Nuclear Reactions
• Nuclear Decay Song on Youtube
•
• Animation of Alpha, Beta, Gamma rays on
youtube
•
• radioactive dating using Uranium on Youtube
•
• Animation Explain Why Nuclear decay and
emissions occurs
•
• One Half-life to Live Song on Youtube
Lesson 1: Nuclear Radioactivity:
• Nucleus- composed of protons and
neutrons
• Strong Force – causes protons and
neutrons to be attracted to each other
–Powerful only when protons and
neutrons closely packed together
–Large nucleus – held less tightly
–Small nucleus – held tightly
Radioactivity:
• Nuclear Decay which happens when
the strong force is not large enough to
hold the nucleus together
• Nucleus gives off matter and energy
– unstable nuclei change by emitting
particles & releasing energy until they
transform into a different isotope or
another element
Side Note:
• Isotopes
• Remember: isotopes are atoms with the
same number of protons, but different
number of neutrons
• C-14
6 protons, 8 neutrons
• C-12
6 protons, 6 neutrons
Stability
• An atoms stability will depend on a
ratio or comparison of protons to
neutrons in the nucleus
• Ideal ratio:
– For light elements  1:1 ratio
– For heavy elements  3:2 ratio of
neutrons to protons
• A nucleus with either too many or to few
neutrons compared to protons is radioactive
Predict if the following Isotopes
are stable or unstable?
1.
2.
3.
4.
5.
6.
7.
8.
Boron-12
Oxygen 16
Carbon – 14
Carbon - 12
Magnesium – 22
Sodium- 23
Phosphorus – 32
Aluminum – 27
History:
• 1896 – Henri Becquerel discovered
radioactivity with the element Uranium
• 1898 – Marie and
Pierre Curie
discovered radioactive
Polonium and Radium
– Nobel Prize in 1903
• First woman to win
Nobel Prize
– 1911 Marie Curie won
2nd Nobel Prize
• First person to win 2nd
Nobel Prize
Exit Slip
•Explain why
nuclear decay
occurs.
Lesson 2: Nuclear Decay
• Nuclear Radiation - Particles and energy
released from decaying nucleus
• 3 types:
– Alpha particles (a)
– Beta particles (b)
– Gamma rays (g)
Alpha Particles
• particle that consists
of two protons and
two neutrons with an
electric charge of +2
– Like a Helium
nucleus
Alpha Particles
• do not travel far due to:
– Massive size
– Leave charged ions in the
path when they travel
through matter due to
stripping off electrons
• Are the least
penetrating form of
nuclear radiation
• Can cause serious
biological damage
Beta Particles (b):
• electron emitted during the radioactive
decay of a neutron into a proton in an
unstable nucleus
Beta Particles (b):
• travels further through matter than
alpha particles
• fast moving because it is so small
Gamma Rays (g):
• high energy electromagnetic radiation
emitted by a nucleus during radioactive
decay
Gamma Rays (g):
• Have no mass and no charge
• can penetrate matter deeply (up to 7
cm of Pb), even buildings
– radon (discovered by the Curie’s) was
found to emit these types of rays by
Paul Villard in 1900
Background radiation
• Low level radiation emitted mainly by
naturally occurring radioactive isotopes found
in the Earth’s rocks, soils, atmosphere
Background radiation
– Largest source (54%) is Radon gas
produced in earth’s crust
– From cosmic rays (8%)
– From radioactive isotopes in the body
(11%)
Radon Gas produced by Decay of
Uranium-238 in earth’s curst
Estimate Your Personal
Radiation Dose
Where you live
Cosmic radiation:
At sea level.....26 mrem
0-1000 ft.........28
ft.......52
1-2000 ft.........31
2-3000 ft.........35
3-4000 ft.........41
4-5000 ft.......47
5-6000
6-7000 ft.......66
7-8000 ft.......79
8-9000 ft.......96
Terrestrial (from the ground):
•If you live in a state that borders the
Gulf or Atlantic Coasts, add 16 mrem
•If you live in the Colorado Plateau area
(around Denver), add 63 mrem
•If you live anywhere else in the
continental US, add 30 mrem.
House Construction:
• If you live in a stone, adobe, brick,
or concrete building, add 7 mrem
Power Plants:
• If you live within 50 miles of a
nuclear power plant, add 0.01
mrem
• If you live within 50 miles of a coalfired power plant, add 0.03 mrem
Food, Water, and Air
Internal Radiation:
•From food (Carbon-14 and Potassium40) & from water (radon dissolved in
water), everyone add 40 mrem
•From air (radon), everyone add
200 mrem
How You Live:
• Weapons test fallout (less than 1)..1 mrem
• Jet Plane Travel (per hour in the air)
.............................……………0.05 mrem
• Have porcelain crowns or false
teeth.................………………0.07 mrem
• Weat a luminous wristwatch...0.06 mrem
• If you go through luggage inspection at
airport..........………………..0.002 mrem
• If you watch TV...........................1 mrem
• If you use video display terminal (computer
screen)……………….1 mrem
• Have a smoke detector……...0.008 mrem
• Use a gas camping lantern…….0.2 mrem
• If you wear a plutonium-powered
pacemaker.............…………….100 mrem
Medical Tests
Medical Diagnostic Tests-Number of millirems
per procedure
X-Rays:
Extremity (arm, hand, foot, or
leg)....1
Dental....1
Chest....6
pelvis/hip...65
Skull/neck...20
Barium enema...405
GI....245
Upper
CAT Scan (head and body).......110
What is your total?
• Add them all up to get your Estimated
Annual Radiation Dose
• Write a statement about How
your dose compares to the
average dose per person of
360 mrems per year?
Lesson 3: Transmutation
• Process of one element’s
changing to another through
nuclear decay
Solving Nuclear Equations:
• A nuclear equation shows how a
nucleus gains or loses subatomic
particles.
• Ex. 1:
1H +
1
4Be --->
9
3Li +
6
2He
4
Rule: The sum of the mass numbers of the
reactants equals the sum of the mass numbers of
the products .
What is the missing part of
this equation?
27
13Al
+ ?? --->
4
2He
30
15P
+
1
0n
Solve this one:
?+
0
-1e
-->
244
94Pu
• 24493Np
•
Lesson 4: Half-life of radioactive
Isotopes
• The length of time it takes half of the
atoms of a sample of the radioactive
isotope to decay
– Vary from fractions of a second to billions
of years
Radioactive Decay Rates
• Radioactive decay is used to determine
the age of old objects.
– Carbon-14 dating can be used to date onceliving materials from the past 50,000 years
– Uranium dating cam be used to date rocks
Radioactive Decay Series for I131
Radioactive Decay Series for I-131
Original sample
Radioactive Decay Series for I-131
1- half life
Radioactive Decay Series for I-131
2 – half lifes
Radioactive Decay Series for I-131
3 – half lives
Examples of Half-lifes for different
Isotopes
Isotope
Half - life
K-40
Pt-239
I-131
Th-219
1,280,000,000 years
24,120 years
8.1 days
0.000 001 05 s
Detecting Radioactivity
•
Radiation Detectors are Instruments
used to identify ions formed when
radiation passes through matter
1.
2.
3.
4.
Cloud Chamber
Bubble Chamber
Electroscope
Geiger counter
Bubble Chamber
Lesson 5: Nuclear Reactions:
Nuclear fission
– process of splitting a nucleus into two
nuclei with smaller masses
Nuclear fission
– a large amount of energy is released
– Used in Nuclear reactors in power
plants and submarines
Historical Events:
• 1938 Otto Hahn and Fritz Strassmann
discovered the that a nucleus could be
split
 struck U-235 with a neutron
nucleus split into smaller nuclei
• 1939 Lise Meitner
Theorized this
process as
“Nuclear Fission”
• Coined the term
“Fission”
• She had worked with
Hahn before fleeing
Nazi Germany
Historical Events:
• Dec 2nd, 1942
– Team lead by
Enrico Fermi
initiates the
First Nuclear
Chain Reaction
– Known as
“Manhattan
Project”
Chain reaction – an
ongoing series of
Fission reactions
• Critical Mass – amount
of fissionable material
required to continue a
reaction at a constant
rate
• Control Rods – used in
nuclear reactors to absorb
neutrons to control the rate
of the fission reaction
• Animation
Controlled/Uncontrolled
Reation
Fission
• Q: Can chain reactions always be
controlled?
• A: Somewhat, but only if materials are
used to absorb some of the neutrons
• Uses of chain reactions:
– 1. controlled: to generate electricity
– 2. not controlled: nuclear bomb
Nuclar Fusion
• Two nuclei with low masses are
combined to form one nucleus of
larger mass
• Can only happen
when nuclei are
moving fast
enough to get
close to each
other
• Temperature in
stars (millions of
°C) are high
enough for fusion
to occur
• It is very difficult to contain the
reaction.
– it must happen at temperatures greater
than 108 oC,
– no known material could contain it
without melting
– some success has been achieved by
containing the reaction in a magnetic
field
Dangers and Benefits of Nuclear
Radiation
• Radioactive substances can be very
useful , but when used carelessly,
nuclear radiation can be extremely
dangerous, even though we are
exposed to some radiation everyday.
Dangers from Nuclear Radiation
• Background radiation
• causing radiation sickness
• causing genetic mutations
Benefits from Nuclear Radiation
• smoke detectors
• radioactive tracers
in medicine
– radioactive
material added to
a substance so
that its location
can be detected
later
• Irradiation of Food
• Radiation Therapy for the
Treatment of Cancer
Benefits to Nuclear Power
• does not produce gaseous pollutants
that cause ozone depletion and acid
rain
• Cheap to make electricity this way but
expensive to build the power plant
• More energy in the known uranium
reserves than in the known reserves of
coal and oil
Dangers to Nuclear Power
• Radioactive products must be handled
correctly
• Safety of the reactors
• Equip with shielding
• Storage of spent nuclear fuel
Countries Generating Most Nuclear Power
Country
USA
France
Japan
Germany
Russia
Canada
Ukraine
United Kingdom
Sweden
South Korea
Total MW
99,784
58,493
38,875
22,657
19,843
15,755
12,679
11,720
10,002
8,170
States with nuclear power plant(s)
World Nuclear Reactors
Nuclear Fuel Cycle
Uranium enrichment
• U-235
– Fissionable at 3%
– Weapons grade at 90%
• U-238
– More stable
• Plutonium-239
– Created from U-238; highly radioactive
Nuclear Power
Nuclear Reactor Structure
• Reactor’s pressure vessel
typically housed in 8” of steel
• 36” concrete shielding
• 45” steel reinforced concrete
Risks of enrichment
and fuel 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.
Nuclear Reactor Process
• 3% enriched Uranium pellets formed into
rods, which are formed into bundles
• Bundles submerged in water coolant inside
pressure vessel, with control rods.
• Bundles must be SUPERCRITICAL; will
overheat and melt if no control rods.
Reaction converts water to steam, which
powers steam turbine
Other reactor accidents
(besides TMI and Chernobyl)
• 1952 Chalk River, Ontario
– Partial core meltdown
• 1957 Windscale, England
– Graphite reactor fire contaminates 200 square
miles.
• 1975 Browns Ferry, Alabama
– Plant caught fire
• 1976 Lubmin, East Germany
– Near meltdown of reactor core .
• 1999 Tokaimura, Japan
– Nuclear fuel plant spewed high levels of
radioactive gas
United States
9/11 jet
passed near
Indian Point
Risk of
terrorism
(new challenge to
industry)
Reprocessing
• Separates reusable fuel from waste
– Large amounts of radioactivity released
• 1960s West Valley, NY
– Radiation leaked into Lake Ontario
• 1970s La Hague, France
– Released plutonium plumes into air
Back end: Radioactive wastes
• Low-level wastes in commercial facilities
• Spent fuel in pools or “dry casks” by plants
• Nuclear lab wastes
– Hanford wastes leaked radiation into Columbia River
• High-level underground repository
– Yucca Mountain in Nevada to 2037
– Wolf River Batholith in Wisconsin after 2037?
– Risks of cracks in bedrock, water seepage
Yucca
Mountain
Transportation risks
• Uranium oxide spills
• Fuel rod spills (WI 1981)
• Radioactive waste risks
“Mobile
Chernobyl”
to Yucca Mtn.
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
Radioactive Waste Recycling
• Disposal of radioactive waste from nuclear
power plants and weapons facilities by
recycling it into household products.
• In 1996, 15,000 tons of metal were received
by the Association of Radioactive Metal
Recyclers . Much was recycled into products
without consumer knowledge.
• Depleted Uranium munitions for military.
Summary
• Nuclear energy has no typical pollutants or
greenhouse gasses
• Nuclear waste contains high levels of
radioactive waste, which are active for
hundreds of thousands of years.
• The controversy around nuclear energy stems
from all parts of the nuclear chain.