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

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At the close of MSRE operation, two major technical issues appeared
unresolved. The first was the control of tritium, which is produced in
fairly large quantities in a molten-salt system and which is known to dif-
fuse through metal walls. Subsequent engineering-scale tests have demon-
strated that tritiUll is oxidized in SOd~Wil flUOrobOPate, the pPQpos@d SeC-
ondary salt for the DMSR, and appears to be handled readily. However, this
process is not yet well understood, and the effects of maintaining an ade-
quate c~ncentrati~n of the oxidant on the long-term compatibility of the
salt with the structural alloy are unknown. The second issue involved the
compatibility of Hastelloy-N with fuel salt. Operation of the MSRE showed
that the general corrosion of Hastelloy-M and graphite in an operating MSR
was near zero, as expected. However, metal surfaces that had been exposed
to fuel salt containing fission products were unexpectedly found to exhibit
grain-boundary attack, which was subsequently shown to be caused by reac-
tion with the fission product, tellurim. Further work has shorn that tel-
lurium attack can be controlled by either a modification sf the Hastelloy-N
alloy or by eo~ltroP of the oxidation potential of the fuel salt.
The major areas of research required for comerciabization of MSWs
would involve improvement of the materials sf construction (Hastelloy-PS
and graphite), the design of in-line instrumentation for high-temperature
use, and the development of fuel processing (at least for the end of reac-
tor life and possibly also for use on-line). The major areas of develop-
ment involve the scale-up of reactor components (eogc9 pumps) and the de-
sign and development of components that were not present in the MSW
(e.g., steam generators and mechanical valves).
pate that the design of some components such as the fuel drain system and
the reaetor cell with its insulation, heating, and cooling requirements
would be extensively modifed to meet currently unspecified licensing re-
quirements.
the temperatures and flows in the primary and secondary salt systems and
in the steam system to avoid salt freezing and excessive thermal stress.
Alternatively, some co~~~ponents might be designed to accommodate such
freezing. Still another area of development would be advanced remote
maintenance techniques, including the replacement of components using
remote pipe cutting and welding.
In addition, we a~tki-
Another large area of development would be the control sf