Dissolution Behaviors of PuO₂(cr) in Natural Waters (2023)

Hye-Ryun Cho, Sangki Cho, Jueun Kim, Sangsoo Han, Hee-Kyung Kim, Wooyong Um

Frontiers in Nuclear Engineering, FNUEN-02-1118594, Volume 2

DOI: https://doi.org/10.3389/fnuen.2023.1118594

ABSTRACT

PuO₂(cr) dissolution in natural water was investigated at 25°C and 60°C under atmospheric conditions. The concentration of Pu in solutions [Pu], was monitored for 1 year of reaction time. PuO₂(cr) dissolution in natural water reached a steady state within 2 months at 25°C. The [Pu] in groundwater and seawater at pH 8 were in the range of [Pu] = 0.9–34 and 3.4–27 nM, respectively. The [Pu] in concrete porewater (rainwater equilibrated with concrete) at pH 8.1–10.9 was in the range of 0.1–3.2 nM. The [Pu] and pH values of groundwater were similar to those of seawater samples having a high ionic strength. The measured [Pu] at equilibrium in all samples was higher than the calculated solubility curves for PuO₂(am, hyd). Experimental evidence is insufficient to confirm the oxidation state of Pu in solution and solid phases. However, the results of geochemical modeling indicate that PuO₂(am, hyd) and aqueous Pu(IV) species are dominant in natural water samples of this work. The dissolution behavior of PuO₂(cr) in natural waters is comparable to the oxidative dissolution of PuO₂(am, hyd) in the presence of PuO₂(coll, hyd). The dissolution of PuO₂ in groundwater decreased at higher temperatures, whereas the influence of temperature in seawater and porewater was not significant under these experimental conditions.