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

[-SO0 kPa (130 psi)].
analysis were obtained from Ref. 8.
46
Graphite and fuel-salt properties used in the
The reference DMSR design satisfies the two most important
thermal-hydraulic considerations: (a> the maximum graphite temperature
is ISW enough to allow it to last the life of the plant (24-full power
years) and (2) regions sf stagnant or laminar flow are avoided. Halay
Variations OR this design W i l l be possible in achieving iipl Optimum core,
but the second consideration must always be noted. Because of the EQW
thermal conductivity of the fuel salt, excessive temperatures can occur
in very small stagnant or laminar flow regions. The graphite elements
must retain their geometric integrity and must not create flow blockages.
Extensive in-pile testing would be necessary to ensure that both of these
cOnsideratiOnS Were met before Const?XC%iQn Sf %! d€SXlonStratiOn plant could
be undertaken.
3.3 Fuel Behavior
Excellent neutron economy is an absolute requirement for a thermal
breeder (such as an MSBR), and fuel co~lponents with acceptably low neutron
CFQSS sections are few. We recognized very early in the MSBR development
effort that (1) only fluorides need to be considered, (2) only LiF and
BeP2 would prove acceptable as fuel solvents (diluents) for the fissile
and fertile fluorides, and (3) the LiF must be highly enriched in 7Li,
For a break-even reactor or for one that, though it retains most of the
fission pr~ducts within the fuel, is to be an effective converter, some
sacrifice in meutron economy may be permissible. However, no likelihood
for success seems possible with diluents other than BeF2 and LiF highly
enriched (probably to 99.99%) in 'Li,
Accordi~gly, the fuel system for a DMSR necessarily will be very
similar to the system that received intensive study for many years in
MSBR development. A considerable fund of information exists about ckem-
ical properties, physical properties, and expected in-reactor behavior
of suck materials.