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Nuclear Physics
Bronze Buddha at Hiroshima
The unleashed power
of the atom has
changed everything
save our modes of
thinking and we thus
drift toward
unparalleled
catastrophe.
-Albert Einstein
Nuclear Power
Is it Green & Safe?
Nuclear Waste
250,000 tons of Spent Fuel
10,000 tons made per year
Half Life used in Radiocarbon
Dating
Biological Effects of
Ionizing Radiation
Nuclear Weapons
What is the World Made of?
1800’s: Spectroscopy was the Game
Burning an element created a unique
spectra but nobody could explain it!
1905 Einstein proves atoms exist by
explaining “Brownian Motion”
Born 1879
This motion makes sense if you imagine
the pollen grain or dust mote being
bombarded on all sides by particles too
tiny to see, that are in constant motion.
Einstein arrived at a mathematical
explanation in terms of atoms, and
integrated it into kinetic theory.
1911: Rutherford’s Planetary
Model of the Atom
•A beam of positively charged alpha
particles hit and are scattered from a
thin foil target.
•Large deflections could not be
explained by Thomson’s model.
(Couldn’t explain spectra!)
Electrons exist in quantized orbitals with energies given by
multiples of Planck’s constant. Light is emitted or absorbed when
an electron makes a transition between energy levels. The energy
of the photon is equal to the difference in the energy levels:
Eγ = Ei − E f = hf
h = 6.626 x10−34 Js
Characteristics
of Atoms
• incredibly tiny
• perpetually in motion
• made of a postively charged nucleus made
of positively charged protons and neutral
neutrons.
• Electrons in shells orbiting the nucleus
• Neutral atoms have equal numbers of
protons and electrons.
Periodic Table of the Elements
Atomic Notation
Atomic Mass Number
A = # protons + neutrons
A
Z
X
Atomic #
Neutron Number N
N = # neutrons
N=A-Z
1
1
H,
3
1
H,
238
92
Atomic Number
Z = # protons
U
Why can’t we see Atoms?
How do we know they exist?
Molecules
Molecules
• consists of two or more atoms bonded together
example:
• H2S is hydrogen sulfide
• 2 atoms of hydrogen and 1 atom of sulfur
Maria Goeppert-Mayer
• 1906 – 1972
• German scientist
• Best known for her
development of the model
of the nucleus
• Shared the Nobel Prize in
1963
– Shared with Hans Jensen
who simultaneously
developed a similar model
Nuclear Structure
Nucleons
The nucleus is composed of two types of particles: protons
and neutrons.
Together, these are referred to as nucleons.
The number of protons Z is the element’s atomic number.
The mass number A is defined to be A = Z + N where N is
the neutron number.
The mass number is the total number of nucleons in a
nucleus.
Atomic Mass
Atomic masses are specified in terms of the atomic mass
unit u, defined such that the atomic mass of the isotope
12C is exactly 12 u.
The conversion to SI
units is 1 u = 1.6605 ×
10−27 kg.
The atomic mass unit
can be written 1 u =
931.49 MeV/c2.
It may seem unusual,
but the units MeV/c2 are
units of mass.
Isotopes and Elements
e
If Helium loses a proton,
it becomes a different element
p
n
n
3H
If Helium loses one of its
neutrons, it becomes an
isotope
3
He
=T
e
p
n p
e
The Hydrogen Atom
• One electron orbiting a nucleus
• 1 proton = Z = atomic number
• 0 neutrons = N
• Total mass = A = Z+N =1
p
• Singly ionized Hydrogen is
missing one electron = 1H+
e
1H
• Add a neutron and you have
Deuterium = 2H = D
• Add 2 neutrons and you have
Tritium = 3H = T
The Helium Atom
e
p n
n p
• Two electrons orbiting a nucleus with:
2 protons = Z = atomic number
2 neutrons = N
• Total mass = A = Z+N
e
4He
• Singly ionized Helium is missing one
electron = 4He+
• Doubly ionized Helium is missing both
electrons = α particle = 4He++
All Elements Have Isotopes
Same # of protons - different # of neutrons
Atomic Mass of an Element is an average of all Isotopes
Isotopes have the same chemistry as the atom.
This is why radioactive isotopes can be so dangerous.
The body doesn’t see the difference between water made
with hydrogen and water made with tritium.
Protons repel each other!
How is an Atomic Nucleus Stable?
Strong Force is STRONGER than
the Coulomb Force over short
distances: Short Range Force
FStrong ~ 100 FCoulomb
Over a range of 10-15 m.
Why are Atoms Not Stable?
Why do Atoms Decay?
As nuclear size
increases, the distance
between nucleons
increases and the strong
force becomes too weak
to overcome the
Coulomb electrical
repulsion.
The nucleus is unstable
and can decay.
Stable Nuclei
Neutrons:
Nuclear Glue
With few exceptions,
naturally occurring stable
nuclei have N ≥ Z.
For Z ≤ 20, N = Z is stable.
Elements with Z ≥83 are
unstable and spontaneously
decay until they turn into
stable lead with Z = 82.
Marie Curie
• 1867 – 1934
• Polish scientist
• Shared Nobel Prize in
1903 for studies in
radioactive substances
– Prize in physics
– Shared with Pierre Curie
and Becquerel
• Won Nobel Prize in 1911
for discovery of radium
and polonium
– Prize in chemistry
Radioactivity
• Radioactivity is the spontaneous emission of
radiation
– Discovered by Becquerel in 1896
– Many experiments were conducted by
Becquerel and the Curies
• Experiments suggested that radioactivity
was the result of the decay, or
disintegration, of unstable nuclei
Nuclear Radiation
Atomic decay by Alpha and Beta radiation causes atomic transmutation.
Gamma radiation does not transmutate the atom, it changes its energy.
Activity (Decay Rate) Units
• The unit of activity, R, is the curie (Ci)
– 1 Ci ≡ 3.7 x 1010 decays/s
• The SI unit of activity is the becquerel (Bq)
– 1 Bq ≡ 1 decay/s
• Therefore, 1 Ci = 3.7 x 1010 Bq
• The most commonly used units of activity are the
millicurie and the microcurie
• There have been around 2,000 nuclear test explosions
• Atomic Tests released approximately 9 MCi of Sr-90
• At equilibrium with the atmosphere, a gram of carbon
shows an activity of about 15 decays per minute.
Conceptual Physics Fundamentals—Chapter 16
When an atom undergoes radioactive decay, it
A.
B.
C.
D.
becomes an ion of the same element.
becomes an isotope of the same element.
turns into a completely different element.
may or may not turn into a completely different element.
Conceptual Physics Fundamentals—Chapter 16
When an atom undergoes radioactive decay, it
A.
B.
C.
D.
becomes an ion of the same element.
becomes an isotope of the same element.
turns into a completely different element.
may or may not turn into a completely different element.
Energy Released: The Mass Defect
Parent atoms have more mass than product atoms.
The difference is converted to Kinetic energy of the products.
E=
2
Δmc
Δm = ( m parents − m products )
1eV = 1.6 x10
−19
19
J OR 1J ~ 10 eV
1MeV = 1.6 x10
−13
J
Energy released with decay of:
Uranium: 25Mev ~ 4 x10-12 J
Carbon: 0.016 MeV~3 x10-15 J
Nuclear Decay: Fission
Beta Decay
Neutron Decay into a Proton
(Neutron Half life ~ 12 minutes)
Alpha Decay
Spontaneous Fission
Heavy elements FISSION into lighter elements, releasing energy
in the process by E = Δmc2, where Δm is the difference in mass
between the parent and products.
~ 25 MeV is released in this reaction
Most of the Energy is released in the form of Kinetic Energy (heat).
Alpha Decay
Atomic Mass Number, A, and charge is conserved for all reactions!
Beta Decay
Atomic Mass Number, A, and charge is conserved for all reactions!
Neutrino: Weak Force
Conceptual Physics Fundamentals—Chapter 16
A certain element emits one alpha particle, and its products then
emit two beta particles in succession. The atomic number of the
resulting element is changed by
A.
B.
C.
D.
zero.
minus 1.
minus 2.
none of these.
Conceptual Physics Fundamentals—Chapter 16
A certain element emits one alpha particle, and its products then
emit two beta particles in succession. The atomic number of the
resulting element is changed by
A.
B.
C.
D.
zero.
minus 1.
minus 2.
none of these.
Explanation:
Removal of the alpha decreases the atomic number by 2, but removal of
two electrons increases it by 2, so there is no net change in atomic
number.
Conceptual Physics Fundamentals—Chapter 16
Which of these particles, in solitude, is quite unstable?
A.
B.
C.
D.
Alpha.
Beta.
Proton.
Neutron.
Conceptual Physics Fundamentals—Chapter 16
Which of these particles, in solitude, is quite unstable?
A.
B.
C.
D.
Alpha.
Beta.
Proton.
Neutron.
Conceptual Physics Fundamentals—Chapter 16
When an element ejects an alpha particle, the mass number of the
resulting element
A.
B.
C.
D.
reduces by 2.
reduces by 4.
increases by 2.
increases by 4.
Conceptual Physics Fundamentals—Chapter 16
When an element ejects an alpha particle, the mass number of the
resulting element
A.
B.
C.
D.
reduces by 2.
reduces by 4.
increases by 2.
increases by 4.
Explanation:
An alpha particle (a helium nucleus) has an atomic mass of 4 (4
nucleons). So ejection of an alpha particle means a loss of 4 nucleons.
Thus, the mass number of the element is lowered by 4.
Fusion
Light elements FUSE into larger elements,
releasing energy in the process by E = mc2.
There is NO Spontaneous Fusion
Only in very extreme conditions like the interior of a star or
in a fusion bomb or reactor can you overcome the Coulomb
repulsion and force nucleons to fuse.
Induced Nuclear Fission
Heavy elements FISSION into lighter elements, releasing energy
in the process by E = Δmc2, where Δm is the difference in mass
between the parent and products. About 250 MeV is released in this
reaction in the form of kinetic energy of the products.
Chain Reaction – U-235
141
92
1
n + 235
U
→
Ba
+
Kr
+
3
(
92
56
36
0n)
1
0
Critical Mass – Chain Reaction
Critical Mass: the minimum
amount of fissionable material
to produce self-sustained chain
reaction, a condition called
criticality.
In a nuclear power plant, the
critical chain reaction must
control the neutron flux to
avoid an exponential increase in
fissions, going supercritical.
In a nuclear bomb, you want a
supercritical chain reaction.
Fissile Material of Choice
U-235 & P-239
Odd number of nucleons is easier to fission
U-235: 0.231 MeV more energy than U-238
Uranium: 238U is >99% in nature 235U
is ~0.7% in nature. Fuels are generally
enriched to at least a few percent 235U
„
Plutonium: 239Pu is not found in
nature, it is reprocessed from nuclear
power plant waste or “bred” from
uranium in breeder reactors
„
Fission & Fusion
Less mass per nucleon occurs in both processes.
Mass per Nucleon
The smaller the mass per nucleon, the greater the binding energy.
Elements fission down or fuse up to Iron, the most stable element,
releasing energy by E = Δmc2.
Fusion
Fission
Binding Energy
It takes energy to break up an atom.
Energy must be put into a stable system to break it apart.
That energy is converted to mass by E = mc2.
That energy is called the Binding Energy.
Binding Energy per Nucleon
The most stable atoms have the most Binding Energy per nucleon.
Radioactive Atoms mutate by fission or fusion until they have
maximum Binding Energy per nucleon which occurs at Iron.
Fission & Fusion
In either FISSION or FUSION, less stable atoms mutate to
more stable atoms, releasing energy in the process by E = mc2.
Radioactive Series
Natural radioactivity: Unstable nuclei found in nature
Artificial radioactivity: Nuclei produced in the
laboratory by bombarding atoms with energetic
particles in nuclear reactions.
Natural Transmutation
Spontaneous Fission
Elements with Z ≥83 are
unstable and spontaneously
decay by alpha and beta
radiation until they turn into
stable lead with Z = 82.
Note: some elements can
decay by both modes.
Decay Series for U-238
Decay Series of 232Th
• Series starts with 232Th
• Processes through a
series of alpha and beta
decays
• The series branches at
212Bi
• Ends with a stable
isotope of lead, 208Pb
Conceptual Physics Fundamentals—Chapter 16
When uranium-238 emits an alpha particle, uranium transforms
to
A.
B.
C.
D.
thorium-242.
thorium-238.
thorium-234.
any of these thorium isotopes.
Conceptual Physics Fundamentals—Chapter 16
When uranium-238 emits an alpha particle, uranium transforms
to
A.
B.
C.
D.
thorium-242.
thorium-238.
thorium-234.
any of these thorium isotopes.
Explanation:
Emitting an alpha particle reduces the atomic mass by 4.
So 238 – 4 = 234.
Conceptual Physics Fundamentals—Chapter 16
Compared with the mass of a uranium atom that undergoes
fission, the combined masses of the products after fission are
A.
B.
C.
D.
less.
more.
the same.
none of these.
Conceptual Physics Fundamentals—Chapter 16
Compared with the mass of a uranium atom that undergoes
fission, the combined masses of the products after fission are
A.
B.
C.
D.
less.
more.
the same.
none of these.
Conceptual Physics Fundamentals—Chapter 16
A nucleon has a greater mass when it is
A.
B.
C.
D.
inside an iron nucleus.
inside a uranium nucleus.
outside a nucleus.
none of these.
Conceptual Physics Fundamentals—Chapter 16
A nucleon has a greater mass when it is
A.
B.
C.
D.
inside an iron nucleus.
inside a uranium nucleus.
outside a nucleus.
none of these.
Explanation:
Work is required to pull a nucleon from the nucleus. This work increases
the energy of the nucleon, which is manifested in greater mass.
Conceptual Physics Fundamentals—Chapter 16
The element with the least mass per nucleon in its composition is
A.
B.
C.
D.
hydrogen.
helium.
iron.
uranium.
Conceptual Physics Fundamentals—Chapter 16
The element with the least mass per nucleon in its composition is
A.
B.
C.
D.
hydrogen.
helium.
iron.
uranium.
Half Life
The half life of a
radioactive
element is the time it
takes for a quantity
to decay to 1/2 its
original amount, N0.
Half Life used in Radiocarbon
Dating
Carbon Dating
While alive, an organic material absorbs
radioactive C-14 from the atmosphere
and has a fixed percent of C-14 in it with
a fixed rate of radioactivity. Once the
plant dies, it stops absorbing C-14 and so
the radioactivity is reduced. Measuring
the Activity gives a measure of the
amount of C-14 remaining and thus the
date when the object died.
Carbon Dating
Carbon-14 decays with a halflife of about 5730 years by the
emission of an electron of energy 0.016 MeV. At equilibrium with
the atmosphere, a gram of carbon shows an activity of about 15
decays per minute.
There is 1 atom of C-14 for every 8.3x1011 atoms of C-12.
C → 147 N + β −
14
6
Conceptual Physics Fundamentals—Chapter 16
The half-life of uranium-238 is 4.5 billion years. Compared with
the amount of uranium-238 in Earth today, only half that amount
will exist in
A.
B.
C.
D.
less than 4.5 billion years.
4.5 billion years.
more than 4.5 billion years.
none of these.
Conceptual Physics Fundamentals—Chapter 16
The half-life of uranium-238 is 4.5 billion years. Compared with
the amount of uranium-238 in Earth today, only half that amount
will exist in
A.
B.
C.
D.
less than 4.5 billion years.
4.5 billion years.
more than 4.5 billion years.
none of these.
Comment:
Since 4.5 billion years is approximately the age of Earth, half has already
decayed to lead.
Conceptual Physics Fundamentals—Chapter 16
A certain isotope has a half-life of one day. This means the
amount of that isotope remaining at the end of two days will be
A.
B.
C.
D.
zero.
one-quarter.
half.
the same.
Conceptual Physics Fundamentals—Chapter 16
A certain isotope has a half-life of one day. This means the
amount of that isotope remaining at the end of two days will be
A.
B.
C.
D.
zero.
one-quarter.
half.
the same.
Biological Effects of Ionizing
Radiation
Energy Released: The Mass Defect
Parent atoms have more mass than product atoms.
The difference is converted to Kinetic energy of the products.
E=
2
Δmc
Δm = ( m parents − m products )
1eV = 1.6 x10
−19
19
J OR 1J ~ 10 eV
1MeV = 1.6 x10
−13
J
Energy released with decay of:
Uranium: 25Mev ~ 4 x10-12 J
Carbon: 0.016 MeV~3 x10-15 J
Nuclear Radiation
Atomic decay by Alpha and Beta radiation causes atomic transmutation.
Gamma radiation does not transmutate the atom, it changes its energy.
Ionizing Radiation Types
„
Alpha particles (4He++)
„
Beta particles (e+ and e-)
„
Gamma-rays (γ)
„
Neutrons (n)
Ionizing Radiation: neutrons
Because of their tremendous
penetrating ability, neutrons can
be very damaging to the human
body. When neutrons strike
atoms of elements that are not
fissionable, they can render them
radioactive by changing their
atomic structure. For example,
in a building near a neutron
bomb explosion, the neutrons
can change stable cobalt in the
steel girders to cobalt 60, an
emitter of highly penetrating
gamma radiation.
Ionizing EM Radiation:
UV, Xray & Gamma
Energy to ionize atom or molecule: 10-1000eV
Gamma Radiation:
Above a few keV are Highly Penetrating
High Intensity: If you were very near a nuclear device as it
exploded, an intense pulse of gamma rays would destroy the
functioning of your nervous system and almost immediately
afterwards cause intense heating throughout your body,
sufficient to vaporize you in about a microsecond.
Lower Intensity: Gamma-rays injure cells by creating highenergy electrons throughout the body, charged particles which
can disrupt any chemical bond they happen to encounter as they
fly along. Electrons (positirons) are produced by the photoelectric effect, compton scattering or pair-production.
Gamma Ray Knife
Mass Extinctions?
Ionizing Radiation Effects on Cells
Ionization Energy ~ few eV ~ 10-18 J
α,β,γ radiation can ionize atoms which break chemical bonds and
damage molecules in cells:
1. Interferes with cell reproduction
2. Destruction of cell’s function or destruction of cell itself.
It has the greatest effect on cells that are rapidly reproducing
because they do not have time to repair the damage:
1. Fetus, infants, children (also in animals and plants)
2. Cancerous cells
Ionizing Radiation can cause cancer or kill cancer!
Routes for radioactive exposure
Internal vs External
Testing for Ingested
Contamination
The most common test for exposure to
radioactive material is a bioassay,
usually by urinalysis. As with most
cases of internal contamination, the
sooner the test is taken after ingesting
or inhaling the contaminant, the more
accurate the results will be. Most major
medical centers are capable of
performing this test.
Exposure vs Dose
“Exposure" refers to how much radioactive material entered a
person's body. Not all radiation entering the body stays there.
Much of it is flushed out through breathing or along with
other waste products.
"Dose" refers to the amount of radioactive energy that is
actually absorbed by tissues in the body. For instance, about a
third of the iodine-131 entering the body is absorbed by the
thyroid. Traces of it are absorbed by other body organs. The
rest is flushed from the body
Units of Radiation Exposure
• The roentgen (R) is defined as
– That amount of ionizing radiation that produces
an electric charge of 3.33 x 10-10 C in 1 cm3 of
air under standard conditions
– Equivalently, that amount of radiation that
increases the energy of 1 kg of air by 8.76 x 103J
• One rad (radiation absorbed dose)
– That amount of radiation that increases the
energy of 1 kg of absorbing material by 1 x 10-2
More Units
• The RBE (relative biological effectiveness)
– The number of rads of x-radiation or gamma
radiation that produces the same biological
damage as 1 rad of the radiation being used
– Accounts for type of particle which the rad
itself does not
• The rem (radiation equivalent in man)
– Defined as the product of the dose in rad and
the RBE factor
• Dose in rem = dose in rad x RBE
RBE Factors, A Sample
Radiation Levels
• Natural sources – rocks and soil, cosmic
rays
– Called background radiation
– About 0.13 rem/yr
• Upper limit suggested by US government
– 0.50 rem/yr
– Excludes background
• Occupational
– 5 rem/yr for whole-body radiation
– Certain body parts can withstand higher levels
– Ingestion or inhalation is most dangerous
Radiation Levels, cont.
• 50% mortality rate
– About 50% of the people exposed to a dose of
400 to 500 rem will die
• New SI units of radiation dosages
– The gray (Gy) replaces the rad
– The sievert (Sv) replaces the rem
SI Units, Table
Radiation Dose
"Dose" the amount of radioactive energy that is actually absorbed
by tissues in the body.
Radiation dose unit (rad) : 1 r = 0.01 J/kg
The biological effect depends on the type of radiation and body part:
RBE: Relative biological effectiveness
Roentgen Equivalent Man: rem = rad x RBE
Type of energy of radiation
X rays
Gamma rays
Beta rays > 30KeV
Beta rays < 30 KeV
Neutrons, slow
Neutrons, fast
Alpha Rays
RBE
1
1
1
1.7
2-5
10 (body) 30 (eyes)
10-20
Dose delivered in less than one day
Possible latent effects (cancer)
Total Average US Background Level Radiation: 382 mrem
Other Units
1 Gray (Gy) = 1 J/kg = 100 rad
1 sievert (Sv) = 100 rem
Conceptual Physics Fundamentals—Chapter 16
All the radiation we normally receive annually from natural
sources is a fraction of 1 rem. Lethal doses of radiation begin at
A.
B.
C.
D.
5 rems.
50 rems.
500 rems.
5000 rems.
Conceptual Physics Fundamentals—Chapter 16
All the radiation we normally receive annually from natural
sources is a fraction of 1 rem. Lethal doses of radiation begin at
A.
B.
C.
D.
5 rems.
50 rems.
500 rems.
5000 rems.
Dose: Acute vs Chronic Dose
An acute radiation dose is defined as a large dose (10 rad or
greater, to the whole body) delivered during a short period of
time (on the order of a few days at the most). If large enough, it
may result in effects which are observable within a period of
hours to weeks.
A chronic dose is a relatively small amount of radiation
received over a long period of time. The body is better
equipped to tolerate a chronic dose than an acute dose. The
body has time to repair damage because a smaller percentage of
the cells need repair at any given time. The body also has time
to replace dead or non-functioning cells with new, healthy cells.
This is the type of dose received as occupational exposure.
Immediate vs Delayed FX
Immediate effects are due to an acute
(short term) exposure: a large exposure
that takes place over a short period of
time.
Delayed effects are due to latency period of
cancer and disease where a health effect of
radiation exposure may not become
apparent for months, years or several
decades after the exposure occurs. Leukemia
has a latency period of 2 years, other
cancers, 15 or more. If a sperm or egg are
damaged then the latency period can be
generations.
Low Dose & Cancer
•It has been estimated that the radioactive fallout from the nuclear
accident at Chernobyl in 1986 will cause an increase of 17,000
cancers over the lifetime of people living in the Northern
Hemisphere.
•Large though this estimate seems, it is dwarfed by the 513 million
cancer deaths that will occur anyway in this population.
•This is why it is difficult to quantify the dangers of low doses.
•Some scientists (very few) claim that low doses are GOOD for
adults because they keep the cells ‘in shape’ to repair themselves.
Background Radiation: ~300 mrem/year
•Sources are UV radiation and cosmic particles, radium,
radon, potassium 40, carbon 12 present in rocks, air, and our
own body cells.
•Exposure to Natural Radiation induced mutations may have
contributed to our evolutionary process. Most geneticists
believe that humanity has reached an evolutionary peak in
beneficial mutations caused by natural radiation that the
species can undergo. Thus any further mutations are
detrimental, causing disease and deformity.
•Although the exact percent is unknown, background
radiation is thought to be responsible for a portion of all
cancers and genetic disorders.
Increasing the Background
Nuclear Fallout:
Bombs, Tests & Accidents
Cs-137, Sr-90, I-131
Fallout is the descent of airborne particles of dust, debris,
and radioactive substances. About 200 different substances
are formed from a nuclear bomb explosion. Millions of
curies of radioactivity in the form of dust and debris get
carried into the upper atmosphere by the mushroom cloud.
Jet stream winds can carry fallout from bomb blasts around
the world within a few months.
There have been around 2,000 nuclear test explosions
Atomic Tests released approximately 9 MCi of Sr-90
Atmospheric Testing:
1945-1963
From 1945 to 1963 the U.S.A. conducted an extensive
campaign of atmospheric nuclear tests, grouped into roughly
20 test "series." After “Starfish Prime” in 1963 the Limited
Test Ban Treaty was signed and testing for the U.S.,
Soviet Union, and Great Britain moved underground. France
continued atmospheric testing until 1974 and China did so until
1980. Testing continued until 1998 Comprehensive Test Ban
Treaty.
http://www.ctbto.org/specials/1945-1998-by-isao-hashimoto/
U-235 Fission Fragments
Nuclear Power and Weapons
Cesium 137 & Strontium 90, and Pu-239
Iodine-131
•Half Life of 8 days
•Decay Mode: BETA (0.606 MeV) and Gamma (0.364
MeV)
•Organ most effected: Thyroid
•Iodine-131 is produced by the fission of U-235 during
operation of nuclear reactors and by plutonium (or
uranium) in the detonation of nuclear weapons.
•Pathways: Inhalation, food chain (milk, vegetables)
•Most serious fallout product from nuclear testing.
Average American alive at the time received a thyroid
radiation exposure of 2 – 300 rads.
•Chernobyl released 83 million curies of I-131
Cesium-137
•Half Life of 30 years
•Decay Mode: BETA (0.19 MeV)
•Decay to Barium-137 that radiates gamma (0.6MeV)
•Behaves like Potassium and is taken up by living
organisms as part of fluid electrolytes.
•Both internal and external hazard from cancer
•Ingested, it is absorbed in the intestine, settles in muscles,
excreted after a few months.
•Radioactive cesium is present in soil around the world
largely as a result of fallout from past atmospheric nuclear
weapons test.
Strontium-90
•Half Life of 28 years.
•Does not occur naturally. It is a by product of fission.
•Beta emitter. Decays to Yttrium-90, also a beta emitter.
•Behaves like Calcium and concentrates in bone where it
damages stem cells of the bone marrow critical to
reproduction of cells that mediate immune function. Causes
leukemia and auto-immune illnesses.
•Interferes with neuron communication leading to brain
damage of developing frontal cortex (dyslexia, autism)
•Y-90 concentrates in the glands which controls hormonal
function – interferes with estrogen and testosterone which
contributes to breast and prostrate cancer, sexual organs.
Strontium-90
•Large amounts of Sr-90 were produced during atmospheric
nuclear weapons tests in the 1950’s and 1960’s.
•Large amounts of Sr-90 was released by Chernobyl.
Worldwide:
•Trace levels of Sr-90 in food especially dairy products and
leafy vegetables which are major sources of dietary calcium.
•Every person alive today has ingested some strontium-90
Plutonium 239
•Half Life of 24,000 years.
•Does not occur naturally. It is a by product of fission.
•Alpha emitter (5.15 MeV)
•Acts like iron and can cross the placental barrier to reach
fetus.
•Concentrates in testicles and ovaries.
•1 pound, if uniformly distributed, could hypothetically
induce lung cancer in every person on Earth.
•5 metric tons of plutonium are dispersed around the Earth
due to nuclear tests, bombs, satellite burn ups, fires,
accidents, spill and leakages.
Uranium U-238
•Half Life of 4.5 billion years.
•Alpha emitter (5 MeV)
•Wherever you find U-238 you will find all the 14
radioactive daughters of U 238 which emit all types of
radiation upt to 100 MeV in energy.
•Concentrates in bone and kidneys.
•Chemically behaves like Calcium.
•A severe exposure (of the order of
one milligram in the kidneys)
causes lesions of the tubular
cells and deterioration of the kidney function.
U-238 Decay Series
Depleted Uranium
• After isotope separation, the remaining
238U is said to be “depleted” as it is
missing 235U – however, 238U is highly
radioactive
• Uranium is a very dense metal (1.7 x
Pb), making it ideal for use in armor
and shell casings
• The USA used depleted Uranium
weapons in the Persian Gulf War
(1991), in Bosnia (1995), Kosovo
(1999) and Iraq (2003), Iraq?
Afghanistan?
Modern
Nuclear
War?
DU Used in Recent Wars:
Balkans: 200 Tons
Afghanistan: 800 Tons
Gulf War 1: 350 Tons
Iraq War: 200 tons???
Genetic Effects and Birth Defects
Radioactive metals bind to DNA molecules.
Genetic effects and birth defects due to radiation exposure occur when
radiation damage to a parent's DNA code is transmitted to a child.
Genetic effects caused by radiation fall into two categories:
(1) effects that appear in the children of an exposed parent and
(2) effects that appear in later generations.
NEURAL TUBE DEFECTS
The neural tube develops into the spinal
cord and brain. Defects occur when the
neural tube fails to close completely
during the early stages of pregnancy.
Why is Radiation More
Damaging to Fetuses &
Babies?
•Cells rapidly reproduce
•Damage to genes is not efficiently repaired
•If cell divides a defect is multiplied.
•Cellular damage can lead to greater risk of leukemia or cancer
•Increased risk of premature birth, low birth weight, birth defects.
In early developmental stages of both humans, fish and other wildlife when cells
rapidly reproduce, damage to the genes is not efficiently repaired, so that if the cell
survives and divides a defect is multiplied. Thus cellular damage can lead to a
greater risk of leukemia or cancer in the new-born than in the mother, typically by
anywhere from ten to a hundred times as great. depending on the stage of
development. Moreover, many studies have shown that there is also an increased
risk of premature birth, low birthweight and birth defects. The damage is known to
involve the developing immune, hormonal and central nervous systems that often
does not become apparent until many years later.
Especially serious is damage to different parts of the developing brain such as the
prefrontal cortex, which can result in dyslexia, autism, inability to control anger,
attention deficit, and reduced cognitive ability leading to academic failure, dropout, selfish behavior, depression, suicide and murder. The reason is that neurons
communicate by sending out calcium ions, so that Strontium 90 and 89 can be
substituted for calcium, with devastating results due to the enormous energy with
which electrons or beta rays are ejected from the nucleus in the course of the
radioactive transformation from Strontiun-90 to Yttrium-90, destroying neurons in
the process.
Nervous System Disease
High-dose exposure: cancerous and benign brain tumors in people
exposed, and small brain size and mental retardation in children of
women who were exposed during pregnancy.
low-dose exposure: brain cancer, neurological diseases, psychological
diseases, dyslexia, autism, attention deficit
Thyroid Tumors, Cancer &
Disease
THYROID NODULES
Thyroid nodules are lumps in the thyroid gland
which may be benign or cancerous. "Cold
nodules" are non-functioning lumps in the
thyroid gland. "Hot nodules" refer to overactive
thyroid lumps.
HYPOTHYROIDISM
Hypothyroidism is a condition caused by too little
thyroid hormone in the body. Symptoms include
fatigue, weight gain, intolerance to cold, decreased
appetite, constipation, hoarseness, menstrual
irregularities, dry skin and hair changes.
Autoimmune Diseases
AUTOIMMUNE DISEASE or AUTOIMMUNE DISORDER
An autoimmune disease is a disease caused by the immune
system attacking the cells of one's own body rather than
attacking foreign cells, such as germs.
AUTOIMMUNE HYPOTHYROIDISM
Autoimmune hypothyroidism: An autoimmune disease that
prevents the thyroid from producing enough thyroid hormone.
AUTOIMMUNE THYROIDITIS
Damage to the thyroid caused when the body's immune
system attacks and destoys cells in the thyroid.
Nuclear Workers & Brain Cancer
Cumulative average whole-body doses ranged from 0.67 - 4.75 rem.
There is a higher than expected number of deaths from brain
cancer among the nuclear industry workers studied. While
chemical exposure may contribute to the risk of cancer, the only
common factor among the workers was exposure to radiation.
Victor Alexander. "Brain Tumor Risk Among United States Nuclear
Workers." Occupational Medicine: State of the Art Reviews.
Philadelphia: Hanley and Belfus, Inc., Vol. 6, No. 4, October-December,
1991, pp. 695-714.
lymphedema
Lymphedema is an accumulation of lymphatic fluid in the
interstitial tissue that causes swelling, most often in the arm(s)
and/or leg(s), and occasionally in other parts of the body.
Acquired lymphedema, can develop as a result of surgery,
radiation, infection or trauma.
John Smitherman
US Navy
"We watched the Baker shot from a
ship about 19 miles away from the
explosion, and mist from the
mushroom fell on the deck of our
ship and sand fell on our deck, little
pieces of metal and rocks. We tried to
wash off as much of it as we could.
The mushroom cloud stayed in the air
for almost two days- we could see
that."
Smitherman later developed lymphedema, a blockage of
the lymph system that causes legs and arms to swell; he
had to have both legs amputated.
On September 11, 1983, he died of cancer of the colon,
liver, stomach, lung and spleen. He had claimed
compensation for radiation damages. The Veterans
Administration turned his claim down seven times. It is
still pending
How do we know about the
Health Effects of
Nuclear Radiation?
Uranium Miner
"I used to go in and
haul the rocks out, and
I guess that's where I
got hurt, because there
was a lot of dust after
they did the blasting
and we went in right
away."
- Bernard Benally
Red Rock Navajo
Reservation, Arizona
Hiroshima
Nagasaki
Radioactive
Man Told
US!
Animal Testing
The black star in the middle of the picture shows the
tracks made by alpha rays emitted from a particle of
pllutonium-239 in the lung tissue of an ape. The alpha
rays do not travel very far, but once inside the body, they
can penetrate more than 10,000 cells within their range.
This set of alpha tracks (magnified 500 times) occurred
over a 48-hour period.
Human Radiation Experiments
Hundreds of Secret Experiments of
Radioactive Material on Humans by the DOE
1944-1960
Obtained by Citizens by the
Freedom of Information Act
Dr. Karl Z. Morgan, the Father
of Health Physics @ Oak Ridge
National Lab
“There is no
safe level of
radiation
exposure.”
http://www.ctbto.org/specials/1945-1998-by-isao-hashimoto/
What is Nuclear Power?
Pressurized Water Reactor (PWR)
U-235 absorbs slow neutrons – they are slowed down by water – the
neutrons become ‘thermalized’. Control rods absorb neutrons and
moderate the chain reaction. A meltdown can happen if they fail.
Basic Design of a Reactor Core
• Fuel elements consist of
enriched uranium
• The moderator material
helps to slow down the
neutrons
• The control rods absorb
neutrons
• All of these are
surrounded by a radiation
shield
Control Rods
• To control the power level, control rods are
inserted into the reactor core
• These rods are made of materials that are very
efficient in absorbing neutrons
– Cadmium is an example
• By adjusting the number and position of the
control rods in the reactor core, the K value can be
varied and any power level can be achieved
– The power level must be within the design of the
reactor
Reactor Safety – Containment
• Radiation exposure, and its potential health risks,
are controlled by three levels of containment:
• Reactor vessel
– Contains the fuel and radioactive fission products
• Reactor building
– Acts as a second containment structure should the
reactor vessel rupture
– Prevents radioactive material from contaminating the
environment
• Location
– Reactor facilities are in remote locations
Reactor Safety – Radioactive
Materials
• Disposal of waste material
– Waste material contains long-lived, highly radioactive
isotopes
– Must be stored over long periods in ways that protect
the environment
– At present, the most promising solution seems to be
sealing the waste in waterproof containers and burying
them in deep geological repositories
• Transportation of fuel and wastes
– Accidents during transportation could expose the public
to harmful levels of radiation
– Department of Energy requires crash tests and
manufacturers must demonstrate that their containers
will not rupture during high speed collisions
Fissile Material of Choice
U-235 & P-239
Odd number of nucleons is easier to fission
U-235: 0.231 MeV more energy than U-238
Uranium: 238U is >99% in nature 235U
is ~0.7% in nature. Fuels are generally
enriched to at least a few percent 235U
„
Plutonium: 239Pu is not found in
nature, it is reprocessed from nuclear
power plant waste or “bred” from
uranium in breeder reactors
„
Cooling Towers
Reactor
Current Status
443 plants world wide (16% energy), 103 in the US (20% energy)