A study into stress relaxation in oxides formed on zirconium alloys
A study into stress relaxation in oxides formed on zirconium alloys
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DOI：
10.1016/j.jnucmat.2014.09.072
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发表时间：
2015-01-01
影响因子：
3.1
通讯作者：
Preuss, M.
中科院分区：
文献类型：
--
作者：
Platt, P.;Polatidis, E.;Preuss, M.
压水反应堆和沸水反应堆含有锆合金，用作核燃料包壳。这些合金的氧化以及相关的氢吸收是燃料寿命的限制因素。为了延长核燃料的燃耗需要控制氧化，因此需要对包壳腐蚀过程有一个机械的理解。同步加速器X射线衍射(S-XRD)已用于分析Zircaloy-4和ZIRLO (TM)原位空气氧化过程中形成的氧化层。分析表明，随着氧化物厚度随时间的推移而增加，单斜晶相和亚稳定四方相中存在的应力都会松弛，并且四方相分数也会减少。为了更好地理解氧化层应力松弛背后的机制，有限元分析被用来模拟氧化过程的机械方面。该模拟首先基于高压釜中形成的氧化物的应力松弛而开发，并使用 S-XRD 进行异位分析。弛豫机制包括金属基底中的蠕变和氢致晶格应变以及氧化物层中的蠕变。随后，有限元分析扩展到通过原位 S-XRD 氧化实验观察到的应力松弛。有限元分析表明，氧化物中蠕变的影响可以忽略不计，金属基体金属中蠕变和氢致晶格应变的影响都很小。这意味着应力松弛必须由另一个来源引起，例如金属-氧化物界面处粗糙度的形成或氧化物层中的断裂。 (C) 2014 年作者。由 Elsevier B.V. 出版
Pressurised and boiling water reactors contain zirconium alloys, which are used as nuclear fuel cladding. Oxidation of these alloys, and the associated hydrogen pick-up, is a limiting factor in the lifetime of the fuel. To extend the burn-up of nuclear fuel requires control of the oxidation, and therefore development of a mechanistic understanding of the cladding corrosion process. Synchrotron X-ray diffraction (S-XRD) has been used to analyse oxide layers formed during in-situ air oxidation of Zircaloy-4 and ZIRLO (TM). Analysis shows that as the oxide thickness increases over time there is a relaxation of the stresses present in both the monoclinic and meta-stable tetragonal phases, and a reduction in the tetragonal phase fraction. To better understand the mechanisms behind stress relaxation in the oxide layer, finite element analysis has been used to simulate mechanical aspects of the oxidation process. This simulation was first developed based on stress relaxation in oxides formed in autoclave, and analysed ex-situ using S-XRD. Relaxation mechanisms include creep and hydrogen-induced lattice strain in the metal substrate and creep in the oxide layer. Subsequently the finite element analysis has been extended to stress relaxation observed by in-situ S-XRD oxidation experiments. Finite element analysis indicates that the impact of creep in the oxide is negligible, and the impact of both creep and hydrogen-induced lattice strain in the metal substrate metal is small. The implication is that stress relaxation must result from another source such as the development of roughness at the metal-oxide interface, or fracture in the oxide layer. (C) 2014 The Authors. Published by Elsevier B.V.