ORNL-4191 - the Molten Salt Energy Technologies Web Site

Toblc 5.2. Reactor Specifications
Average core power density, kw/liter
Power, Mw
Number required for 1000 Mw (electrical)
Vessel diameter, ft
Vctssel height, Et
Core diameter, ft
Core height, ft
Core volume, it'
Fraction of fuel in core
Fraction of blanket in core
Fraction of graphite in core
Blanket thickness, ft
Fraction of salt in blanket
Breeding ratio
Fuel yield, %/year
Fuel cycle cost, inills/kwhr
Fissile inventory, kg
Fertile inventory, kg
Specific power, Mur (thermal)/kg
Nurrrber of core elements
Velocity of fuel in core, fps
Average flux >@.82 Mev
Fuel volume, ft'
React or cure
Plenums
Entrance nipples
Heat exchangers and piping
Processing
Total
Peaklaverage flux ratio
20
556
4
14
22
10
13.2
1040
0.134
0. of34
0.802
1.25
0.58
1.06
4.1
0.52
314
54,000
1.8
420
4.8
3.33 1013
139
37
13
160
6
355
'"2
to the inside of the cylindrical graphite extrusion
and returns to the bottom of the reactor and the
outlet plenum. The average velocity of the fuel
in the core is about 4.8 fps as it is heated Erom
lOOOOF to 1300°F. The effective height of the
core is approximately 13 ft, and the total length
of the two-pass flow channel, plenum to plenum,
is about 27 ft.
'The hexagonal graphite pieces have a cylindrical
portion about 12 in. long turned at the bottom to
which a Hastelloy N nipple, 1% in. OD by 1/16 in.
in wall thickness, is brazed. The other ends of
these nipples are welded to discharge openings
in the upper plate of the inlet fuel plenum. Inner
Hastelloy N nipples, 12 in. OD by t6 in. in wall
thickness, are welded to the outlet plenum tube
sheet and have an enlarged upper end which fits
75
snugly, but is not brazed, into the inner 1 %-in.-ID
hole in the inner graphite cylinder of the fuel element.
The lower end of the core assembly is thus
fixed in place by attachment to the plenums, but
the upper end is free to expand or contract in the
vertical direction.
The graphite fuel pieces extend 15 in. above the
end of the fuel flow passages in order to serve as
the top axial reflector for the core. The top 3 in.
of each fuel element is turned to a smaller diameter
to establish a shoulder, as shown in Fig.
5.10. Triangular stampings of Hastelloy N sheet
are slipped down to this shoulder and engage
three of the elements, as shown in Fig. 5.8. These
stampings are interleaved to maintain the radial
spacing of the fuel channels, yet eliminate the
need for a large-diameter upper diaphragm drilled
to close tolerances. The center six fuel channels
engage a ring which is attached through six ribs
to the vessel itself, thus stabilizing the entire
ass emb ly .
Immediately outside the cure region of the reactor
are graphite tubes around and through which the
fertile salt of the radial blanket is circulated.
These tubes displace the more expensive fertile
salt and also, by scattering the neutrons, promote
more effective capture by the thorium atoms in the
blanket. The ratio of fertile fraction to graphite
is about 58% in this region, as determined by the
code used for optimization of the reactor design.
The graphite tubes are slipped over short nipples
extending from a mounting plate at the bottom of
the reactor, as shown in Fig. 5.9. The tubes are
radially positioned at the top by overlapping connectors
in much the same manner as the fuel elements.
Solid cylinders of graphite, 5 in. in diameter,
are arranged on the outer circumference of the reactor
to serve as a reflector. A can of ?4-in, wall
thickness surrounds the reflector graphite and
serves to direct the entering fertile salt down the
inside wall of the vessel and to the bottom oE the
core. The fertile salt stream then divides; part
of it moves upward through the interstices between
the fuel elements, while the major portion flows
through the graphite tubes in the blanket region.
It may be noted that the fuel channels themselves
provide sufficient graphite for moderation
of the reactor and for the lop reflector without use
of any special shapes or pieces, ;is was required
in earlier MSHR concepts. All the graphite consists
of extrusions which require little in the way