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

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cooled drain tank. The system primary containment, which is defined as
the set sf hermetically sealed concrete-shielded equipment cells, would
probably not be threatened by such a spill, but cleanup operations would
be d5fficult e
A unique safety feature of the DMSR is that, under accident shutdown
conditions, the fuel material would be led to the emergency core cooling
system gECCS> (represented by drain tank cooling) rather than vice versa.
The reactor and containment must be designed SO that the decay-heated fuel
salt reaches the drain tamk under any credible accident conditions. In
any case, the decay heat is associated with a very large mass of fuel salt
so that melt-through (or “China Syndrome”) is apparently not a problem.
The safety philosophy for accidents involving the reactor core is
very different for fluid-fueled than for solid-fueled react~rs because
the heat source is mainly in the liquid-fuel salt and not in a solid,
which requires csntinuous cooling to avoid melting. An LMFBR, for exam-
ple, has a large amount of stored energy (which must be removed under
any accident conditions) in the fuel pins. DPy~ut, which means immediate
meltdown in an LMFBR, would not be nearly as severe in the DMSR because
the heat source is removed along dth the cooling capability. First-order
analysis has shsm that a flow blockage of a central coolant channel of
the reference DKSR which reduces the flow to less than -20% of nominal
will probably result in local voiding of that channel. This was not true
of the old MSBR design8 because the channels were more strongly themally
coupled. Whether the safety implications of this will lead to modifica-
tions of the DMSR reference design must be shorn by future safety analy-
sis studies. Under any off-nsmal conditions, the fuel salt will be chan-
neled to the drain tank, which must have reliable systems for decay heat
removal. No credible means exists for achieving recrfticality once the
fuel salt has left the graphite-moaeratea cores
There are no significant differences in the enviromental effects of
routine operations between an MSl? and reactors presently in commercial
operation. No gaseous or liquid radioactive effluent discharge occurs