Monazite as a promising long-term radioactive waste matrix: Benefits of high-structural flexibility and chemical durability
Monazite as a promising long-term radioactive waste matrix: Benefits of high-structural flexibility and chemical durability
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DOI：
10.2138/am.2013.4307
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发表时间：
2013-05-01
影响因子：
3.1
通讯作者：
Podor, Renaud
中科院分区：
文献类型：
--
作者：
Dacheux, Nicolas;Clavier, Nicolas;Podor, Renaud
独居石(Ln(3+)PO(4))和相关的固溶体是地球上稀土元素的著名来源。它们还可以容纳大量的钍和铀，而不会因自辐射而对结构造成损害。这些观察结果导致独居石型结构被提议作为一种潜在的宿主基质，用于隔离核燃料循环期间产生的长寿命放射性核素和/或从已拆除的核武器中分离钚和Am。独居石作为遏制放射性废物(或“放射性废物”)的基质有两个主要优点。第一种是一种高度灵活的结构，允许容纳高浓度的吖系元素。三价元素的掺入可以通过直接合成An(3+)PO(4)(An(3+)=钚、钚到爱因斯坦、Es)来实现，而四价阳离子的掺入则需要在阴离子中心(导致独居石-绿柱石固溶体)或在阳离子中心(独居石-绿柱石固溶体)上进行偶联取代。本文总结了制备这类化合物的各种方法，以及生产烧结球团所需的实验条件，特别是对含钚化合物的研究。独居石的第二个非常有利的性能是它的高化学耐久性。综述了几种测定归一化浸出率的实验方法，以及从天然独居石和合成独居石中获得的结果。考虑了溶解过程中形成的潜在相，因为它们也部分地控制了介质中放线系元素的浓度。给出了这些感兴趣的相的初步列表，以及相应的热力学数据。
Monazite (Ln(3+)PO(4)) and related solid solutions are a well-known source of rare earth elements on earth. They may also accommodate large amounts of thorium and uranium without sustaining damage to the structure by self-irradiation. Such observations led to monazite-type structures being proposed as a potential host matrix for sequestering long-lived radionuclides produced during the nuclear fuel cycle and/or plutonium and americium from dismantled nuclear weapons. Monazite has two main advantages as a matrix for the containment of radioactive waste (or "radwaste"). The first is a highly flexible structure that permits accommodation of high concentrations of actinides. The incorporation of trivalent elements may be achieved by direct synthesis of An(3+)PO(4) (An(3+) = plutonium, Pu to einsteinium, Es), while tetravalent cation incorporation requires coupled substitutions, either on the anionic site (leading to monazite-huttonite solid solution) or on the cationic site (monazite-cheralite solid solution). Various methods developed for the preparation of such compounds are summarized here, as well as the experimental conditions required for the production of sintered pellets, with a particular focus on plutonium-bearing compositions. The second highly favorable property of monazite is its high chemical durability. Several experimental procedures developed to determine normalized leaching rates are reviewed, as well as results obtained from natural and synthetic monazite. Potential phases formed during dissolution were considered because they also partially control the concentration of actinides in the media. A preliminary list for such phases of interest, as well as corresponding thermodynamic data, is presented.