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[en] The AD-2 experiment will begin irradiation in the EBR-II reactor in August 1980. Specimens provided by the DAFS program were included in the experiment. The specimens are transmission electron microscopy (TEM) disks of several ferritic alloys including two pressure vessel steels and several iron-nickel-chromium alloys. These specimens are being irradiated in EBR-II to study their response to neutron irradiation in a fast neutron environment

[en] The effect of pulsed electron irradiation on microstructure evolution was studied in a simple Fe-Ni-Cr alloy and the results compared with a theoretical model. Pulse periods of 2.5 to 60 seconds (duty factor near 50%) at 600⁰C significantly reduced the maximum swelling rate compared to continuous irradiation. The void concentration was observed to increase and void size and swelling rates to decrease for the pulsed cases compared to the steady irradiation. Preliminary model calculations were used to guide the experiments and in the qualitative interpretation of the results. While there are several areas of agreement with experiment, the results indicate that further development of the models is required

[en] A rate-theory-based model has been developed which includes the simultaneous evolution of the dislocation and cavity components of the microstructure of irradiated austenitic stainless steels. Previous work has generally focused on developing models for void swelling while neglecting the time dependence of the dislocation structure. These models have broadened our understanding of the physical processes that give rise to swelling, e.g., the role of helium and void formation from critically-sized bubbles. That work has also demonstrated some predictive capability by successful calibration to fit the results of fast reactor swelling data. However, considerable uncertainty about the values of key parameters in these models limits their usefulness as predictive tools. Hence the use of such models to extrapolate fission reactor swelling data to fusion reactor conditions is compromised

[en] The evolution of radiation-induced alterations of dimensional and mechanical properties has been shown to be a direct and often predictable consequence of radiation-induced microstructural changes. Recent advances in understanding of the nature and role of each microstructural component in determining the property of interest has led to a reappraisal of the type and priority of data needed for further model development. This paper presents an overview of the types of modeling and analysis activities in progress, the insights that prompted these activities, and specific examples of successful and ongoing efforts. A review is presented of some problem areas that in the authors' opinion are not yet receiving sufficient attention and which may benefit from the application of advanced techniques of microstructural characterization. Guidelines based on experience gained in previous studies are also provided for acquisition of data in a form most applicable to modeling needs

[en] This program was conducted to generate an extensive bank of irradiated and aged pressure vessel steels, to test them for the effects of irradiation on mechanical properties, and to analyze the data in support of the development of a comprehensive relationship between pressure vessel steel embrittlement and both irradiation and material variables. Over 100 alloys were prepared which had variations in composition and heat treatment and included both model alloys and commercial steels. Ten different specimen geometries were fabricated from these alloys and subjected to both neutron irradiation and thermal aging treatments. The neutron irradiations were performed at the University of Virginia Reactor (UVAR) in two phases, including fluxes in the range of /approximately/0.3--5 x 10¹² n/cm² - s, fluence in the range of /approximately/0.14--2.6 x 10¹⁹ n/cm² and temperatures in the range of /approximately/271/degree/C--327/degree/C. Aging was performed in He-filled capsules or in He-environment furnaces for simple alloys and in air furnaces for commercial steels. Aging temperatures ranged from 271/degree/C--550/degree/C and times ranged from 1h to 5555h. Mechanical testing was performed using Vickers microhardness miniaturized tensile specimens. Results of testing and data tabulation are presented in this document. 40 refs., 87 figs., 20 tabs

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[en] Neutron hardening and embrittlement of pressure vessel steels is due to a high density of nm scale features, including copper-manganese-nickel rich precipitates and what are generally believed to be defect cluster-solute complexes. It has been postulated that the sub nanometer defect cluster-solute complexes form directly in displacement cascades. Cluster-complexes that are thermally unstable mediate the effect of flux on embrittlement kinetics. Larger cluster-complexes, that are relatively thermally stable for irradiation times up to 1 Gs, cause embrittlement in low copper steels. Robust characterization of these two types of so-called matrix defects has been an elusive goal. In this work, Kinetic Lattice Monte Carlo (KLMC) simulations of the long term evolution of the vacancy-rich cascade core regions were carried out for both pure iron and dilute iron-copper alloys at the nominal irradiation temperature of 563 K up to times when the vacancy clusters completely dissolve. Energetics were based on lattice embedded atom method potentials, Special time scaling and pulse annealing techniques were used to deal with the enormous range of inherent time scales involved, viz., rapid free vacancy jumps to slow emission from large complexes. Three-dimensional clusters rapidly form, containing a wide range of vacancies, as well as copper atoms in alloys. Small complexes are very mobile and growth takes place primarily by coalescence. The vacancy clusters ultimately dissolve at times from less than 0.1 to more than 100 MS. These simulations support the hypotheses that cascade cluster-complexes constitute both thermally stable and unstable matrix defect features