ORNL-4191 - the Molten Salt Energy Technologies Web Site
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ORNL-4191 - the Molten Salt Energy Technologies Web Site

ORNL-4191 - the Molten Salt Energy Technologies Web Site ORNL-4191 - the Molten Salt Energy Technologies Web Site

moltensalt.org
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05.08.2013 Views

I 43ft 3in REACTOR ’ t 40in. ! 3in. MIN 5 375 in 1 1 2 2 3 1 ~ ~ t in ID \ \ , ! c t 74 Fig. 5.10. Fuel Cell Element. I I ORNL-DWG 67-10646A i -, SIX1/2-x14/2-in SLOTS 4 33/41n. i DlAM GRAPHITE TO METAL BRAZE 47/,in ODx13/4(n ID 1‘14 in. 0 D x 1 ‘/e in. I D FUEL INLET PLENUM FUEL OUT1 E T PLENUM

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

I<br />

43ft 3in<br />

REACTOR ’<br />

t<br />

40in.<br />

!<br />

3in. MIN<br />

5 375 in<br />

1<br />

1<br />

2 2 3 1 ~ ~<br />

t<br />

in ID \ \ , !<br />

c<br />

t<br />

74<br />

Fig. 5.10. Fuel Cell Element.<br />

I<br />

I<br />

<strong>ORNL</strong>-DWG 67-10646A<br />

i<br />

-, SIX1/2-x14/2-in SLOTS<br />

4 33/41n.<br />

i<br />

DlAM<br />

GRAPHITE TO<br />

METAL BRAZE<br />

47/,in ODx13/4(n ID<br />

1‘14 in. 0 D x 1 ‘/e in. I D<br />

FUEL INLET PLENUM<br />

FUEL OUT1 E T PLENUM

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