Mechanism of dissolution of nuclear fuel in nitric acid relevant to nuclear fuel reprocessing

Desigan, N.; Bhatt, Nirav; Pandey, N. K.; Mudali, U. Kamachi; Natarajan, R.; Joshi, Jyeshtharaj B.

doi:10.1007/s10967-017-5208-z

Cited by 28 publications

(12 citation statements)

References 29 publications

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“…The conditions used in the PUREX process, such as temperature (up to 121.9 °C), nitric acid concentration (up to HNO 3 azeotropic level, 15.2 M) varies throughout the different industry engineering designers [1,2]. Generally, two different nitric acid concentrations have been reported in PUREX: 3.5 M, that is one of the most cited concentration for the U/Pu TBP-solvent extraction step [3] and 8 M that is a typical concentration for spent fuel dissolution [4]; the concentration of 8 M is also the limit of use of the austenitic stainless steel 304L (304 L SS) [1].…”

Section: Introductionmentioning

confidence: 99%

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Badet

Poineau

2020

SN Appl. Sci.

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In order to better understand the role of uranium on the corrosion behavior of stainless in aqueous nuclear fuel reprocessing and decontamination operations, 304L stainless steel coupons were treated with nitric acid media at 45 °C and 90 °C in the presence of 0.3 M of uranyl nitrate. The impact of time, temperature, nitric acid concentration and uranyl nitrate concentration has been studied over a 183 days period and corrosion rates determined. After 183 days, corrosion rates (μm y −1) at 90 °C are: 33.7 ± 3.4 for 8 M HNO 3 with [U] = 0 M; 39.7 ± 0.1 for 8 M HNO 3 with [U] = 0.3 M; 5.3 ± 0.1 for 3.5 M HNO 3 with [U] = 0 M and 5.9 ± 0.2 for 3.5 M HNO 3 with [U] = 0.3 M. After 183 days, the corrosion rates at 45 °C are all below 2 μm y −1 for the nitric acid concentration and uranyl nitrate concentration studied. Analysis of the data indicate that the corrosion domain remains passive, no uranium uptake onto stainless steel has been observed but only an increase of corrosion rate with temperature (major effect) and nitric acid concentration (minor effect) were reported. When both temperature and nitric acid concentration increased and drive the system into a transpassive corrosion domain, the presence of uranium promote the increase of corrosion rate after 3 months. Analyses of the coupon by scanning electron microscopy indicates that at the first stage low homogeneous dissolution of the steel occurs; intergranular corrosion appears at 10 days and finally grain loss is observed after 6 months treatment.

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Section: Introductionmentioning

confidence: 99%

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Badet

Poineau

2020

SN Appl. Sci.

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“…Cordara et al 27 performed dissolution experiments in less concentrated nitric acid solutions (0.1 to 4 mol.L -1 ) and observed that the duration of the induction period was variable depending on temperature and nitric acid concentration, but ended systematically after a UO 2 weight loss of 0.5%, indicating that the required concentration of catalytic species might be reached at this stage. Nitrous acid is suspected to be the species increasing the dissolution rate of UO 2 [28][29][30][31][32] .…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Microstructural evolution of UO2 pellets containing metallic particles of Ru, Rh and Pd during dissolution in nitric acid solution: 3D-ESEM monitoring

et al. 2019

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Uranium dioxide containing 3 mol.% platinum group metals (PGMs) (Ru, Rh, Pd) was synthesized by hydroxide precipitation. The powders were converted to oxides, pelletized and sintered to prepare dense pellets of UO 2 incorporating PGMs particles. The characterization techniques performed revealed a microstructure similar to that of spent nuclear fuel (SNF). Dissolution tests in nitric acid demonstrated that in the presence of PGMs, the uranium dissolution rate was increased and the induction period was shortened. We used a new method based on the acquisition of Environmental Scanning Electron Microscopy (ESEM) micrographs recorded at three tilt angles and at different dissolution times. This method allowed the reconstruction of the topography of the solid/liquid interface. By monitoring the evolution of the solid/liquid interface during dissolution by means of 3D reconstructions, we were able to observe preferential dissolution zones in the vicinity of the PGMs particles and to determine microscopic dissolution rates for several regions of interest. PGMs particles were found mainly at the grain boundaries. In 0.1 M HNO 3 solution at 60˚C, the normalized dissolution rate for uranium at the grain boundaries reached R L (U) = (7 ± 1)×10-2 g.m-2 .d-1 , a value similar to the normalized dissolution rate determined for the whole image over the first 30 days of the experiment. This result showed that the dissolution occurred mainly at the UO 2 grain boundaries in the vicinity of PGMs particles. Furthermore, the 3D reconstructions of the solid/liquid interface were used to determine the evolution of the surface area of the pellet. By combining the weight losses determined at the macroscopic scale using the uranium concentrations in solution with the reactive surface area values, it was possible to estimate an effective normalized dissolution rate for the whole pellet.

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“…12−14 Furthermore, during the analysis of nuclear samples for quality assurance and nuclear forensics, the sample dissolution procedure utilizes the timeconsuming repetitive evaporation steps with hazardous concentrated acids (HNO 3 and HF) 15 for routine chemical analysis of U and Pu and gives rise to problems of a large volume of harmful NO and NO 2 gases along with increased neutron and γ-ray background due to (α, nγ) reactions on 19 F nuclei. 16,17 Therefore, it is necessary to develop an innovative, environmentally safe, sustainable, and economical low-waste technology for the advancement of the NFC. This should be capable of managing nuclear wastes, reprocessing of SNF, and fast dissolution using less hazardous chemicals.…”

Section: ■ Introductionmentioning

confidence: 99%

New Greener and Sustainable Methodology for Direct Sequestering and Analysis of Uranium Using a Maline Supramolecular Scaffold and Mechanistic Understanding through Speciation and Interaction Studies

Srivastava

Dumpala

Sahu

et al. 2021

ACS Sustainable Chem. Eng.

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Research, based on the development of an economical innovative green technology, is the quintessential requirement for the advancement of the nuclear fuel cycle (NFC). The present studies show that Maline, with a preorganized supramolecular scaffold, would be considered as the workhorse for its potential efficacy in diverse facets of the NFC, specifically as an elegant metal hijacker for processing of uranium (U) matrices, designer solvent for green analysis of U, and a promising U chelator for a greener alternative for the cleanup of U contamination. Seven U matrices (UO3, UN, UO2, Rb2U(SO4)3, U metal, U3Si2, and (U, Pu)O2) were dissolved in Maline without any external additives and cyclic voltammetry was performed to investigate the redox speciation, viz., redox thermodynamics (E p and E f) and kinetic (D 0, k 0, and αn) parameters and mechanistic electron transfer of the dissolved U species. To get an insight into the molecular speciation, the structural analysis on UO3 dissolved in Maline was conducted by extended X-ray absorption fine structure, which indicates an interesting observation of the formation of UO2 2+ kind of species with malonic acid and H2O at equatorial coordination. Molecular dynamics and density functional theory simulations were carried out to acquire diffusion, optimized structure, binding energy, and molecular orbital diagram of U species in Maline, to corroborate the experimental results and to shed light on the hydrogen-bond network in Maline with aqueous dilution. The interaction of uranyl with Maline was probed by luminescence, absorption spectroscopy, and calorimetry titration. Green analysis methodology was developed based on Maline digestion followed by voltammetric determination of U in nuclear material samples. Green chemistry metrics were evaluated to authenticate the greener aspects of the present methodology. The present developed methodology of direct sequestration and analysis of U matrices represents an appropriate replacement of the existing method, viz., hazardous acidic processing of U matrices followed by biamperometry analysis.

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Mechanism of dissolution of nuclear fuel in nitric acid relevant to nuclear fuel reprocessing

Cited by 28 publications

References 29 publications

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Corrosion studies of stainless steel 304 L in nitric acid in the presence of uranyl nitrate: effect of temperature and nitric acid concentration

Microstructural evolution of UO2 pellets containing metallic particles of Ru, Rh and Pd during dissolution in nitric acid solution: 3D-ESEM monitoring

New Greener and Sustainable Methodology for Direct Sequestering and Analysis of Uranium Using a Maline Supramolecular Scaffold and Mechanistic Understanding through Speciation and Interaction Studies

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