Howard Matis

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Nuclear Science Merit Badge

• Howard Matis
• Lawrence Berkeley National Laboratory

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Radiation gives Superhuman Powers to Spiderman
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Radiation gives Superhuman Powers to The Hulk
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Chernobyl
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Radiation is

• Plot device for fiction
• Scary
• Deadly
• Life saving
• Misunderstood
• Useful

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Radiation Hazard Symbol
The symbol is placed on a placard with the word
CAUTION or DANGER or GRAVE DANGER centered about
it. Under the symbol is the information
addressing the types of hazards. Examples
are Radiation Area High Radiation
Area Airborne Radioactivity Area Contaminated
Area Radioactive Materials Area
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Radiation is Energy

• The energy is given off by unstable (radioactive)
  atoms and some machines.

We will be focusing on ionizing radiation and its
health effects.
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Atoms Building Blocks of Matter

• All matter is made up of atoms
• The nucleus is in center
• almost all of the mass
• Electrons go around
• At this scale, electrons are at the edge of town

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What is a Nucleus?

• Quarks determine if proton or neutron
• Neutrons
• Protons
• Protons determine chemical properties
• Ratio of neutrons to protons make a nucleus
  stable or unstable

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Isotopes

• Many elements have nuclei with the same number of
  protons
• same name
• same chemistry
• but different numbers of neutrons
• different masses

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Examples - Isotopes

• Hydrogen (1H)
• 1 proton, 0 neutrons, mass 1
• Deuterium (2D)
• 1 proton, 1 neutron, mass 2
• Tritium (31T)
• 1 proton, 2 neutrons, mass 3

• Helium (4He) (a-particle)
• 2 protons, 2 neutrons, mass 4
• Helium-3 (3He)
• 2 protons, 1 neutron, mass 3

• Uranium-238 (238U)
• 92 protons, 146 neutrons, mass 238
• Uranium-235 (235U)
• 92 protons, 143 neutrons, mass 235

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Types of Radioactivity
Six Common Types Alpha Decay Beta Decay Gamma
Decay Fission Fusion Cosmic Rays

• Each type of radiation is ionizing
• But different properties
• affect the hazards they pose
• the detection mechanism
• shielding

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How Does it Decay?

• Alpha - lose an alpha particle (? - helium
  nucleus)
• Beta - emit a beta particle (? - electron or
  anti-electron)
• Gamma - emit a gamma (? or photon or light
  particle)

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Alpha Decay

• Alpha particle or helium nucleus emitted
• Nucleus changes mass by four units and charge by
  two units
• Common for heavy elements
• Changes chemical properties
• Alpha particle easily stopped
• 4 x nucleon mass
• 2 Charge
• Big

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Beta Decay

• Beta minus - neutron converts to electron and
  anti-neutrino
• Beta plus - proton converts to a anti-electron
  and neutrino
• Nucleus changes charge but not mass number
• Changes chemical properties
• Radiation moderately penetrating
• 1 charge
• Small electron

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Gamma Decay

• Nucleus changes energy level
• Emits gamma ray or photon
• Nucleus stays the same
• No change in chemical properties
• Very penetrating
• Almost no size
• Neutral

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Absorption of Radiation
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Fission
The heavy parent nucleus fissions
Sometimes a very heavy nucleus will fall apart
before it can emit an alpha particle.
into two lighter (radioactive) fission fragment
nuclei plus some left over neutrons
Fission can release an enormous amount of energy
and is utilized in power plants and fission bombs
(A-bomb).
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Fusion

• When two nuclei collide and stick together
• Process that powers the sun and stars
• All life arises from it
• Not usually found in every day experience on
  Earth
• Component of the H-bomb

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How Unstable Is It?

• The Half-life describes how quickly Radioactive
  Material decays away with time.It is the time
  required for half of the unstable atoms to decay.
• Some Examples
• Some natural isotopes (like uranium and thorium)
  have half-lives that are billions of years
• Since Earth is about 5 billion years old, short
  lived naturally produced isotopes gone
• Most medical isotopes (like 99mTc) last only a
  few days

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Half-Life Experiment

• Guess the number I am thinking
• from 1 to 4

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Some Isotopes Their Half Lives
ISOTOPE HALF-LIFE APPLICATIONS
238U Uranium billions of years Natural uranium is comprised of several different isotopes. When enriched in the isotope of 235U, its used to power nuclear reactor or nuclear weapons.
14C  Carbon  5730 y Found in nature from cosmic interactions, used to carbon date items and as radiolabel for detection of tumors.
137Ce Cesium  30.2 y Blood irradiators, tumor treatment through external exposure. Also used for industrial radiography.
3H Tritium  12.3 y Labeling biological tracers.
192Ir  Iridium 74 d Implants or "seeds" for treatment of cancer. Also used for industrial radiography.
99Mo   Molybdenum 66 h Parent for 99mTc generator.
99mTc Technetium  6 h Brain, heart, liver (gastroenterology), lungs, bones, thyroid, and kidney imaging, regional cerebral blood flow, etc.
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How do we Measure the Amount of Radiation?
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Radiation Quantities and Units
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Convert from Curies to Rad

• Curie is the number of decays/s
• 1 Curie 3.7 ? 1010 decays/s (exactly)
• Rad is the absorbed dose or physical dose
• Amount of energy deposited in unit mass
• human tissue or other media
• 1 Rad 100 erg/g
• Often use gray
• 1 J/kg
• 1 gray 100 rad

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Need Biological Dose REM

• To convert from rad to rem multiply by
  appropriate value of Q
• Q is the Quality Factor
• Q reflects the damage

rad ? Q rem
Q
Gamma x-ray 1
Beta 1
Neutron 3-20
Alpha 20
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Radiation and Health

• Does radiation affect you?

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Ionizing Radiation can Damage DNA
Ionizing radiation has the ability to ionize
atoms and molecules, possibly altering structure
and function.
ionize produce positive and negative
electrical charge
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Alpha Radiation Is Only a Hazard When Inside Your
Body (Internal Hazard)
Your skin will stop it
cant penetrate skin
internal hazard
stopped by paper
found in soil, radon and other radioactive
materials
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Beta Radiation Is a Skin, Eye and Internal Hazard
skin, eye and internal hazard
stopped by plastic
found in natural food, air and water
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X-ray and Gamma Radiation Are Penetrating
Radiation and an External Hazard
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How does Radiation Injure Cells?

• High energy radiation breaks chemical bonds.
• This creates free radicals, like those produced
  by other insults as well as by normal cellular
  processes in the body.
• The free radicals can change chemicals in the
  body.
• These changes can disrupt cell function and may
  kill cells.

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Types of Exposure Health Effects

• Acute Dose - Deterministic
• Large radiation dose in a short period of time
• Large doses may result in observable health
  effects
• Early Nausea vomiting
• Hair loss, fatigue, medical complications
• Burns and wounds heal slowly
• Examples medical exposures andaccidental
  exposure to sealed sources
• Chronic Dose - Stochastic
• Radiation dose received over a long period of
  time
• Body more easily repairs damage from chronic
  doses
• Does not usually result in observable effects
• Examples Background Radiation andInternal
  Deposition

Inhalation
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At HIGH Doses, We KNOW Radiation Causes Harm

• High Dose effects seen in
• Radium dial painters
• Early radiologists
• Atomic bomb survivors
• Populations near Chernobyl
• Medical treatments
• Criticality Accidents
• Cancer
• Leukemia (A-bomb data)
• Thyroid (Chernobyl data)
• Bone and other solid cancers (A-bomb data)
• Birth defects (A-bomb data)
• Genetic effects (only animal data)
• .

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Effects of ACUTE (Deterministic) Exposures
Dose (rads) Effects
25-50 First sign of physical effects (drop in white blood cell count)
100 Threshold for vomiting (within a few hours of exposure)
320 - 360 50 die within 60 days (with minimal supportive care)
480 - 540 50 die within 60 days (with supportive medical care)
1,000 100 die within 30 days
For common external exposures 1 rad 1 rem
1,000 mrem
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At LOW Doses, We PRESUME Radiation Causes Harm

• No physical effects have been observed
• The Bad News Radiation is a carcinogen and
  a mutagen
• The Good News Radiation is a very
  weak carcinogen and mutagen!

Very Small DOSE Very Small RISK
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Sources of Radiation

• Average radiation exposure in the United States
• 360 mrem or
• 0.360 rem
• Very location dependent

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Manufactured Sources of Radiation Contribute an
Average of 60 mrem/year
cigarette smoking - 1300 mrem
lung dose


medical - 53 mrem

building materials - 3.6 mrem


smoke detectors - 0.0001 mrem
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Risks in Perspective

• 1 in 1 million chance of fatality
• 40 tablespoon peanut butter (aflotoxin)
• 2 days in New York City (air quality)
• 3 mrem radiation (cancer)
• 1 mile on motorcycle (collision)
• 300 miles in car (collision)
• 10 charbroiled steaks
• Smoking 1 cigarette

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ALARA
ALARA stands for As Low As Reasonably Achievable

• Reduce radiation dose by using
• Time
• Distance
• Shielding

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Reduce Time
Spend as short as time as necessary to complete
the task
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Activity

• Demonstrate Time (t)

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Increase Distance
Twice the distance ¼ of the dose
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Activity

• Demonstrate Distance (d)

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Use Shielding
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Activity

• Demonstrate Shielding (s)

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Reactors Glow in the Dark

• Reactor core emits electrons
• Electrons move faster than the speed of light in
  water
• At that speed they emit blue light
• Cherenkov Radiation
• Similar to sonic boom or wake of a boat

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Can You Glow in the Dark?

• Ingest a very hot radiation source
• Beta needed
• Short half life
• Do not swallow
• Unless your midriff is exposed
• Or inject source into your blood
• Dont be in direct light
• Usually too faint for sunlight

• Try it for Halloween?

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Summary

• Radiation is part
• Our natural environment
• Technology
• Health effects
• Known for high doses
• Unknown for low
• You deal with it regularly

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The End