S.V. Fedotova

The Effect of Radiation-Induced Structural Changes under Accelerated Irradiation on the Behavior of Water-Cooled Reactor Pressure Vessel Steels

In this paper the influence of fast neutron flux on the structural features and properties of VVER-1000 reactor pressure vessel steels was studied. It is shown that for high Ni steels the flux effect is due to hardening and non-hardening mechanisms of radiation embrittlement.

A Round Robin Experiment: Analysis of Solute Clustering from Atom Probe Tomography Data.

1. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, U.S.A. 2. Groupe de Physique des Matériaux, UMR CNRS 6634, Université de Rouen, Saint Etienne du Rouvray Cedex, France 4. NRC “Kurchatov Institute”, Moscow, Russia 3. Institute of Nuclear Safety System, Inc., Kyoto, Japan 5. Commissariat à l’Energie Atomique (CEA), Saclay, France 6. Department of Materials, University of Oxford, U.K. 7. Institute for Materials Research, Tohoku University, Oarai Japan 8. Materials Science Research Laboratory, Central Research Institute of Electric Power Industry, Nagasaka, Japan 9. Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, U.S.A. 10. Department of Physics, Chalmers University of Technology, Chalmers, Sweden 11. Departement Métallurgie, EDF, Moret sur Loing, France 12. Electric Power Research Institute, Palo Alto, CA, U.S.A.

Intergranular Embrittlement of Nuclear Reactor Pressure Vessel Steels

Service life of VVER-type nuclear reactor is limited by decrease in brittle fracture resistance of reactor pressure vessel produced of low-alloy low-carbon steel under effect of irradiation and/or elevated temperatures. In this work fracture surfaces were studied by Auger-electron spectroscopy in order to estimate the contribution of intergranular embrittlement to the degradation of reactor pressure vessel steels under the influence of operating conditions. It was demonstrated that irradiation induced segregation leads to an increase of P content in grain boundaries that promotes intergranular brittle fracture on fracture surfaces. The similar effect but to a lesser degree was shown in the case of long-term temperature exposure. The grain boundary structure was examined and an effect of carbides located on the grain boundaries is supposed due to increased phosphorus segregation on carbide/matrix interface boundaries.

On the Use of Density-Based Algorithms for the Analysis of Solute Clustering in Atom Probe Tomography Data

Because atom probe tomography (APT) provides three-dimensional reconstructions of small volumes by resolving atomic chemical identities and positions, it is uniquely suited to analyze solute clustering phenomena in materials. A number of approaches have been developed to extract clustering information from the 3D reconstructed dataset, and numerous reports can be found applying these methods to a wide variety of materials questions. However, results from clustering analyses can differ significantly from one report to another, even when performed on similar microstructures, raising questions about the reliability of APT to quantitatively describe solute clustering. In addition, analysis details are often not provided, preventing independent confirmation of the results. With the number of APT research groups growing quickly, the APT community recognizes the need for educating new users about common methods and artefacts, and for developing analysis and data reporting protocols that address issues of reproducibility, errors, and variability. To this end, a round robin experiment was organized among ten different international institutions. The goal is to provide a consistent framework for the analysis of irradiated stainless steels using APT. Through the development of more reliable and reproducible data analysis and through communication, this project also aims to advance the understanding between irradiated microstructure and materials performance by providing more complete quantitative microstructural input for modeling. The results, methods, and findings of this round robin will also apply to other clustering phenomena studied using APT, beyond the theme of radiation damage.