PNNL

Abstract

Electrospray ionization - mass spectrometry (ESI-MS) was tested for its use in monitoring spent nuclear fuel (SNF) consittuents include U, Pu, dibutyl phosphate (DBP) and tributyl phosphate (TBP). Both positive and negative ion modes were used to evaluate the speciation of the 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 determind for [UO2 (no3)z(TBP)z], [UO2(NO3)z(H20)(TBP)z], and Uo2(NO3)z(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(DPB)r]. Analyzing mixtures of U or Pu with TBP and DBP yielded the formation of tenary complexes whose stoichiometry was directly related to the ration 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.