Electrochemical Investigation of Exchange Current Density of Uranium and Rare-earths Couples (M3+/M0) in LiCl-KCl Eutectic Electrolyte

The objective of this work is to use electrochemical techniques to quantify the electrode reaction rate of some rare-earth elements and uranium in a LiCl-KCl eutectic electrolyte at 500oC. The exchange current densities of the oxidation-reduction couples of M3+/M0 (La3+/La0, Ce3+/Ce0, Pr3+/Pr0, Nd3+/Nd0,Gd3+/Gd0, Y3+/Y0, U3+/U0) on a tungsten electrode were measured by applying a linear polarization resistance technique. A region of linear dependence of potential on applied current could be found to describe the reaction rate of oxidation-reduction system. From these measurements, the estimated exchange current density was 0.38 mA/cm2 for uranium, and was within the range of 0.27 to 0.38mA/cm2 for rare-earth elements.open0

Reference Electrode at Molten Salt: A Comparative Analysis of Electroceramic Membranes

A reference electrode is important for controlling electrochemical reactions. Evaluating properties such as the reduction potential of the elements is necessary to optimize the electrochemical processes in pyroprocessing, especially in a multicomponent environment. In molten chloride systems, which are widely used in pyroprocessing, a reference electrode is made by enclosing the silver wire and molten salt solution containing silver chloride into the membranes. However, owing to the high temperature of the molten salt, the choice of the membrane for the reference electrode is limited. In this study, three types of electroceramic, mullite, Pyrex, and quartz, were compared as reference electrode membranes. They are widely used in molten salt electrochemical processes. The potential measurements between the two reference electrode systems showed that the mullite membrane has potential deviations of approximately 50 mV or less at temperatures higher than 650??C, Pyrex at temperatures lower than 500??C, and quartz at temperatures higher than 800??C. Cyclic voltammograms with different membranes showed a significant potential shift when different membranes were utilized. This research demonstrated the uncertainties of potential measurement by a single membrane and the potential shift that occurs because of the use of different membranes

Insights on uranium uptake mechanisms by ion exchange resins with chelating functionalities: Chelation vs. anion exchange

X-ray absorption fine structure analysis has been successfully used to determine the coordination environment and therefore uptake mechanism towards the uranyl cation for a selection of commercially available ion exchange resins in non-saline and saline conditions ([Cl−] = 22.7 g L−1, 0.64 M) similar to those found in sea water. The resins tested were Purolite S985, S910 and S957, Dowex M4195, Ps-EDA, Ps-DETA and Ps-PEHA, which contain polyamine, amidoxime, mixed sulfonic/phosphonic acid, bispicolylamine, ethylenediamine, diethylenetriamine and pentaethylenehexamine functional groups, respectively. Purolite S910 and S957 were both found to extract the uranyl cation through a chelation mechanism. The uranium coordination environment on uranyl loaded Purolite S910 was found to be either tetra- or hexa-coordinate in the equatorial plane, with a 2:1 ratio of amidoxime:uranium in the fit suggesting either monodentate or η2 coordination by two amidoxime groups. The uranium environment for uranyl loaded Purolite S957 was found to be tetra-coordinate in the equatorial plane, with both sulfonic and phosphonic acid groups being involved in sorption. The presence of chloride in the loading solution had no effect on the uranyl coordination environment observed on any of the resins. In contrast, Dowex M4195, Purolite S985, Ps-EDA, Ps-DETA and Ps-PEHA exhibited an anion exchange mechanism for uranyl uptake as the corresponding extended X-ray absorption fine structure (EXAFS) data best fit a [UO2(SO4)3]4− structure

Nonproliferation drivers from civil nuclear power: South Korea's external constraints and internal beneficiaries

Civil nuclear power, currently supplying fourteen percent of the world's electricity, triggers concerns because of its inevitable technical connection with nuclear weapons. Moreover, a civil nuclear program lives under the threat of sabotage or the theft of fissile or radioactive materials. Managing these nuclear risks requires exploring how a civil nuclear program affects states 'proliferation risk and organizational culture since nuclear expansion will continue in many developing countries despite the Fukushima accidentopen0

Effects of Nuclear Technology Export Competition on Nuclear Nonproliferation

While nuclear suppliers compete in markets, they simultaneously partner in other fields. This produces a delicate relationship between civilian nuclear programs and nuclear weapon proliferation. This study explores how export competition affects suppliers??? conditions of supply related to nuclear nonproliferation. We investigated three export cases (India, North Korea, and South Korea) and identified four effects that competition has on the conditions of supply related to nonproliferation. First, under highly competitive conditions, suppliers might hesitate to enforce the conditions of supply to avoid negotiation conflicts with recipients. Second, suppliers focus on politically and economically attractive recipients while mostly ignoring unattractive ones, perhaps allowing proliferation problems to fester out of view in marginal states. Third, suppliers can build consensus on the conditions of supply to avoid being the only party experiencing negotiation conflicts. Fourth, suppliers can constrain others from relaxing the conditions of supply to maintain economic benefits and nonproliferation norms. The first two effects accelerate proliferation while the last two promote nonproliferation. Although the extent of these effects can vary with changes in nonproliferation norms, they can contribute to our understanding of the relationship between nonproliferation and civilian nuclear programs.clos