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A Comparison of Mechanical Advantage and
Efficiency
Kyle Barefoot
Senior Seminar
Spring 2009
A Comparison of Mechanical Advantage and Efficiency
• The Basic Physics of Nuclear Physics
• Advanced Boiling Water Reactor
• S-Prism Reactor
• Comparing the ABWR and S-Prism Reactor
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EXAMPLE:
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• There must be
enough fissile
material inside the
fuel to maintain the
reaction
• When this is true
the fuel can be said
to have reached
critical mass; if not
enough fissionable
material is present
then it has subcritical
mass
Sample chain reaction of U235
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Important factors that influence power
• The effective nuclear multiplication factor, k, acts as a
signifier for the level of reactivity within the reactor
• k is defined as the average number of neutrons from one
fission that induce another fission
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CONTROL RODS AND ABSORBERS
• A control rod acts as a shield/absorber of
neutrons in the reactor and are capable of such
because of their chemical make-up
• Large capture cross-sections
• Do not fission
• Helps to control neutron flux
• Removed in order to induce chain reactions
• Typical material: Boron
• Boron alloys
Example of CR in a fuel
assembly
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CONTROL RODS AND
ABSORBERS
• Nuclear/Neutron poisons
• Neutron poisons act like control rods,
absorbing neutrons without actually
fissioning
• Poisons can also come from fission
products
•Example: 135Xe
• Removed rods still have about 95% of their
original fuel still available that can be used
after reprocessing
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• Reactors can use up to two loops of the same or different material in
order to transfer energy (MWth) to turbines that generate power (Mwe)
• Circulation is maintained by pumps that regulate the flow of material
either to the reactor or to the turbines
• Tandem Turbines allow more efficient conversion of power to
electricity by utilizing the steam generated by the reactor even after it
loses pressure
Advanced
Boiling
Water
Reactor
(Direct Cycle BWR)
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• The ABWR employs the
process of moderation to transfer
and transport energy from the
fuel to run the reactor
• BWRs are unique because they
contain both moderator (water)
and vapor inside the reactor
core
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MODERATION
• A Neutron Moderator acts as a medium for fast
neutrons to transfer energy in the process of
becoming thermal neutrons
• Most reactors use Light water (H2O) because it
has the ability to absorb a large amount of the
neutrons energy through collision
•Mean logarithmic reduction of neutron energy per
collision
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Moderator
• The amount/level
of moderator in the
core is regulated by
RIPs
• Regulation is
needed in order to
control the void
coefficient between
fuel rods
Void Coefficient
• Can be used to estimate how the
reactivity will change as voids
(bubbles) are accumulated within
the reactor moderator
Fuel assembly Critical
Power is also a function
of…
• Max flux and
enthalpy at inlet
• Pressure at exit
•Axial and radial
power distribution
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Critical Mass
• Minimum mass of fissile material
• Constant power, temperature, and neutron
population in a reactor
• Effective neutron multiplication factor, k
• k -> average number of neutrons released in a
fission that produce another fission
• Nuclear reactors run with k=1
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Enriched Uranium
• Natural/mined Uranium only consists of ~ 0.7%
fissile
• ABWR requires a higher concentration of fissile
material (~5%)
• Enrichment process
•There are three popular methods to enrich
natural Uranium (yellowcake)
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• ABWRs typically use
stainless steel tubes
filled with boron
carbide (B2C) powder
compacted to
approximately 75% of
theoretical density
• The tubes are aligned
to form a cross along
the blades of a sheath
that extend the length
of the fuel rods
• bottom mounted
drive mechanisms
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Conceptually, 1 loop that
extends
from RPV to the turbines
A Modular Diversion Resistant Fast Reactor
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Introducing the S-Prism
• Utilizing the leftovers
• Maintaining a sustainable
reaction
• Control rods/Neutron Absorbers
• Energy transfer
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Recycled Fuel
• Composition of S-Prism fuel
is approximately
• 10% Zr
• 30% Transuranics
• the remaining is a
mixture of Uranium
isotopes of mass 235 and
238
•
is a very fertile isotope
• Transuranics have a higher
efficiency of fissioning in fast
reactors
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• S-Prism
is a burner reactor
(produces less fissionable
material than it uses, k<1)
• NO moderator
• Neutrons are reflected by
circulating sodium back into
the reactor fuel
• Produce another reaction
• Absorbed by transuranics or
uranium
• Minor actinides have a
much higher probability of
fissioning when interacting
with neutrons of higher
energy
FAST NEUTRON ~110keV 1MeV
THERMAL NEUTRON
~0.075MeV
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• Screw like design
• geometric power distribution
• Composed of Boron Carbide
• B4C
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Engineers chose sodium because it does not slow down fast neutrons substantially
and because it conducts heat very well,
(1)Nuclear fire heats liquid sodium
and transfers heat to
intermediate sodium
(2)Thermal energy/separate loop
of sodium
(3) Final heat exchanger/steam
generator
(4) Steam turbines/elec.
Producing generators
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Three main differences:
• Use of a moderator
• Reactions (Thermal/Fast Neutrons)
• Fuel
ABWR
S-Prism
• Light Water (H2O)
• No Moderator
• Water is relatively the
size of neutron particle
• Na molecules are
comparatively much
larger than neutrons
• Moderator level helps
control the neutron flux
• Sodium flow helps
control the neutron flux
• Thermal energy used to
directly change state of
moderator and carry
energy
• Sodium carries thermal
energy but does not
change state
ABWR
S-Prism
•Thermal neutrons induce
fission
• Fast neutrons induce fission
• Fission produces 1-3
neutrons on average
• Fission produces 2-3
neutrons on average
• Large absorption cross
section of Uranium
• transuranics/minor
actinides are far more likely
to fission
• Neutrons transfer a lot of
collision energy
• Energy comes mostly from
gamma radiation
ABWR
S-Prism
• Enriched Uranium
• Recycled waste of ABWR
• Utilizes ~ 5% of original fuel
(95% waste)
• Utilizes a majority of
original fuel (>90%)
• Fuel is manually replaced
• Fuel is cycled and replaced
by a mechanical arm inside
the core
• The combined usage of the ABWR and the
utilization of its wastes in the S-PRISM provide an
unmatched step in helping to close the nuclear fuel
cycle
• Currently, the presence of an S-Prism reactor would
be dependent on the availability of fuel that would
be produced by working ABWRs
• Both reactors have extreme safety measures that
limit the probability of a major problem to almost
nothing (~1 per 23 million years)
• S-Prism provides more efficient consumption
of fuel
• Waste
• ABWR has potential to provide more energy
per reactor
• S-Prism complexity is a detour to its usage
• Sodium, Fast Neutrons, Energy Transfer
• ABWR provides more cost efficient
availability
Aktas, Birol. BWR and ABWR experience. Wilmingon, September 2008.
GE Energy. ABWR General Description. General Description. Wilmington: GE, 2006.
—. Advanced Boiling Water Reactor. 1997-2009. Feburary 2009
<http://www.gepower.com/prod_serv/products/nuclear_energy/en/new_reactors/abwr.htm>.
—. S-Prism A Modular Diversion Resistant Fast Reactor. Compendium. Wilmington: GE, 2000.
NationMaster. Transuranic. 2005. April 2009 <http://www.statemaster.com/encyclopedia/Transuranic>.
Nave, R. Nuclear Binding Energy. 2005. Feburary 2009 <http://hyperphysics.phyastr.gsu.edu/hbase/nucene/nucbin.html#c5>.
Naves, R. Fast Breeder Reactors. 2005. Feburary 2009 <http://hyperphysics.phyastr.gsu.edu/hbase/NucEne/fasbre.html>.
Richard E. Barrans Jr., Ph.D. Transuranic Element Production. March
2009
<http://www.newton.dep.anl.gov/askasci/phy00/phy00094.htm>.
U.S. NRC. Uranium Enrichment. 20 September 2007. March 2009
<http://www.nrc.gov/materials/fuel-cycle-fac/urenrichment.html>.
Web Elements. Periodic Table of Elements. 2009. March 2009
<http://www.webelements.com/nmr.html>.
World Nuclear Association. The Nuclear Fuel Cycle. January 2009.
March 2009 <http://worldnuclear.org/info/default.aspx?id=428&terms=uranium>.
Y.I. Chang, P.J. Finck, and C. Grandy. Advanced Burner Test Reactor.
Preconceptual Design Report. Argonne: Argonne National Labratory,
2006.
• Dr. Liping Gan
University of North Carolina Wilmington
• Arielle Miller
Project Manager, GE Hitachi Energy