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

. .. . . . . . . .
;.:w
b
133
the isotope 099.99%) would be required, and the mixture would gradu-
ally build up a significant inventory of ffssio~-p~odu~t and higher-
actinide fluorides. This mixture would have adequate neutronic $ physical $
thermal-hydraulic, and chemical characteristics to function for 30 years
as a fuel and primary reactor coolant. Routine maintenance of the salt
34-
would be required to keep some of the uranium in the partly reduced U
state for the preferred chemical behavior.
Although severe contamination of the salt with oxide ion could lead
to precipitation of plutonium and uranium oxides, the solubility of these
oxides is high enough that an increase in oxide ion concentration probably
could be detected and stopped before suck precipitation occurred. In ad-
ditlion, cleanup of the salt on a routine basis to maintain the required
Bow oxide concentration would be relatively easy* '%he fuel salt is also
highly compatible, both chemically and physically, with the proposed
structural alloy, Hastelloy-N, and with the prsposed unclad graphite mod-
erator e
The radiation resistance of the fuel salt i s well established, and
no radiation decomposition would be expected except at very low tempera-
tures (below -I0OaC>. The noble-gas fission products, xenon and krypton,
are only sparingly soluble in fuel salt and would be removed csntinususEy
during reactor operation by a helium sparging system. Portions of some
other volatile fission products might also be removed by this system.
Another class of fission products, the noble and seminoble metals, would
be expected to exist in the metallic state and to plate out mostly on
metal surfaces in the primary circuit. Keeping tellurium, which can be
harmful to Hastelloy-N when deposited on its surface, in solution in the
salt may be possible by appropriate control of the reduction/oxidation
potential of the salt. Most of the fission products would remain in solu-
tion in the fuel salt. It appears (but must be demonstrated) that a full
30-year inventory of these materials could be tolerated without exceeding
solubility limits.
Because routine additions of uranium would be required to maintain
crlticality in the reactor, additions of lithium and beryllium would also
be required to maintain the desired chemical composition.
Some of these
additions, conceivably, could be used to help control the oxidation state