کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5746539 1618792 2017 46 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal
ترجمه فارسی عنوان
عقب انداختن اورانیوم و توریم توسط یک سیلندر زدایی که برای دفع زباله های رادیواکتیو طراحی شده است
کلمات کلیدی
اورانیوم، توریم، انحلال پذیری، از طریق انتشار، سیمان،
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم محیط زیست شیمی زیست محیطی
چکیده انگلیسی
The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH)2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40 μm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemosphere - Volume 179, July 2017, Pages 127-138
نویسندگان
, , , , , ,