Small scale mechanical testing of irradiated materials
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Small scale mechanical testing of irradiated materials P. Hosemanna) Department of Nuclear Engineering, University of California Berkeley, Berkeley 94720, California, USA
C. Shin Department of Materials Science and Engineering, Myongji University, Yongin 449-728, Korea
D. Kiener Department Materials Physics, Montanuniversität Leoben, Leoben 8700, Austria (Received 14 October 2014; accepted 8 January 2015)
Small specimen testing techniques have a long history in nuclear material research due to the limitations posed by nuclear facilities. The limited space in reactors and the fact that the samples are oftentimes radioactive in addition to the increasing need to obtain mechanical properties from ion beam irradiated samples require small specimen mechanical testing. With the application of modern focused ion beam sample preparation techniques and the enhancement of nanoindentation instruments, the size scale has been moved to even smaller scales and new geometries. Micrometer and even nanometer size samples are feasible, but raise the question of comparability to large scale properties for engineering applications. In this review, we summarize available small scale materials testing techniques and potential shortcomings based on examples from the literature, as well as introduce novel experimental approaches conducted using microcompression testing, microbend bar testing, and nanoindentation at ambient and nonambient conditions.
I. INTRODUCTION
Since the beginning of the nuclear age, the question about material degradation in a nuclear environment being influenced by the radiation has always been a key issue. Wigner was one of the first who brought attention to this issue.1,2 The question on reliability of materials in nuclear environments is still prominent, in civil as well as defense related applications. Today, for all nuclear reactor concepts proposed or in service, it is the material issues that pose the greatest challenge. If no material is available or qualified to be used in a nuclear environment, it is impossible to realize future concepts with greater demands on the material performance. The material challenges not only in fission but also in fusion applications are subject of many publications, and well summarized in recent reviews.3–8 While the material reliability for up to 80 years is the main issue to consider for light water reactor applications and their lifetime extension, advanced reactor concepts ask for new materials and alloys to be tested in rather harsh environments. For the light water reactor (LWR) case,9 material issues for reactor pressure vessels (RPV) come from aging structures and localized issues such as welds and joints in combination with old materials from the time the Contributing Editor: Djamel Kaoumi a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.26 J. Mater. Res., 2015
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structure was fabricated. Since the RPV is one of the most critical safety related items in a LWR plant, a
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