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Fabrication, chemical and thermal stability studies of crystalline ceramic wasteform based on oxyapatite phosphate host LaSr4(PO4)3O for high level nuclear waste immobilization.
Journal of Hazardous Materials ( IF 12.2 ) Pub Date : 2020-03-16 , DOI: 10.1016/j.jhazmat.2020.122552
Ramya Ravikumar 1 , Buvaneswari Gopal 1 , Hrudananda Jena 2
Affiliation  

Reprocessed high-level nuclear waste (HLW) contains range of radioactive components. Crystalline oxyphosphate apatite ceramic of the formula LaSr4(PO4)3O [LSS] was investigated as a host for HLW immobilisation. The systematic study of solid solubility limit of individual rare earth ion substitution leads to the formulation of simulated wasteform of the formula La0.6Pr0.1Nd0.1Sm0.1Gd0.1Sr4(PO4)3O (WF1) with the waste loading of 17.95 wt% of rare-earth ions. Both parent and WF1 were synthesized by precipitation method. The thermal stress and groundwater inventory at the repository site can severely affect the wasteform performance, in addition to radiation and mechanical effects. Hence, the fabricated composition with high-level nuclear waste loading must be screened basically for chemical, thermal and radiation resistance. The present study investigated the thermal stability (by TGA), thermal expansion behaviour (by HT-XRD) and chemical durability (MCC-5) of the composition (WF1). The weight loss of WF1 being 2.2% and the average thermal expansion co-efficient (αavg) of 10.7 ± 1.2 × 10-6 K-1 in the temperature range (298-973 K) were comparatively lower than the parent phase, LaSr4(PO4)3O. The WF1 showed resistance to leaching of RE3+ and P5+ with only the leaching of Sr2+ ion whose leach rate was of the order 10-3-10-4 gm-2d-1.

中文翻译:

基于磷酸氧磷灰石基质LaSr4(PO4)3O的结晶陶瓷废料的制备,化学和热稳定性研究,用于高水平固定核废料。

再处理的高级别核废料(HLW)包含一系列放射性成分。研究了分子式为LaSr4(PO4)3O [LSS]的结晶性磷酸氧磷灰石陶瓷作为HLW固定的主体。对单个稀土离子取代的固体溶解度极限的系统研究导致了公式为La0.6Pr0.1Nd0.1Sm0.1Gd0.1Sr4(PO4)3O(WF1)的模拟废物形式的制备,废物装载量为17.95 wt%稀土离子。母体和WF1都是通过沉淀法合成的。除了辐射和机械作用外,储存场所的热应力和地下水库存还会严重影响废料的性能。因此,必须对具有高水平核废料装载量的加工组合物进行化学,耐热和辐射耐受性筛选。本研究研究了组合物(WF1)的热稳定性(通过TGA),热膨胀行为(通过HT-XRD)和化学耐久性(MCC-5)。WF1的失重为2.2%,并且在温度范围(298-973 K)内的平均热膨胀系数(αavg)为10.7±1.2×10-6 K-1,相对低于母相LaSr4( PO4)3O。WF1对RE3 +和P5 +的浸出具有抵抗力,仅Sr2 +离子的浸出率约为10-3-10-4 gm-2d-1。LaSr4(PO4)3O。WF1对RE3 +和P5 +的浸出具有抵抗力,仅Sr2 +离子的浸出率约为10-3-10-4 gm-2d-1。LaSr4(PO4)3O。WF1对RE3 +和P5 +的浸出具有抵抗力,仅Sr2 +离子的浸出率约为10-3-10-4 gm-2d-1。
更新日期:2020-03-16
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