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Degradation of Thermal Creep by Hydrides of Zr-2/5Nb Pressure Tube

Zr-2.5Nb 압력관의 수소화물에 의한 고온 크리프의 열화거동

  • Published : 2006.12.01

Abstract

The aim of this research was to confirm the existence of the thermal creep degradation by hydrides of Zr-2.5Nb pressure tube materials. Small punch creep tests were performed to obtain the relationship between a creep displacement and a loading period at $300^{\circ}C$. A creep stress and a creep strain rate were also converted from the previous results. The creep material constants and the creep stress exponents at the different hydride contents were compared. Finally the hydrides of the axial and circumferential section were observed using OM, SEM and TEM. The following conclusions were made: 1) The degradation of the thermal creep by hydrides was existed and it strongly depended on the hydride contents. 2) As the hydride contents were increased, the creep stress exponents (m) were also increased. 3) Even though the hydride was not precipitated in 50 ppm materials at $300^{\circ}C$, the degradation of thermal creep was found. Therefore, it was believed that this phenomenon strongly related to the hydride precipitation at room temperature.

Keywords

Hydride;Pressure Tube;Small Punch Creep Test;Degradation;Thermal Creep;Hydrogen Embrittlement

References

  1. Oh, D. J., Boo, M. H. and Kim, Y. S., 2003, ?'Hydrogen Embrittlement of Zr-2.5Nb Pressure Tube at Room Temperature by Precipitated Hydride,' Transaction of KSME (A), Vol. 27, No. 3, pp. 455-463 https://doi.org/10.3795/KSME-A.2003.27.3.455
  2. Oh, D. J., and Kim, Y. S., 2004, 'Effect of Hydride of the PHWR Pressure Tube on the LBB Evaluation,' Transaction of KSME (A), Vol. 28, No. 5, pp. 610-616 https://doi.org/10.3795/KSME-A.2004.28.5.610
  3. Moan, G D., Coleman, C. E., Price, E. G., Rodgers, D. K. and Sagat, S., 1990, 'Leak-Before-Break in the Pressure Tubes of CANDU Reactors,' International Journal of Pressure Vessel. & Piping, Vol. 43, pp. 1-21 https://doi.org/10.1016/0308-0161(90)90089-Z
  4. AECL, 1996, 'Fitness for Service Guidelines for Zirconium Alloy Pressure Tubes in Operating CANDU Reactor,' AECL Report COG-91-66
  5. Shewfelt, R. S. W., Lyall, L. W. and Godin, D. P., 1984, 'A High Temperature Creep Model for Zr-2.5 wt% Nb Pressure Tubes,' Journal of Nuclear Materials, Vol. 125, pp. 228-235 https://doi.org/10.1016/0022-3115(84)90548-8
  6. Parker, J. D. and James, J. D., 1993, 'Disc-Bend Creep Deformation Behavior of $\frac{1}{2}$Cr $\frac{1}{2}$Mo $\frac{1}{4}$V Low Alloy Steel,' Fifth International Conference on Creep and Fracture of Engineering Material and Structures, pp. 651-660
  7. Parker, J. D. and James, J. D., 1994, 'Creep Behavior of Miniature Disc Specimens of Low Alloy Steel,' ASME PVP Vol. 279, Developments in a Progressing Technology, pp. 167-172
  8. KAERI, 1999, 'Characterization Testing Procedures of Zr-2.5Nb Pressure Tubes,' KAERI/TR-1329/99
  9. Sim, Sang Hoon, 2003, 'Assessment of High Temperature Creep Constants of Isotropic Materials Using Small Punch Creep Testing,' PhD Thesis, Chung Ang University
  10. Park, T. G, Ma, Y. W., Jeong, I. S. and Yoon, K. B., 2003, 'A Study on Applicability of SP Creep Testing for Measurement of Creep Properties of Zr-2.5Nb Alloy,' Transaction of KSME (A), Vol. 27, No. 1, pp. 94-101 https://doi.org/10.3795/KSME-A.2003.27.1.094
  11. KAERI, 1998, 'Characterization of Zr-2.5Nb Pressure Tube,' KAERI/TR-I137/98
  12. Urbanic, V. E. and Griffiths, M., 2000, 'Micro-Structural Aspects of Corrosion and Hydrogen Ingress in Zr-2.5Nb,' Zirconium in the Nuclear Industry, ASTM STP 1354, pp. 614-657
  13. Betten, J., 2005, Creep Mechanics, 2nd Ed., Springer, Berlin