Laser‐Based Spectroscopic Studies of Actinide Complexes

Abstract

The purpose of this article is to introduce laser spectroscopic studies for the chemical speciation of actinide complexes to those who are interested in the highly sensitive analytical techniques used in the nuclear industry. The chemical speciation of actinide complexes is considered to be a key concept for the safe management of spent nuclear fuels in the back‐end of a nuclear fuel cycle. Time‐resolved laser fluorescence spectroscopy (TRLFS) and laser‐induced photoacoustic spectroscopy (LPAS) are accepted as very effective techniques to analyze trace amounts of actinide complexes in aqueous solutions. In the present case study, TRLFS and LPAS are primarily used for the chemical speciation of U(VI)‐ and Pu(VI)‐hydroxo complexes, respectively. For the practical application of TRLFS, the chemical speciation of trace amounts of Ca–U(VI)‐carbonate species dissolved in groundwater is described. A spectrophotometry coupled with a liquid waveguide capillary cell is applied for the chemical speciation of U(IV)‐hydroxo complex as an alternative technique to LPAS. The absorption and luminescence characteristics of Am(III) species are also described.

Dimeric and Trimeric Uranyl(VI)–Citrate Complexes in Aqueous Solution

“…Then, hydrolysis occurring already in strongly acidic media is caused by the metal ion’s Lewis acidity. Accordingly, hydrolysis of U 4+ , as a significantly stronger acid, happens even at pH <1. , …”

“…Accordingly, hydrolysis of U 4+ , as a significantly stronger acid, happens even at pH <1. 68,69 A repeatedly arising argument, and supposedly a misleading belief in previously proposed U−CA complex structures, is that strong complexing, that is, polydentate (chelating) ligands prevent U(VI) hydrolysis and formation of polynuclear species. The U(VI)−CA system is a superb but not the only example disproving this reasoning, see also considerations on issue (iv) below.…”