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

12
2. The radial reflector is graphite 0.8 m thick and is attached to
the reactor vessel at the 18-m diam. This leaves a gap of 0.05 m filled
with fuel salt surrounding the core laterally.
3. The inlet and outlet plena cover both the core and radial gap to
their full diameter and are each 0.28 m thick. They consist of 50% struc-
tural graphite and 50X fuel.
1Q-m diam.
4. The axial reflectors are each 0.65 m thick and extend to the full
5. All reflector regions contain a small amount of fuel salt for
cooling, which is estimated as 1 vol X at operating temperature.
6. All stated dimensions are assumed to apply at nominal operating
conditions. During system heatup, the length and diameter of the core
vessel are assumed to increase at the rate of expansion of Hastelhy-N.
The reflectors are assumed to expand at the expansion rate of graphite
but to remain attached to the vessel. Because graphite expansion is less
than that of the vessel, this will result in admatting additional salt to
the reflector zones. The core and plenum regions are assumed to expand
radially only at the expansion rate of graphite, which will establish the
thickness sf the radial gap. The axial configuration is affected by the
logs floating upward in the salt and by the lower plenum being constructed
so that it always contains 58% salt. The thicknesses of the core and the
upper plenum, then, increase at the graphite expansion rate, but the lower
plenum grows at such a rate as to span the gap between the core and the
bottom reflector.
Mechanical properties used for the principal constituents are sum-
marized in Table 1. The salt is taken to have the nominal chemical corn-
position shown in Table 2. The tern "actinides'o in this study refers to
all elements of atomic numbers -
> 90 and not just to transplutonium ele-
merits. The actinide percentage is subject to small variations depending
on the fuel cycle and the history of the fuel.
The inventory of- fuel salt, both in and out of the core, is summa-
rized in Table 3. This is believed to be a generous estimate sf the re-
quired inventory for a I-GWe system. The thermal energy yield per fission
is assumed to be 190 MeV for translation of abss%ute fission rates to ef-
fective power level.