What is Radiation?

Our sun is a large source of radiation. Radiation is energy that travels through space.

IONIZING RADIATION FROM NUCLEAR SOURCES

Ionizing radiation occurs in various forms principally alpha particles, beta particles, and gamma rays. All of these have various penetrating

abilities.

α, β, and γ penetrating power

Various Forms of Ionizing Radiation

• Alpha particles are super-energized helium nuclei; alpha sources are dangerous if inhaled or ingested; they have very limited penetration distance. They will not penetrate the skin.

• Beta particles are high energy, negatively-charged electrons; they are a skin, inhalation and ingestion hazard; They can be stopped by normal clothing.

• Gamma rays are highly energetic electromagnetic energy and can only be stopped by very dense materials.

• Neutrons are particles produced by the decay of some radioactive substances or through a process called nuclear fission. Some neutrons are high energy, fast moving particles while others are low velocity, low energy particles.

TYPE ALPHA BETA GAMMA NEUTRON

PENETRATING POWER

VERY SMALL

SMALL VERY GREAT

VERY GREAT

HAZARD INTERNAL INTERNAL/EXTERNAL

EXTERNAL EXTERNAL

SHIELDING MATERIAL

AIR OR PAPER

PLASTIC OR ALUMINUM

LEAD, STEEL OR CONCRETE

WATER, CONCRETE, STEEL

Radioactive particle

Symbol Atomic Mass

Change

Atomic No.

change

Alpha -4 -2

Beta 0 +1

Gamma 0 0

 152Dy* ----> 152Dy + γ

WHEN AN ELEMENT LOSES A GAMMA RAY, IT IS STILL THE SAME ELEMENT.

23892U 234

90Th +

23490Th 234

91Pa + 23492U +

RADIOACTIVITY REFERS TO PARTICLES EMITTED BY UNSTABLE ATOMIC NUCLEI.

ATOMIC NUCLEI CONTAIN PROTONS AND NEUTRONS.

IF THE MIX OF PROTONS AND NEUTRONS IS NOT QUITE RIGHT, THE NUCLEI CAN BECOME UNSTABLE AND EMIT RADIOACTIVE PARTICLES AND IN SOME CASES BREAK APART.

THE PROCESS OF BREAKING APART IS CALLED NUCLEAR FISSION.

As atoms decay, they give up radiation and produce various unstable elements on their way to producing a stable element. Uranium-238 goes through 14 transformations on its way to becoming Lead-206.

The uranium decay chain

Uranium-238

∝ Rays Thorium-234

_ Rays Protactinium-234

_ Rays Uranium-234 ∝ Rays Thorium-230 ∝ Rays Radium-226 ∝ Rays Radon-222 ∝ Rays

Polonium-218 ∝ Rays Lead-214 _ Rays Bismuth-214 _ Rays Polonium-214 ∝ Rays Lead-210 _ Rays Bismuth-210 _ Rays Polonium-210 ∝ Rays Lead-206 stable

The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope.

How dangerous a radioactive element is depends both on the amount of material, the half life, and the kind of radiation given off.

The shorter the half life, the more disintegrations per unit time will occur.

No. of half lives elapsed

Fraction Remaining Percentage Remaining

0 1/1 100

1 ½ 50

2 ¼ 25

3 1/8 12.5

N 1/2n 100(1/2n)

Isotope Half-life Use

Carbon 11 20 minutes Agriculture

Iodine-131 8 days Medical therapy

Krypton-85 11 years Industry

Cesium-137 30 years Treat cancers,

Sterilize garbage and medicinal wastes

Calibrate equipment

Irradiate blood for transfusions

Carbon-14 5730 years Test new drugs for harmful by-products

Carbon dating of ancient artifacts

Iodine-129 15.7 million years Check radioactivity counters at in-vitro diagnostic labs

Uranium-238 4.5 billion years Color brighteners in dental fixtures; dating old rocks

Radiation is not to be feared. Radiation safety is essential for its proper usage. Knowing the nature of a source of radiation, the source location

and its intensity allows us to take advantage of nuclear materials without subjecting ourselves and others to the negative consequences

we fear.

Radiation signage

EVERYTHING AND EVERYBODY AROUND YOU IS RADIOACTIVE TO SOME EXTENT.

THE UNIT WE USE TO MEASURE RADIATION IS THE rem.

ONE rem IS THE EQUIVALENT OF YOUR BODY ABSORBING ONE TWO MILLIONTH OF A CALORIE OF ENERGY.

COMPARED TO THE RADIATION YOU NORMALLY ABSORB, THAT’S A LARGE AMOUNT.

SO WE USE THE mrem OR millirem (1/1000 of a rem) OR WE CAN USE THE microrem.

THE NATURALLY OCCURING RADIOACTIVE MATERIALS IN OUR BODIES EXPOSE US TO ABOUT 25 mrem PER YEAR.

NO ILL EFFECTS HAVE BEEN SEEN FOR PEOPLE RECEIVING 5,000 mrem PER YEAR.

ON A SHORT TERM BASIS, IT TAKES ABOUT 300,000 mrem TO CAUSE A FATALITY.

YOU ARE EXPOSED TO ABOUT 200 mrem FROM AIR EACH YEAR.

YOUR EXPOSURE INCREASES THE HIGHER ABOVE SEA LEVEL YOU LIVE.

A DENTAL X-RAY EXPOSES YOU TO ABOUT 1 mrem.

RADIATION REACTS WITH MATTER BY KNOCKING ELECTRONS OFF ATOMS AND FORMING IONS.

THE EFFECT ON LIVING CELLS CAN VARY.

1. CELLS COULD BE UNDAMAGED.

2. CELLS ARE DAMAGED. THE DAMAGE IS REPAIRED, AND CELLS OPERATE NORMALLY.

3. CELLS ARE DAMAGED. THE DAMAGE IS REPAIRED, BUT THE CELLS OPERATE ABNORMALLY.

4. CELLS DIE AS A RESULT OF THE DAMAGE.

THE RISK FROM RADIATION IS HOW MUCH YOU GET ALL AT ONCE.

300,000 mrem MIGHT BE FATAL IF RECEIVED ALL AT ONCE, BUT SPREAD OVER A NUMBER OF YEARS, IT MIGHT CAUSE NO DAMAGE AT ALL.

DNA DAMAGE CAN CAUSE TUMORS OR CANCER.

THE DECREASE IN LIFE EXPECTANCY FROM 1 mrem IS 1.2 MINUTES – ABOUT THE SAME AS:

-CROSSING THE STREET THREE TIMES

-THREE PUFFS FROM A CIGARETTE

-10 EXTRA CALORIES FOR AN OVERWEIGHT PERSON

THE AVERAGE PERSON RECEIVES ABOUT 360 mrem PER YEAR.

THE DECREASE IN LIFE EXPECTANCY FROM 1 mrem IS 1.2 MINUTES – ABOUT THE SAME AS:

-CROSSING THE STREET THREE TIMES

-THREE PUFFS FROM A CIGARETTE

-10 EXTRA CALORIES FOR AN OVERWEIGHT PERSON

THE AVERAGE PERSON RECEIVES ABOUT 360 mrem PER YEAR.

THE MOST COMMON WAY TO DETECT RADIATION IS USING A GEIGER COUNTER.

The detector is a tube with a wire running down the center. A high voltage (600v) is applied between the wire and the envelope. When ionizing radiation hits the gas in the tube, ions are formed, and a current pulse flows through the meter. The number of pulses is a measure of radiation intensity.

Other devices include film badges and scintillation counters.

HOW CAN YOU AVOID EXPOSURE TO IONIZING RADIATION?

1)TIME – THE SHORTER THE, TIME THE LESS THE DANGER

2)DISTANCE – EXPOSURE DECREASES WITH THE SQUARE OF THE DISTANCE

3)SHIELDING – DIFFERENT KINDS OF SHIELDING STOP DIFFERENT KINDS OF RADIATION

YOU CAN BE EXPOSED TO IONIZING RADIATION

1)NATURALLY2)HANDLING RADIOACTIVE MATERIAL