141
Ind. Eng. Chem. Res. 1991,30, 141-145 s = solid
w = in wall region
Literature Cited (1) Gelperin, N. I.; Einstein, V. G. In Fluidization; Davidson, J. F., Harrison, D., Eds.; Academic Press: Orlando, FL, 1971; p 471. (2) Botterill, J. S. M. Fluid-Bed Heat Transfer; Academic Press: Orlando, FL, 1975. Denloye, A. E.; Botterill, J. S. M. Powder Technol. 1977, 19, 197. (3) Xavier, A. M.; Davidson, J. F. In Fluidization, 2nd ed.;Davidson, J. F., et al., Eds.; Academic Press: Orlando, FL, 1984; p 437. (4) Baskakov, A. P. In Fluidization, 2nd ed.; Davidson, J. F., et al., Eds.; Academic Press: Orlando, FL, 1984; p 465. (5) Kunii, D.; Smith, J. M. AIChE J. 1960,6, 71. (6) Kunii, D.; Suzuki, M. Roc. 3rd Int. Heat Transfer Conf. Chicago 1966, 4, 344. (7) Floris, F.; Glicksman, L. R. XVI ICHMT Symposium, Dubrovnik, Paper 2-2, 1984. (8) Yagi, S.; Kunii, D. AIChE J . 1960, 6, 97; Int. Devel. Heat Transfer, Boulder, Part IV, Paper 90, p 742, 1961. (9) Mickley, H. S.; Fairbanks, C. A. AIChE J. 1955, 1, 374. Mickley, H. S.; Fairbanks, D. F.; Hawthorn, R. D. Chem. Eng. Prog. Symp. Ser. 1961, 57 (32), 51. (10) Glicksman, L. R.; Decker, N. Heat Transfer in Fluidized Beds of Large Particles. Report from Mech. Ena. - Dept., - MIT, Cambridge; MA, 1983. (11) ~. Botterill. J. S. M.: Williams. J. R. Trans. Inst. Chem. Ene. 1963. 41, 217. Botterill,' J. S. M.;' et al. In Proc. Intern. S y k p . o n Fluidization; Drinkenburg, A. A. H., Ed.; Netherlands Univ. Press: Amsterdam, 1967; p 442. (12) Kunii, D.; Levenspiel, 0. Fluidization Engineering; John Wiley: New York, 1969. (13) Baskakov, A. P.; et al. Powder Technol. 1973,8, 273; Fluidization and Its Applications; Cepadues: Toulouse, 1974; p 293. (14) Martin, H. XVI ICHMT Symposium, Dubrovnik, Paper 2-5, 1984; Chem. Eng. Process. 1984, 18, 157, 199. (15) Wicke, E.; Fetting, F. Chem.-Ing.-Tech. 1954, 26, 30. (16) Goosens, W. R. A.; Hellinckx, L. Fluidization and its Applications; Capedues: Toulouse, 1974; p 303.
(17) Catipovic, N. M.; et al. In Fluidization; Grace, J. R., Matsen, J. M., Eds.; Plenum: New York, 1980; p 225. (18) Xavier, A. M.; et al. In Fluidization; Grace, J. R., Matsen, J. M., Eds.; Plenum: New York, 1980; p 209. (19) Levenspiel, 0.; Walton, J. S. Chem. Eng. h o g . Symp. Ser. 1954, 50 (9), 1. (20) Martin, H. Chem. Eng. Commun. 1981, 13, 1. (21) Bock, H. J.; Molerus, 0. German Chem. Eng. 1983,6,57. Bock, H. J.; et al. German Chem. Eng. 1981, 4, 23; 1983, 6, 301. (22) Chandran, R.; Chcn, J. C. AIChE J. 1985, 31, 244. (23) Yoshida, K.; et al. Chem. Eng. Sci. 1974, 29, 77. (24) Filtris, Y.; et al. Chem. Eng. Commun. 1988, 72, 189. (25) Kunii, D.; Levenspiel, 0. Powder Technol. 1990,61, 193. (26) Chen, G.; Sun, G.; Chen, G. T. In Fluidization V; 0stergaard, K., Ssrensen, A., Eds.; Engineering Foundation: New York, 1986; p 305. (27) Bachovchin, D. V.; Beer, J. M.; Sarofim, A. F. Paper presented at the AIChE Annual Meeting, Nov 1979; AIChE Symp. Ser. 1981, 77 (205), 76. (28) Hoggen, B.; Lendstad, T.; Engh, T. A. In Fluidization V; (astergaard, K., Ssrensen, A., Eds.; Engineering Foundation: New York, 1986; p 297. (29) Walsh, P. M.; Mayo, J. E.; Beer, J. M. AIChE Symp. Ser. 1984, 80 (234), 119. (30) Zhang Qi; et al. Proc. CIESCIAIChE Joint Meeting; Chem. Ind. Press: Beijing, 1982; p 374. In Fluidization '85,Science and Technology; Kwauk, M., et al., eds.; Science Press: Beijing, 1985; p 95. (31) Nazemi, A.; Bergougnou, M. A.; Baker, C. G. J. AIChE Symp. Ser. 1974, 70 (141), 98. (32) Lewis, W. K.; Gilliland, E. R.; Lang, P. M. Chem. Eng. Prog. Symp. Ser. 1962,58 (38), 65. (33) Beeby, C.; Potter, 0. E. AIChE J . 1984, 30, 977. (34) Kunii, D.; Levenspiel, 0. Fluidization Engineering, 2nd ed.; Butterworth: Stoneham, MA, 1991. (35) Wunder, R.; Mersmann, A. Chem.-Ing.-Tech. 1979,51,241. (36) Guigon, P.; et al. Proc. Second Intern. Conf. Circulating Fluidized Beds; Compiegne: 1988; p 65.
Received f o r review January 31, 1990 Accepted July 27, 1990
Chemical Basis for Pyrochemical Reprocessing of Nuclear Fuel John P.Ackerman Chemical Technology Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439-4837
The integral fast reactor (IFR) is an advanced breeder reactor concept that includes on-site reprocessing of spent fuel and wastes. Spent metallic fuel from the IFR is separated from fission products and cladding, and wastes are put into acceptable forms by use of a compact pyrochemical process based on partition of fuel and wastes between molten salt and liquid metal. To minimize reagent usage and, consequently, waste volume, electrotransport between metal phases is used extensively for feed dissolution and product recovery, but chemical oxidation and reduction are required for some operations. This paper describes the processes that are used and presents the chemical theory that was developed for quantitatively predicting the results of both chemical and electrotransport operations.
Introduction On-site processing of spent metal fuel is a basic part of the integral factor reactor (IFR)concept (Till and Chang, 1988, 1989; Burris et al., 1987). A pyrochemical process to reclaim fuel is being developed and is expected to be economically attractive for on-site use, to return essentially all actinides to the reactor, and to result in a waste form that can be stored on site but is expected to be well suited to eventual permanent disposal. The fundamentally thermodynamic theory used to predict the results of chemical and electrotransport operations on which the 0888-5885/91/2630-0141$02.50/0
pyrochemical process is based was verified at the scale of roughly 1 mol of plutonium (Tomczuk et al., 1991). This paper presents that theory and then briefly describes its application to pyrochemical reprocessing of IFR fuel.
Theory of Distribution of Elements Pyrochemical processing is based on the partition of elements between one or more metal phases (where they exist as pure metals, as solutes in metal solution, or as intermetallic compounds) and a molten salt phase (where they are present as metal chlorides). A t the processing 1991 American Chemical Society
142 Ind. Eng. Chem. Res., Vol. 30, No. 1, 1991 Table I. Free Energies of Formation of Selected Chlorides (Kilocalories/Mole of Chlorine at 775 K) (Fuger et al., 1983; Pancratz. 1984) CsCl -87.8 CeCl, -68.6 UC13 -55.2 KCI -86.7 NdCl3 -67.9 ZrCll -46.6 SrCI, -84.7 YC13 -65.1 CdClz -32.3 LiCl -82.5 AmCI, -64" FeCl, -29.2 NaCl -81.1 CmCl, -64' MoC1, -16.8 LaCl, -70.2 PUCI, -62.4 TcCl, -11.0 PrC1, NpCI, -58" -69.0
'Signifies estimated value. temperature (775 K, 930 OF), exchange reactions of the class defined by reaction 1 are rapid. reaction 1 yMC1, + xM' yM + xM'C1, Here, M and M' are any two different metallic elements; x and y are the respective oxidation states of their stable chlorides. A reaction of this kind can be written to de-
termine the distribution of each of the possible element pairs between the salt and metal phases. The free-energy change (AG) in reaction 1 is AG = xAGP(M'C1,) - yAG,"(MCl,) (1) where AGfomeans the free energy of formation from the pure elements in their standard states. The equilibrium constant for the reaction, Keq, is calculated from the standard free-energy change: Concentrations of the metals and their chlorides can be determined from the equilibrium constant and the activity coefficients of metal and chloride species. For this class of reactions, the equilibrium constant expression is
Here, the ai's are the activities of the various species, the N ( s are the mole fractions, and the yi's are the activity coefficients. Selected free-energy values from Pancratz (1984) and the IAEA chemical thermodynamics compilation (Fuger et al., 1983) are given in Table I for the most important constituents of metal fuel. Metal activities can be greatly reduced (y
