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Nuclear Science Merit Badge. Howard Matis Lawrence Berkeley National Laboratory. Radiation gives Superhuman Powers to Spiderman. Radiation gives Superhuman Powers to The Hulk. Chernobyl. Radiation is . Plot device for fiction Scary Deadly Life saving Misunderstood Useful. 60°. 60°.

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nuclear science merit badge

Nuclear Science Merit Badge

Howard Matis

Lawrence Berkeley National Laboratory

Howard Matis - [email protected]

radiation is
Radiation is
  • Plot device for fiction
  • Scary
  • Deadly
  • Life saving
  • Misunderstood
  • Useful

Howard Matis - [email protected]

radiation hazard symbol

60°

60°

R

1.5R

5R

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
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
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
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
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
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
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
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 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 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
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

Paper

Plastic

Lead

Concrete

a++

Alpha

0b-

Beta

0g

Gamma and X-rays

1n

Neutron

Absorption of Radiation

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fission
Fission

Sometimes a very heavy nucleus will fall apart before it can emit an alpha particle.

The heavy parent nucleus fissions …

… 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
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
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

Half-Life Experiment

Guess the number I am thinking

from 1 to 4

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radiation quantities and units

Radiation Absorbed Dose

Qty: Dose

Unit: rad (Gray)

1 rad = 1000 mrad

1 rad = 100 erg/gram

1 Gy =100 rad

Radioactivity

Qty: Activity

Unit: Curie (Bequerel)

1 Ci = 1000 mCi

1 Bq = 1 disintegration/sec

1 Ci = 3.7  1010 Bq

Roentgen

equivalent

man

Radiation Risk

Qty: Dose Equivalent

Unit: rem (Sievert)

1 rem = 1000 mrem

1 Sv=100 rem

Radiation Quantities and Units

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convert from curies to rad
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
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

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radiation and health

Radiation and Health

Does radiation affect you?

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ionizing radiation can damage dna
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
Alpha Radiation Is Only a Hazard When Inside Your Body (Internal Hazard)

Your skin will stop it

can’t 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
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

found in medical uses

stopped by lead

naturally present in soil and cosmic radiation

X-ray and Gamma Radiation Are Penetrating Radiation and an External Hazard

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how does radiation injure cells

-

+

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 killcells.

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types of exposure health effects
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
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
Effects of ACUTE (Deterministic) Exposures

* For common external exposures 1 rad ~ 1 rem = 1,000 mrem

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at low doses we presume radiation causes harm
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
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
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
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

ALARA stands for As Low As Reasonably Achievable

Reduce radiation dose by using:

  • Time
  • Distance
  • Shielding

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reduce time
Reduce Time

Spend as short as time as necessary to complete the task

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activity

Activity

Demonstrate Time – (t)

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increase distance
Increase Distance

Twice the distance = ¼ of the dose

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activity44

Activity

Demonstrate Distance – (d)

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activity46

Activity

Demonstrate Shielding – (s)

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reactors glow in the dark
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
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
  • Don’t be in direct light
    • Usually too faint for sunlight
  • Try it for Halloween?

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summary
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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