The complete oxidation of nuclear graphite waste via thermal treatment: An alternative to geological disposal
The complete oxidation of nuclear graphite waste via thermal treatment: An alternative to geological disposal
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DOI：
10.1016/j.jnucmat.2018.05.002
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发表时间：
2018-08
影响因子：
3.1
通讯作者：
A. Theodosiou;A. Jones;D. Burton;M. Powell;M. Rogers;V. B. Livesey
中科院分区：
文献类型：
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作者：
A. Theodosiou;A. Jones;D. Burton;M. Powell;M. Rogers;V. B. Livesey
本文介绍了一种新的方法，通过学术界和工业界的合作，产生的反应堆退役和氧化物燃料组件拆卸的核石墨废物的热处理。该工艺的关键部分是通过等离子炉对石墨进行热氧化。石墨的实验室规模处理发现氧化速率随温度增加而增加，在T > 1000 °C时CO/CO2产生比显著增加。还有一个线性增加的氧化速率与空气流速，高达100毫升/分钟，之后，该过程变得效率较低，由于氧气的浪费。发现石墨粒度在0.5-10.0 mm范围内的影响相对较小，重要的是，还发现石墨来源对氧化速率的影响最小。在相同条件下，原始石墨和辐照石墨类似物的处理在氧化行为上几乎没有差别，这使人们相信，这一过程可以扩大规模，并有效地用于处理反应堆堆芯。实验表明，实验室规模和中试规模之间的可比条件显示出相似的氧化行为，71.6 kg（相当于90%）的石墨在6小时内气化，与英国监管机构的合作表明，可能需要进一步研究石墨衍生14 C的隔离和限制的可能性，（t1/2= 5730年）的情况可能是对基线战略的改进，基线战略是将其以固体形式作为未经处理的石墨储存在地质储存库中。
This paper introduces a novel approach, developed through an academic and industrial collaboration, to the thermal treatment of nuclear graphite waste arising as a result of reactor decommissioning and oxide fuel assembly dismantling. A crucial part of the process is the thermal oxidation of the graphite via a plasma furnace. Laboratory scale treatment of the graphite found the oxidation rate to increase with temperature, with a significant increase in the CO/CO2production ratio at T > 1000 °C. There was also a linear increase of oxidation rate with air flow rate, up to 100 ml/min, after which, the process became less efficient due to oxygen wastage. Effects of graphite particle size, over the range 0.5–10.0 mm, was found to be relatively small and importantly the effect of the graphite provenance on the oxidation rate was also found to be minimal. Treatment of virgin and irradiated graphite analogues, under the same conditions, showed little difference in oxidation behaviour, providing confidence that this process could be scaled up and used effectively in the disposal of reactor cores.Scale-up of this work was carried out on a “nuclear-ready” full-scale industrial facility, demonstrating graphite feeding, furnace operation and graphite destruction successfully. Experiments showed that comparable conditions between lab scale and pilot-scale showed similar oxidation behaviour, with 71.6 kg (equating to 90%) of graphite gasified in 6 h, giving an oxidation rate of ∼12 kg/h.Engagement with UK regulators has indicated that it is likely to be desirable to further investigate the possibility that isolation and confinement of graphite-derived14C (t1/2= 5730 yrs) in a carbon sequestration scheme may be an improvement on the baseline strategy, which is to store it in its solid form as untreated graphite in a geological repository.