• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.22 no.1
• /
• pp.67-80
• /
• 2024

Fundamental aspects of creating passivation layers for corrosion resistance in nuclear engineering applications, specifically the ability to form complete layers versus porous ones, are being explored in this study. Utilizing a laser ablation technique, 1,064 nm fire at 10 Hz with 60 pulses per shot and 0.5 mm between impact points, aluminum samples are treated in an attempt to create a fully formed passivation layer that will be tested in a LiCl-KCl eutectic salt. By placing these samples into an electrochemical environment mimicking a pyroprocessing system, corrosion rates, resistances and material characteristics are tested for one week and then compared between treated and untreated samples. In initial testing, linear sweep voltammetry indicates corrosion current density for the untreated sample at -0.038 mA·cm^-2 and treated samples at -0.024 mA·cm^-2 and -0.016 mA·cm^-2, respectively. This correlates to a control sample corrosion rate of -0.205 mm·yr^-1 and treated rates of -0.130 mm·yr^-1 and -0.086 mm·yr^-1 for samples 1 and 2. In addition, electrochemical impedance spectroscopy circuits show application of a longer-lasting porous passivation layer on the treated metal, compared to the naturally forming layer. However, the current technique fails to create a uniform protection layer across the sample.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2004.06a
• /
• pp.337-337
• /
• 2004

As one of researches for the P ＆ T purposes, a basic experiment on the recovery of actinide elements from the mixture with rare earth elements by means of electrorefining using a liquid cadmium cathode in the LiCl-KC1 eutectic melt was carried out. In order to examine the behaviors of electrodeposition of metal ions on a liquid electrode, recovery experiments of rare earth metals resulting from forming electrodeposits were performed by a galvanostatic electrolysis method at various current densities. A cyclic voltammetric technique was applied to determine reduction-oxidation potential of each metal element in the melt and to detect the changes of the multi component melt composition for on-line monitoring. Also, a collaboration study with RIAR was completed to test the preliminary feasibility on a recovery of actinide elements from the mixture with rare earth elements using a liquid cadmium cathode and actinide metals. Experimental results showed that the ratio of actinides to rare earths, 9: 0.5∼1 led to the rare earth content of about 5∼10 wt% in the deposit.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2003.11a
• /
• pp.180-185
• /
• 2003

The reductions in final waste form and material costs, which were induced from an introduction of salt waste regeneration system, have been estimated and compared with those of the present pyrochemical process, which is under development in KAERI. The results calculated on the basis of published data and proper assumption showed that the final waste form of LiCl waste from the Advanced Conditioning Process would be reduced about 3.7 to#ton HM (from 5.4 to 1.7 ton/ton HM). For the case of LiCl-KCl eutectic salt waste from the electro-refining process, the final waste form would be reduced 2.3 ton/ton U. Thus, these estimation suggested that the introduction of salt waste regeneration system was essential to improve the economical efficiency of the pyrochemical process.

• Journal of the Korean Electrochemical Society
• /
• v.18 no.3
• /
• pp.102-106
• /
• 2015

The performance of Li-B alloy as anode for molten salt electrolysis was firstly investigated. The crystalline phase of the prepared Li-B alloy was identified as $Li_7B_6$. The potential profile of Li-B alloy anode was monitored during the electrodeposition of $Nd^{3+}$ onto an LCC (liquid cadmium cathode) in molten LiCl-KCl salt at $500^{\circ}C$. The potential of Li-B alloy was increased from -2.0 V to -1.4 V vs. Ag/AgCl by increasing the applied current from 10 to $50mA{\cdot}cm^{-2}$. It was found that not only the anodic dissolution of Li to $Li^+$ but also the dissolution of the atomic lithium ($Li^0$) into the LiCl-KCl eutectic salt was observed, following the concomitant reduction of $Nd^{3+}$ by the $Li^0$ in Li-B alloy. It was expected that the direct reduction could be restrained by maintaining the anode potential higher that the deposition potential of neodymium.

• Applied Chemistry for Engineering
• /
• v.18 no.4
• /
• pp.361-365
• /
• 2007

The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.3
• /
• pp.175-182
• /
• 1992

Freezing of the binary solution ($H_2O-NaCl$) saturating a packed bed of spheres is investigated experimentally. The system is cooled through its top surface, and the bottom is maintained at a temperature above the liquidus. Experiments are performed on the hypolutectic side, and the cold wall temperature is lower than the eutectic point. The effects of initial mixture concentration, superheat and glass bead diameter on temperature and concentration distributions are investigated. Supercooling was observed only at early times of the freezing process for experiments with 5% initial salt concentration. Flow visualization experiments and mushy-liquid interface position observations revealed natural convection in the liquid region. Remelting phenomena was not observed at both the solid-mushy and mushy-liquid interfaces.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2004-2010
• /
• 2022

Quantification of sensitive material is of vital importance when it comes to the movement of nuclear fuel throughout its life cycle. Within the electrorefiner vessel of electrochemical separation facilities, the task of quantifying plutonium by neutron analysis is especially challenging due to it being in a constant mixture with curium. It is for this reason that current neutron multiplicity methods would prove ineffective as a safeguards measure. An alternative means of plutonium verification is investigated that utilizes the (𝛼,n) signature that comes as a result of the eutectic salt within the electrorefiner. This is done by utilizing the multiplicity variable a and breaking it down into its constituent components: spontaneous fission neutrons and (𝛼,n) yield. From there, the (𝛼,n) signature is related to the plutonium content of the fuel.

• Nuclear Engineering and Technology
• /
• v.56 no.1
• /
• pp.42-47
• /
• 2024

The electrochemical extraction of uranium in ternary low melting LiCl-KCl-CsCl eutectic on inert and reactive electrodes via different electrochemical techniques was investigated. It was established that the electrochemical reduction process of U(III) ions on the inert W electrode was irreversible and proceeded in one stage. On reactive liquid Ga and liquid Cd electrodes the reduction of uranium ions took place with the considerable depolarization with the formation of UGa₂, UGa₃ and UCd₁₁ intermetallic compounds. Thermodynamic characteristics of uranium compounds and alloys were calculated. The conditions for the extraction of uranium from the electrolyte in the form of alloys on both liquid reactive electrodes via potentiostatic electrolysis were found.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.1
• /
• pp.59-64
• /
• 2018

In case of high contents of rare earths in the LiCl-KCl salt, it is not easy to recover U and TRU metals as a usable resource form from LiCl-KCl eutectic salts generated from the pyroprocessing of spent nuclear fuel. In this study, a conversion of $UCl_3$ into an oxide form using $K_2CO_3$ and an electrodeposition of $NdCl_3$ into a metal form in $LiCl-KCl-UCl_3-NdCl_3$ system were conducted to resolve the problem. Before conducting the conversion, experimental conditions for the conversion were determined by performing a thermodynamic equilibrium calculation. In this study, almost all of $UCl_3$ disappeared in the LiCl-KCl salt when the injection of $K_2CO_3$ reached theoretical equivalent for the conversion, and then $NdCl_3$ was effectively electrodeposited as a metal form using liquid zinc cathode. After that, the LiCl-KCl salt became transparent, and uranium oxides were precipitated to the bottom of the LiCl-KCl salt. These results will be utilized in designing a process to separate U and rare earths in LiCl-KCl salt.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.1
• /
• pp.55-64
• /
• 2023

There is a gap in our understanding of the behavior of fused and molten fuel salts containing unavoidable contamination, such as those due to fabrication, handling, or storage. Therefore, this work used calorimetry to investigate the change in liquidus temperature of PuCl₃, having an unknown purity and that had been in storage for several decades. Further research was performed by additions of NaCl, making several compositions within the binary system, and summarizing the resulting changes, if any, to the phase diagram. The melting temperature of the PuCl₃ was determined to be 746.5℃, approximately 20℃ lower than literature reported values, most likely due to an excess of Pu metal in the PuCl₃ either due to the presence of metallic plutonium remaining from incomplete chlorination or due to the solubility of Pu in PuCl₃. From the melting temperature, it was determined that the PuCl₃ contained between 5.9 to 6.2mol% Pu metal. Analysis of the NaCl-PuCl₃ samples showed that using the Pu rich PuCl₃ resulted in significant changes to the NaCl-PuCl₃ phase diagram. Most notably an unreported phase transition occurring at approximately 406℃ and a new eutectic composition of 52.7mol% NaCl-38.7mol% PuCl₃-2.5mol% Pu which melted at 449.3℃. Additionally, an increase in the liquidus temperatures was seen for NaCl rich compositions while lower liquidus temperatures were seen for PuCl₃ rich compositions. It can therefore be concluded that changes will occur in the NaCl-PuCl₃ binary system when using PuCl₃ with excess Pu metal. However, melting temperature analysis can provide valuable insight into the composition of the PuCl₃ and therefore the NaCl-PuCl₃ system.