Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
Field of the Invention
-
This invention relates to steam generators and more
particularly to steam generators utilized with liquid metal
fast breeder reactors.
Descrlption of the Prior Art
The demand for electrical power in the United
States approximately doubles every ten years. Presently,
fossil fuel provides the ma~ority of the heat energy
necessary for produclng electrical power~ However, it is
estimated that in the next thirty years over 50% of our elec-
trical power will be produced by nuclear energy~ The supply
of fissionable material is limited so that the ~uture of
nuclear power generation depends on developing fast breeder
reactors, which produce more fissionable material than they
consume. Such a system, because of the high heat density
in the core of the reactor vessel requires the use of a
primary coolant fluid, such as liquid sodium or some other
liquid metal to remove the heat. The liquid metal becomes
slightly radioactive and because liquid metals react
violently with water or steam, an intermediate liquid metal
~,
s --1--
~038366
transfer loop is utilized to preclude the possibility of
reacting the radioactive liquid metal with water or steam.
The intermediate liquid metal takes heat from liquid metal
utilized to cool the reactor core and transfer this heat to
water and/or steam in a steam generator~ thus utilizing an
intermediate heat exchanger, re~uires additional liquid
metal circulating pumps and all the ass~ciated controls for
the intermediate liquid metal system, thereby, increasing the
cost of the liquid metal fast breeder reactor system~
10SUMMARY OF THE INVENTI~N
Among the ob~ects of thls invention is the pro-
vision of a heat exchanger, which can safely transfer heat
: from a slightly radioactive liquid metal to water and/or
steam and have the possibility of a reaction between the
liquid metal and water and/or steam so remote so as not to
compromise the safety of the operators or of the community in
which the nu¢lear power unit is located~
In general, a heat exchanger which utilizes a
primary fluid to heat a secondary fluid~ when made in
accordance with this invention, comprises a plurality of
tubes through which the primary fluid flows, a plurality of
tubes through which the secondary fluid flows, a vessel en-
closing the tubes, particulate material partially filling the
vessel, a device for fluidizing the particulate material to
form a fluidized bed within the vessel and means for pro-
ducing circulation of the particulate material within the
fluidized bed, whereby a portion of the heat in the primary
fluid is transferred to the particulate material and from
the particulate material to the secondary fluid~
10;~8~66
BRIEF DESCRIPTION OF THE DRAWINGS
The ob~ects and advantages of this invention will
become more apparent from reading the following detailed
description in connection with the accompanying drawings, in
which:
Fig. 1 is a sectional view of heat exchanger made
in accordance wlth this invention;
Fig. 2 is a sectional view taken on line II-II of
Fig. l;
Fig. 3 is a sectional view of an alternate heat
exchanger made in accordance with this invention;
Fig. 4 is a sectional view of another alternate
heat exchanger made in accordance with this invention;
Fig~ 5 is a sectional view of an alternate heat
exchanger utilizing separate vessels for each tube bundle;
and
Fig. 6 is a schematic diagram of a plurality of
fluidized bed heat exchangers arranged to form a steam
generator.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings in detail and
particularly to Fig 1, there is shown a heat exchanger,
a steam generator, or a vapor generator 1~ which utilizes
the heat in a primary fluid, such as sodium or other liquid
metal, to heat, boil or evaporate, and/or superheat a second-
ary fluid, such as water and/or steam~
The heat exchanger 1 comprises a plurality of tubes
3, grouped to form a tube bundle through which the primary
fluid flow and a plurality of secondary tubes 5, grouped to
form a tube bundle through which a secondary fluid flows.
-3-
~0 ~ 36U6
The tube bundles made up of the tubes 3 and 5 are
juxtaposed in a vessel or shell 7 and have disposed there-
between separating means, such as plates, baffles, bars
or a space separation. The separating means 9 are gen-
erally transversely disposed with respect to the tubes to
prevent a broken or ruptured tube from entering the other
tube bundle where it may cause a tube in the other tube
bundle to fail, thus causing a violent reaction between the
liquid metal and water and/or steam. A distribution plate
11 is disposed in the lower portion of the vessel 7 and has
a plurality of apertures 13 disposed therein.
Smooth spheres or irregular shaped particles of
particulate material ranging in size from 50 to 1,000 microns
in diameter partially fill the vessel 7 occupying the major
portion of the space between the distributor plate 11 and a
level maintained ~ome distance above the tube bundle.
Fluidizing gas such as helium or other suitable
gas is supplied to the vessel 7 below the distribution plate
11 at a velocity Or 0.2 to approximately 2.0 feet per second
and at a pressure ranging from atmospheric to slightly less
than the pressure of the sodium in the primary tubes 3. The
arrangement, distribution or allotment of the apertures 13 in
portions of the distribution plate 11 cooperates with the
separating means 9 and/or baffles 15 shown in Fig. 2, to cause
the fluidization and circulation of particulate material
within the vessel 7.
Fig. 3 shows an alternate arrangement wherein one
tube bundle is disposed above the other and bars 9 are
utilized as a separating means to prevent a rupture tube
from entering the adjacent tube bundle.
Still another alternate arrangement is shown in
~103~366
Fig. 4. In this arrangement, the tube bundles are formed
from U-shaped tubes and the bundle containing the primary
fluid is inserted inside the bundle containing the second-
ary fluid. Separating means are again bars disposed between
the tube bundles. Headers 17 for the tube bundles are dis-
posed above the fluldized bed and the distributlon plate 11
ls disposed below the largest diameter bend~
As shown in Flg. 5 the tube bundles 3 and 5 can be
disposed in separate vessels 7a and 7b. Such an arrangement
utilizes ducts 19 or other means for circulating particulate
material between the fluidized bed maintalned in each vessel~
- A system utllizing a plurallty of fluidized bed
heat exchangers to perform the function of preheating,
evaporating and superheating is shown in Fig~ 6
Liquid metal flows in series through the primary
tube bundle 3 in the various fluidized bed and in counter-
flow relation to the water and/or steam flowing in the
secondary tube bundle 5 ~uxtaposed wlth the primary tube
bundles 3 in the fluidized bed.
Fluidizing air is ~upplied to each fluid~zed bed
from a common duct 21 and a cyclone separator 23 removes
particulate material from the effluent gases and an analyzer
25 is cooperatively associated with the separators 23 to
detect water, liquld metal or both within the effluent
gases. Leaving the cyclone separators 23 the effluent gases
flow through a filter 26 and a heat exchanger 27 which heats
the influent gas~ After being cooled in the heat exchanger
27 the effluent gases flow through a gas cooler 29, A pump
or blower 31 takes its suction from the gas cooler 29 and
returns the gases via the heat exchanger 27 to the fluidized
beds.
~038366
The heat exchangers or steam generators herein-
before described advantageously reduce the possibility of
an interaction between the liquid metal and the water and/or
steam as it facilitates rapidly detection of either primary
or secondary fluid and enables the system to be inspe.cted,
repaired or replaced rapidly and ec.onomically.
