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Effects of Neutron Irradiation on Fe-Cu Model Alloys and RPV Steels Probed by Positron Annihilation and Hardness Measurements

Hempel, A
Visiting Researcher, Graduate Course Student, Research Associate and Professors,Institute for Materials Research, Tohoku University,

Saneyasu, M
Visiting Researcher, Graduate Course Student, Research Associate and Professors,Institute for Materials Research, Tohoku University,

Tang, Z
Visiting Researcher, Graduate Course Student, Research Associate and Professors,Institute for Materials Research, Tohoku University,

Hasegawa, M
Visiting Researcher, Graduate Course Student, Research Associate and Professors,Institute for Materials Research, Tohoku University,

Brauer, G
Group Leader,Institut für Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf e.V.,

Plazaola, F
Professor,Elektrika eta Elektronika Saila, Euskal Herriko Unibertsitatea,

Yamaguchi, S
Visiting Researcher, Graduate Course Student, Research Associate and Professors,Institute for Materials Research, Tohoku University,

Kano, F
Researchers,Power and Instrumental Systems Research and Development Center, Toshiba Co.,

Kawai, A
Researchers,Power and Instrumental Systems Research and Development Center, Toshiba Co.,

Pages: 19    Published: Jan 2000

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Source: STP1366-EB

Abstract

To study the formation of microvoids and Cu precipitates in Fe-Cu mode alloys (0–1.0 wt. % Cu) and A533B reactor pressure vessel (RPV) steel, positron lifetime and Vickers microhardness have been measured after fast neutron irradiation to a fluence of 8.3×10¹⁸n/cm² below 150°C. Long positron lifetimes for the Fe-Cu alloys ranging from 300 to 420 ps and 270 to 350 ps for A533B RPV steels have been observed, which show microvoid formation. The long lifetimes in the Fe-Cu alloys depend on the Cu content and thermal aging at 550°C before irradiation. This fact suggests incorporation of irradiation-induced vacancies at Cu atoms and their precipitates leading to suppression of the microvoid formation. The long lifetime component for the Fe-Cu alloys recovers around 350°C, while that for A533B steel recovers around 300°C. To estimate the microvoid sizes, superimposed-atom model calculations of positron lifetimes in microvoids consisting of 1 (V¹) to 66 (V⁶⁶) vacancies have been performed, respectively. Based on these calculations, the formation and post-irradiation annealing behaviour of microvoids are examined.

In addition, irradiation-induced hardening monitored by Vickers microhardness is discussed with reference to positron annihilation experiments.

Keywords:
neutron irradiation, positron annihilation, reactor pressure vessel steels, Fe-Cu model alloys, microvoids, isochronal annealing, irradiation-induced hardening

Paper ID: STP12415S
Committee/Subcommittee: E10.08
DOI: 10.1520/STP12415S
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