ANS Congressional Sessions

Welcome to Session 1 – What is Radiation?

Future Sessions:Session 2 - Reactor/OperatorsSession 3 - The Fuel-CycleSession 4 - NonproliferationSession 5 - Other Uses of Radiation

Radiation Basics

Mary Lou Dunzik-Gougar, Ph.D.Acting Chair of Nuclear Engineering at Idaho State University with joint appointment at Idaho National Laboratory

Candace Davison, M. Engineer Research and Education SpecialistPennsylvania State UniversityRadiation Science and Engineering Center

Presented by

Radiation in the Media

“Iodine 131 was also detected at levels 10,000 times the safety limit in groundwater near Reactor No. 1.”

“…our  Geiger counter registered a brief spike to 6 microsieverts per hour”

“My electronic arming dosimeter registers a .3 millirem, its first detection of radiation.”

Inside New York's Indian Point nuclear power plant

Radiation: WHY SO SCARY?

Invisible, tasteless, odorless, and…

Misunderstood.

• What is radiation?• Where does radiation come from?• What is radioactivity?• What’s the difference between

contamination and irradiation?• What are some beneficial applications of

radiation? • How to identify credible information on

radiation.

Questions we’ll answer . . .

What is Radiation?

Transmission of energy via . . . Particles

orWaves

Types of Radiation

Non-IonizingRadiowavesMicrowaves

InfraredUltraviolet

Visible Light

and Ionizing

Types of Radiation

Non-IonizingRadiowavesMicrowaves

InfraredUltraviolet

Visible Light

IonizingAlphaBeta

Gamma (rays)X-Rays

Neutrons

Electromagnetic Spectrum

What is it? The range of wavelengths or frequencies over which electromagnetic radiation extends.

Electromagnetic Spectrum

What is it? The range of wavelengths or frequencies over which electromagnetic radiation extends.

The Nature of Radiation

Alpha ()2 protons, 2 neutronspositively charged particle

Beta ()like an electronnegatively charged particle

Gamma ()Wave energy (not a particle)

n

p+n

p+

_

Penetrating Ability

a

_

b g

n

p+n

p+

Shielding

Paper

alpha

beta

gamma

Wood

Lead

Concrete

Where does radiation come from?

Atoms . . .from radioactive or unstable atoms

Atoms

What part of atoms?

The Nucleus!Hence, we have terms such as:nuclear sciencenuclear medicinenuclear reactors

Atoms

HELIUM’S subATOMICCOMPOSITION

2 Protons

2 Neutrons

2 Electrons

Atomic structure?

e-

n

e-p+

n

p+

The Helium Atom

n

Neutrons have large mass, approximately equal to proton mass, but no charge.

p+

Protons have a large mass and a positive charge.

Electrons have a very small mass and a negative charge. Electrons travel outside the nucleus.

e-

More on this helium isotope

42He ELEMENT

SYMBOL

MASS NUMBERis total number ofprotons and neutrons

ATOMIC NUMBER is number of protons & identifies the element

Why is it called ionizing?

Because it creates ions . . . atoms with a charge.

Ionizing Radiation

Ejected Electron

If radiation comes from atoms and everything is made of atoms, is there radiation around us right now?

But, of course!It is called

background radiation.

Background Radiation

Radiation can be read and heard. “Listen” to the background radiation with a

Geiger counter.

Geiger Counter

Is all radiation harmful?

Radiation produced by nuclear science provides for a vast range of beneficial applications.

Commercial Industrial ApplicationsElectricity Medical UsesFood Irradiation Reactor SafetyHydrogen Generation Space

Geiger Demonstration

What type of radiation source do you have on your table?

Shielding

Paper

alpha

beta

gamma

Wood

Lead

Concrete

What is radioactivity?

The spontaneous emission of “fragments” or “bundles” of energy from energetic nuclei creating more stable nuclei.

Radioactive atom

Different, more stable atom formed

Energy and radiation released

What is radioactivity?

Radioactive atoms emit radiation.

What is radioactivity?

“If I’m exposed to radiation, do I become (more) radioactive?”

Radioactivity

No!You’ve been irradiated, exposed to radiation.

Which is not to be confused with . . .contamination.

Radioactivity

Radioactive Contamination is radioactive material in an unwanted place.

Radioactive Contamination

What are some applications of irradiation?

Irradiation

Alpha radiation is used to- Power space probes- Remove static in copiers

Beta radiation is used for gauging– Thickness of aluminum during production– Eggshell thickness before shipping

Irradiation

Gamma radiation is used for the following:- Sterilizing medical supplies- Preserving food- Inspecting welds and large structures

Irradiation

Question...

How are radioactive atoms formed?

Supernova Explosion

Answer . . .

Supernovae

How do we make a stable atom radioactive?

Question...

How do we make a stable atom radioactive?– By adding energy to the nucleus– This is done by adding a particle such as a

neutron from a reactor or a high energy charged particle such as an electron or proton from a particle accelerator

Answer

Ok, so I don’t become radioactive from being irradiated, but are there other healtheffects to radiation exposure?

Question...

• Radiation is part of our natural environment.• We are exposed to radiation from materials in the earth itself.• Naturally occurring radon in the air, from outer space, and from inside our

own bodies (as a result of the food and water we consume). This• Radiation is measured in units called millirems (mrems).• The average dose per person from all sources is about 620 mrems per year.

Answer

Provide examples of exaggerated headlines or reports levels of radiation that suggest unsafe levels.

How to recognize credible reports on radiation and nuclear in the media

Slides 44 to the end are technical, and negative with a lot of information about cancer. Audience take-away is very negative.Can the information regarding dose, half-life, radon, dose vs. risk (risk implies a negative) be reviewed and reworked to present the information in a more relative way? Show DOSE in context and provide examples that are positive.• I.e. radiation is part of cancer treatment-show more benefits

Slides 44 - end

Thank you for your participation in today’s session.We hope you have a better understanding of radiation and nuclear.Please give us your feedback with a brief 5 question survey (provide link):

Thank you!

ANS Congressional Sessions

Join us in April for Session 2 - Reactor/Operators

Future Sessions:Session 3 - The Fuel-CycleSession 4 - NonproliferationSession 5 - Other Uses of Radiation

American Nuclear Society

Radon Gas More Deadly Than Carbon Monoxide Poisoning!!!!• By Robert Preidt • SUNDAY, Jan. 27 (HealthDay News) -- Radon, an invisible

radioactive gas that seeps into homes through foundation cracks, causes 100 times more deaths than carbon monoxide poisoning, says the U.S. Environmental Protection Agency.

• To heighten awareness of that potential danger, the agency has designated January as National Radon Action Month.

• Radon is the second leading cause of lung cancer behind smoking, and about 20,000 people in the United States will die this year due to breathing too much radon without even knowing it, the EPA said.

• "It's remarkably easy to protect our loved ones by testing for radon and building new homes with radon-resistant features that allow everyone to breathe freely and safely," EPA Deputy Administrator Marcus Peacock said in a prepared statement.

• http://abcnews.go.com/Health/Healthday/story?id=4510215

Radon Gas – Decay products

Image: http://www.sanitred.com/RadonHealth.htm

Why are we concerned about Radiation?

Ionizing Radiation

Human Cells

Atoms in Cells Form Ions

Change in Cell Cell DiesNo/Neutral Change in Cell

Not Replaced

ReplacedReproduces

Malignant Growth Benign Growth

How much is too much dose?

DOSE

Dose

• Radiation is energy – when it interacts with a material, it transfers some or all of that energy to the material

• The amount of energy transfer is called dose

• Most international bodies use the GRAY• In the US, the common unit is the RAD

– 1 Gray = 100 Rad

Energy Deposited

Mass of MaterialDose

Dose Perspective

Dose (mrem) Source

1 Dental xray

25 Round trip flight to South Africa

40 Your body

110 Head and body CAT scan

620 Average dose in U.S.

5500 Average dose in Guarapari, Brazil

10,200 Average dose in Ramsar, Iran

0 – 25,000 No observable effect

Types of Dose and Effects

Acute dose vs. Chronic dose

• Acute is short term• Chronic is spread over

a long time period

Somatic effects vs. Hereditary effects

• Somatic effects in person exposed

• Hereditary effects in offspring of exposed person

Internal dose vs. External dose

• Some radiation is not harmful externally, but is internally (e.g. alpha and low energy betas) 50

Early Effects of Acute Whole-Body Radiation Doses

Dose (rem) Effect

0-25 No observable effect

25-100 Slight blood changes

100-200 Vomiting (5-50%)Moderate blood changesFull recovery within a few weeks

200-600 Vomiting (50-100%)Severe blood changesHemorrhage, infections, hairlossDeath (0-80%) within 2 mos.Survivors recover in 1 mo. to 1 yr.

600-1000 Same as aboveDeath (80-100%) within 2 mos.

51

Risk at low doses

A lot of people say, ‘Gee, we don't know a lot about the risks of radiation’ … I say: ‘We know a whole lot. We've studied populations all over the world since the turn of the last century. We know what happens at high doses. We know what happens at medical doses. And we know that at low doses the risks are low. The controversy is just how low are they. Are they really low or are they really, really low?’

--- Dr. John Boice, Jr., Founder of the radiation epidemiology section at the National Cancer InstitutePresident, National Council on Radiation Protection and Measurements

Risk at low doses

• Cancer risk can be experimentally proven for doses above about 0.1 Sv (10 rem)

• It is essentially impossible to design an experiment to directly measure risk at low doses

• We apply a conservative model to estimate the risks at low dose, assuming that any radiation dose carries some risk (there is no threshold) and that risk at low dose is proportional to risk at higher doses (linear)– Called the Linear, No-Threshold (LNT) model

Dose vs. Risk Theory

54

Linear-No-Threshold (LNT)

Dose Limits in US Regulations

5000(radiation workers)

&

100(members of the public)

per year in milli-rem(or 50 and 1 in milli-Sievert)

How do we protect ourselves?

• Time– Limit time of the exposure

• Distance – Increase distance between you and dose

• Shielding– Between you and

the source of radiation

ALARA

• All radiation dose must be made ALARA (As Low As Reasonably Achievable)– Takes into account the effort needed to reduce

the dose, how much risk is saved, and what side effects might result .

• Pushes us to reduced dose where possible, even below the dose limits.

• Reinforces higher doses is certain situations (medical procedures, emergency conditions, etc.).

Important information to remember about radiation and nuclear

1. Radiation and radioactivity are a natural part of our world.

2. Nuclear technology works. 3. Nuclear technology enhances our quality of life.

Acute Effects -“Radiation Sickness”

• Result of a very high one-time or short-term burst of radiation exposure– Nuclear weapons, criticality accidents, etc.

• Symptoms may be temporary or fatal, depending upon amount of radiation exposure

• Only occurs above a threshold– A “yes or no” effect

• Localized radiation exposure may cause acute effects – usually seen as skin burns

Delayed Effects -- Cancer

• Radiation exposure in large enough quantities is known to increase the risk of cancer

• Cancer in a particular person cannot be tied to a particular cause – roughly 4 in 10 people have cancer at some point in their lives

• For this, we want some way to quantify the amount of risk associated with radiation exposure

Radiation is Radiation (or is it?)

Is there a difference between radiation from different sources?

– Cosmic rays– Weapons testing fallout– Medical x-ray/CT scan– Radon– Nuclear waste– …

Radiation – not created equal

• Energy alone is not the whole story• Different types of radiation can cause

different amounts of biological damage for the same amount of energy deposited

• We multiply the dose by a quality factor to account for this:– Gamma (& x-ray) QF = 1– Beta QF = 1– Alpha QF = 20

-

+

+

Radiation – still not created equal

• Different tissues respond differently to the same radiation dose (or dose equivalent)

• Particularly important for radioactive material intake, where material may concentrate in particular organs

• To account for this, we take a weighted average of dose to organs to account for this

Radiation – still not created equal

• We call this Effective Dose• Dose to each tissue is multiplied by a

tissue weighting factor and summed

• Effective dose allows us to compare the risk from one kind of radiation dose to another

• International standard unit is the Sievert • US commonly uses the REM

– 1 Sievert = 100 rem

(Effective Dose) T TT

E w D

=

Radiation – still not created equalTissue ICRP 26 (1977) ICRP 60 (1991) ICRP 103 (2007)

Reproductive organs 0.25 0.20 0.08

RBM 0.12 0.12 0.12

Colon 0.12 0.12

Lung 0.12 0.12 0.12

Stomach 0.12 0.12

Bladder 0.05 0.04

Breast 0.15 0.05 0.12

Liver 0.05 0.04

Esophagus 0.05 0.04

Thyroid 0.03 0.05 0.04

Skin 0.01 0.01

Bone Surfaces 0.03 0.01 0.01

Brain 0.01

Salivary glands 0.01

Remainder* 0.3 0.05 0.12

Effective Dose

• The most important factor in this weighted average is the risk of cancer fatality

• Cancer incidence (getting cancer, but not necessarily dying from it) is partially included, particularly for cancers with very high treatability and survivability

• We can estimate the risk of fatal cancer at approximately 4-5% per Sievert (per 100 rem)

• The total dose, and not the rate it is received, is what matters

Dose Limits in US Regulations

• Dose limits are maximums for normal occupational sources– No authority to limit medical exposures– Very limited authority over dose from

natural sources (drinking water is key exception)

“Safe Level of Radiation”

• Dose limits are chosen as a guideline to assure an acceptable margin of safety– Does not mean that 99 millirem is automatically

“safe” and 101 millirem is “unsafe”

• These limits are used to derive “safe levels” of radioactive materials in food/water/air– Assume a consistent intake at normal rates over

a whole year