Characterization of Actinides Complexed to Nuclear Fuel Constituents Using ESI-MS

Abstract

Electrospray ionization-mass spectrometry (ESI-MS) was tested for its use in monitoring spent nuclear fuel (SNF) constituents including U, Pu, dibutyl phosphate (DBP), and tributyl phosphate (TBP). Both positive and negative ion modes were used to evaluate the speciation of U and Pu with TBP and DBP. Furthermore, apparent stability constants were determined for U complexed to TBP and DBP. In positive ion mode, TBP produced a strong signal with and without complexation to U or Pu, but, in negative ion mode, no TBP, U-TBP, or Pu-TBP complexes were observed. Apparent stability constants were determined for [UO2(NO3)2(TBP)2], [UO2(NO3)2(H2O)(TBP)2], and [UO2(NO3)2(TBP)3]. In contrast DBP, U-DBP, and Pu-DBP complexes were observed in both positive and negative ion modes. Apparent stability constants were determined for the species [UO2(DBP)], [UO2(DBP)3], and [UO2(DBP)4]. Analyzing mixtures of U or Pu with TBP and DBP yielded the formation of ternary complexes whose stoichiometry was directly related to the ratio of TBP to DBP. The ESI-MS protocols used in this study will further demonstrate the utility of ESI-MS and its applicability to process control monitoring in SNF reprocessing facilities.

Rapid paper spray mass spectrometry characterization of uranium and exemplar molecular species

“…No uranyl–TBP complexes were observed in negative‐ion mode; however, the 1:2 and 1:3 uranyl nitrate complexes were observed. These findings are similar to those reported by Pacific Northwest National Laboratory for ESI‐MS characterization of aqueous uranyl–TBP mixtures, although several differences were observed . At low cone voltages (20 V), only the 1:3 uranyl–TBP complex was observed in the ESI mass spectrum and no unbound uranyl was detected.…”

Determination of the Structures of Uranyl–Tri‐n‐butyl‐Phosphate Aggregates by Coupling Experimental Results with Molecular Dynamic Simulations

“…This kind of exchange reaction is commonly observed during fragmentation steps and was recently reported by McDonald et al. for dibutyl phosphate (DBP) and tributyl phosphate complexes with UO 2 2+ in methanol–water media …”

“…IR, UV/Vis, and X‐ray absorption spectroscopy results are also consistent with the formation of the UO 2 (NO 3 ) 2 (TBP) 2 complex . The presence of UO 2 (NO 3 ) 2 (TBP) 3 species was, however, suggested by the groups of Hlushak and McDonald at low uranyl nitrate concentration, but direct experimental evidence of this 1:3 complex was obtained only in the gas phase by using ESI‐MS …”

Collision‐induced dissociation of [UVIO2(ClO4)]+ revisited: Production of [UVIO2(Cl)]+ and subsequent hydrolysis to create [UVIO2(OH)]+

“…outside the influence of solvent or other condensed phase effects) in a species‐specific fashion . Since then, ESI has been used to create gas‐phase uranyl species for a range of tandem mass spectrometry (MS/MS), anion photoelectron spectroscopy, and ion mobility studies . ESI and MS/MS have also been used to study and compare the intrinsic dissociation and ion‐molecule reactions of transuranic species …”