Attachment 1-Sample PED Figure.pdf

KCl–LiCl–NdCl3

Fig. 16760—System KCl-LiCl-NdCl3. (A) Temperature (◦C)-composition phase diagram for the LiCl-K2NdCl5 non-binary join. Isothermal sections of the ternary KCl-LiCl-NdCl3 phase diagram at (B) 400◦C, (C ) 450◦C, and (D) 550◦C. (E ) Liquidus projection; dashed lines indicate extrapolated temperatures. (F ) Scheil reaction scheme corresponding to the liquidus projection of the KCl-LiCl-NdCl3 system; e1, e2, e3, e4 = binary eutectics;

m = thermal minimum; p = binary peritectic at 66.5% KCl; E1, E2 = ternary eutectics;

P = ternary peritectic; L = liquid.

S. Ghosh, R. Ganesan, R. Sridharan, and T. Gnanasekaran, J. Phase Equilib. Diffus., 39

[6] 916-932 (2018).

A thermodynamic assessment of the ternary LiCl-KCl-NdCl3 system was performed using previously published data as well as experimental data collected in this study.

Samples corresponding to binary and ternary compositions were prepared using anhydrous lithium chloride (ultra dry and 99.995% pure on a metal basis), neodymium chloride (99.99% pure), and anhydrous potassium chloride (99.995% pure on a metal basis). Anhydrous KCl was further purified by heating to its melting point under dry argon saturated with HCl. The melting points of the three compounds were measured by differential thermal analysis and found to be 605◦, 756◦, and 772◦C, respectively, in agreement with previously published data, and confirming their purities.

Samples were mixed under argon, loaded in decarburized iron tubes, hermetically closed by arc welding, sealed in quartz tubes under high vacuum, and then heated above their liquidus temperatures for 1 h to achieve homogenization. Specimens were then slowly cooled to selected temperatures and equilibrated at those temperatures for 300 h, followed by quenching in liquid nitrogen. Products were pulverized under argon and characterized by differential thermal analysis and X-ray diffraction.

As a result of the evaluation, Figs. (A) through (F ) were constructed. It was found that LiCl and K2NdCl5 form a non-binary section instead of a quasi-binary eutectic.

Figure (A) illustrates this system. The thermal minimum (m) and its composition were calculated to be 450◦ ± 2◦C and 55.8 mol% LiCl, respectively. This non-binary join divides the LiCl-KCl-NdCl3 system into two quasi-ternary sections, namely LiCl-KCl-K2NdCl5 and LiCl-K2NdCl5-NdCl3. The latter has a ternary eutectic (E1) at 376◦ ± 9◦C and molar composition 46.2:32.5:21.3 LiCl:K2NdCl5:NdCl3. The former has a ternary eutectic (E2) at 316◦ ± 3◦C and molar composition 53.9:38.7:7.4 LiCl:KCl:K2NdCl5.

A quasi-ternary peritectic reaction was also observed at 445◦ + 1◦C, molar composition

37.7:36.2:26.1 LiCl:KCl:K2NdCl5.

The ternary isothermal sections at 400◦, 450◦, and 550◦C (Figs. (B)-(D)) were obtained using the evaluation of coexisting phases identified during the analysis. These isothermal sections and other sections taken at 50◦C intervals through 650◦C were used to construct the liquidus projection in Fig. (E ). Finally, the Scheil reaction scheme in Fig. (F ) was generated to summarize the liquidus relations of the LiCl-KCl-NdCl3 system.

These phase diagrams are of relevance in the high-temperature electrochemical reprocessing of spent nuclear fuels, which are dissolved in molten chloride salts to separate fission products from fuel elements.

Contributing Editor M. Gagliardi

General Editors M.D. Hill

T.A. Vanderah

Fig. 16760-A

Fig. 16760-B

Fig. 16760-C

Fig. 16760-D

Fig. 16760-E

Fig. 16760-F