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

3-3.3.3 Fuel maintenance ol3tions and methods
The initial fuel charge for a INSR can be prepared in a high state
of purity and introduced into the reactor by minor variamts of the
methods* used for the MSRE4 and proposed for the MSBR.8 For a once-
through BMSR that proposes no chemical repr~cessing to remove fission
products, the required fuel maintenance olperati~ns are relatively fewe
They include (1) continu~t~s removal (by the sparging and stripping sec-
tion of the reactor) of fission-product krypton and xenon, (2) addition
of 2 3 5 ~ and '3% to replace that lost by burnup and to keep the fuel suf-
ficiently denatured, and (3) in situ pr~du~tion of UF3 to keep the redox
potential of the fuel at the desired level; they probably also include
(4) removal of inadvertent oxide contaminants from the fuel; in addition,
they may include (5) addition of "4 to replace that lost by tranmuta-
tion or stored with fuel removed from the operating circuit and (6) re-
moval 05 a portion of the insol~bke noble and seminoble fission products.
Each of these is discussed briefly in the following sections.
Continuous removal of fission-product krypton and XC~OEB. Stripping
of krypton and xenon makes possible their continuous removal from the re-
actor circuit by the purely physical means of stripping with helium. For
the reference-design MSBR,* helim flowing at 0.005 m3/s (10 cfm) was to
be injected continuously into and withdram from fuel-salt side streams
carrying a total of 0.35 m'/s or about 10% of the total fuel flow rate,
generally similar operation should prove optimal for the DMSR. Such
a stripping circuit would remove an appreciable (but not a major) fraction
of the tritium and a small (perhaps very small) fraction of the noble and
seminoble fissiom products as gas-bor~ne particulates. In addition, the
stripper would remove BF3 if leaks sf secodary coolant iRtO the fuel
were to occur.
None of these removals (except possibly the last) appre-
ciably affect the chemical behavior of the fuel system.
Addition sf fissionable and fertile uranium. Adding -4,470 kg of
"'u and -18,400 kg of 23% during the lifetime of the once-through DNSR
*
FWI for the MSRE was prepared in relatively small ~atches.22s85
If DKSRs were to be of commercia% consequence, continuous purification
systems would certainly be devised for initial fuel preparation.