Journal Article

FZJ-2018-04024

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Influence of temperature on the dissolution kinetics of synthetic LaPO4-monazite in acidic media between 50 and 130 °C

Arinicheva, Y. (Corresponding author)FZJ* ; Gausse, C. ; Neumeier, S.FZJ* ; Brandt, F.FZJ* ; Rozov, K. ; Szenknect, S. ; Dacheux, N. ; Bosbach, D.FZJ* ; Deissmann, G.FZJ*

2018
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.jnucmat.2018.07.009

Abstract: Single-phase monazite-type ceramics are discussed as waste forms for the safe disposal of surplus plutonium or separated minor actinides. To gain a deeper insight into the mechanism governing the dissolution of monazite-type compounds, the dissolution kinetics of synthetic LaPO4-monazite was systematically studied by dynamic dissolution experiments carried out in the temperature range from 50 to 130 °C in acidic media (0.01 M HNO3). The dissolution rates at far from equilibrium conditions increased from 3.2 × 10−5 g m−2 d−1 at 50 °C to 2.5 × 10−4 g m−2 d−1 at 130 °C. Two different temperature regions were observed, in which the normalised dissolution rates of LaPO4 have a diverging temperature dependence, indicating two different mechanisms of dissolution: namely surface-controlled dissolution (T = 50–90 °C; Ea = 44 kJ mol−1) and transport-controlled dissolution (T = 90–130 °C; Ea = 7.5 kJ mol−1). Complementary thermodynamic modelling studies of the dissolution of LaPO4 at the experimental conditions show that La-rhabdophane (LaPO4·0.667H2O) is the thermodynamically favoured phosphate phase in aqueous environments below about 100 °C. Apparently, the hydration of monazite and the formation of a thin surface layer consisting of rhabdophane is an intermediate step controlling the dissolution kinetics of the LaPO4 monazite ceramics in low temperature aqueous environments.Keywords

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Contributing Institute(s):

1. Nukleare Entsorgung und Reaktorsicherheit (IEK-6)
2. Werkstoffsynthese und Herstellungsverfahren (IEK-1)

Research Program(s):

1. 161 - Nuclear Waste Management (POF3-161) (POF3-161)

Appears in the scientific report 2018

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Database coverage:
Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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