Thermodynamics of rare earth chlorides in LiCl–KCl–CsCl eutectic based melts

E. A. Kharina, R. Yu. Kaychenkova, A. S. Dedyukhin,

A. V. Shchetinskiy, L. F. Yamshchikov, V. A. Volkovich

ABSTRACT

In this paper, the temperature dependences of formal standard potentials of some rare earth metals such as lanthanum, neodymium, praseodymium, gadolinium, holmium and erbium and the thermodynamic characteristics of the formation of their chlorides in molten eutectic mixture of lithium, potassium and cesium chlorides were calculated using the experimental data on determination of their equilibrium potentials.

KEYWORDS:

rare earth metals, melts, chlorides, quasi-standard potentiafls, emf method

DOI: 10.1134/S0235010619010079

Corrosion of various types of stainless steels in chloraluminate melts

V. V. Karpov, A. V. Abramov, K. V. Dedov, A. V. Shak, A. Yu. Zhlyakov,

I. B. Polovov, S. V. Belikov, O. I. Rebrin

ABSTRACT

In the present work the corrosion behavior of 08Kh17T (analogue of AISI 439) ferritic steel, 12Kh13 (analogue of AISI 410) and 16Kh12MVSFBR ferritic-martensitic steels, and AISI 316L (analogue of 03Kh16N15M3), 12Kh18N10T (analogue of AISI 321) and 06KhN28MDT austenitic alloys was studied at 550°C in fused KCl–AlCl3 mixture with the initial AlCl3EtoEKCl ratio of 1.1. The corrosion rates of the studied materials in the KCl–AlCl3 were determined. The corrosion processes in all the studied iron-based steels were caused by the red-ox reactions resulting in dissolution of the most electronegative alloy components (Cr, Fe and Mn), that indicate the electrochemical nature of corrosion phenomena.

KEYWORDS

corrosion, stainless steel, chloraluminate melts, intergranular corrosion, molten salt reactor

DOI: 10.7868/S0235010619010067

Formation of phosphates of rare earth elements in melts based on the equimolar mixture of sodium and potassium chlorides

A. B. Ivanov, V. V. Sukhikh, V. A. Volkovich, B. D. Vasin, A. V. Chukin

ABSTRACT

Processes taking part during reaction of chlorides of 15 rare earth elements (yttrium, lanthanum and all lanthanides except for promethium) with sodium orthophosphate in the melts based on NaCl–KCl equimolar mixture under inert atmosphere at 750°C. Phase composition and particle size distribution of the phosphates of rare earth elements (REE) formed was determined. The effect of the mole ratio of phosphate to REE on the composition and particle size of the phosphates formed was studied. Conditions required for the quantitative precipitating from the melt individual REE and a mixture of REE imitating the content of rare earth fission products in the spent nuclear fuels arriving for the reprocessing.

KEYWORDS

rare earth elements, chloride melts, phosphates, precipitation, spent nuclear fuels

DOI: 10.7868/S0235010619010055

Electrical conductivity of molten alumophosphate and borosilicate glasses containing simulated high-level waste from nuclear fuel processing

O. Yu. Tkacheva, V. B. Remisov, P. V. Kozlov, E. A. Belanova, N. V. Vlasova, Yu. P. Zaikov

ABSTRACT

The electrical conductivity of the borosilicate and aluminophosphate glasses containing simulated high-level waste from the reprocessing of spent nuclear fuel VVER‑440 has been studied by the impedance spectroscopy method. It was found that the electrical conductivity of the aluminophosphate and borosilicate glasses was determined mainly by the sodium oxide concentration and significantly changes with temperature. An empirical equation of the electrical conductivity dependence on the sodium oxide content and temperature is obtained for the borosilicate glasses. The effect of the HLW simulators on the electrical conductivity of molten glasses was insignificant in the concentration range being studied.

KEY WORDS

spent nuclear fuel, high-level waste, aluminophosphate glass, borosilicate glass, melt, electrical conductivity

Li2O solubility in LiCl-KCl melt

V. A. Kovrov, A. R. Mullabaev, V. Yu. Shishkin, Yu. P. Zaikov

ABSTRACT

Crystallization temperatures (liquidus and solidus) in the systems LiCl-Li2O and (LiCl-KCl)-Li2O with the KCl containing 10 and 20 mol.% were obtained with independent methods of thermal analysis of cooling curves, isothermal saturation, and differential scanning calorimetry. The linear sweep voltammetry was applied to control the time of the equilibrium establishment in the molten system after the Li2O addition, which depended on the composition of the base melt and the concentration of Li2O. The fragments of the binary LiCl-Li2O and quasi-binary [LiCl-KCl(10 mol.%)]-Li2O and [LiCl-KCl(20 mol.%)]-Li2O phase diagrams in the Li2O concentration range from 0 to 12 mol.% were obtained. The presence of KCl in the LiCl-KCl-Li2O molten mixture in the amount of 10 and 20 mol.% reduces the liquidus temperature by 30 and 80 degrees, respectively, but the region of the homogeneous molten state of the system is considerably narrowed, which complicates its practical application. The Li2O solubility in the molten LiCl, LiCl-KCl(10 mol.%) and LiCl-KCl(20 mol.%) decreases with increasing of KCl content and is equal to 11.5, 7.7 and 3.9 mol.% at 650 °C, respectively.

KEY WORDS

lithium chloride, potassium chloride, lithium oxide, liquidus, solidus, solubility, pyro-chemical reprocessing, spent nuclear fuel.