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首页> 外文会议>STP 1467; International Symposium on Zirconium in the Nuclear Industry; 20040613-17; Stockholm(SE) >Predicting Oxidation and Deuterium Ingress for Zr-2.5Nb CANDU Pressure Tubes
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Predicting Oxidation and Deuterium Ingress for Zr-2.5Nb CANDU Pressure Tubes

机译：Zr-2.5Nb CANDU压力管的氧化和氘进入的预测

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摘要

The pressure boundary of a CANDU~® fuel channel is composed of a cold-worked Zr-2.5Nb pressure tube, which has each end rolled into a stainless-steel end fitting. Heavy-water (D_2O) coolant (250-310℃) flows over and through twelve or thirteen fuel bundles contained in each pressure tube. During operation, some deuterium generated by aqueous corrosion of the tube surface enters the metal. Additional deuterium also enters through the rolled joint between the tube and the end fitting. Predictive models for deuterium ingress are required for fitness-for-service assessments for operating pressure tubes and for the development of new reactor designs. A predictive model for assessing the long-term oxidation of, and deuterium ingress into, the body of the pressure tubes has been developed from in-reactor tests of samples which had been pre-oxidized to obtain oxide thickness values representative of long-term behavior. Deuterium ingress is modeled based on a fraction (2-10%) of the corrosion-freed deuterium entering the metal. The current version of the model contains relationships describing the oxidation rate as a function of oxide thickness, temperature, concentration of dissolved oxygen in the water, and fast neutron flux and fluence. It can successfully predict the observed deuterium-uptake history of pressure tubes in existing CANDU reactors. The model projects a slight increase in the rate of oxidation and deuterium ingress over time. This increase is much less than for Zircaloy-2, a material used in early CANDU units. In parallel with model development, there are experimental programs involving detailed surface analysis of removed pressure tubes and irradiation tests focused on elucidating the mechanisms of oxidation and deuterium ingress. As the results of these programs become available, they will be incorporated into the predictive model. This presentation will focus on the model and recent results from the supporting experimental programs.
机译：CANDU〜®燃料通道的压力边界由冷加工的Zr-2.5Nb压力管组成，该压力管的两端均压制成不锈钢端部接头。重水（D_2O）冷却剂（250-310℃）流过并流经每个压力管中包含的十二或十三个燃料束。在操作过程中，由管表面的水腐蚀产生的一些氘进入金属。额外的氘也通过管和端接头之间的滚动接头进入。对于工作压力管的适应性评估以及新反应堆设计的开发，需要氘进入的预测模型。通过对已被预氧化以获得代表长期行为的氧化物厚度值的样品进行反应器内测试，开发了一种评估模型，用于评估压力管体的长期氧化和氘进入该压力管。基于进入金属的无腐蚀氘的分数（2-10％）来模拟氘的进入。该模型的当前版本包含一些关系，这些关系描述了氧化速率与氧化物厚度，温度，水中溶解氧的浓度以及快速中子通量和通量的关系。它可以成功预测现有CANDU反应器中观察到的压力管的氘吸收历史。该模型预计随着时间的推移氧化和氘的进入速率会略有增加。这种增加远小于早期CANDU单元中使用的材料Zircaloy-2。在模型开发的同时，还有一些实验程序，涉及对拆下的压力管进行详细的表面分析和辐照试验，重点是阐明氧化和氘的侵入机理。随着这些程序的结果变得可用，它们将被合并到预测模型中。本演讲将重点介绍该模型以及支持实验程序的最新结果。

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