Chapter 4. Power From Fission 1.Introduction 2.Characteristics of Fission 3. General Features 4....
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Chapter 4. Power From Fission 1. Introduction 2. Characteristics of Fission 3. General Features 4. Commercial Reactors 5. Nuclear Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel, neutron moderator, control rod, neutron detector and radioactivity detectors, products
Chapter 4. Power From Fission 1.Introduction 2.Characteristics of Fission 3. General Features 4. Commercial Reactors 5. Nuclear Reactor Safety 6. Nuclear
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. General Features 4. Commercial Reactors 5. Nuclear
Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
Slide 2
Source: IEA (2007)
Slide 3
Slide 4
Slide 5
Delivery Construction times for nuclear plants Global average
66 months in mid-1970s 116 months (nearly 10y) in late 1990s 82
months (nearly 7y) during 2001-05
Slide 6
Energy Estimate the energy released by the fission of 1.0 kg of
235 U. (3.15e-11 J) 1000 g = 8.06e13 J (per kg). Discussion This is
a large amount of energy, and it is equivalent to the energy
produced by burning tones of coal or oil. 1 mol 235 g 6.023e23 1
mol 235 U 92 142 Nd 60 + 90 Zr 40 + 3 n + Q Q = (235.043924 -
141.907719 - 89.904703 - 3x1.008665) = 0.205503 amu ( 931.4812 MeV
/ 1 amu ) = 191.4 MeV per fission( 1.6022e-13 J / 1 MeV ) =
3.15e-11 J This amount of energy is equivalent to 2.210 10
kilowatt-hour, or 22 giga-watt- hour. This amount of energy keeps a
100-watt light bulb lit for 25,000 years. 2. Characteristics of
Fission
Slide 7
7 Fission Energy Budget Kinetic energy of fission fragments
Prompt (< 10 6 s) gamma ( ) ray energy Kinetic energy of fission
neutrons Gamma ( ) ray energy from fission products Beta ( ) decay
energy of fission products Energy as antineutrinos ( v e ) 168 MeV
7 5 7 8 12 Energy (MeV) distribution in fission reactions
Slide 8
Fission neutron energy spectrum
Slide 9
The total and fission cross section for 235 U based on
NJOY-processed ENDF/B (version V) data. Neutron interactions
Slide 10
The fast fission cross section for three fissionable uranium
isotopes based on NJOY processed ENDF/B (version V) data
Slide 11
The Cyclotron and Fission Research 7 Li (p, n) 7 Be 3 T (p, n)
3 He 1 H (t, n) 3 He 2 D (d, n) 3 He 2 D (t, n) 4 He 3 T (d, n) 4
He Fusion reactions studied using the cyclotron
Slide 12
12 The Cyclotron and Fission Research Threshold* Energy range
(keV) Reactionenergy(keV) narrow-energy neutron 51 V (p, n) 51
Cr2909 5.6-52 45 Sc (p, n) 45 Ti1564 2.36-786 57 Fe (p, n) 57
Co1648 2-1425 __________________________________ * The threshold
energy is the minimum energy of proton required for the reaction.
Neutrons of desirable energy is required for fission research.
Slide 13
Nuclear Fission13 The Cyclotron and Fission Research For
neutron sources from the cyclotron, energy can be varied. Energy
dependence of neutron induced fission studied. The cross section
data enabled nuclear reactor design. fast neutrons - 10 MeV to 10
KeV) slow neutrons - 0.03 to 0.001 eV for neutron induced
fission
Slide 14
Nuclear Fission 14 Fission Products nuclides produced in
nuclear fission Data on fission products are required for reactor
design, operation, and accident responses. The study of fission
products requires the separation, identification, and quantitative
determination of various elements and isotopes. Fission products
emit particles until they are stable, n also. Mass number range: 40
- 170 Elements range: all the elements in the 4 th, 5 th, and 6 th
periods. including the lanthanides. 2. Characteristics of
Fission
Slide 15
Nuclear Fission 15 Fission Products Fission yield is the
relative amounts of nuclides formed in fission reactions. The
fission yield curve shown here shows most fission reactions split
fission atoms into two unequal fragments.
Slide 16
Nuclear Fission Products Fission-product and their decay data
are needed for social and environmental concerns, and for the
management of used fuel. Fission nuclides usually have very short
half lives. Typical medium-life fission products: 85 K 10.7 y, 90
Sr 29 y, 137 Cs 30 y, Typical long-life fission products: 126 Sn
1.0e5 y, 126 Tc 2.1e5 y, 91 Tc 1.9e6 y, 135 Cs 3.0e6 y, 107 Pd
6.5e6 y, and 129 Tc 1.6e7 y. Xenon poisoning: 115 Xe, c = 2,640,000
b, and t 1/2 = 9.2 h
Slide 17
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. General Features 4. Commercial Reactors 5. Nuclear
Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
Slide 18
Simplified schematic layout of a typical reactor power plant.
3.1 A nuclear power plant
Slide 19
Control rods, containing neutron-absorbing elements (boron or
cadmium) pressure vessels must be capable of withstanding internal
pressures up to 160 bar. A biological shield, normally several feet
of concrete, surrounds the entire system. Its purpose is to
attenuate the intensity and neutron radiations to levels that are
safe for humans outside the plant The coolant is pumped through the
core inside the pressure vessel and through heat exchangers
outside, where steam is generated and used to drive turbines for
generating electric power. The melting point of uranium is 1403 K,
The melting point of UO 2 is 3138 K
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fastabso rp. 3.2 The neutron cycle
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subcritical supercritical self-sustainingcritical
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3.3 Moderator Properties of materials used as moderators
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3.4 Optimizing the design f is a decreasing function and p an
increasing function of moderator-to-fuel ratio N M / N F Uranium ~
graphite assemblies
Slide 24
Diffusion length the root-mean-square distance a neutron will
diffuse in the medium before being absorbed Diffusion and
slowing-down constants for moderators.
Slide 25
R, The reaction probability per unit time for N nuclei; M is
the mass of fissile material if each fission liberates an amount E
of recoverable energy, the power output is Reactor power and fuel
consumption
Slide 26
example calculate the power output, rating and fuel consumption
for a thermal reactor containing 150 tonnes of natural uranium
operating with a neutron flux of energy per fission E = 200
MeV
Slide 27
Fuel consumption, leading to a loss of 235 U, depends on the
total 235 U absorption cross section = 5.9 x 10 26 /year one-fifth
of the initial amount of 235 U refueling
Slide 28
5.2 Reactor Kinetics A Simple Reactor Kinetics Model Consider a
core in which the neutron cycle takes l' seconds to complete The
change n in the total number of thermal neutrons in one cycle at
time t or
Slide 29
=1.001 Uncontrollable !
Slide 30
Revised Simplified Reactor Kinetics Models Consider a thermal
reactor fueled with 235 U The average or effective generation time
required for all the neutrons produced in a single neutron cycle is
thus Delayed neutron average lifetime is A fraction of the fission
neutrons requires a cycle time of while a fraction (1 -) is the
prompt-neutron fraction and requires a cycle time of only =0.083
s
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-> 0.083 s controllable !
Slide 32
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. General Features 4. Commercial Reactors 5. Nuclear
Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
Slide 33
Key Reactor Power Terms Availability Fraction of time over a
reporting period that the plant is operational If a reactor is down
for maintenance 1 week and refueling ( 2 weeks every year, the
availability factor of the reactor would be (365-3 * 7) / 365 =
0.94
Slide 34
Key Reactor Power Terms Capacity Fraction of total electric
power that could be produced If reactor with a maximum thermal
power rating of 1000 MWt only operates at 900 MWt, the capacity
factor would be 0.90 Efficiency Electrical energy output per
thermal energy output of the reactor Eff=W/Q R (MWe/MWt) ~33%
Carnot efficiency,
Slide 35
4. Commercial Reactors Piecing Together a Reactor 1. Fuel 2.
Moderator 3. Control Rods 4. Coolant 5. Steam Generator 6.
Turbine/Generator 7. Pumps 8. Heat Exchanger Simplified schematic
layout of a typical reactor power plant
Slide 36
Basic Diagram of a PWR (Pressurized Water Reactor)
http://www.nrc.gov/ two water loops: The water in the primary loop
is pumped through the reactor to remove the thermal energy. The
loop 2, water is converted to high temperature and high pressure
steam that turns the turbo-generator unit.
Slide 37
The great disadvantage of water as a coolant: must remain in
liquid form, steam is a much poorer coolant than liquid water. must
be pressurized to prevent boiling at high temperatures (15.5 MPa).
For water, the critical temperature is 375 C, above which liquid
water cannot exist. Typically, coolant temperatures are limited to
about 340 C.
Slide 38
The steam cycle of a pressurized water reactor. [Westinghouse
Electric Corp.
Slide 39
It is about 13 meters tall with a diameter of about 4 to 6 m.
The vessel is built from low-alloy carbon steel and has a wall
thickness of about 23 cm The primary coolant enters the vessel
through two or more inlet nozzles, flows downward between the
vessel and core barrel
Slide 40
Parameters for a typical 1000 MW(e) PWR sold in the early
1970s.
Slide 41
Boiling-water reactor a pressurized-water reactora
direct-cycle, boiling-water reactor water is allowed to boil
self-stabilizing behaviour
Slide 42
Breeder Reactor The uranium cycle breeder reactors require fast
neutrons. Liquid metal and steam may be used as coolants for fast
breeding
Slide 43
CANDU reactor
Slide 44
Reactor Generations Gen I Prototypes in 50s & 60s Gen II
70s & 80s Todays Operational Reactors BWR, PWR, CANDU, Gen III
ABWR, APWR Approved 90s Some Built around the World Gen III+
Current Advanced Designs in the Approval Process Pebble Bed Reactor
Gen IV Deploy in 2030 Economical Safe Minimize Waste Reduce
Proliferation
Slide 45
World Nuclear Power 443 Nuclear Reactors in 30 Countries in
Operation, January 2006 Provided ~16% World Production of Energy in
2003 24 Nuclear Power Plants under Construction
http://www.insc.anl.gov
Slide 46
Alternatives Renewable energy Wind Bioenergy Solar Hydro Wave
Tidal Geothermal Energy efficiency Combined heat & power (CHP)
Building insulation Efficient lighting Efficient appliances
Efficient vehicles Controlling demand Behaviour change Carbon
capture and storage burial of carbon from fossil fuels
Slide 47
Source: IEA (2001)
Slide 48
Alternatives Renewable energy Wind Bioenergy Solar Hydro Wave
Tidal Geothermal Energy efficiency Combined heat & power (CHP)
Building insulation Efficient lighting Efficient appliances
Efficient vehicles Controlling demand Behaviour change Carbon
capture and storage burial of carbon from fossil fuels
Slide 49
Slide 50
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. General features 4. Commercial Reactors 5. Nuclear
Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
Slide 51
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What is the Public Hazard? chemical? biological? physical?
radiological? psychological? Chlorine for water treatment None
Nuclear explosion impossible Small risk of delayed effects, very
small risk of prompt Chernobyl, Fukushima, nuclear tests
Slide 54
What Is the Goal of Reactor Safety? To prevent prompt effects
with a high degree of assurance and minimize the risk of delayed
effects Typically frequency of a large release < 10 -6 per
reactor-year frequency of a core melt (intact containment) < 10
-5 per year
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Careful, cautious, scrupulous!
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8. Nuclear Reactor Accidents
Slide 63
Safety Public remains wary of nuclear power due to Chernobyl
and three mile island accidents Nuclear plants vulnerable to
terrorist attacks Safer, more efficient, and more secure plants
planned for the future
Slide 64
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. The Chain Reaction in a Thermal Fission 4. The Finite
Reactor 5. Reactor Operation 6. Commercial Reactors 7. Nuclear
Reactor Safety 8. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
Slide 65
Three Mile Isle
Slide 66
March 28, 1979, 4:00 am Secondary cooling loop stops pumping.
Rising temperatures caused emergency valve to open to release
pressure, but indicator light malfunctioned Due to loss of steam,
water level drops, water overheats and burns out pump Reactor core
overheats and begins to melt (a meltdown)
Slide 67
March 28, 1979, 6:30 am Overheated water contains 350 times
normal level of melted down radioactive matter A worker sees the
open valve and closes it To prevent an explosion, he reopens it,
releasing radioactive steam into the atmosphere
Slide 68
March 28, 1979, 8:00 am Nuclear Regulatory commission is
notified White House is notified TMI is evacuated All small
children and pregnant women within a five mile radius are evacuated
A fifteen-year clean up project awaits
Slide 69
No Nukes Words: Pat DeCou, Music: Tex LaMountain, 1977, ASCAP
Look across the sky from your home, Can you see the tower blinking
while you sit a spell at home? Can you see the branches growing?
Can you feel the awesome power? Can you sense its evil purpose and
its doom? It grows in ways we all can understand, And its limbs are
spreading all across the land. The leaves they look like dollars
and the sap it aint so sweet. It rests upon the profits hungry
people cannot eat. With promises of quiet, comfort, and peace, The
hanging tree can lure to its side. But the darkness of its shadow
gives us warning of the greed That tries to sell us more electric
power than we need. No nukes for me, cause I want my air to be Free
from radiation poison falling over me. These reactors that theyre
building are a giant hanging tree. Dont you build a hanging tree
over me. People soon will stop this money tree, And well stop its
hangin people, you and me. And as we struggle all together all the
powers that be will go down with their own hanging tree. And out of
this struggle we can plant a seedling tree, A tree that lets the
sunlight share its space. A tree in tune with living, whose
branches lift the soul, When youre watching from a distance and
youre sitting all alone.
Slide 70
Uranium Mining There are three main methods: Underground mining
Open pit mining In Situ Leaching (ISL)
Slide 71
Underground Mining The Case of the Olympic Dam Mine
Slide 72
Olympic Dam mine is located in South Australia Most of the
mines profit actually comes from the copper that they mine as well
Tunnels are dug into the earth, where ore is extracted The ore is
crushed into a powder, then soaked in a lake. The impurities
precipitate and the rest is dried by heat.
Slide 73
Ya Got Trouble. Lake uses an intense amount of water Rabbit
popluation has crashed as a result of drinking from the lake The
Western Mining Corporation (WMC) is owned by BP
Slide 74
In Situ Leaching ( Wells are drilled into aquifers , the water
is removed, and a solvent, such as hydrogen peroxide , is pumped in
The peroxide dissolves the uranium, and the solution is pumped back
up An ion exchange system causes the uranium to precipitate in the
form of UO 4 2H 2 O (uranium peroxide)
Slide 75
In Situ Leaching
Slide 76
ISL has its woes Ground water supply has radioactive residues
There are ISL mines in Texas, Wyoming, and Nebraska that share the
same aquifers as residents
Slide 77
Chapter 4. Power From Fission 1.Introduction 2.Characteristics
of Fission 3. General Features 4. Commercial Reactors 5. Nuclear
Reactor Safety 6. Nuclear Reactor Accidents Key elements: fuel,
neutron moderator, control rod, neutron detector and radioactivity
detectors, products
