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

of the salt, which would have to be adjusted r~uti~lely to compensate for
the oxidizing effect of the fission process. Also, the total salt inven-
tory possibly would have to be limited through o~casional withdrawals sf
some salt.
The DMSR, in common with other systems that would rase molten flus-
ride salts, would require a special primary str~ctural alloy and, pos-
sib~y, graphite for the ana -~'efiecto~. me alloy that
was originally de~el~ped for molten-salt service, Hastelloy-N, was found
to be excessively embrittled by neutron irradiation and to experience
shallow intergranular attack by fission-product tellrarim. Subsequently,
minor composition modifications were made which appear to provide ade-
quate resistance to both radiation embrittlemewt and tellurium attack.
While extensive testtng and development would still be required to fully
qualify the modified Hastelloy-N as a reactor structural material, the
fundamental technical issue of an adequate material appears to be re-
solved o
The requirements imposed on the graphite in a DMSW are much less se-
vere than those that would apply to a high-performance breeder reactor.
The low flux levels in the core would lead to damage fluences of less than
3 X lo25 neutrons/m2 iFl 30 years, 88 Some CUPPent tC!ChnO%Ogy glPaphiteS
could last for the life of the plant.
In addition, the low power density
may eliminate the need to seal the graphite surfaces to limit X ~~Q%I in-
trusion and poisoning. This would substantially reduce the technology
development effort a%sOeht@d With the tlmaFiufactuPe Of BXSB graphite.
The generic safety features of a DMSR would differ significantly
from those of other reactor types primarily because of the fluid nature
of the fuel ana the circulating inventory of fission products. kcarase
the fuel in a DMSR would be unclad, the three levels of fission-product
confinement for this system would be the RCPB and two separate levels of
containment. The primary containment would be a set of sealed and in-
ertea equipment cells that would be inaccessible to personnel after the
onset of plant operation,
finement of radioactivity in accidents involving failure of the RCPB.
They could also provide auxiliary cooling of spilled fuel salt if that
salt failea to flow to the cooled drain tank.
These cells would provide the principal con-
TBSS of cooling accidents