Hydrolysis of Np(V) in Ι.ΟΛί NaCIO, was investigated by radiometric pH-titration of 23, NpOj under C0 2 -free Ar atmosphere. From the resulting solubility curve the first and second hydrolysis constant (3, and ß 2 as well as the solubility product Ksp were evaluated: log ß 1 = 2.3, log ß 2 = 4.89 and log Ksp = -8.81.

Solubilities of Pu from leaching of a simulated HLW glass (C31–3-EC) spiked with 5 wt % Pu and from PuO2 are determined in salt solutions of different NaCl concentration and in groundwaters which are representative for the Gorleben area. Th.e leaching experiment is carried out either in an autoclave at 200 °C or under normal conditions (1 atm, 25°C). Solubilities of Pu in all investigated solutions are observed to be considerably higher than the values known from theoretical estimates. The predominant Pu species in solutions are found to be microcolloids, which are characterized by means of ultrafiltration and pulsed laser-induced photoacoustic spectroscopy.