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W. R. GRIMES,N. V. SMITHAND G. M. WATSON
Acknowledgments.-This work was done under a cooperative agreement between the Bureau of Mines, United States Department of the Interior, and the University of Wyoming. Assistance was
Vol. 62
rendered in various phases of the work by D. R. Latham, C. R. Ferrin, A. W. Decora, G. U. Dinneen, J. C. Morris, A. P. Marr and D. G. Earnshaw.
SOLUBILITY OF NOBLE GASES IN MOLTEN FLUORIDES. I. I N MIXTURES OF NaF-ZrF4 (53-47 MOLE %) AND NaF-ZrF4-UF4 (50-46-4 MOLE %) BY W. R. GRIMES,N. V. SMITH AND G. M. WATSON Oak Ridge National Laboratory, P. 0. Box Y , Oak Ridge, Tennessee Received April $1, 1368
Solubilities of He, Ne, A and Xe have been determined a t pressures from 0.5 to 2 atmospheres in NaF-ZrF4 (53-47 mole
%) a t 600, 700 and 800". The solubilities increase linearly with gas pressure, decrease with increasing atomic weight of
the solute and increase with increasing temperature. Henry's law constants in moles of solute/( ~ msolution)( . ~ atmosphere) a t 600' are 21.6 + 1 X 11.3 & 0.3 X 10-8, 5.06 f 0.15 X 10-8 and 1.94 & 0.2 X 10-8 while heats of solution are 6.2, 7.8, 8.2 and 11.1 kcal./mole for He, Ne, A and Xe, respectively. Solubilities and heats of solution for H e and Xe in NaF-ZrFa-UFc (50-46-4 mole %) are very similar to the values obtained with these gases in the NaF-ZrFd mixture.
Introduction Solubilities of gases in liquids have been studied by many investigators; reviews covering much of the work in this field are a ~ a i l a b l e . l - ~Recent studies of noble gases as solutes include measurements with He, Ne, A, Kr and X e in organic l i q ~ i d s ~and - ~ with radon in organic materials reHowever, lated t.0vegetable oils and animal no information regarding solubilities of noble gases in molten salt systems appears to have been published. A molten fluoride mixture containing UF4 has served as the fuel in a high temperature nuclear r e a c t ~ r . ~ - 'Xe ~ and Kr are produced in such a fuel as fission products; Xe is a serious nuclear poison. Ease of removal of these elements from the liquid fuel depends on their solubility in the molten fluoride. Since He (or A) is commonly used as a protective blanket and/or sparging gas during reactor operation the fluoride fuel is saturated with He a t the contact temperature; bubble formation, which could lead €0 undesirable perturbations in nuclear reactivity, might be a consequence of the dependence of He solubility on temperature within the reactor fuel circuit. Accordingly, both absolute solubility and its temperature dependence for noble gases in molten fluorides are of importance in operation of such reactors. (1) A. E. Markham and I
