The document discusses different types of breeder reactors, including liquid-metal cooled fast breeder reactors (LMFBRs), gas-cooled fast breeder reactors, molten salt breeder reactors, and light water breeder reactors. It provides details on the design and operation of each type of breeder reactor.
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3. Breeder reactor
The reactors which are designed so that
breeding will take place is known as breeder
reactor.
Breeder reactors are capable of producing more
fissile material than they consume during the
fission chain reaction (by converting fertile U-238
to Pu-239, or Th-232 to U-233). Thus, a uranium
breeder reactor, once running, can be re-fueled
with natural or even depleted uranium, and a
thorium breeder reactor can be re-fueled with
thorium; however, an initial stock of fissile
material is required.
4. Types of breeder reactors:
Liquid-metal cooled fast breeder-
reactor (LMFBR)
Gas-cooled fast breeder-reactor
(GCFR)
Molten Salt Breeder reactor
Light Water Breeder Reactor
5. Liquid-metal cooled
fast breeder reactor
The first experimental breeder
reactor was a small plutonium-
fueled, mercury-cooled device,
operating at a power level of 25 kW,
cooled with a mixture of sodium and
potassium, was placed in operation
in 1 95 1 at the Argonne National
Laboratory in Idaho.
6. This reactor, the Experimental Breeder
Reactor-I (EBR-I), produced steam in a
secondary loop that drove a turbine
generator. The system produced 200 kW
of electricity, the world's first nuclear-
generated electricity-and it came from
LMFBR . Since these early experiments,
dozens of LMFBRs have been
constructed around the world.
7. Sodium has been universally chosen as
the coolant for the modern LMFBR.
With an atomic weight of 23, sodium does
not appreciably slow down neutrons by
elastic scattering, although, it does
moderate neutrons to some extent by
inelastic scattering. Sodium is also an
excellent heat transfer agent, so that an
LMFBR can be operated at high power
density.
8. Its melting point, 980oC is much higher
than room temperature, so the entire
coolant system must be kept heated at all
times to prevent the sodium from
solidifying. This is accomplished by
winding a spiral of insulated heating wire
called tracing along coolant piping, valves,
and so forth.
9. Unfortunately, sodium absorbs neutrons,
even fast neutrons, leading to the
formation of the beta-gamma emitter
24Na, with a half-life of 15 hours.
Therefore, sodium that passes through
the reactor core becomes radioactive.
LMFBR plants operate on the steam
cycle-that is, the heat from the reactor is
ultimately utilized to produce steam in
steam generators.
10. Gas cooled fast breeder-
reactor .
It is a helium-cooled reactor fueled with a
mixture of plutonium and uranium.
The core of the GCFR is similar to that of an
LMFBR, with mixed PUO2 and UO2 pellets in
stainless steel pins, except that the pins are
not as close together as they are in the
LMFBR. Also, the pins in the GCFR have a
roughened outer surface to enhance heat
transfer to the passing coolant.
11. Molten salt breeder-
reactor (MSBR)
This is a thermal breeder that operates on the
233 U-thorium cycle. It is recalled that 233U is
the only fissile isotope capable of breeding in a
thermal reactor.
The MSBR concept is a unique design among
reactors in that the fuel, fertile material, and
coolant are mixed together in one
homogeneous fluid. This is composed of
various fluoride salts that, at an elevated
temperature, melt to become a clear,
nonviscous fluid.
12. Advantages of MSBR:
Because of the low vapor pressure of the
molten salts, the MSBR operates at just a
little above atmospheric pressure and
thus no expensive pressure vessel i s
required.
High temperatures are possible with the
molten salts, the MSBR can produce
superheated steam at 24 MPa and
540 C, which leads to a very high overall
plant efficiency of about 44% .
13. Light water breeder
reactor
Even when a special effort is made in the design of
the LWBR to reduce neutron losses, its overall
breeding gain will be very small-too small to make
the reactor a net producer of 233U for other
reactors of this type.
To see whether breeding can actually be achieved
in a light-water reactor,the U.S. Department of
Energy developed an LWB R core that was installed
in the government-owned pressurized water reactor
at Shippingport, Pennsylvania.