Study on the identification of organic and common anions in the pyrohydrolysis distillate of mixed uranium-plutonium carbide for the interference free determination of chlorine and fluorine by ion chromatography

Abstract

Identification of various soluble organic acids formed during the pyrohydrolysis of uranium-plutonium mixed carbide [(U,Pu)C] was carried out using ion chromatography. This has significant importance as the soluble organic acids can cause severe interferences during the ion chromatography separation and determination of Cl − and F − in the pyrohydrolysis distillate of (U,Pu)C. Determination of Cl and F is important in the chemical quality control of nuclear materials as these two elements can cause corrosion and hence, their concentrations in all nuclear materials are restricted to certain specified values. Since the pyrohydrolysis distillates contain both inorganic and organic acid anions, for the sake of separating and identifying organic acid anions from the common inorganic anions, three independent isocratic elutions using varying concentrations of NaOH eluent were employed for the separation of weakly, moderately and strongly retained anions. It was observed that pyrohydrolysis of (U,Pu)C also produced soluble organic acids as in the case of nitric acid dissolution of UC. The present investigation revealed the presence of formic, acetic, propionic, butyric, oxalic acid anions in the pyrohydrolysis distillate of (U,Pu)C in trace or ultra-trace concentrations. The presence of each organic acid identified in the chromatogram was confirmed with spike addition as well as by separating them by capillary electrophoresis method. The presence of lower aliphatic acids viz. formic and acetic acids was reconfirmed by carrying out an independent separation with tetraborate eluent. It is suggested that nitric acid being formed during pyrohydrolysis could be responsible for the formation of organic acids. Based on the findings, an ion chromatography separation method has been proposed for the interferencefree determination of chloride and fluoride in pyrohydrolysis distillate of (U,Pu)C.

Thermal Processing of Chloride-Contaminated Plutonium Dioxide

“…It is seen that there was quite a wide variation in can 1 from <2000 to >5000 ppm Cl (i.e., μgCl g –1 of the original sample, denoted as OS) measured, whereas the range is less for can 2 (from ∼4600 to ∼5400 ppm Cl). All measurements used ambient temperature caustic leaching to recover chloride from PuO 2 except for aliquot 1.6, where a more aggressive pyrohydrolysis method was used (steam flowed over PuO 2 at 960 °C to remove chloride prior to analysis by an ion selective electrode (ISE) , ); curiously, the chloride content in this case was the lowest of all the aliquots measured, but note that no further experiments were performed on this aliquot to confirm the low value. The variations in the initial leachable chloride between samples taken from the same aliquot are generally rather low (<10% RSD, see Table ) indicating that powders are quite well homogenized within any taken aliquot, but the significant differences between aliquots is probably linked to the location of sampling of the powder within the can and the local conditions that the can experienced over several decades of storage.…”

Determination of Chlorine in Crude Oil by High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry Using AlCl, InCl, and SrCl Molecules

“…In this way, the determination of chlorine in crude oil samples is a challenging task . The main methods used for chlorine determination are based on extraction procedures, − combustion methods, − pyrohydrolysis, − neutron activation analysis (NAA), , X-ray fluorescence spectrometry (XRF), , and, more recently, high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) …”