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

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made in the primary circuit to remove and return fuel salt without opening
the primary containment and to add fuel-salt c ~ n s t i t u as ~ ~ required t ~ to
maintain the chemical condition o f the salt,
The secondary, ar coolant-salt, circuits for the DMSR w~uld be iden-
tical to those developed for the reference-design MSBR. The nominal flow
rate of the secondary salt (a eutectic mixture of NaBF4 and NaF) would be
about 1.26 m3/s (20,000 gpm> in each of the four loops, with a temperature
rise from 454 to 621°C in the primary heat exchangers. This salt would be
used t o generate supercritical steam at about 540°C and 25 MPa to drive
the turbine-generator system. *
In addition to its primary functi~ns of isolating the highly radis-
active primary circuit from the steam system and serving as an inteme-
diate heat-transfer fluid, the socliuw flusroborate salt mix-eure t a~~ld
play a major role in limiting the release of tritium from the DNSR sys-
tem. Engineering-scale tests in 2-9-16 (Ref. 10) demonstrated that this
salt is capable of trapping large quantities of tritium and transforming
it to a less mobile, but still volatile, chemical form that transfers to
the cover-gas system rather than diffusing through the steam generators
to the water system.
Consequently, the majority of the tritium (-80%)
wsuEd be trapped or condensed out of the secondary circuit cover gas, and
less than 0.2% of the total be releasea.
2.3 Balance-of-Plant
The balance-of-plant for a DNSR primarily would be identical to that
for an MSBR. Because the same salts and basic parameter values are Pn-
volved, there would be no basis for changing the normal auxiliary systems
required for m~mnz~l plant operation. Differences, however, could appear
in same of the safety systems. Because of the l~wer power density in the
ha he supercritical steam cycle appears to be particularly well suited
to this concept because of the relatively high melting temperature (385'6)
of the secondary salt and the desire to avoid salt freezing in the steam
generators.