial alloys, and SZA-4 was slightly better than SZA-6. However, the SZA-6 alloy seemed to be less susceptible to hydrogen pick-up compared to SZA-4 alloy. In addition, the mechanical properties of two new zirconium alloys met the design criterion. Conclusion: Considering the outstanding corrosion resistance and low hydrogen pick-up in simulated water chemistry conditions and satisfied mechanical performances, the SZA-4 and SZA-6 alloys were suggested as promising alloys used for CAP1400 fuel assembly in the future.

Key words: New zirconium alloy, Alloy composition, Manufacturing process, Microstructure, Corrosion resistance

CLC Number: 

  • TL341