Electrochemical decontamination of irradiated nuclear graphite from corrosion and fission products using molten salt,Energy & Environmental Science

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Electrochemical decontamination of irradiated nuclear graphite from corrosion and fission products using molten salt
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2021-09-03 , DOI: 10.1039/d1ee00332a
Tatiana Grebennikova _{1,

2} , Abbie N. Jones ₂ , Clint A. Sharrad ₁

Affiliation

Irradiated graphite waste management is one of the major challenges of nuclear power-plant decommissioning throughout the world and significantly in the UK, France and Russia where over 85 reactors employed graphite as moderator or core material. To date, the considerable volume (>300 000 tonnes worldwide) and heterogeneity of contamination observed in irradiated graphite designates this material as higher activity waste, which resides predominately intact, at multiple reactor sites awaiting disposal in a deep or near-surface Geological Disposal Facility (GDF) yet to be built. This study presents a novel and non-destructive method for the treatment suitable for irradiated graphite materials, with the aim to remove contamination from corrosion and fission products and therefore downgrade the category of waste and enable accelerated disposal which does not require managed storage and disposal as intermediate level waste in a GDF. A novel electrochemical decontamination approach in a high-temperature molten salt medium was applied to irradiated UK Magnox grade graphite, fixed on the working electrode immersed in LiCl–KCl eutectic at 723 K. By selecting the appropriate value of the absolute magnitude of current and the number of transitions between positive and negative current, substantial removal of radionuclide contamination (⁶⁰Co, ¹³³Ba, ¹³⁷Cs, ¹⁵⁴Eu) from the graphite was achieved. Up to 80% reduction of total initial activity for ⁶⁰Co was achieved without significant degradation of the graphite material (<7% mass loss). The magnitude of activity removed from the graphite was sufficient to reclassify the remaining graphite material from intermediate level waste to low level waste.

中文翻译：

使用熔盐对来自腐蚀和裂变产物的辐照核石墨进行电化学净化

辐照石墨废物管理是全世界核电站退役的主要挑战之一，在英国、法国和俄罗斯尤为突出，其中超过 85 座反应堆采用石墨作为慢化剂或堆芯材料。迄今为止，在辐照石墨中观察到的大量（> 300 000 吨）和污染的异质性将这种材料指定为高活性废物，主要完好无损，在多个反应堆场址等待在深部或近地表地质处置设施中处置(GDF) 尚未建成。本研究提出了一种适用于辐照石墨材料的新型无损处理方法，目的是去除腐蚀和裂变产物中的污染，从而降低废物类别并实现加速处置，这不需要在 GDF 中作为中级废物进行管理存储和处置。将高温熔盐介质中的新型电化学净化方法应用于辐照英国 Magnox 级石墨，固定在工作电极上，工作电极浸入 723 K 的 LiCl-KCl 共晶中。通过选择合适的电流绝对值和正负电流之间的转换次数，大量去除放射性核素污染（⁶⁰ Co,¹³³ Ba,¹³⁷ Cs,¹⁵⁴ Eu) 来自石墨。⁶⁰ Co的总初始活性降低了 80%，而石墨材料没有显着降解（<7% 的质量损失）。从石墨中去除的活性程度足以将剩余的石墨材料从中级废物重新分类为低级废物。

更新日期：2021-09-13

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