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Fluoride materials for fuel and cooling systems of the IV generation reactor
T.B. Syngrapova1, V.I. Lutsyk1,2, .E. Zelenaya2, M.D. Parfenova3 1 Buryat State University, Ulan-Ude, Russia 2 Institute of Physical Materials Science SB RAS, Ulan-Ude, Russia Tomsk State University of Control Systems and Radio-electronics, Tomsk, Russia E-mail: vluts@ipms.bscnet.ru

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Fluoride systems have been described as one of the possible fuels for molten salt reactor application [1-3]. Besides the lowest melting point another criterion is the same important for the salt fuel: a concentration of fissile material. To optimize the molten salt fuel parameters the computer models of fluoride systems are to be built. Computer model is based on the detailed geometrical description of a diagram: dots, curves, surfaces, phase regions. As a result it permits to use a phase diagram (PD) as an instrument to solve different applied tasks of heterogeneous design and physics-chemical analysis [4-8]. E. g., construction of the arbitrary taken diagram's vertical or horizontal cuts is provided with a table containing the detailed information of the surfaces and phase regions sections. For the given center of masses it is possible to receive a vertical diagram of the material balance, and the isothermal state of arbitrary taken isopleth could be illustrated by the horizontal diagram of material balance. By means of PD computer model, it is convenient to compare and analyze the contradictions between the methods to determine eutectical and peritectical fragments borders of three-phase region [9]. The LiF-KF-LaF3 system [3], as a prototype of the possible fuels for molten salt reactor application, can be made as the modification of T-x-y diagram with binary compound decomposed before melting and appeared on the ternary liquidus [10] and T-x-y diagram with incongruently melting binary compound [11]. Computer Model of T-x-y Diagram LiF-KF-LaF3 System The kinematical method is used for the unruled and ruled diagram surfaces simulation. In this case, a diagram surface is presented as the pseudo-ruled one, that is, a space curve, given by the interpolation polynomial, moves along the analogously given directing curves [4-8]. Data for binary systems LiF-KF [12], KF-LaF3 [13-14], LiF-LaF [15] concerning the melt temperatures of initial components (LiFA, KFB, LaF3C), points coordinates of binary eutectics and peritectic (eLiF-KF, eKF-LaF3, eLiF-LaF3, pKF-LaF3) and compounds (R1 KF·LaF3 and R23KF·LaF3) are used as initial data at PD simulation. The form of binary curves (i.e. curve convex downwards or upwards) are taken into consideration while liquidus simulation. The coordinates of ternary eutectic (E), peritectic (P) and two quasi-peritectics (Q1 and Q2) [3] also was given as initial data. As solid phase solubility in this system are not present, the solidus and solvus surfaces are absent. As a result the given PD includes five surfaces of primary crystallization (with contours QLiF: LiFeLiF-KFEQ2Q1eLiF-LaF3; QKF: KFeLiF-KFEPeKF-LaF3; QLaF3: LaF3eLiF-LaF3Q1pKF-LaF3; QKF-LaF3: eKF-LaF3PQ2Q1pKF-LaF3; QR: EPQ2) and sixteen ruled surfaces (QrAC: eLiF-LaF3Q1AQ1AeLiF-LaF3, QrCA: eLiF-LaF3Q1CQ1CeLiF-LaF3, QrAB: eLiF-KFEAEAeLiF-KF, QrBA: eLiF-KFEBEBeLiF-KF, QrCR1: pKFr r r LaF3Q1CQ1CR1, Q R1C: pKF-LaF3Q1R1Q1R1, Q R1B: eKF-LaF3PR1PR1eKF-LaF3, Q BR1: eKF-LaF3PBPBeKFr r r r r LaF3, Q AR1: Q1Q2AQ2AQ1, Q R1A: Q1Q2R1Q2R1Q1, Q R2A: EQ2R2Q2R2E, Q AR2: EQ2AQ2AE, Q R1R2: PQ2R1Q2R1P, QrR2R1: PQ2R2Q2R2P, QrBR2: PEBEBP, QrR2B: PER2ER2P), four horizontal complexes at the temperature of invariant points (HE: AEBER2EE; HP: BPR2PR1PP; HQ1: AQ1CQ1R1Q1Q1; HQ2: AQ2R1Q2R2Q2Q2) and two vertical planes of triangulation (VR1: AQ1A0R01R1Q1; VR2: AQ2A0R02R2Q2) (Fig. 1). The surfaces curvature can be corrected according to the experimental data or thermodynamic calculation results.
B B B B

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Considered phase diagram of LiF-KF-LaF3 system [16, 17] includes a one-phase region L, seven two-phase regions and eleven three-phase regions (Table 1).

Fig. 1 Computer model of LiF-KF-LaF3 system in prizm (a) and its XY projection (b)

Symbol L+A L+B L+C L+R1 L+R2 A+R1

Bounding Sufaces QLiF, QrAB, QrAC QrAR1, QrAR2 QKF, QrBA, QrBR1, L+A+B QrBR2 QLaF3, Q
r CA,

Table 1 Phase Regions Structure Bounding Symbol Sufaces , A+R2 VR2 QrAB, Q QrAC, Q
r BA, r CA,

Symbol L+B+R2 L+C+R1 L+R1+R2

HE HQ1

QrCR1

L+A+C

QKF-LaF3, QrR1R2, L+A+R2 QrR1A,QrR1B, QrR1C QR, QrR2R1, QrR2A, L+A+R1 QrR2B VR1 L+B+R1

QrR2A, QrAR2, A+B+R2 HQ2, VR2 QrAR1, QrR1A, A+C+R1 HQ1, HQ2, VR1 QrR1B, QrBR1, HP A+R1+R2

Bounding Surfaces QrBR2, QrR2B, HE, HP QrCR1, QrR1C, HQ1 QrR1R2, QrR2R1, HP, HQ2 HE, VR2 HQ1, VR1 HQ2, VR1, V
R2

Horizontal and Vertical Sections of T-x-y Diagram LiF-KF-LaF3 System The arbitrary horizontal and vertical sections can be made for obtained computer model of LiF-KF-LaF3 system. So horizontal sections at TpKF-LaF3
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Fig. 2 Horizontal sections at TpKF-LaF3>T>TeKF-L

aF3

(a) and TP>T>TQ2

Fig. 3 Arrangment of vertical sections on XY proejction (a); vertical sections || LiF-KF S1(0.8; 0; 0.2)-S2(0; 0.8; 0.2) (b); || LiF-LaF3 S1(0.4; 0.6; 0)-S2(0; 0.6; 0.4) (c); || KF-LaF3 S1(0.33; 0.67; 0)-S2(0.33; 0; 0.67) (d)

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Summary The elaborated phase diagrams computer models makes possible to study fluoride and other systems and can be used at the design of materials employing as possible fuel components for molten salt reactor. To ensure reliable exploitation of new generation reactor, exhaustive information are to be used about the chemical processes and equilibria in the fluoride melts of this type. As neither experimental data, nor thermodynamic calculation itself do not guarantee the validity of multidimensional phase diagram for multicomponent system and its isothermal sections and isopleths, then an assemblage of a whole diagram from its geometrical elements should be realized too. REFERENCES 1. Benes O., Konings R.J.M. J. Nucl. Mater. 2008. V. 375. P. 202-208. 2. Benes O., Konings R.J.M. J. Nucl. Mater. 2008. V. 377. P. 449-457. 3. Benes O., Konings R.J.M. Calphad. 2008. V. 32. P. 121-128. 4. Lutsyk V.I. Electrochem. Soc. Proc. PV2002-19. 2002. ­ P. 386-398. 5. Lutsyk V.I., Zelenaya A.E., Zyryanov A.M. J. Materials, Methods & Technologies, Inter. Sci. Publ. 2008. V. 2. P. 176-184. 6. Lutsyk V.I., Zyryanov A.M., Zelenaya A.E. Russ. J. Inorg. Chem. 2008. V. 53. P. 792798. 7. Lutsyk V.I., Zelenaya A.E., Zyryanov A.M. Crystallogr. Rep. 2009. V. 54. P. 13001307. 8. Lutsyk V.I., Zelenaya A.E., Savinov V.V. IOP Conf. Ser.: Mater. Sci. Eng. 2011. V. 18. P. 1-4. 9. Lutsyk V., Vorob'eva V., Zyryanov A. J. Guangdong Non-Ferrous Metals. 2005. V. 15. P. 174-178. 10. Khaldoyanidi K.A. Russ. J. Inorg. Chem. 2001. V. 46. P. 1069-1073. 11. Prince A. Alloy Phase Equilibri. Elsevier Publ. Comp., Amsterdam-London-N.Y. 1966. 290 P. 12. Chartrand P., Pelton A.D. Metall. Mater. Trans. 2001. V. 32A. P. 1385-1396. 13. Dergunov E.P. Dokl. Akad. Nauk SSSR. 1948. V. 60. P. 1185-1188. (In Russian) 14. Bukhalova G.A., Sementsova D.V. Russ. J. Inorg. Chem. 1965. V. 10. P. 1886-1889. (In Russian) 15. Posypaiko V.I., Alekseeva E.A. et al. Phase Diagrams of Salt Systems. Reference book, Part 2, Metallurgia Publishing House, Moscow, 1977. (in Russian) 16. Parfenova M.D. Intern. scientific school for young researchers «Strategy design of youth science and innovation environment as fundamentals for modern engineer training» (Tomsk, Russia. 27-29 March 2013), p. 77-80. Scientific advisor: Dr, Prof V. Lutsyk 17. Parfenova M., Lutsyk V., Zelenaya A. III International Scientific Conference "Chemical Thermodynamics and Kinetics". Russia, Great Novgorod, 27-31 May 2013. Proceedings of Reports. Scientific ed. Great Novgorod: "Novgorod's Technopark" Ltd. P. 115117. (In Russian)

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