Novel long-term immobilization method for radioactive iodine-129 using a zeolite/apatite composite sintered body.
Novel long-term immobilization method for radioactive iodine-129 using a zeolite/apatite composite sintered body.
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DOI：
10.1021/am900251m
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发表时间：
2009-06
影响因子：
9.5
通讯作者：
Yujiro Watanabe;T. Ikoma;H. Yamada;Y. Suetsugu;Y. Komatsu;G. Stevens;Y. Moriyoshi;J. Tanaka
中科院分区：
文献类型：
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作者：
Yujiro Watanabe;T. Ikoma;H. Yamada;Y. Suetsugu;Y. Komatsu;G. Stevens;Y. Moriyoshi;J. Tanaka
随着核能生产的扩散，核电站产生的放射性碘的量预计会增加，需要开发此类放射性元素的长期固定方法以使核能可持续发展。放射性元素的标准固定方法——玻璃化，对于放射性碘129来说不是很有效，因为碘在硅酸盐熔体中的溶解度很低，在标准玻璃化工艺温度下挥发性非常高，并且在300 m以下深层地质层的碱性环境中不稳定。我们开发了一种通过烧结工艺生产的新型三相陶瓷复合材料。通过铵与钙的交换反应，吸附在Ca型沸石A上的碘被羟基磷灰石纳米层覆盖。沸石结构内的 30 nm 碘簇被发现在高达 1253 K 的温度下保持热稳定，这是因为铵离子部分堵塞了 α 笼孔，并且在 473 K 时部分从结晶相转变为非晶相。在烧结过程中没有发现碘分子发生气化。外相是高度结晶的羟基氟磷灰石，其中羟基磷灰石纳米层对于成功烧结起着重要作用。碘在低双氧水中的洗脱与地壳内的情况相似，经过研究发现仅发生在烧结体的表层。
The amount of radioactive iodine generated from nuclear power plants is expected to increase with the proliferation of nuclear energy production, and long-term immobilization methods for such radioactive elements need to be developed to make nuclear energy sustainable. The standard immobilization method of radioactive elements, vitrification, is not very effective for radioactive iodine-129 because of the low solubility of iodine in silicate melts, its very high volatility at standard vitrification process temperatures, and its instability in the alkaline environment of deep geological layers below 300 m. We have developed a novel three-phase ceramic composite produced by a sintering process. Iodine adsorbed onto Ca-type zeolite A was covered with a hydroxyapatite nanolayer through the exchange reaction of ammonium with calcium. Clusters of iodine of 30 nm within the zeolite structure were found to be thermally stable up to 1253 K because of the partial blockage of the alpha-cage apertures by ammonium ions and the partial change from a crystalline phase to an amorphous phase at 473 K. No gasification of iodine molecules was found to occur during the sintering process. The outer phase was highly crystalline hydroxyfluorapatite in which the hydroxyapatite nanolayer plays an important role for successful sintering. The elution of iodine in low-dioxygen water, similar to that found within the Earth's crust, was investigated and was found to occur only in the surface layer of the sintered body.