Solubility Products of Plutonium(IV) Oxide and Hydroxide

Solubility Studies of Transuranium Elements for Nuclear Waste Disposal: Principles and Overview

“…Rai et al [11] determined the solubility of amorphous Am(OH) 3 in solutions from pH 7 to pH 13. Comparison of the studies by Silva and by Rai et al show that the solubility of the amorphous Am(OH) 3 is about one order of magnitude higher than for the crystalline material; e.g., at pH 7, 10" 3 5 Μ compared with 10" 4 · 5 M. Kim and Kanellakopulos [12] measured the solubility of amorphous 239 Pu(OH) 4 and of crystalline 239 Pu0 2 in 1 Μ HC10 4 . They found a significantly lower solubility for the oxide compared with the hydroxide.…”

Thermodynamics of water sorption on PuO2: Consequences for oxide storage and solubility

“…Kim and Kanellakopulos [6] suggest that dioxide solubility is enhanced by formation of a more soluble (less stable) surface hydroxide like PuO 2 (hyd) [14]. PuðOHÞ 0 4 (aq) is the only significant solution species at chemical potentials of near-neutral solutions [16].…”

“…Formation of surface hydroxide is identified as a key step in catalytic cycles that enhance Pu corrosion in moist air [4] and promote formation of a high-composition oxide, PuO 2+x , and H 2 [5]. A higher-than-expected PuO 2 solubility is attributed to formation of surface hydroxide [6] similar to the more soluble amorphous hydrous oxide, Pu(OH) 4 (am), formed by precipitation of aqueous Pu(IV).…”

Near-field/altered-zone models report

“…The solubility products of amorphous Pu(OH) 2 and crystalline PuO 2 at 20°C have been determined by Kim and Kanellakopulos (1989) The solubility of amorphous PuO 2 áxH 2 O, with x near 2, has been investigated at room temperature (Rai, 1984 [6][7][8] There is a large spread (3 to 4 orders of magnitude) in the solubility of amorphous PuO 2 áxH 2 O, colloidal Pu(IV) hydrous oxide, and crystalline PuO 2 at room temperature. The differences in solubility may be related to differences in particle size and degree of hydration, similar to the situation for various forms of silica (Iler, 1979).…”