The Promise and Problems of Nuclear Energy II

1
The Promise and Problems of Nuclear Energy II
Lecture 13 HNRS 228 Energy and the Environment
2
Chapter 6 Summary Again

• History of Nuclear Energy
• Radioactivity
• Nuclear Reactors
• Boiling Water Reactor
• Fuel Cycle
• Uranium Resources
• Environmental and Safety Aspects of Nuclear
  Energy
• Chernobyl Disaster
• Nuclear Weapons
• Storage of High-Level Radioactive Waste
• Cost of Nuclear Power
• Nuclear Fusion as a Energy Source
• Controlled Thermonuclear Reactions
• A Fusion Reactor

3
Review of Fission

• 235U will undergo spontaneous fission if a
  neutron happens by, resulting in
• two sizable nuclear fragments flying out
• a few extra neutrons
• gamma rays from excited states of daughter nuclei
• energetic electrons from beta-decay of daughters
• The net result lots of banging around
• generates heat locally (kinetic energy of tiny
  particles)
• for every gram of 235U, get 65 billion Joules, or
  about 16 million Calories
• compare to gasoline at roughly 10 Calories per
  gram
• a tank of gas could be replaced by a 1-mm pellet
  of 235U!!

4
Enrichment

• Natural uranium is 99.27 238U, and only 0.72
  235U
• 238U is not fissile, and absorbs wandering
  neutrons
• In order for nuclear reaction to self-sustain,
  must enrich fraction of 235U to 35
• interestingly, it was so 3 billion years ago
• now probability of wandering neutron hitting 235U
  is sufficiently high to keep reaction crawling
  forward
• Enrichment is hard to do a huge technical
  roadblock to nuclear ambitions

5
iClicker Question

• Which is closest to the half-life of a neutron?
• A 5 minutes
• B 10 minutes
• C 15 minutes
• D 20 minutes
• E 30 minutes

6
iClicker Question

• Which is closest to the half-life of a neutron?
• A 5 minutes
• B 10 minutes
• C 15 minutes
• D 20 minutes
• E 30 minutes

7
iClicker Question

• What is the force that keeps the nucleus
  together?
• A weak force
• B strong force
• C electromagnetic force
• D gravitational force

8
iClicker Question

• What is the force that keeps the nucleus
  together?
• A weak force
• B strong force
• C electromagnetic force
• D gravitational force

9
iClicker Question

• A neutron decays. It has no electric charge. If a
  proton (positively charged) is left behind, what
  other particle must come out if the net charge is
  conserved?
• A No other particles are needed.
• B A negatively charged particle must emerge as
  well.
• C A positively charged particle must emerge as
  well.
• D Another charge will come out, but it could be
  either positively charged or negatively
  charged.
• E Neutrons cannot exist individually.

10
iClicker Question

• A neutron decays. It has no electric charge. If a
  proton (positively charged) is left behind, what
  other particle must come out if the net charge is
  conserved?
• A No other particles are needed.
• B A negatively charged particle must emerge as
  well.
• C A positively charged particle must emerge as
  well.
• D Another charge will come out, but it could be
  either positively charged or negatively
  charged.
• E Neutrons cannot exist individually.

11
iClicker Question

• How many neutrons in U-235?
• A 141
• B 142
• C 143
• D 144
• E 145

12
iClicker Question

• How many neutrons in U-235?
• A 141
• B 142
• C 143
• D 144
• E 145

13
iClicker Question

• How many neutrons in Pu-239?
• A 141
• B 142
• C 143
• D 144
• E 145

14
iClicker Question

• How many neutrons in Pu-239?
• A 141
• B 142
• C 143
• D 144
• E 145

15
iClicker Question

• If a substance has a half-life of 30 years, how
  much will be left after 90 years?
• A one-half
• B one-third
• C one-fourth
• D one-sixth
• E one-eighth

16
iClicker Question

• If a substance has a half-life of 30 years, how
  much will be left after 90 years?
• A one-half
• B one-third
• C one-fourth
• D one-sixth
• E one-eighth

17
iClicker Question

• If one of the neutrons in carbon-14 (carbon has 6
  protons) decays into a proton, what nucleus is
  left?
• A carbon-13, with 6 protons, 7 neutrons
• B carbon-14, with 7 protons, 7 neutrons
• C boron-14, with 5 protons, 9 neutrons
• D nitrogen-14, with 7 protons, 7 neutrons
• E nitrogen-15, with 7 protons, 8 neutrons

18
iClicker Question

• If one of the neutrons in carbon-14 (carbon has 6
  protons) decays into a proton, what nucleus is
  left?
• A carbon-13, with 6 protons, 7 neutrons
• B carbon-14, with 7 protons, 7 neutrons
• C boron-14, with 5 protons, 9 neutrons
• D nitrogen-14, with 7 protons, 7 neutrons
• E nitrogen-15, with 7 protons, 8 neutrons

19
iClicker Question

• Basically, what is the nature of the alpha
  particle?
• A an electron
• B a proton
• C a helium nucleus
• D a uranium nucleus
• E an iron nucleus

20
iClicker Question

• Basically, what is the nature of the alpha
  particle?
• A an electron
• B a proton
• C a helium nucleus
• D a uranium nucleus
• E an iron nucleus

21
iClicker Question

• Basically, what is the nature of the beta
  particle?
• A an electron
• B a proton
• C a helium nucleus
• D a uranium nucleus
• E an iron nucleus

22
iClicker Question

• Basically, what is the nature of the beta
  particle?
• A an electron
• B a proton
• C a helium nucleus
• D a uranium nucleus
• E an iron nucleus

23
Brief History of Nuclear Power
1938 Scientists study Uranium nucleus 1941
Manhattan Project begins 1942 Controlled
nuclear chain reaction 1945 U.S. uses two
atomic bombs on Japan 1949 Soviets develop
atomic bomb 1952 U.S. tests hydrogen bomb 1955
First U.S. nuclear submarine
24
Atoms for Peace
Program to justify nuclear technology Proposals
for power, canal-building, exports First
commercial power plant, Illinois 1960
25
Emissions Free

• Nuclear energy annually prevents
• 5.1 million tons of sulfur
• 2.4 million tons of nitrogen oxide
• 164 metric tons of carbon
• Nuclear often pitted against fossil fuels
• Some coal contains radioactivity
• Nuclear plants have released low-level radiation

26
Early knowledge of risks

• 1964 Atomic Energy Commission report
• on possible reactor accident
• 45,000 dead
• 100,000 injured
• 17 billion in damages
• Area the size of Pennsylvania contaminated

27
States with nuclear power plant(s)
28
Nuclear power around the globe

• 17 of worlds electricity from nuclear power
• U.S. about 20 (2nd largest source)
• 431 nuclear plants in 31 countries
• 103 of them in the U.S.
• Built none since 1970s
• U.S. firms have exported nukes.
• Push from Bush/Obama for new nukes.

29
Countries Generating Most Nuclear Power
Country Total MW
USA 99,784
France 58,493
Japan 38,875
Germany 22,657
Russia 19,843
Canada 15,755
Ukraine 12,679
United Kingdom 11,720
Sweden 10,002
South Korea 8,170
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Nuclear Fuel Cycle

• Uranium mining and milling
• Conversion and enrichment
• Fuel rod fabrication
• POWER REACTOR
• Reprocessing, or
• Radioactive waste disposal
• Low-level in commercial facilities
• High level at plants or underground repository

33
iClicker Question

• About what percentage of U.S. electricity is
  derived from nuclear power?
• A 10
• B 20
• C 30
• D 40
• E 50

34
iClicker Question

• About what percentage of U.S. electricity is
  derived from nuclear power?
• A 10
• B 20
• C 30
• D 40
• E 50

35
iClicker Question

• Which of the following countries has the highest
  percentage of electricity generated by nuclear
  power?
• A United States
• B United Kingdom (Great Britain)
• C Japan
• D France
• E Russia

36
iClicker Question

• Which of the following countries has the highest
  percentage of electricity generated by nuclear
  power?
• A United States
• B United Kingdom (Great Britain)
• C Japan
• D France
• E Russia

37
Front end Uranium mining and milling
38
Uranium tailingsand radon gas
Deaths of Navajominers since 1950s
39
Radioactivity Basics

• Radioactivity The spontaneous nuclear
  transformation of an unstable atom that often
  results in the release of radiation, also
  referred to as disintegration or decay.
• Units
• Curie (Ci) the activity in one standard gram of
  Radium 3.7 x 1010 disintegrations per second
• Becquerel (Bq) 1 disintegration per second
  International Units (SI)

40
Radioactivity Basics

• Radiation Energy in transit in the form of
  electromagnetic waves (gamma-? or x-ray), or high
  speed particles ( alpha-a, beta-ß, neutron-?,
  etc.)
• Ionizing Radiation Radiation with sufficient
  energy to remove electrons during interaction
  with an atom, causing it to become charged or
  ionized.
• Can be produced by radioactive decay or by
  accelerating charged particles across an electric
  potential.

41
Radioactivity Basics

• Roentgen R the unit of exposure to Ionizing
  Radiation. The amount of ? or x-ray radiation
  required to produce 1.0 electrostatic unit of
  charge in 1.0 cubic centimeter of dry air.
• Rad the unit of absorbed dose. Equal to 100 ergs
  per gram of any material from any radiation.
• SI unit Gray
• 1 Gray 100 rads
• REM the unit of absorbed dose equivalent. The
  energy absorbed by the body based on the damaging
  effect for the type of radiation.
• REM Rad x Quality Factor
• SI unit Sievert 1 Sv 100 Rem

42
iClicker Question

• Which of the following describes the Roentgen?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

43
iClicker Question

• Which of the following describes the Roentgen?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

44
iClicker Question

• Which of the following describes the RAD?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

45
iClicker Question

• Which of the following describes the RAD?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

46
iClicker Question

• Which of the following describes the REM?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

47
iClicker Question

• Which of the following describes the REM?
• A the unit of absorbed dose equivalent.
• B the unit of absorbed dose.
• C the unit of exposure to ionizing radiation
• D all of the above
• E none of the above

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ALARA

• A philosophy, necessary to maintain personnel
  exposure or the release of radioactivity to the
  environment well below applicable limits by means
  of a good radiation protection plan, through
  education, administrative controls and safe lab
  practices.
• As Low As Reasonably Achievable

49
ALARA Principles

• Distance
• Inverse Square Law radiation intensity is
  inversely proportional to the square of the
  distance from the source
• Use remote handling tools, or work at arms length
• Maximize distance from source of radiation

50
ALARA Principles

• Shielding
• Any material between a source of radiation and
  personnel will attenuate some of the energy, and
  reduce exposure
• Select proper shielding material for type of
  radiation, use less dense material for ßs, to
  minimize Bremsstrahlung (braking) radiation

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Background Radiation
Below are estimates of natural and man-made
background radiation at sea level at middle
latitudes. The total averages 400 500 mREM/yr

• Natural Sources (300 mREM) "Natural" background
  radiation consists of radiation from cosmic
  radiation, terrestrial radiation, internal
  radionuclides, and inhaled radon.
• Occupational Sources (0.9 mREM) According to
  NCRP Report No. 93, the average dose for workers
  that were actually exposed to radiation in 1980
  was approximately 230 mREM.
• The Nuclear Fuel Cycle (0.05 mREM) Each step in
  the nuclear fuel cycle can produce radioactive
  effluents in the air or water.
• Consumer Products (5-13 mREM) The estimated
  annual dose from some commonly-used consumer
  products such as cigarettes (1.5 pack/day, 8,000
  mREM) and smoke detectors (1 mREM) contribute to
  total annual dose.
• Miscellaneous Environmental Sources (0.6 mREM) A
  few environmental sources of background radiation
  are not included in the above categories.
• Medical Sources (53 mREM) The two contributors
  to the radiation dose from medical sources are
  diagnostic x-rays and nuclear medicine. Of the
  estimated 53 mREM dose received annually,
  approximately 39 mREM comes from diagnostic
  x-rays.

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Metric Conversions

• 1 rem 0.01 Sv 10 mSv
• 1 mrem 0.00001 Sv 0.01 mSv 10 µSv
• 1 Sv 100 rem 100,000 mrem (or millirem)
• 1 mSv 100 mrem 0.1 rem
• 1 µSv 0.1 mrem

53
Maximum Permissible Dose Equivalents for
Radiation Workers
Avg dose/ week (rem) Max 13 week dose (rem) Max yearly dose (rem) Max lifetime dosea (rem)
Radiation controlled areas
Whole body, gonads, blood-forming organs, and lens of eye 0.1 3 5 5(N - 18)d
Skin of whole body 10 30
Hands and forearms, head neck, feet, and ankles 25 75
Environs
Any part of body .01 0.5
Notes Avg week dose is for design purposes
only 1 REM assumed 1 R Note a N age in
years For minors, dose limits are 10 of adult
limits and radiation work is not
permitted Source National Bureau of Standards
Handbook 59 (1958) with addendums.
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Occupational Exposure

• In terms of absolute energy content, 1 RAD is not
  a lot (i.e., 0.01 joule absorbed/kg).
• The main risks associated exposure to analytical
  X-rays are
• High Intensity Exposures Skin burns and lesions
  and possible damage to eye tissue
• Long-term chronic Exposures Possible chromosomal
  damage and long term risk of skin cancer
• Goal of all Radiation Safety practice is ALARA
  As Low as Reasonably Achievable

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Long-term Effects of Radiation Exposure

• Long-term effects are usually related to
  increased risk of cancer, summarized in the table
  below

Disease Additional Cases per 100,000 (with one-time 10 REM dose)
Adult leukemia 95
Cancer of digestive system 230
Cancer of respiratory system 170
Source Biological Effects of Ionizing
Radiation V (BEIR V) Committee

• Radiation-induced life shortening (supported by
  animal experiments) suggests accelerated aging
  may result in the loss of a few days of life as a
  result of each REM of exposure

• Genetic Effects of radiation fall into two
  general categories
• Effect on individuals Can change DNA and create
  mutation but long term effects not well
  understood. Biological repair mechanisms may
  reduce importance.
• Effect of offspring Exposure to a fetus in utero
  can have profound effects on developing organs
  resulting in severe birth defects. For this
  reason pregnant women should avoid any
  non-background exposures

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Bioeffects on Surface tissues

• Because of the low energy (8 keV for Cu) of
  analytical x-rays, most energy will be absorbed
  by skin or other exposed tissue
• The threshold of skin damage is usually around
  300 R resulting in reddening of the skin
  (erythema)
• Longer exposures can produce more intense
  erythema (i.e., sunburn) and temporary hair
  loss
• Eye tissue is particularly sensitive if working
  where diffracted beams could be present, eye
  protection should be worn

57
Uranium Enrichment

• U-235
• Fissionable at 3
• Weapons grade at 90
• U-238
• More stable
• Plutonium-239
• Created from U-238 highly radioactive

58
Radioactivity of Plutonium

• Life span at least
• 240,000 years
• Compare to
• Last Ice Age glaciation
• 10,000 years ago
• Neanderthal Man died out
• 30,000 years ago

59
Risks of Enrichment andFuel Fabrication

• Largest industrial users of water, electricity
• Paducah, KY, Oak Ridge, TN, Portsmouth, OH
• Cancers and leukemia among workers
• Fires and mass exposure.
• Karen Silkwood at Oklahoma fabrication plant.
• Risk of theft of bomb material.

60
Nuclear Fission Reactors

• Nuclear fission is used simply as a heat source
  to run a heat engine
• By controlling the chain reaction, can maintain
  hot source for periods greater than a year
• Heat is used to boil water
• Steam turns a turbine, which turns a generator
• Efficiency limited by familiar Carnot efficiency
• ? (Th - Tc)/Th (about 3040, typically)

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Nuclear Plant Layout
62
The Core of the Reactor
not shown are the control rods that
absorb neutrons and thereby keep the process
from running away
63
Fuel Packaging

• Want to be able to surround uranium with fluid to
  carry away heat
• lots of surface area is good
• Also need to slow down neutrons
• water is good for this
• So uranium is packaged in long rods, bundled into
  assemblies
• Rods contain uranium enriched to 3 235U
• Need roughly 100 tons per year for a 1 GW plant
• Uranium stays in three years, 1/3 cycled yearly

64
Control Rod Action

• Basic Concept
• need exactly one excess neutron per fission event
  to find another 235U
• Inserting a neutron absorber into the core
  removes neutrons from the pool
• Pulling out rod makes more neutrons available
• Emergency procedure is to drop all control rods
  at once

65
California Nuclear Plant at San Onofre

• 10 miles south of San Clemente
• Easily visible from I-5
• 2 reactors brought online in 1983, 1984
• older decommissioned reactor retired in 1992
  after 25 years of service
• 1.1 GW each
• PWR (Pressurized Water Reactor) type
• No cooling towers
• the ocean is used

66
The relative cost of nuclear power
safety regulations tend to drive cost
67
Sidebar Regarding Nuclear Bombs

• Since neutrons initiate fission, and each fission
  creates more neutrons, there is potential for a
  chain reaction
• Have to have enough fissile material around to
  intercept liberated neutrons
• Critical mass for 235U is about 15 kg
• for 239Pu its about 5 kg
• need highly enriched (about 90 235U for uranium
  bomb)
• Bomb is relatively simple
• separate two sub-critical masses and just put
  them next to each other when you want them to
  explode!
• difficulty is in enriching natural uranium to
  mostly 235U

68
Sources of Radiation Exposure
From National Institutes of Health
69
Useful Radiation Effects INuclear
Power Nuclear fission for electricity Thermoelec
tric for spacecraftMedical Diagnostic scans,
tracers Cancer radiation treatment Plutonium
powered pacemaker Medical, dental sterilization
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Useful Radiation Effects IIPolymer
cross-linking Shrink tubing (e.g., turkey
wrapping) Ultra-strong materials (e.g.,
Kevlar) Tires (replaces vulcanization) Flooring
Food irradiation Sterilization of
meat De-infestation of grain and
spices Increase shelf life (e.g., fruits,
veggies)
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The radura symbol on foodstuffs
72

• Useful Radiation Effects III
• Sterilization of food for
• hospitals and space travel
• Radioactive dating
• Insect control
• Semiconductor doping
• Testing of space-hardened computer technology
• Environmental studies in
• air purity, global warming, ozone

73
The finite uranium resource

• Uranium cost is about 23/kg
• about 1 of cost of nuclear power
• more expensive to get as we deplete the easy
  spots
• Estimated 3 million tons available at cost less
  than 230/kg
• Need 200 tons per GW-yr
• Now have 100 GW of nuclear power generation
• about 100 plants _at_ 1 GW each
• 3 million tons will last 150 years at present
  rate
• only 30 years if nuclear replaced all electricity
  production

74
Breeder Reactors

• The finite resource problem goes away under a
  breeder reactor program
• Neutrons can attach to the non-fissile 238U to
  become 239U
• beta-decays into 239Np with half-life of 24
  minutes
• 239Np beta-decays into 239Pu with half-life of
  2.4 days
• now have another fission-able nuclide
• about 1/3 of energy in normal reactors ends up
  coming from 239Pu
• Reactors can be designed to breed 239Pu in a
  better-than-break-even way

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Breeders, continued

• Could use breeders to convert all available 238U
  into 239Pu
• all the while getting electrical power out
• Now 30 year resource is 140 times as much (not
  restricted to 0.7 of natural uranium), or 4200
  yr
• Technological hurdle need liquid sodium or other
  molten metal to be the coolant
• but four are running in the world
• Enough 239Pu falling into the wrong hands spells
• BOOM!!

77
Reactor Risks

• Once a vigorous program in the U.S.
• in France
• 80 of electricity is nuclear
• No new orders for reactors in U.S. since late
  70s
• aftershock of Three-Mile Island
• Reactor failure modes
• criticality accident runaway chain reaction
• ?meltdown
• loss of cooling not runaway, but overheats
  ?meltdown
• steam or chemical explosions are not ruled out
  ?meltdown
• N.B. reactors are incapable of nuclear explosion

78
Risk Assessment

• Extensive studies by agencies like the NRC
• 1975 report concluded that
• loss-of-cooling probability was 1/2000 per
  reactor year
• significant release of radioactivity 1/1,000,000
  per RY
• chance of killing 100 people in an accident about
  the same as killing 100 people by a falling
  meteor
• 1990 NRC report accounts for external disasters
  (fire, earthquake, etc.)
• large release probability 1/250,000 per RY
• 109 reactors, each 30 year lifetime ? 1 chance

79
Close to home Three Mile Island
80
The Three-Mile Island Accident, 1979

• The worst nuclear reactor accident in U.S.
  history
• Loss-of-cooling accident in six-month-old plant
• Combination of human and mechanical errors
• Severe damage to core
• but containment vessel held
• No major release of radioactive material to
  environment
• Less than 1 mrem to nearby population
• less than 100 mrem to on-site personnel
• compare to 300 mrem yearly dose
• Instilled fear in American public, fueled by
  movies like The China Syndrome

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Health around TMI

• In 1979, hundreds of people reported nausea,
  vomiting, hair loss, and skin rashes. Many pets
  were reported dead or showed signs of radiation
• Lung cancer, and leukemia rates increased 2 to
  10 times in areas within 10 miles downwind
• Farmers received severe monetary losses due to
  deformities in livestock and crops after the
  disaster that are still occurring today.

83
Plants near TMI

• -lack of chlorophyll
• -deformed leaf patterns
• -thick, flat, hollow stems
• -missing reproductive parts
• -abnormally large

TMI dandelion leaf at right
84
Animals Nearby TMI

• Many insects disappeared for years.
• Bumble bees, carpenter bees, certain type
  caterpillars, or daddy-long-leg spiders
• Pheasants and hop toads have disappeared.

85
The Chernobyl Disaster

• Disregard of safety standards plus unstable
  design led to disaster
• Chernobyl was a boiling-water, graphite-moderated
  design
• unlike any in the USA
• used for 239Pu weapons production
• frequent exchange of rods to harvest Pu meant
  lack of containment vessel like the ones in USA
• positive-feedback effect
• It gets too hot, it runs hotter
• runaway possible
• once runaway, control rods ineffective

86
Chernobyl, continued

• On April 25, 1986, operators decided to do an
  experiment as the reactor was powering down for
  routine maintenance
• disabled emergency cooling system!!!
• withdrew control rods completely!!!
• powered off cooling pumps!!!
• reactor went out of control, caused steam
  explosion that ripped open the reactor
• many fires, exposed core, major radioactive
  release

87
Chernobyl after-effects

• Total of 100 million people exposed (135,000
  lived within 30 km) to radioactivity much above
  natural levels
• Expect from 25,000 to 50,000 cancer deaths as a
  result
• compared to 20 million total worldwide from other
  causes
• 20,000,000 becomes 20,050,000 (hard to notice
• unless youre one of those 50,000
• 31 died from acute radiation exposure at site
• 200 got acute radiation sickness

88
Fallout from Chernobyl
89
400 million people exposed in 20 countries
90
Radiation and Health

• Health effects as a result of radiation exposure
• -increased likelihood of cancer
• -birth defects including long limbs, brain
• damage, conjoined stillborn twins
• -reduced immunity
• -genetic damage

91
It Cant Happen Here

• Soviet reaction to Three-Mile Island, 1979
• Blamed on Capitalism and pressurized-water
  reactor design
• U.S. reaction to Chernobyl, 1986
• Blamed on Communism and graphite reactor design
• No technology 100 safe
• Three-Mile Island bubble almost burst

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iClicker Question   Consider all of the people
throughout history who have been exposed to
man-made nuclear radiation, such as Hiroshima and
Nagasaki, Chernobyl, Three Mile Island, nuclear
bomb tests, accidental spills, etc.
Which number most nearly approximates how many
children conceived and born later to these people
suffered genetic damage due to a parents
exposure, excluding exposure during
pregnancy? A. millions B.
thousands C. hundreds D. zero
93
iClicker Question   Consider all of the people
throughout history who have been exposed to
man-made nuclear radiation, such as Hiroshima and
Nagasaki, Chernobyl, Three Mile Island, nuclear
bomb tests, accidental spills, etc.
Which number most nearly approximates how many
children conceived and born later to these people
suffered genetic damage due to a parents
exposure, excluding exposure during
pregnancy? A. millions B.
thousands C. hundreds D. zero
94
Nuclear Proliferation

• The presence of nuclear reactors means there will
  be plutonium in the world
• and enriched uranium
• If the world goes to large-scale nuclear power
  production (especially breeder programs), it will
  be easy to divert Pu into nefarious purposes
• But other techniques for enriching uranium may
  become easy/economical
• and therefore the terrorists top choice
• Should the U.S. abandon nuclear energy for this
  reason?
• perhaps a bigger concern is all the weapons-grade
  Pu already stockpiled in the U.S. and former
  U.S.S.R.

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Nuclear Waste

• Each reactor has storage pool, meant as temporary
  holding place
• originally thought to be 150 days
• 40 years and counting
• Variety of radioactive products, with a wide
  range of half-lives
• 1GW plant waste is 70 MCi after one year 14 MCi
  after 10 years 1.4 MCi after 100 years 0.002
  MCi after 100,000 years
• 1 Ci (Curie) is 37 billion radioactive decays per
  second

97
Storage Solutions

• No failsafe storage solution yet developed
• EPA demands less than 1000 premature cancer
  deaths over 10,000 years!!
• hard to design and account for all contingencies
• USA proposed site at Yucca Mountain, NV
• Good and bad choice
• geologically cracks and questionable stability

98
Burial Issues

• Radioactive emissions themselves are not
  radioactive
• just light, electrons/positrons and helium nuclei
• but they are ionizing they rip apart
  atoms/molecules they encounter
• Absorb emissions in concrete/earth and no effect
  on biology
• so burial is good solution
• Problem is the patience of time
• half lives can be long
• geography, water table changes
• nature always outlasts human structures
• imagine building something to last 10,000 years!!

99
Yucca Mountain
100
Transportation risks

• Uranium oxide spills
• Fuel rod spills (WI 1981)
• Radioactive waste risks

101
Transport to Yucca Mountain
102
Kyshtym waste disaster, 1957
Orphans

• Explosion at Soviet weapons factory forces
  evacuation of over 10,000 people in Ural Mts.
• Area size of Rhode Island still uninhabited
  thousands of cancers reported

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Risk of terrorism(new challenge to industry)
9/11 jet passed near Indian Point
105
iClicker Question Suppose that all of the
electrical energy for the world for the next 500
years were obtained from nuclear reactors.
Further suppose that all of the nuclear waste
from these reactors were dissolved and spread
uniformly throughout the oceans of the world.
Which statement is true A. The oceans would be a
vast wasteland, unable to support life. B. Much
death and damage to ocean life would be
caused. C. Any effect would be so small that it
would be virtually impossible to see.
106
iClicker Question Suppose that all of the
electrical energy for the world for the next 500
years were obtained from nuclear reactors.
Further suppose that all of the nuclear waste
from these reactors were dissolved and spread
uniformly throughout the oceans of the world.
Which statement is true A. The oceans would be a
vast wasteland, unable to support life. B. Much
death and damage to ocean life would be
caused. C. Any effect would be so small that it
would be virtually impossible to see.
107
Fusion The big nuclear hope

• Rather than rip nuclei apart, how about putting
  them together?

alpha (4He)

• Iron is most tightly bound nucleus
• Can take loosely bound light nucleiand build
  them into more tightly boundnuclei, releasing
  energy
• Huge gain in energy going from protons(1H) to
  helium (4He).
• Its how our sun gets its energy
• Much higher energy content than fission

tritium
dueterium
proton
108
Thermonuclear Fusion in the Sun

• Sun is 16 million degrees Celsius in center
• Enough energy to ram protons together (despite
  mutual repulsion) and make deuterium, then helium
• Reaction per mole 20 million times more
  energetic than chemical reactions, in general

4 protons mass 4.029
neutrinos, photons (gamma rays)
4He nucleus mass 4.0015
109
Emc2 balance sheets

• Helium nucleus is lighter than the four protons!
• Mass difference is 4.029 4.0015 0.0276 a.m.u.
• 0.7 of mass disappears, transforming to energy
• 1 a.m.u. (atomic mass unit) is 1.6605?10-27 kg
• difference of 4.58?10-29 kg
• multiply by c2 to get 4.12?10-12 J
• 1 mole (6.022?1023 particles) of protons ?
  2.5?1012 J
• typical chemical reactions are 100200 kJ/mole
• nuclear fusion is 20 million times more potent
  stuff!
• works out to 150 million Calories per gram
• compare to 16 million Cal/g uranium, 10 Cal/g
  gasoline

110
Artificial Fusion

• 15 million degrees in Suns center is just enough
  to keep the process going
• but Sun is huge, so it seems prodigious
• In laboratory, need higher temperatures still to
  get worthwhile rate of fusion events
• like 100 million degrees
• Bottleneck in process is the reaction
• 1H 1H ? 2H e ? (or proton-proton ?
  deuteron)
• Better to start with deuterium plus tritium
• 2H and 3H, sometimes called 2D and 3T
• but give up some energy starting higher on
  binding energy graph
• Then
• 2H 3H ? 4He n 17.6 MeV (leads to 81 MCal/g)

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Deuterium everywhere

• Natural hydrogen is 0.0115 deuterium
• Lots of hydrogen in sea water (H2O)
• Total U.S. energy budget (100 QBtu 1020 J per
  year) covered by sea water contained in cubic
  volume 170 meters on a side
• corresponds to 0.15 cubic meters per second
• about 1,000 showers at two gallons per minute
• about one-millionth of rainfall amount on U.S.
• 4 gallons per person per year

113
Tritium Nowhere

• Tritium is unstable, with half-life of 12.32
  years
• thus none naturally available
• Can make it by bombarding 6Li with neutrons
• extra n in D-T reaction can be used for this, if
  reaction core is surrounded by lithium blanket
• Lithium on land in U.S. would limit D-T to a
  hundred years or so
• maybe a few thousand if we get lithium from ocean
• D-D reaction requires higher temperature, but
  could be sustained for many millennia

114
By-products?

• Not like radioactive fission products
• Building stable nuclei (like 4He)
• Tritium is only radioactive substance
• energy is low, half-life short not much worry
  here
• Extra neutrons can tag onto local metal nuclei
  (in surrounding structure) and become radioactive
• but this is a small effect, especially compared
  to fission

115
Why dont we embrace fusion?

• A huge technological challenge
• Always 20 years from fruition
• must confine plasma at 50 million degrees
• 100 million degrees for D-D reaction
• all the while providing fuel flow, heat
  extraction, tritium supply, etc.
• hurdles in plasma dynamics turbulence, etc.
• Still pursued, but with decreased enthusiasm,
  increased skepticism
• but payoff is huge clean, unlimited energy

116
Fusion Successes?

• Fusion has been accomplished in labs, in big
  plasma machines called Tokamaks
• got 6 MW out of Princeton Tokamak in 1993
• but put 12 MW into it to sustain reaction
• Hydrogen bomb also employs fusion
• fission bomb (e.g., 239Pu) used to generate
  extreme temperatures and pressures necessary for
  fusion
• LiD (lithium-deuteride) placed in bomb
• fission neutrons convert lithium to tritium
• tritium fuses with deuterium

117
Other Forms of Nuclear Power?

• Three main nuclear power reaction types
• Radioactive Decay
• Atomic Batteries
• Passive beta decay collectors
• Radioisotope thermoelectric generators
• Passive application of Peltier and Seebeck
  effects
• Nuclear Fusion
• Already discussed
• Nuclear Fission
• Already discussed

118
Passive Radioactive Decay

• Radioisotope Thermoelectric Generator
• Obtains power from passive radioactive decays
• Utilized in satellites and space probes
• Seebeck/Peltier effect
• Junction of two dissimilar metals at different
  temperatures create a current
• Fuel
• Long half life, low shielding (beta decay)
• Plutonium 238 most common

119
The Peltier/Seebeck Effect
By Jacob McKenzie, Ty Nowotny, Colin Neunuebel

• Discovered by Thomas Johann Seebeck in 1821.
• He accidentally found that a voltage existed
  between two ends of a metal bar when a
  temperature gradient existed within the bar.

120
The Seebeck Effect

• A temperature difference causes diffusion of
  electrons from the hot side to the cold side of a
  conductor.
• The motion of electrons creates an electrical
  current.
• The voltage is proportional to the temperature
  difference as governed by
  
  Va(Th-Tc)

where a is the Seebeck coefficient of the couple
121
History of Peltier devices

• The Peltier effect is named after Jean Charles
  Peltier (1785-1845) who first observed it in
  1834.
• The Peltier effect had no practical use for over
  100 years until dissimilar metal devices were
  replaced with semiconductor Peltiers which could
  produce much larger thermal gradients.
• Peltier Cooler - produce a temperature gradient
  that is proportional to an applied current

122
Peltier Effect With Dissimilar Metals

• At the junction of two dissimilar metals the
  energy level of conducting electrons is forced to
  increase or decrease.
• A decrease in the energy level emits thermal
  energy, while an increase will absorb thermal
  energy from its surroundings.
• The temperature gradient for dissimilar metals is
  very small.

The figure of merit is a measure
of thermoelectric efficiency.
123
Sidebar Semiconductor Peltier

• Bismuth-Telluride n and p blocks
• An electric current forces electrons in n type
  and holes in p type away from each other on the
  cold side and towards each other on the hot side.
• The holes and electrons pull thermal energy from
  where they are heading away from each other and
  deliver it to where they meet.

124
Sample PeltierTemperature Gradient
Carnot Efficiency
Nc _at_ 12v 1-Tc/Th 1-283.6/342.3 17.1
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Applications

• Deep space probes
• Microprocessor cooling
• Laser diode temperature stabilization
• Temperature regulated flight suits
• Air conditioning in submarines
• Portable DC refrigerators
• Automotive seat cooling/heating

Radioisotopic Thermoelectric Generator (RTG)
126
RTG Pros and Cons

• Pros
• Solid state (no moving parts)
• No maintenance
• Long service lifetime
• Relatively constant power production
• Solar Panels not needed
• Cons
• Good for low electrical power requirements
• Inefficient compared to phase change cooling
• Decays over time
• Requires shielding
• Radioactive waste

127
Fukushima Nuclear Power Plant
128
Wikipedia Reports on Disaster at Fukushima An
earthquake categorized as 9.0 on the moment
magnitude scale occurred on 11 March 2011, at
1446 Japan Standard Time (JST) off the northeast
coast of Japan. On that day, reactor units 1, 2,
and 3 were operating, but units 4, 5, and 6 had
already been shut down for periodic inspection.
When the earthquake was detected, units 1, 2 and
3 underwent an automatic shutdown (called
scram). After the reactors shut down,
electricity generation stopped. Normally the
plant could use the external electrical supply to
power cooling and control systems, but the
earthquake had caused major damage to the power
grid. Emergency diesel generators started
correctly but stopped abruptly at 1541, ending
all AC power supply to the reactors. The plant
was protected by a sea wall, but tsunami water
which followed after the earthquake topped this
sea wall, flooding the low lying generator
building After the failure of the diesels,
emergency power for control systems was supplied
by batteries that would last about eight hours.
Batteries from other nuclear plants were sent to
the site and mobile generators arrived within 13
hours, but work to connect portable generating
equipment to power water pumps was still
continuing as of 1504 on 12 March. Generators
would normally be connected through switching
equipment in a basement area of the buildings,
but this basement area had been flooded by the
tsunami.