Determination of low concentrations of hydrogen in zirconium alloys using neutron radiography as a non-destructive technique

ABSTRACT Zircon base alloys (Zr) are used in the manufacture of fuel sheaths and structural components of power reactors because of their low neutron absorption. These alloys are susceptible to damage by hydrogen (H) because the concentration of the alloys can be increased locally in response to temperature or stress gradients. This causes a general degradation of its mechanical properties, and can generate a degradation process known as Delayed Hydride Cracking (DHC). H content in zirconium alloys is generally determined by destructive techniques. In this work we determine the H content in the range 0-300 wt ppm with a sensitivity of ~5 wt ppm and a spatial resolution of ~0.1 mm using neutron radiography as a nondestructive technique. In order to compare the capacity of different neutrography facilities for this type of analysis, the studies were carried out in four laboratories with different characteristics in terms of the flow and the energy distribution of the incident neutrons on the sample, as well as the maximum spatial resolution available in each case (L/D parameter). The facilities were ANTARES in the FRM-II reactor (Germany), Engin-X in the pulsed source ISIS (UK), BOA in the SINQ (Switzerland) sputtering source, and the neutron facility at the Bariloche RA-6 reactor (Argentina). The spatial resolution obtained allows to determine the diffusion coefficient of H in Zr-alloys using samples of 5x10x10 mm3, approximately.

摘要：锆基合金（Zr）凭借低中子吸收特性，被用于制造动力反应堆的燃料包壳与结构部件。但这类合金易受氢（H）的损伤：合金中的氢浓度会随温度或应力梯度发生局部升高，进而导致其力学性能全面劣化，还会引发被称为氢致延迟开裂（Delayed Hydride Cracking, DHC）的劣化过程。目前锆合金的氢含量通常采用破坏性技术进行检测。本研究采用中子照相（neutron radiography）技术作为无损检测手段，实现了0~300 wt ppm范围内氢含量的检测，检测灵敏度约为5 wt ppm，空间分辨率约为0.1 mm。为对比不同中子照相装置在该类分析中的性能表现，本研究在四家实验室开展了相关实验，这些实验室的入射中子流强、样品处入射中子的能量分布，以及各自可实现的最高空间分辨率（L/D参数）均存在差异。本次实验涉及的装置包括德国FRM-II反应堆的ANTARES装置、英国脉冲源ISIS的Engin-X装置、瑞士SINQ散裂源的BOA装置，以及阿根廷巴里洛切RA-6反应堆的中子实验装置。本次实验获得的空间分辨率，可依托尺寸约为5×10×10 mm³的样品，完成锆合金中氢扩散系数的测定。