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

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particularly if such activities were undertaken after an RCPB failure.
However, in a shutdown situation, substantial confinement can be achieved
through access limitation and controlled ventilation because, as shown
by MSRE experience, fission products are not readily released and dis-
persed from stagnant salt. Thus, whether fission-product confinement
would be a net favorable or unfavorable factor for a BMSR in a licensing
proceeding is not clear at this time.
At the end of reactor life, a DMSR without fuel processing would
contain the entire fissio~-pr~duct inventory associated with the 30-year
operating history of the plant. Some of the volatile nuclides, especially
85Kr and 3H, would have been accumulated in storage containers outside the
primary circuit, and the noble metals would have plated out on surfaces in
the primary circuit. The inventories of these nuclides, which would not
be strongly affected by nuclear burnup, would be about the same as those
produced in a solid-fuel reactor wPth the same thermal power level and
duty factor. However, because the BMSR would generate only about two-
thirds as much thermal power as an EWR for the same electrical output,
it would produce a ~o~~espondingly smaller inventory of fission products.
Most of the other fission products and all the transuranium nucltcles
wou%dl remain with the fuel salt in a DMSR. The inventories of these mate-
rials would be further reduced by nuclear burnup resulting from exposure
of the nuclides to the neutron flux in the reactor core. This effect
would be particularly important for the high-cross-section nucPides such
as the major plutonium isotopes. Consequently, the net production of plu-
tonium would be much smaller for a DMSR than for a comparable solid-fuel
reactor, but the production of higher actinides would be much greater be-
cause of the long effective fuel exposure time.
Although a DMSW WQUI~ produce a much smaller total inventory of some
important nuclides over its lifetime than an LWR, the actual in-plant in-
ventory could be substantially higher for the DMSR because there would be
no periodic removal during refueling operations. (There would also be no
major shipments of highly radioactive spent fuel from the plant during
its lifetime arid no out-of-reactor storage of suck materials until after
the final shutdown.) Thus, if a major release of in-p%ant radionuclides
could occur, the consequence might be more serious in a DMSR than in an