Impact of the microstructural and micromechanical variability on the long term behavior prediction of Zr-2.5Nb pressure tubes used in CANDU reactors

该项目旨在了解CANDU反应堆压力管蠕变行为的变异性及其与这些压力管内发现的微观结构差异的关系。这种变异性导致了这些材料(通常是Zr-Nb合金)寿命预测的不确定性，这是该行业的一个主要问题。我们提出了一种组合实验方法，包括对微观结构的广泛表征和对典型微结构的整体蠕变测试。这将提供蠕变行为与压力管微观结构之间的直接关联。先进的显微技术将识别和表征在CANDU反应堆管内发现的具有代表性的微结构和位错亚结构，并用统计方法获得微观结构参数。这些先进的电子显微镜技术是在场发射扫描电子显微镜(FE-SEM)上获得的电子背散射衍射图案(EBSD)，使用EBSD和X射线显微分析的组合聚焦离子束(FIB)和FE-SEM显微镜的三维微结构，以及具有亚埃分辨率的Cs像差校正器和EDS X射线探测器的场发射扫描透射电子显微镜(FE-STEM)。纳米压痕也将被用来评估这些微结构及其各个相的机械性能。描述这些合金微观组织的参数将被用来根据Levitin理论[1]建立模型来预测CANDU压力管用Zr-Nb合金的寿命。在温室气体成为问题、需要减少对石油和煤炭等传统燃料的依赖之际，准确预测CANDU反应堆压力管的寿命将有助于更有效地利用核能。由于Gentilly II将于2011年重新配备，该项目需要在2010年底之前生成预测性数据。

This project aims to understand the variability of the creep behavior of the pressure tubes in CANDU reactors and its relations to microstructural differences found within these pressure tubes. This variability results in an uncertainty in the lifetime prediction for these materials (typically Zr-Nb alloys), a major problem for this industry. We propose a combined experimental approach including extensive characterization of the microstructure and bulk creep testing on representative microstructures. This will provide direct correlation between creep behavior and the microstructure of a pressure tube. Advanced microscopy techniques will identify and characterize representative microstructures and dislocation sub-structures found in CANDU reactor tubes with micro structural parameters obtained with statistical methods. These advanced electron microscopy techniques are electron backscattering diffraction patterns (EBSD) obtained in a field emission scanning electron microscope (FE-SEM), three dimensional microstructure with combined focus ion beam (FIB) and FE-SEM microscopes using EBSD and x-ray microanalysis and start of the art field emission scanning transmission electron microscopy (FE-STEM) with a Cs aberration corrector having sub - Angstrom resolution equipped with an EDS x-ray detector. Nanoindentation will also be used to evaluate the mechanical properties of these microstructures and also of their individual phases. The parameters describing the microstructure of these alloys will be used to create model, based on Levitin's theory [1], to predict the lifetime of Zr-Nb alloys for CANDU pressure tubes. An accurate prediction of the lifetime of pressure tubes for CANDU reactors will allow for more efficient use of nuclear energy at a time when green house gas are an issue and a reduced dependence on conventional fuels, such as oil and coal, is needed. Since Gentilly II will be refurnished in 2011, this project needs to generate predictive data by the end of 2010.