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Conference Article: Material properties of a high-dose irradiated martensitic wrapper: Steel 1.4914

Abstract

The post-irradiation examinations of a wrapper made of martensitic X18CrMoVNb12 1 steel were performed after a two years operation in the French fast breeder reactor PHENIX. A maximum dose of 105 dpa_NRT was accumulated. Particular attention was paid to the welds connecting the martensitic wrapper material with the austenitic (AISI 316) top and bottom sleeves. Another area of importance was that of the highest dose in the center of the wrapper. The irradiation temperature varied from 380 deg. C entry temperature of the sodium at the foot of the wrapper up to the top of the wrapper with about 630 deg. C. The unirradiated reference material showed a typical increase in ductility with higher temperature. During welding, the material lost plasticity. The structure of the material was investigated and the irradiation induced microstructure exhibited characteristic features dependent on irradiation temperature and doses. In the lower part of the wrapper the formation of fine coherent alpha-precipitates with a high concentration was detected. The material received an increase in strength. In the center of the wrapper voids and bubbles could be observed, but they did hardly influence the mechanical behaviour. The measured swelling attained a value of max. 0.05%. Towards higher temperatures the voids disappeared and the density of bubbles increased. The effects of sodium corrosion showed a minimum influence to the tensile strength in the lower welded seam.

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Reference:

Influence of high dose irradiation on core structural and fuel materials in advanced reactors. Technical committee meeting, Obninsk (Russian Federation), 16-19 Jun 1997

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--1039, pp:129-138