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Evolution of thermo-physical properties and annealing of fast neutron irradiated boron carbide
Journal of Nuclear Materials ( IF 2.8 ) Pub Date : 2017-12-09 , DOI: 10.1016/j.jnucmat.2017.11.027
Dominique Gosset , Bernard Kryger , Jean-Pierre Bonal , Caroline Verdeau , Karine Froment

Boron carbide is widely used as a neutron absorber in most nuclear reactors, in particular in fast neutron ones. The irradiation leads to a large helium production (up to 1022/cm3) together with a strong decrease of the thermal conductivity. In this paper, we have performed thermal diffusivity measurements and X-ray diffraction analyses on boron carbide samples coming from control rods of the French Phenix LMFBR reactor. The burnups range from 1021 to 8.1021/cm3. We first confirm the strong decrease of the thermal conductivity at the low burnup, together with high microstructural modifications: swelling, large micro-strains, high defects density, and disordered-like material conductivity. We observe the microstructural parameters are highly anisotropic, with high micro-strains and flattened coherent diffracting domains along the (00l) direction of the hexagonal structure. Performing heat treatments up to high temperature (2200 °C) allows us to observe the material thermal conductivity and microstructure restoration. It then appears the thermal conductivity healing is correlated to the micro-strain relaxation. We then assume the defects responsible for most of the damage are the helium bubbles and the associated stress fields.



中文翻译:

快速中子辐照碳化硼的热物理性质演变和退火

碳化硼在大多数核反应堆中,特别是在快中子反应堆中,被广泛用作中子吸收剂。辐照导致大量的氦气产生(高达10 22 / cm 3),并且热导率大大降低。在本文中,我们对来自法国Phenix LMFBR反应器控制棒的碳化硼样品进行了热扩散率测量和X射线衍射分析。燃尽范围从10 21到8.10 21 / cm 3。我们首先确认在低燃耗时热导率会大大降低,并伴随着高的微观结构变化:溶胀,大的微应变,高的缺陷密度和无序状的材料电导率。我们观察到微观结构参数是高度各向异性的,沿着六角形结构的(00l)方向具有高的微应变和平坦的相干衍射域。进行高达2200°C的高温热处理,使我们能够观察材料的导热性和微观结构的恢复。然后看来,导热率的恢复与微应变的松弛有关。然后,我们假定造成大部分破坏的缺陷是氦气气泡和相关的应力场。

更新日期:2017-12-09
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