TOPIC 1: HISTORY OF RADIATION (PART 2)

TOPIC 1 : History of Radiation (PART II)

1.0 History of Radiation1.1 Radiation Source1.2 Radiation Types1.3 Radiation Uses1.4 Radiation Hazard

1.1 Radiation Source 1.1.1 Natural Radiation

1.1.2 Artificial Radiation

1.1 RADIATION SOURCE

Humans are exposed to radiation all the time. This radiation is called background radiation. Most

of the background radiation is from natural sources (natural

background radiation). A small amount of the background

radiation is from artificial sources (Artificial background

radiation).

1.1 RADIATION SOURCE

BACKGROUND RADIATION

Natural Background

Artificial Radiation

1.1.1 NATURAL RADIATION1.1.1a Cosmic Ray1.1.1b Rocks and Soils1.1.1c Human body/Food

Natural sources

1. Cosmic radiation 2. Earth's crust /

Radioactive rock/ Soil

(Terrestrial Radiation)

3. Human body/ Food

(Internal sources)

1.1.1 Natural Background

1.1.1a Cosmic Ray

ORIGIN•Sun and outer space

DOSE LEVEL• At sea level: Average cosmic radiation dose is 26

mrem /year

• At higher elevations, the dose increases (amount of atmosphere shielding cosmic rays decreases)

Cosmic Ray

Sun emits radiation composed of high energy infrared

radiation, visible light, and ultraviolet radiation

collectively

shortwave radiation (SW)

Other energetic rays such as

gamma rays can make it through

the atmosphere to the Earth's

surface.

Absorbed by atmosphere but

the more energetic

radiations interact with the atoms in the atmosphere

creating energetic neutrons and radioactive nuclides.

1.1.1a Cosmic Ray

1.1.1a Cosmic Ray

Path of incoming solar radiation

Some other cosmogenic radionuclides are : 10Be, 26Al, 36Cl, 80Kr, 14C, 32Si, 39Ar, 22Na, 35S, 37Ar, 33P, 32P, 38Mg, 24Na,38S, 31Si, 18F, 39Cl, 38Cl, 34m

Cl.

Cosmogenic Nuclides

Nuclide Symbol Half-life Source Natural Activity

Carbon 14 14C 5730 yr Cosmic-ray interactions, 14N(n,p)14C

6 pCi/g (0.22 Bq/g) in organic

material

Hydrogen 3 (Tritium)

3H 12.3 yrCosmic-ray interactions with N and O, spallation from cosmic-

rays, 6Li(n, alpha)3H

0.032 pCi/kg (1.2 x

10-3 Bq/kg)

Beryllium 7 7Be 53.28 days

Cosmic-ray interactions with N and O

0.27 pCi/kg (0.01 Bq/kg)

1.1.1b - Rocks and soil

Rocks and soil

ORIGINGround, rocks,

building materials and drinking water

supplies

CONTRIBUTORSNatural radium,

uranium and thorium.

EXAMPLE During the

radioactive decay of Uranium, Radon

gas is produced which seeps

through rocks underground and

introduced into the atmosphere

Natural Radioactivity by the Square Mile, 1 Foot Deep

Nuclide Activity usedin calculation Mass of Nuclide Activity found in the

volume of soil

Uranium 0.7 pCi/g (25 Bq/kg) 2,200 kg 0.8 curies (31 GBq)

Thorium 1.1 pCi/g (40 Bq/kg) 12,000 kg 1.4 curies (52 GBq)

Potassium 40 11 pCi/g (400 Bq/kg) 2000 kg 13 curies (500 GBq)

Radium 1.3 pCi/g (48 Bq/kg) 1.7 g 1.7 curies (63 GBq)

Radon 0.17 pCi/g (10 kBq/m3) soil 11 µg 0.2 curies (7.4 GBq)

Total: >17 curies (>653 GBq)

Natural Radioactivity by the Ocean

Nuclide Activity used in calculation

Activity in Ocean

Pacific Atlantic All Oceans

Uranium 0.9 pCi/L (33 mBq/L)

6 x 108 Ci (22 EBq)

3 x 108 Ci (11 EBq)

1.1 x 109 Ci (41 EBq)

Potassium 40 300 pCi/L (11 Bq/L)

2 x 1011 Ci (7400 EBq)

9 x 1010 Ci (3300 EBq)

3.8 x 1011 Ci (14000 EBq)

Tritium 0.016 pCi/L(0.6 mBq/L)

1 x 107 Ci (370 PBq)

5 x 106 Ci (190 PBq)

2 x 107 Ci (740 PBq)

Carbon 14 0.135 pCi/L (5 mBq/L)

8 x 107 Ci (3 EBq)

4 x 107 Ci (1.5 EBq)

1.8 x 108 Ci (6.7 EBq)

Rubidium 87 28 pCi/L (1.1 Bq/L)

1.9 x 1010 Ci (700 EBq)

9 x 109 Ci (330 EBq)

3.6 x 1010 Ci (1300 EBq)

1.1.1c - Human Body/Food

HUMAN BODY/ FOOD

ORIGIN Our bodies also contain natural radionuclides

INTERACTIONIntroduced into the body when Eaten

or via the food chain when meat

or milk from animals grazing on

the crops are consumed

EXAMPLESPotassium 40,

carbon-14 (Breathing),

Fruits (soil and carbon-14)

Natural Radioactivity in your body

NuclideTotal Mass of

Nuclide Found in the Body

Total Activity of Nuclide

Found in the BodyDaily Intake of

Nuclides

Uranium 90 µg 30 pCi (1.1 Bq) 1.9 µg

Thorium 30 µg 3 pCi (0.11 Bq) 3 µg

Potassium 40 17 mg 120 nCi (4.4 kBq) 0.39 mg

Radium 31 pg 30 pCi (1.1 Bq) 2.3 pg

Carbon 14 22 ng 0.1 µCi (3.7 kBq) 1.8 ng

Tritium 0.06 pg 0.6 nCi (23 Bq) 0.003 pg

Polonium 0.2 pg 1 nCi (37 Bq) ~0.6 fg

Natural Radioactivity in Food

Food40K

pCi/kg226Ra

pCi/kg

Banana 3,520 1

Brazil Nuts 5,600 1,000-7,000

Carrot 3,400 0.6-2

White Potatoes 3,400 1-2.5

Beer 390 ---

Red Meat 3,000 0.5

Lima Beanraw 4,640 2-5

Drinking water --- 0-0.17

1.1.2 ARTIFICIAL SOURCE

1.1.2 Artificial Source (Definition)

This is background radiation resulting from human activity through the creation and use

of artificial sources of radiation.

ARTIFICIAL RADIATION

1. Medical sources

2. Nuclear power

stations

3. Nuclear weapons

4.Consumer products



Humans are exposed to

radiations by medical procedures such as x-rays and

radiotherapy.

1-Medical sources 2- Nuclear power stations

•Major incidents from nuclear power stations

have released radiations into the environment. •Nuclear waste from

power station also accounts for a small

proportion of artificial background radiation


Nuclear weapon testing in the 1950s and 1960s resulted in an increase

of radiation in the environment.

•Examples: TV's, older luminous dial watches, some smoke detectors, and lantern mantles

•Dose is relatively small

3- Nuclear weapon

4-Consumer products

Human Produced Nuclides

Nuclide Symbol Half-life Source

Tritium 3H 12.3 yrProduced from weapons testing and fission reactors; reprocessing facilities, nuclear weapons manufacturing

Iodine 131 131I 8.04 daysFission product produced from weapons testing and fission reactors, used in medical treatment of thyroid problems

Iodine 129 129I 1.57 x 107 yr

Fission product produced from weapons testing and fission reactors

Cesium 137 137Cs 30.17 yr Fission product produced from weapons testing and fission reactors

Strontium 90 90Sr 28.78 yr Fission product produced from weapons testing and fission reactors

Technetium 99

99Tc 2.11 x 105 yr Decay product of 99Mo, used in medical diagnosis

Plutonium 239

239Pu 2.41 x 104 yr

Produced by neutron bombardment of 238U ( 238U + n--> 239U--> 239Np +ß--> 239Pu+ß)

SUMMARY

•As a whole, these sources of natural and human-made radiation are referred to as background radiation.

•The pie chart below shows the average contribution from the various sources to background radiation.

NATURAL SOURCE

ARTIFICIAL SOURCE

VIDEO 1 VIDEO 2

1.2 RADIATION TYPES1.2.1 Ionizing Radiation1.2.2 Non-ionizing Radiation

Radiation Types

Ionizing radiation

Non-ionizing radiation

1.2 RADIATION TYPE

Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because they have an excess of energy or mass or both.Unstable atoms are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation.Radioactive decay is the spontaneous decay of atoms by emitting alpha, beta or gamma particles.New elements are always formed during alpha and beta decay

Extra Notes…. Ionization & Radioactive decay

1.2.1 Ionizing Radiation

• Definition: “ It is a type of radiation that is able to disrupt

atoms and molecules on which they pass through, giving rise to ions and free radicals”.

Ionizing Radiation

Higher energy electromagnetic

waves (x-ray, gamma) or

heavy particles (beta and alpha)

Enough energy to pull electron from orbit


Types

Alpha particles

Beta particles

Gamma rays (photons)

X-Rays (photons)

Neutrons

neutron


Photon

X-rays

emitted from electron orbits

(KeV's)

Gamma rays

from nucleus(often as part of radioactive decay)

(Mev's)

PHOTON 1.2.1 Ionizing Radiation

Ionizing Radiation

alpha particle

beta particle

Radioactive Atom

X-ray

gamma ray


Dr. Nik Noor Ashikin Bt Nik Ab Razak

Type of Radiation Alpha particle Beta particle Gamma ray (EM)

What is it? Helium Nucleus Electron Photon

Symbol

Origin Nucleus Nucleus Nucleus

Mass (atomic mass units) 4 1/2000 0

Charge +2 -1 0

Speed slow fast speed of light

Ionizing ability high medium indirectly

Penetrating power low(paper/10cm in air)

medium(5mm of aluminum)

high(30 cm lead)

LET High (QF=20) heavy damage

Low (QF=1) light damage

Low (QF=1) light damage

Hazard Inhaled

Internal hazard, but high beta can be

an external hazard to skin

Internal hazard

VIDEO 3VIDEO 4

Alpha Decay


• Beta decay involved the ejection of a beta particle (could either be an electron or a positron)

• Electrons come from a neutron and change it to a proton!!

eBaCs 01

13756

13755

Beta Decay


• The “*” denotes high energy• Gamma rays are emitted when a particle has too much

energy. No new elements are formed.

Gamma Decay

Balancing Nuclear Equations

• Both MASS and CHARGE must be conserved in any nuclear reaction

• This means that the sum of masses and atomic numbers on the right and left sides of the equations must be equal!

eg. The decay of Uranium-238:

ThHeU 23490

42

23892


Balancing examples:

HeRa 42

22688

eK 01

4219

nHeK 10

42

24195 2

Rn22286

Ca4220

Bk24397


“ They are electromagnetic waves incapable of producing ions while

passing through matter, due to their lower energy.”

1.2.2 Non-Ionizing Radiation

Non-ionizing Radiation

Lower energy electromagnetic

waves

Not enough energy to pull electron from orbit, but can excite

the electron


Examples on Non-ionizing Radiation Sources

• Visible light• Microwaves• Radios• Video Display Terminals• Power lines• Radiofrequency Diathermy (Physical Therapy)• Lasers


• Pet Scans – Uses positrons to get moving 3d image by reacting with radioactive injections

• Cat Scans – 3D X-ray image• X Rays (do not include Cat Scans)• Food irradiation• Tracers, leakage, and wear in industry, density and

thickness measurements• Cancer Treatment• Activation analysis, crime solving – composition

determining using spectrometry• Smoke detectors• Microwave ovens• Cell/mobile phones

1.3 Radiation Uses

• Both high frequency electromagnetic radiation and particle radiation can ionize atoms (give them a charge).

• Ionized atoms can change the DNA leading to the reproduction of cancerous cells

• Genetic changes

1.4 Radiation Hazard

Effects waves /cell phone Radiofrequency Ranges (10 kHz to 300 GHz)

– Effects only possible at ten times the permissible exposure limit

– Heating of the body (thermal effect)– Cataracts– Some studies show effects of teratoginicity and

carcinogenicity.

1.4 Radiation Hazard

VIDEO 5

TOPIC 1: HISTORY OF RADIATION (PART 2)

Science

Transcript of TOPIC 1: HISTORY OF RADIATION (PART 2)