SEDL / STP / STP1125-EB / STP17898S

Radiation-Induced Segregation in 20Cr/25Ni/Nb Stainless Steel

Norris, DIR
Nuclear Electric plc, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire

Baker, C
Nuclear Electric plc, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire

Taylor, C
AEA Technology, Northern Research Laboratories, Windscale, Cumbria

Titchmarsh, JM
AEA Technology, Harwell Laboratory, Oxfordshire

Pages: 18    Published: Jan 1992

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Abstract

Intergranular corrosion of irradiated austenitic steels has been attributed to compositional changes produced by radiation-induced segregation at grain boundaries, and the effect has been investigated for the 20Cr/25Ni/Nb stainless steel employed as fuel cladding in advanced gas-cooled reactors. Analytical electron microscopy has been used to determine compositional profiles at grain boundaries in irradiated samples.

The observations are explained in terms of a model based on the inverse Kirkendall effect. At higher doses, interpretation is complicated by grain boundary migration, and compositional changes are found to persist after a boundary has moved away. The compositional profiles are compared with corrosion data for the same irradiated material. Results of Strauss corrosion tests are found to correlate with widths of chromium-depleted zones.

Silicon segregation towards boundaries is a feature of the observations at the lower irradiation temperatures.