SEDL / STP / STP1354-EB / STP14295S

Irradiation-Enhanced Deformation of Zr-2.5Nb Tubes at High Neutron Fluences

Causey, AR
Senior researcher, AECL, Chalk River Laboratories, Chalk River, Ontario

Holt, RA
Division director, AECL, Chalk River Laboratories, Chalk River, Ontario

Christodoulou, N
Senior researcher, AECL, Chalk River Laboratories, Chalk River, Ontario

Ho, ETC
Senior researcher, Ontario Hydro, Kipling Laboratories, Toronto, Ontario

Pages: 12    Published: Jan 2000

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Abstract

The effects of neutron flux and temperature on irradiation creep of 10-mm- diameter Zr-2.5Nb tubes are being assessed in end-of-life experiments in the Osiris reactor in France. The tubes have crystallographic texture, grain shape, and dislocation densities that are similar to those of full-size CANDU reactor pressure tubes. The experiments are performed at nominal operating temperatures of 553 and 583 K in fast neutron fluxes up to 2.0 × 10¹⁸ n · m^-2 · s^-1 (E > 1 MeV). Transverse and axial strains are reported as functions of fluence for specimens internally pressurized to hoop stresses from 0 to 160 MPa and irradiated to fluences up to 1.5 × 10²⁶ and 1.3 × 10²⁶ n · m^-2 at 553 and 583 K, respectively. The measured transverse and axial strain rates in these high-fluence experiments are shown to be in good agreement with a creep model relating crystallographic texture to the in-reactor deformation of CANDU pressure tubes. The anisotropy of irradiation creep does not change with fluence, but the temperature dependencies of creep and growth are changing; the activation temperature for creep is increasing, while the magnitude of the activation temperature for irradiation growth (a negative value) is becoming less negative with fluence.