ORNL-TM-7207 - the Molten Salt Energy Technologies Web Site

52
preparation in a pure homogeneous form for introduction into the reactor.
In addition, the fuel must (1) be compatible with the structural and the
moderator materials during normal operation, (2) be stable to intense
radiation fields, and (3) tolerate €issfon of uranium and plutonium and
the development of significant concentrations of fission products and
p%tttomium and other actinides. Also, without dangerous consequences, it
must be able to withstand a variety of off-design situations such as
heat-exchanger leaks or possible ingress of air. Finally, although not
presently necessary, it is desirable that at end-of-life the fuel be ame-
nable to recovery of fissile, fertile, and other valuable materials. The
ability of the fuel to meet or not to meet these diverse and conflicting
demands largely depends on the chemical properties sf the fuel. ~ost of
the details of fission-prsduet behavior are deferred to a subsequent sec-
tion, but much of the basis for expected fuel performance is presented in
the foBkowing discussion.
Thermodynamics of molten fluoride solutions. The thermodynamic
properties of many pertinent species in molten LIF-BeF2 solutions and a
smaller number in LiF-BeF2-ThFq solutions have been studied in a long-
continued experimental program. A variety of experimental techniques was
employed. Much of the data was obtained by direct measurement of equilib-
rium concentrations and partial pressures for reactions such as
and
(where g, c, I, and d represent
and solute respectively) us%ng
dium. Maray studies of solubility behavior of sparingly s~l~ble fluoride
species have also been made, 13aes25926 has reviewed all these studies
amd has tabulated themodynamic data for many species in molten Li2BeFq.
Table 26 shows values for standard free energy of fomstfsm of major
constituents and s~me possible corrosion products. has also
. ,. . . . . . ..
x;&.;* .