Bubble Swelling in Ferritic/Martensitic Steels Exposed to Radiation Environment with High Production Rate of Helium.

Stanislav Sojak,Vladimir Krsjak,Vladimir Slugen,Jarmila Degmova,Tielong Shen,Pavol Noga

doi:10.3390/ma14112997

Abstract

Reduced-activativon ferritic/martensitic (RAFM) steels are prospective structural materials for fission/fusion nuclear applications because their radiation and swelling resistance outperforms their austenitic counterparts. In radiation environments with a high production rate of helium, such as fusion or spallation applications, these materials suffer from non-negligible swelling due to the inhibited recombination between vacancy and interstitial-type defects. In this work, swelling in helium-implanted Eurofer 97 steel is investigated with a focus on helium production rates in a wide range of helium/dpa ratios. The results show virtually no swelling incubation period preceding a steady-state swelling of about 2 × 10−4%/He-appm/dpa. A saturation of swelling above 5000 He-appm/dpa was observed and attributed to helium bubbles becoming the dominant sinks for new vacancies and helium atoms. Despite a relatively low irradiation temperature (65 ± 5 °C) and a rather high concentration of helium, transmission electron microscope (TEM) results confirmed a microstructure typical of ferritic/martensitic steels exposed to radiation environments with high production rates of helium.

Highlights

The present study provided a new perspective on the behaviour of reduced-activation ferittic/martensitic (RAFM) steels exposed to radiation environments having a high production rate of helium
Despite relatively low irradiation temperature (65 ± 5 ◦ C) and a rather high helium concentration, the transmission electron microscope (TEM) showed a microstructure typical for Reduced-activativon ferritic/martensitic (RAFM) steels exposed to harsh radiation environments
This suggested that low-temperature helium implantation can be a valuable tool in an experimental simulation of challenging radiation conditions, such as the environment of fusion reactors or spallation neutron sources

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Volumetric void, or bubble swelling, is one of the major degradation mechanisms of materials exposed to harsh radiation conditions. It is a key factor limiting the safe operational lifetime of nuclear power plants (NPP) and other nuclear installations. Austenitic steels are used as structural materials at NPPs but their low swelling resistance to neutron irradiations limits their application in environments with high temperatures and dpa rates, which is expected for future nuclear facilities. Similar behaviour can be observed at irradiation by charged particles [1]

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