Absorption spectroscopic properties for Pu(III, IV and VI) in nitric and hydrochloric acid media

FY-2010 Process Monitoring Technology Final Report

“…With the increase in acid from 3.8 M to 5.1 M HNO 3 , the increase in the 815 nm band is consistent with the dominant formation of the trinitrato Pu(VI) complex at higher acid strength [46]. Characteristic Pu(VI) bands at 948, 983, and 1160 nm were also observed in the NIR spectra (Figure A.5) [44,46]. At lower acid strengths (HNO 3 = 0.3 -2.5 M), the 983 nm Pu(VI) band is partially occluded by the [NpO 2 + ], species in solution due to the predominance of neptunium being in the Np(V) form in solution at these lower acid strengths, and the prevalence of plutonium in the Pu(IV) oxidation state over Pu(VI).…”

“…The absorbance bands associated with Pu(VI) are negligible at low HNO 3 concentration and greatly enhanced for the nitric acid solutions of 3.8 and 5.1 M. The absorbance bands at 831 nm and 815 nm are assigned to the mono-and dinitrato complexes PuO 2 (NO 3 ) + and PuO 2 (NO 3 ) 2 (831 nm) and to the trinitrato complex, PuO 2 (NO 3 ) 3 -(815 nm) indicating that these complex ions of Pu(VI) are present in the fuel feed solutions. With the increase in acid from 3.8 M to 5.1 M HNO 3 , the increase in the 815 nm band is consistent with the dominant formation of the trinitrato Pu(VI) complex at higher acid strength [46]. Characteristic Pu(VI) bands at 948, 983, and 1160 nm were also observed in the NIR spectra (Figure A.5) [44,46].…”

“…e. Pu total is sum of Pu(IV) and Pu(VI). f. Pu(IV) was determined by Vis-NIR spectroscopic method using 640 nm band; ε = 25 M -1 cm -1 [46]. -3 M, respectively.…”

“…Prominent features of this series of spectra are the absorption bands associated with Pu(IV) (observed 648-662, 707, 790, 860, and 1075 nm) [15,18,[42][43][44] and Pu(VI) (observed 625, 817, 831, 857, 948, 983, and 1160 nm) [44][45][46]. The absorbance bands associated with Pu(IV) are attributed to Pu(NO 3 ) n 4-n nitrato complexes determined to be dominant below 5 M nitric acid [15,46,47].…”

“…Prominent features of this series of spectra are the absorption bands associated with Pu(IV) (observed 648-662, 707, 790, 860, and 1075 nm) [15,18,[42][43][44] and Pu(VI) (observed 625, 817, 831, 857, 948, 983, and 1160 nm) [44][45][46]. The absorbance bands associated with Pu(IV) are attributed to Pu(NO 3 ) n 4-n nitrato complexes determined to be dominant below 5 M nitric acid [15,46,47]. The absorbance bands associated with Pu(VI) are negligible at low HNO 3 concentration and greatly enhanced for the nitric acid solutions of 3.8 and 5.1 M. The absorbance bands at 831 nm and 815 nm are assigned to the mono-and dinitrato complexes PuO 2 (NO 3 ) + and PuO 2 (NO 3 ) 2 (831 nm) and to the trinitrato complex, PuO 2 (NO 3 ) 3 -(815 nm) indicating that these complex ions of Pu(VI) are present in the fuel feed solutions.…”