SEDL / STP / STP1125-EB / STP17902S

Microstructural Characterization of Irradiated Nimonic PE16

Fisher, SB
Group head and research officers, Nuclear Electric plc Berkeley Nuclear Laboratories, Berkeley, Gloucestershire

Callen, VM
Group head and research officers, Nuclear Electric plc Berkeley Nuclear Laboratories, Berkeley, Gloucestershire

Rose, PK
Group head and research officers, Nuclear Electric plc Berkeley Nuclear Laboratories, Berkeley, Gloucestershire

Pages: 22    Published: Jan 1992

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Abstract

The tie bar component of the advanced gas-cooled reactor (AGR) is manufactured from the nickel-based superalloy Nimonic PE16. During service the component undergoes microstructural and associated mechanical property changes attributable to irradiation-induced and thermally induced processes. The extent of these changes varies with local temperature/flux variations along the tie-bar length. Most importantly, a region of relatively poor stress rupture properties is created towards the bottom of exposed bars, where the irradiation temperature is in the range 350 to 400°C.

In this paper, the microstructure and microchemistry of two highly irradiated bars are reported and the particular features associated with the stress rupture “trough” are identified.

A mechanism is proposed for the intergranular failure observed within this region.