Physical SciencePhysical Science

Nuclear PhysicsNuclear Physics

Slides subject to changeSlides subject to change

AtomsAtoms Each chemical element is composed of Each chemical element is composed of

tiny, indivisible particles called tiny, indivisible particles called atomsatoms, , which are identical for that element but which are identical for that element but different (masses and chemical properties) different (masses and chemical properties) from atoms of other elements.from atoms of other elements.

Planetary ModelPlanetary Model

Consists of negatively Consists of negatively charged electrons and a charged electrons and a small positively charged small positively charged nucleus.nucleus.

NucleusNucleus Nucleus consists of positively charged Nucleus consists of positively charged

protonsprotons and, electrically neutral and, electrically neutral neutronsneutrons.. Protons and neutrons are collectively called Protons and neutrons are collectively called

nucleonsnucleons.. Relative size - a marble in a football Relative size - a marble in a football

stadium.stadium.

Atom Atom diameterdiameter

Nucleus Nucleus diameterdiameter

1x101x10-10-10 m m 1x101x10-14-14 m m

LabelsLabels Each element is assigned a chemical symbol. Each element is assigned a chemical symbol.

This symbol usually originates from its name This symbol usually originates from its name or its Latin name. or its Latin name. H = HydrogenH = Hydrogen He = HeliumHe = Helium C = CarbonC = Carbon

Number of protons Number of protons ZZ is the is the atomic numberatomic number. . All the atomsAll the atoms of an of an elementelement have the have the samesame atomic number.atomic number.

Mass NumberMass Number

Number of protons is the atomic Number of protons is the atomic number, number, ZZ..

Number of protons Number of protons plusplus neutrons neutrons is the mass number, is the mass number, AA..

XXAA

ZZ UU238238

9292

In GeneralIn General UraniumUranium

Mass Mass NumberNumber

Atomic Number, or Atomic Number, or number of protonsnumber of protons

ElementElement

Details on a Uranium NucleusDetails on a Uranium Nucleus

How many protons? How many protons? 9292 How many neutrons? 238 – 92 = How many neutrons? 238 – 92 = 146146 Mass number? Mass number? 238238

UU238238

9292

UraniumUranium

Background on Uranium

Discovered in 1789, named after planet Uranus discovered 8 years earlier.

Common element in Earth’s crust. One of the radioactive elements responsible for molten layer between Earth’s crust and core (more uranium in Earth’s crust than silver).

First radioactive material discovered in 1896.

IsotopesIsotopes Forms of an element with different Forms of an element with different

numbers of neutrons.numbers of neutrons. Have same chemical properties, may have Have same chemical properties, may have

different physical properties. different physical properties.

UU238238

9292

Uranium 238 Uranium 238 plentiful in plentiful in

nature, 99.3%nature, 99.3%

UU235235

9292Uranium 235 rare in Uranium 235 rare in

nature but needed for nature but needed for power/weapons, 0.7%power/weapons, 0.7%

Strong Nuclear ForceStrong Nuclear Force

Overcomes Coulomb Overcomes Coulomb repulsion force.repulsion force.

Short range, only nearest Short range, only nearest neighbor nucleons involved. neighbor nucleons involved.

Large nucleus becomes very Large nucleus becomes very unstable.unstable.

When over 83 protons, When over 83 protons, nucleus is subject to nucleus is subject to spontaneous disintegration.spontaneous disintegration.

Nucleus of U-235: Nucleus of U-235: protons in red, protons in red,

neutrons in grey.neutrons in grey.

RadioactivityRadioactivity

Some nuclei spontaneously Some nuclei spontaneously decay.decay.

Discovered in 1896 by Discovered in 1896 by Henri BecquerelHenri Becquerel studying fluorescence and studying fluorescence and phosphorescence, and working with uranium phosphorescence, and working with uranium salts and photographic plates. salts and photographic plates.

The spontaneous process of nuclei The spontaneous process of nuclei undergoing a change by emitting particles or undergoing a change by emitting particles or rays is called rays is called radioactive decayradioactive decay..

An Alpha Decay ProcessAn Alpha Decay Process

Alpha particles: He nuclei (2 protons, 2 Alpha particles: He nuclei (2 protons, 2 neutrons)neutrons)

Mass numbers and atomic numbers add Mass numbers and atomic numbers add up and match. Uranium decays to thorium.up and match. Uranium decays to thorium.

UU238238

9292 ++ HeHe44

22ThTh

234234

9090

++

++

Beta DecayBeta Decay Beta particles: Electrons. A neutron decays in Beta particles: Electrons. A neutron decays in

the nucleus to a proton and a neutron.the nucleus to a proton and a neutron. Atomic mass and atomic numbers add up and Atomic mass and atomic numbers add up and

match.match. Example is Cobalt-60. Decays to an unstable Example is Cobalt-60. Decays to an unstable

nickel atom.nickel atom.

CoCo6060

2727 ++ ee00

-1-1

6060

Ni*Ni*2828

Gamma DecayGamma Decay

Gamma rays consist of high energy photons Gamma rays consist of high energy photons with energies above about 100,000 eV with energies above about 100,000 eV (>10(>101919 Hz). Hz).

Due high energy content, gamma rays can Due high energy content, gamma rays can cause serious damage when absorbed by cause serious damage when absorbed by living cells (photons strike DNA).living cells (photons strike DNA).

Ni*Ni*6060

2727 NiNi6060

2727++ γγ

UraniumUranium

Pitchblende ore Pitchblende ore contains uraniumcontains uranium

Commercial Commercial Uranium : Uranium :

“Yellow Cake”“Yellow Cake”

Lisbon Valley, UTLisbon Valley, UT

RadiumRadium

Discovered by Discovered by Pierre and Pierre and Marie CurieMarie Curie in 1898. Discovered mixed in 1898. Discovered mixed with uranium. Shared 1903 Nobel Prize with uranium. Shared 1903 Nobel Prize with Henri Becquerel.with Henri Becquerel.

Million times more radioactive than Million times more radioactive than uranium.uranium.

RaRa226226

8888 Radium dust mixed with water Radium dust mixed with water

and glue used to make and glue used to make radioluminescent paintradioluminescent paint during during 1920’s: watch dials, instruments.1920’s: watch dials, instruments.

Early ApplicationEarly Application

When a radium atom decays, one of the When a radium atom decays, one of the particles it ejects (an alpha particle) hits a particles it ejects (an alpha particle) hits a phosphor molecule in the surrounding phosphor molecule in the surrounding paint that the manufacturer used to paint paint that the manufacturer used to paint the watch dial's numbers.  the watch dial's numbers. 

Then the phosphor glows a Then the phosphor glows a faint blue-green light.faint blue-green light.

The radium, however, does The radium, however, does not glow; only the phosphor not glow; only the phosphor glows.glows.

Radium GirlsRadium Girls

U.S. Radium Corporation Orange, NJ, ca.1920

Radium GirlsRadium Girls The employees hired to paint the dials were The employees hired to paint the dials were

mostly young women. Paint was applied with a mostly young women. Paint was applied with a small brush.small brush.

The women "pointed" the brushes on their The women "pointed" the brushes on their tongues between applications, and ingested a tongues between applications, and ingested a small quantity of radium each time. small quantity of radium each time.

““But everyone knew the stuff was harmless. The But everyone knew the stuff was harmless. The women even painted their nails and their teeth to women even painted their nails and their teeth to surprise their boyfriends when the lights went out. surprise their boyfriends when the lights went out.

Danger to Radium GirlsDanger to Radium Girls

Radium is chemically similar to calcium, and is Radium is chemically similar to calcium, and is therefore a “bone seeker.” It emits alpha-therefore a “bone seeker.” It emits alpha-particles.particles.

226226Ra that accumulated in the bone marrow Ra that accumulated in the bone marrow irradiated nearby tissue, and produced bone irradiated nearby tissue, and produced bone cancer and other genetic damage. cancer and other genetic damage.

Curie herself died of radium poisoning in 1934. Curie herself died of radium poisoning in 1934. The right of individual workers to sue for damages from corporations due to The right of individual workers to sue for damages from corporations due to

labor abuse was established as a result of the Radium Girls case. labor abuse was established as a result of the Radium Girls case. See article..

Decay in Decay in threethree common ways: common ways: Emit Emit alphaalpha particles: particles:

Helium nuclei (2 protons, 2 Helium nuclei (2 protons, 2 neutrons). neutrons).

Emit Emit betabeta particles: particles: Electrons.Electrons.

Emit Emit gammagamma rays: rays: High energy photons.High energy photons.

Products of RadioactivityProducts of Radioactivity

αα

ββ

γγ

Half-LifeHalf-Life

Half-life is the time it takes for half of the Half-life is the time it takes for half of the nuclei of a sample to decay.nuclei of a sample to decay.

Radioactive isotopes have characteristic Radioactive isotopes have characteristic half-lives.half-lives.

100 g of X100 g of X

50 g of X50 g of X25 g of X25 g of X

First half lifeFirst half life Second half lifeSecond half life

50 g of50 g of

other atomsother atoms 75 g of75 g of

other atomsother atoms

Example Half-LivesExample Half-Lives

Carbon-14Carbon-14 5,730 years5,730 years

Cobalt-60Cobalt-60 5.26 years5.26 years

Strontium-90Strontium-90 29.12 years29.12 years

Radium-226Radium-226 1600 years1600 years

Uranium-238Uranium-238 4.46 billion years4.46 billion years

Uranium-235Uranium-235 703 million years703 million years

αα decay to decay to 222222Rn (radon)Rn (radon)

After cigarettes, After cigarettes, radon is the radon is the second leading second leading cause of lung cause of lung cancer. − cancer. − EPAEPA

Quantity of RadioisotopeQuantity of Radioisotope

Years, in half-livesYears, in half-lives

Am

ount

of

subs

tanc

e, in

%A

mou

nt o

f su

bsta

nce,

in % 100100

5050

00

2525

FissionFission

Large unstable nucleus splits into two Large unstable nucleus splits into two intermediate-size nuclei, emits neutrons.intermediate-size nuclei, emits neutrons.

Example: Uranium-235 fission. Bombard Example: Uranium-235 fission. Bombard with one low-energy “thermal” neutron with one low-energy “thermal” neutron (Otto Hahn and Lise Meitner experiment).(Otto Hahn and Lise Meitner experiment).

UU235235

9292nn11

00BaBa

142142

5656nn

11

00KrKr9292

3636++ +2+2++- one of several U-235 decay processes- one of several U-235 decay processes

Lise MeitnerLise Meitner Otto HahnOtto Hahn

U-235 FissionU-235 Fission

142142

Missing MassMissing Mass

Element or Element or ParticleParticle

Mass Mass (in units of amu, (in units of amu, 1.660x101.660x10-27-27 kg) kg)

TotalTotal

BeforeU-235 235.043924

236.052589nn 1.0086651.008665

After

Ba-142 141.916453

235.859939Kr-92 91.926156

2n 2.017330

Mass DifferenceMass Difference––0.19265 amu0.19265 amu

~3.2x10~3.2x10––2828 kg kg

How Masses Add UpHow Masses Add Up

Resulting masses are lighter.Resulting masses are lighter. Where did the mass go?Where did the mass go?

Lise Meitner proposed that it goes into Lise Meitner proposed that it goes into energy from Einstein’s equation energy from Einstein’s equation EE = = mcmc22..

Mass Difference =Mass Difference = ––3.2x103.2x10––2828 kg kg

mcmc22 = (0.19265) = (0.19265)cc2 2 == – –180 MeV180 MeV

SummarySummary

One neutron absorbed by U-235, One neutron absorbed by U-235, momentarily becomes U-236, unstable, momentarily becomes U-236, unstable, and splits into smaller atoms with and splits into smaller atoms with tremendous kinetic energy (Coulomb tremendous kinetic energy (Coulomb repulsion) (~200 MeV) plus a few repulsion) (~200 MeV) plus a few neutrons.neutrons.

Visualize with Niels Bohr water drop Visualize with Niels Bohr water drop model.model.

FissionFission

Critical MassCritical Mass

When the process is self-sustaining, the When the process is self-sustaining, the sample has a sample has a critical masscritical mass..

For every 2 or 3 neutrons released, at least For every 2 or 3 neutrons released, at least one must strike another uranium nucleus. one must strike another uranium nucleus. If less than 1, then the reaction will die If less than 1, then the reaction will die

out.out. Greater than one it will grow unless Greater than one it will grow unless

controlled (chain reaction).controlled (chain reaction).

Controlled ReactionControlled Reaction

Slow Fission Down!Slow Fission Down! A control rod (neutron-absorbing element A control rod (neutron-absorbing element

boron or cadmium) absorbs a large number of boron or cadmium) absorbs a large number of neutrons in the reaction.neutrons in the reaction.

Speed Fission Up!Speed Fission Up! Fission works best with Fission works best with slowslow neutrons. neutrons. Need a Need a moderatormoderator (e.g., graphite, water) to (e.g., graphite, water) to

slow down high-speed neutrons that are slow down high-speed neutrons that are created. created.

WarningsWarningsAug 2, 1939Aug 2, 1939

Einstein to Einstein to FDR.FDR.

Possibility Possibility that Nazis that Nazis were were developing an developing an atomic bomb.atomic bomb.

First Controlled FissionFirst Controlled Fission

December 2, 1942.December 2, 1942. Enrico Fermi, University of Chicago.Enrico Fermi, University of Chicago. Natural uranium, cadmium control rods.Natural uranium, cadmium control rods. 315 tons of graphite used as a moderator 315 tons of graphite used as a moderator

to slow down the neutrons.to slow down the neutrons.

Manhattan ProjectManhattan Project

In an atomic bomb, a mass of fissile In an atomic bomb, a mass of fissile material greater than the critical mass material greater than the critical mass must be assembled instantaneously.must be assembled instantaneously.

Held together for about a millionth of a Held together for about a millionth of a second to permit the chain reaction to second to permit the chain reaction to propagate before the bomb explodespropagate before the bomb explodes

Manhattan ProjectManhattan Project

HiroshimaHiroshima

““Little Boy,” dropped on Hiroshima, Japan, Little Boy,” dropped on Hiroshima, Japan, August 8, 1945.August 8, 1945.

Explodes 1,900 feet above city.Explodes 1,900 feet above city. 140,000 people die immediately.140,000 people die immediately. Equivalent to 13 kilotons of dynamite.Equivalent to 13 kilotons of dynamite. Used 60 kg (132 lbs) of U-235.Used 60 kg (132 lbs) of U-235. August 15, 1945, Japan announces surrender, August 15, 1945, Japan announces surrender,

ending WWII. (Germany had surrendered May ending WWII. (Germany had surrendered May 7, 1945)7, 1945)

HiroshimaHiroshima

Nuclear Tests in Nevada

Interview

Controlled Nuclear PowerControlled Nuclear Power

Three-Mile Island, Three-Mile Island, Middletown, PAMiddletown, PA

Nuclear Power PlantNuclear Power Plant

Nuclear Nuclear EnergyEnergy

Nuclear Nuclear EnergyEnergy

Thermal Thermal EnergyEnergy

Thermal Thermal EnergyEnergy

Mechanical Mechanical EnergyEnergy

Mechanical Mechanical EnergyEnergy

Electrical Electrical EnergyEnergy

Electrical Electrical EnergyEnergy

Light and Heat Light and Heat EnergyEnergy

Light and Heat Light and Heat EnergyEnergy

Nuclear Fuel Life CycleNuclear Fuel Life Cycle

Cameco Corp.'s uranium mine in Cameco Corp.'s uranium mine in northern Saskatchewannorthern Saskatchewan

Uranium MineUranium MineUranium MineUranium Mine

Ore ProcessingOre ProcessingOre ProcessingOre Processing

EnrichmentEnrichmentEnrichmentEnrichment

Fuel ProductionFuel ProductionFuel ProductionFuel Production Power ReactorPower ReactorPower ReactorPower Reactor

Used Fuel DisposalUsed Fuel DisposalUsed Fuel DisposalUsed Fuel Disposal

Road transport of spent fuel in Road transport of spent fuel in JapanJapan

Uranium Uranium enrichment enrichment centrifugescentrifuges

Nuclear WasteNuclear WastePercent of Radioactive Waste

Worldwide

High Level3%

Intermediate Level7%

Low Level90%

Intermediate Level4%

Low Level1%

High Level95%

Percent of Radioactive Percent of Radioactive Waste WorldwideWaste Worldwide Percent of Total Percent of Total

RadioactivityRadioactivity

High-Level WasteHigh-Level Waste

Thermally hot, highly radioactive, and Thermally hot, highly radioactive, and potentially harmful used nuclear reactor potentially harmful used nuclear reactor fuel. fuel.

Converted into granules and mixed with Converted into granules and mixed with molten glass and stored. Licensees must molten glass and stored. Licensees must safely store this fuel at their reactors.safely store this fuel at their reactors.

Disposal of high-level radioactive waste Disposal of high-level radioactive waste was defined by the Nuclear Waste Policy was defined by the Nuclear Waste Policy Act of 1982.Act of 1982.

High-Level WasteHigh-Level Waste

Nuclear Waste Policy Act of 1982: Dispose high-Nuclear Waste Policy Act of 1982: Dispose high-level waste at Yucca Mountain, Nevada.level waste at Yucca Mountain, Nevada. 80 miles northwest of Las Vegas, NV.80 miles northwest of Las Vegas, NV. No official date for opening the $12 billion facility.No official date for opening the $12 billion facility.

3/7/09 Obama proposed budget closed the facility. 3/7/09 Obama proposed budget closed the facility. Satisfies Harry Reid (D-Nev).Satisfies Harry Reid (D-Nev).

What to do with existing 57,000 tons of highly What to do with existing 57,000 tons of highly toxic waste at 121 above-ground sites?toxic waste at 121 above-ground sites?

Existing plants create 2,000 tons each year.Existing plants create 2,000 tons each year. DOE study underway to find an alternative.DOE study underway to find an alternative.

Low-Level WasteLow-Level Waste

Slightly radioactive.Slightly radioactive. Includes things like protective clothing, Includes things like protective clothing,

laboratory equipment, paper towels, laboratory equipment, paper towels, gloves, etc. Hospital, industry waste. gloves, etc. Hospital, industry waste.

Compacted using a high Compacted using a high force compactor. Bury in force compactor. Bury in shallow pits.shallow pits.

WIPP Waste Isolation Pilot Project

(WIPP), Carlsbad, NM, is the nation’s only permanent, deep geologic repository for nuclear waste.

Storage for radioactive drums with the plutonium-laden detritus of America’s nuclear weapons program.

3,000-ft salt layer.

Forbes, 2/13/12 p. Forbes, 2/13/12 p. 91.91.

Clean Nuclear Process?Clean Nuclear Process?

Are there heavier elements that can be Are there heavier elements that can be fused into a lighter element (so missing fused into a lighter element (so missing mass goes off as mass goes off as EE==mcmc22 energy)? energy)?

Fusion energyFusion energy would be “clean.” No would be “clean.” No radioactive waste products.radioactive waste products.

n

Binding Energy per NucleonBinding Energy per Nucleon

Isotopes of HydrogenIsotopes of Hydrogen HydrogenHydrogen

DeuteriumDeuterium ““Heavy hydrogen DHeavy hydrogen D22O.”O.” Abundant in oceans (1 Abundant in oceans (1

in 6,500 molecules is in 6,500 molecules is “heavy water.”“heavy water.”

DD22

11

HH11

11

FusionFusion

n

Candidate Fusion EquationCandidate Fusion Equation

Isotopes of HydrogenIsotopes of Hydrogen DeuteriumDeuterium DD

DD22

11HeHe

33

22nn

11

00++ ++DD

22

11

Fusion ProcessFusion Process

Element or Element or ParticleParticle

Mass Mass (in units of amu, (in units of amu,

1.660539x101.660539x10-27-27 kg) kg)

TotalTotal

BeforeDeuterium 2.014103

4.028206Deuterium 2.014103

AfterHelium-3 3.016029

4.024694n 1.008665

Mass Mass DifferenceDifference

-0.003512 -0.003512 amuamu

ΔΔmcmc22 -3.3 MeV-3.3 MeV

Example ConstructionExample Construction

Lithium and Deuterium H-Lithium and Deuterium H-Bomb.Bomb.

Must overcome Coulomb Must overcome Coulomb repulsion, get close repulsion, get close enough for strong nuclear enough for strong nuclear force to take over.force to take over.

Fission bomb provides Fission bomb provides energy to bring them energy to bring them close to each otherclose to each other..

Castle Bravo TestCastle Bravo Test

15 Megatons (equivalent of dynamite).15 Megatons (equivalent of dynamite). February 28, 1954, Bikini Atoll in South February 28, 1954, Bikini Atoll in South

Pacific.Pacific. ““One of the atolls has been totally One of the atolls has been totally

vaporized, disappearing into a gigantic vaporized, disappearing into a gigantic mushroom cloud that spread at least 100 mushroom cloud that spread at least 100 miles wide and dropping back to the sea miles wide and dropping back to the sea in the form of radioactive fall-out.”in the form of radioactive fall-out.”

15 Megatons.15 Megatons.

February 28, 1954, Bikini Atoll in South Pacific.February 28, 1954, Bikini Atoll in South Pacific.

Big IvanBig Ivan

Tsar BombaTsar Bomba

““Big Ivan,” the largest bomb ever tested, Big Ivan,” the largest bomb ever tested, October 30, 1961October 30, 1961

Commissioned by Nikita Kruschev.Commissioned by Nikita Kruschev. Exploded with 50-Megaton force.Exploded with 50-Megaton force. Burst at 13,000 feet, fireball reached the Burst at 13,000 feet, fireball reached the

Earth.Earth. Designed so delivery aircraft could safely fly Designed so delivery aircraft could safely fly

25 miles away before detonation.25 miles away before detonation. Film

Controlled FusionControlled Fusion Need kinetic energy to overcome Coulomb Need kinetic energy to overcome Coulomb

repulsion.repulsion. National Ignition Facility

Inertial confinement fusion experiments.Inertial confinement fusion experiments. Implode a microcapsule simultaneously Implode a microcapsule simultaneously

irradiated by 192 giant lasers.irradiated by 192 giant lasers. Facility certified to operate March 27, 2009.Facility certified to operate March 27, 2009.

NIF: Recipe for a Small StarNIF: Recipe for a Small Star

Hollow, spherical plastic capsule about two millimeters in Hollow, spherical plastic capsule about two millimeters in diameter (about the size of a small pea) diameter (about the size of a small pea)

Filled with 150 micrograms of a mixture of deuterium and Filled with 150 micrograms of a mixture of deuterium and tritium, the two heavy isotopes of hydrogen. tritium, the two heavy isotopes of hydrogen.

Take a laser that for about 20 billionths of a second can Take a laser that for about 20 billionths of a second can generate 500 trillion watts – the equivalent of five million generate 500 trillion watts – the equivalent of five million million 100-watt light bulbs. million 100-watt light bulbs.

Focus all that laser power onto the surface of the Focus all that laser power onto the surface of the capsule. capsule.

Wait ten billionths of a second. Wait ten billionths of a second. Result: one miniature star. Result: one miniature star.

Controlled FusionControlled Fusion International approach under construction.International approach under construction. International Thermonuclear Experimental International Thermonuclear Experimental

Reactor (ITER), located in southern France.Reactor (ITER), located in southern France. Magnetic confinement fusion Magnetic confinement fusion

experiments.experiments. Contain plasma in Contain plasma in

magnetic fields while magnetic fields while energy is added. energy is added.

Impact on HumansImpact on Humans

Dosimeters – used to measure radiation.Dosimeters – used to measure radiation.

Radiation Impact on HumansRadiation Impact on Humans

Passage of an Passage of an energetic charged energetic charged nuclear particle through nuclear particle through a cell produces a region a cell produces a region of of dense ionizationdense ionization along its track. along its track.

Destroys or damages Destroys or damages DNA.DNA.

DNA Radiation Damage DNA Radiation Damage – artist concept– artist concept

Radiation DosageRadiation Dosage

Radiation dosageRadiation dosage is the energy deposited is the energy deposited per kilogram of living tissue.per kilogram of living tissue.

Traditional U.S. unit is Traditional U.S. unit is rad (radiation rad (radiation absorbed doseabsorbed dose), 0.01 J per kilogram of ), 0.01 J per kilogram of living tissue. living tissue.

Does not make a distinction between Does not make a distinction between various types of radiation and the resulting various types of radiation and the resulting damage.damage.

RBE Damage to HumansRBE Damage to Humans

RBERBE (relative biological effectiveness). (relative biological effectiveness). Photon (x-ray and Photon (x-ray and γγ-ray) -ray) radiation and radiation and ββ

radiation are assigned the base value of 1.radiation are assigned the base value of 1. RBE for neutron radiation has the value of 10.RBE for neutron radiation has the value of 10. RBE for alpha-particle radiation has the value RBE for alpha-particle radiation has the value

of 20.of 20. Thus, 1 rad of alpha radiation is 20X more Thus, 1 rad of alpha radiation is 20X more

damaging than 1 rad of X-rays.damaging than 1 rad of X-rays.

Radiation TherapyRadiation Therapy

Injure or destroy cells in the area being treated Injure or destroy cells in the area being treated (the “target tissue”) – damage their genetic (the “target tissue”) – damage their genetic material, making it impossible for these cells to material, making it impossible for these cells to continue to grow and divide.continue to grow and divide.

Damages both cancer cells and normal cells –Damages both cancer cells and normal cells –most normal cells can recover from the effects most normal cells can recover from the effects of radiation.of radiation.

Radiation therapy – damage as many cancer Radiation therapy – damage as many cancer cells as possible, while limiting harm to nearby cells as possible, while limiting harm to nearby healthy tissue.healthy tissue.

Treatment TypesTreatment Types

External radiation therapy External radiation therapy X-rays and gamma X-rays and gamma rays.rays. Particle beams.Particle beams.

LLUMC“LLUMC“Proton Treatment Center.”.” Proton treatment deposits energy in Proton treatment deposits energy in

very small region, protecting organs in very small region, protecting organs in front of and behind the target.front of and behind the target.

Treatment Types

Radioactive implants are devices that are placed directly within cancerous tissue or tumors, in order to deliver radiation therapy intended to kill cancerous cells.

With use of radioactive implants, tumor is subjected to radioactive activity over a longer period of time, as compared to external beam therapy.

Permanent BrachytherapyPermanent Brachytherapy

Doctor implants radioactive (iodine- 125 or Doctor implants radioactive (iodine- 125 or palladium-103) seeds into the prostate gland. palladium-103) seeds into the prostate gland. Anywhere from 40 to 100 seeds are commonly Anywhere from 40 to 100 seeds are commonly implanted.implanted.

The implants remain in place permanently, and The implants remain in place permanently, and become biologically inert (no longer useful) after a become biologically inert (no longer useful) after a period of months. This technique allows a high dose period of months. This technique allows a high dose of radiation to be delivered to the prostate with of radiation to be delivered to the prostate with limited damage to surrounding tissues.limited damage to surrounding tissues.

Isotopes of HydrogenIsotopes of Hydrogen Hydrogen (in “light water” Hydrogen (in “light water”

HH22O)O) DeuteriumDeuterium

““Heavy hydrogen.”Heavy hydrogen.” Stable isotopeStable isotope

TritiumTritium Radioactive isotope of Radioactive isotope of

hydrogen.hydrogen. Half-life = 4,500 days Half-life = 4,500 days

HH22

11

HH33

11

HH11

11

Paper can blockPaper can block

Use aluminum to Use aluminum to blockblock

Use lead to blockUse lead to block

A Nuclear Decay ChainA Nuclear Decay Chain The natural decay chain of uranium-238 is as follows:The natural decay chain of uranium-238 is as follows:

decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234 which decays, through beta-emission, with a half-life of 24 days to protactinium-234which decays, through beta-emission, with a half-life of 24 days to protactinium-234 which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234 which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230 which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226 which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon-222which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon-222 which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218 which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214 which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214 which decays, through beta-emission, with a half-life of 20 minutes to polonium-214which decays, through beta-emission, with a half-life of 20 minutes to polonium-214 which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210 which decays, through beta-emission, with a half-life of 22 years to bismuth-210which decays, through beta-emission, with a half-life of 22 years to bismuth-210 which decays, through beta-emission, with a half-life of 5 days to polonium-210which decays, through beta-emission, with a half-life of 5 days to polonium-210 which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a

stable nuclide.stable nuclide.

- Wikipedia- Wikipedia

Carbon DatingCarbon Dating

Carbon DatingCarbon Dating

Trace amounts of Carbon-14 are present in all Trace amounts of Carbon-14 are present in all organic materials.organic materials.

Created by the Sun in Earth’s upper Created by the Sun in Earth’s upper atmosphere and mixed through atmosphere in atmosphere and mixed through atmosphere in COCO22..

Absorbed by all living things. When the living Absorbed by all living things. When the living body dies, the amount in the body is “fixed.”body dies, the amount in the body is “fixed.”

Half-life of Half-life of 1414C is 5,730 years.C is 5,730 years. Measure the ratio of Measure the ratio of 1212C to C to 1414C to estimate age.C to estimate age.

ExampleExample

Bones were found in Texas that had only Bones were found in Texas that had only 25% of their carbon-14 left. Estimate their 25% of their carbon-14 left. Estimate their age.age.

Half was lost in the first 5,730 Half was lost in the first 5,730 years: down to 50%years: down to 50%

Half of what was left was lost in Half of what was left was lost in the next 5,730 years, down to the next 5,730 years, down to 25%.25%.

Total elapsed time is Total elapsed time is approximately 11,460 years.approximately 11,460 years.

Example Carbon−14Example Carbon−14

Carbon-14Carbon-14 5,730 years5,730 years

Cobalt-60Cobalt-60 5.26 years5.26 years

Strontium-90Strontium-90 29.12 years29.12 years

Radium-226Radium-226 1600 years1600 years

Uranium-238Uranium-238 4.46 billion years4.46 billion years

Uranium-235Uranium-235 703 million years703 million years

14C Decay

ββ decay to decay to 1414NN