RADIATION AND NUCLEAR ENERGY

SCIENCE 10 – EARTH SCIENCE

LESSON 1: RADIATION

RADIATION• Radiation is energy given off by

matter in the form of electromagnetic rays or high-speed particles.

• Radiation can be nonionizing or ionizing depending on how it affects matter.

• Ionizing radiation is harmful.

RADIATION SOURCESNATURAL SOURCES INCLUDE:• Cosmic radiation (video)

• Sun

• radioactive isotopes in soil, air and water

HUMAN INTRODUCED SOURCES INCLUDE:

• Electronics

• Medical X-Rays

• Medical Isotope exposure

• Nuclear power Artificial radiation

PHYSICAL FORMS OF RADIATION

Particles

• Radiation in the form of high - speed particles comes from nuclear decaying atoms; atoms that undergo nuclear change.

• These particles can be alpha particles or beta particles.

• These can be high - speed neutrons

PHYSICAL FORMS OF RADIATIONWaves

• Radiation in the form of waves or rayshas no weight and is pure energy.

• This form of radiation — known as electromagnetic radiation.

• These harmful waves include gamma rays, x-rays, and cosmic rays.

The electromagnetic spectrum is the range of all types of electromagnetic radiation:

ELECTROMAGNETIC SPECTRUM

• radio waves• Microwaves

• Infrared• Visible light

• UV• X-ray

• Gamma rays

ELECTROMAGNETIC SPECTRUM• Each type of electromagnetic radiation can be represented by

frequency (Hertz), wavelength (meters) and energy (electric Volts).

• The differences in these characteristics creates specialized properties for the each type of electromagnetic radiation.

WAVELENGTH AND FREQUENCY• Wavelength - the distance between successive crests of a wave, especially points in a sound

wave or electromagnetic wave.• Frequency - the number of wave crests passing by a given point in one second.

c=λνwhere λ is the wavelength, ν is the frequency and c is the speed of light.

Speed of light (c) = 300,000,000m/s 300,000Km/s

3X108m/sNote:

• The higher the frequency, the shorter the wavelength.

• Light would travel 7.5 times around the Earth in one second

• All electromagnetic rays travel at the speed of light in a vacuum

(λ)

NONIONIZING RADIATION VS. IONIZING RADIATION

IONIZING RADIATION

Subatomic Particles:

• Alpha particles• Beta particles• High – energy Neutron

Electromagnetic waves:

• UV waves• X-Rays• Gamma Rays

Ionizing radiation is harmful.

• Ionizing radiation that carries enough energy to liberate electrons from atoms or molecules, therefore ionizing them.

• Ionizing radiation can be subatomic particles or high-energy electromagnetic waves.

ALPHA PARTICLES

• Charged particle that resembles a Helium nuclei

• Emitted naturally decaying atoms, such as uranium, thorium, radium

• Emitted from manmade decaying atoms, such as plutonium and americium

• Used in smoke detectors

• Slow moving and easily stopped by a sheet of paper, skin, or even a few inches of air

• Dangerous if they are inhaled or swallowed, but external exposure generally does not pose a danger.

• Charged particles that are similar to electrons

• emitted from naturally occurring materials, such as, strontium-90

• Such beta emitters are used in medical applications, such as treating eye disease.

• Lighter than alpha particles

• Thin sheet of metal or plastic or a block of wood can stop beta particles

BETA PARTICLES 0 0-1 -1 or eβ

NEUTRON

• high-speed nuclear particles

• Exceptional ability to penetrate other materials

• Neutron activation: the ability to create unstable nuclei of atoms

• Radioactive sources created from neutron activation include items used in medical, academic, and industrial applications (including oil exploration).

• Concrete or water can block them

• neutron radiation primarily occurs inside a nuclear reactor, where effective shielding occurs.

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IONIZING RADIATION - WAVES

• This from of ionizing energy can strip electrons off of atoms or even destabilize the nucleus of an atom.

• These waves consist of high in energy, high frequencies and small wavelengths.

• Can often penetrated other materials but do not make them radioactive.

• Can be stopped by lead or concrete.

IONIZING RADIATION - WAVE TYPES

• X-Rays:used to provide static images of body parts (such as teeth and bones), and are also used in industry to find defects in welds.

• Gamma Rays:cobalt – 60 releases gamma radiation it is used to treat cancer and sterilize medical instruments.

• Cosmic Radiation: the suns and stars emit a constant stream of cosmic radiation, on Earth we are protected by the magnetic field.

NONIONIZING RADIATION

• Nonionizing radiation refers to the low energy portion of the electromagnetic spectrum.

• Radio waves, microwaves and infrared do not have enough energy to ionize atoms or molecules; they cannot completely remove an electron.

• Extremely low-frequency (ELF) waves that are produced by electrical power lines and wiring are also nonionizing radiation.

LIGHT SPECTRUM – VISIBLE LIGHT

• Visible light is considered nonionizing radiation. However, it can excite electrons to a higher energy state without producing an ion.

• Visible light has photochemical effects.

• 380–750 nm (visible from 400-700nm)

Electron Excitation

CONTINUOUS LIGHT SPECTRUM VS. DISCRETE LIGHT SPECTRUM

Continuous Spectrum:

• A beam of white light that shows a continuous spectrum of all of the physical quantities (waves or energy) for its colors of light.

• Dispersing light through a prism can show all of its colors.

CONTINUOUS LIGHT SPECTRUM VS. DISCRETE LIGHT SPECTRUM

Discrete Spectrum:

• A physical quantity (wave or energy) is said to have a discrete spectrum if it takes only distinct values, with positive gaps between one value and the next.

• Spectral lines are often used to identify atoms and molecules.

DISCRETE LIGHT SPECTRUM:ABSORPTION VS. EMISSION SPECTRUM

Absorption Spectrums:• Light passes through a cloud of gas.

• Black bands are present in the spectrum where energy for those wavelengths has been absorbed by the gas.

• All other light wavelengths are visible.

• Also called DARK-LINE SPECTRUM

A given atom will absorb and emit the SAME frequencies of electromagnetic (E-M) radiation.

These frequencies match the energy levels of the atom

DISCRETE LIGHT SPECTRUM:ABSORPTION VS. EMISSION SPECTRUM

Emission Spectrum: • Observation of the gas not the star.• Color bands represent the emission of

light given off by the gas in the cloud. • Also called BRIGHT-LINE SPECTRUM

A given atom will absorb and emit the SAME frequencies of electromagnetic (E-M) radiation.

These frequencies match the energy levels of the atom.

UNDERSTANDING THE STARS

• Stars are large celestial bodies of gas that emit electromagnetic energy

• This energy comes from Nuclear changes in the atoms of the star, called Nuclear Fusion

• Nuclear Fusion is the combination of light atomic nuclei into heavier atomic nuclei

UNDERSTANDING THE STARS

• Astronomers study the stars by looking at the light emitted

• The light runs through a spectrograph that separated light into a spectrum

• The stars spectrum reveals its composition and temperature.

UNDERSTANDING THE STARS –COMPOSITION OF THE STARS

• Hydrogen is the most common element in the stars

• Helium is the second most common element in the stars

• Carbon, oxygen and nitrogen make up less than 1% of stars

By studying the light spectrum of the stars, scientists have learned that:

UNDERSTANDING THE STARS –TEMPERATURE OF THE STARS

• The color of the star indicates its temperature

• Stars range from 2,800◦C to 24,000◦C and hotter

• The color of a star related to the energy of the star:

Blue - 35,000◦C

Yellow (the Sun) - 5,550◦C

Red – 3,000◦C

HOMEWORK

• Radiation worksheet• Tomorrow - Spectrum Lab

LESSON 2: RADIOACTIVE DECAY AND NUCLEAR ENERGY

ISOTOPES

• Are different atoms of the same element, with a different number of neutrons.

• changing the # of neutrons changes the mass number• Remember: mass # = # protons + # neutrons

• isotopes still have the same number of protons and the same element symbol

Atomic Mass (the decimal #’s)Atomic mass = average of the mass numbers for all isotopes of an element.

39 40 4119 19 19K, K, K

REPRESENTING ISOTOPES• Isotopes are written two ways

• with the mass number at the end Ex. Potassium – 40

• With its chemical symbol Ex. 4019 K

Mass number

Atomic number

39 40 4119 19 19K, K, K

19 19 19

19 19 19

20 21 22

RADIOACTIVE DECAY

Can result in new atoms forming.• Radioactivity results from having an unstable nucleus.• Radioactive Decay = when nuclei break apart + release energy

from the nucleus.• Radioactive decay continues until a stable element forms.

• An element may have isotopes that are radioactive called radioisotopes

Ex. carbon-12, carbon-13 and carbon-14 (only C-14 is radioactive)

RADIOACTIVE DECAY OF URANIUM - 238

Rutherford identified three types of radiation using an electric field.

• Positive alpha particles were attracted to the negative plate.

• Negative beta particles were attracted to the positive plate.

• Neutral gamma particles did not move towards any plate.

• Example: the alpha decay of Radium - 226

226 222 4 226 222 488 86 2 88 86 2oRa Rn + Ra Rn + er H→ α →

Alpha Decay 4 42 2 or Heα

BETA RADIATION:

Beta particles are represented by the symbols

• electrons are very tiny, so beta particles are assigned a mass of 0.• one electron gives a beta particle a charge of 1–• It takes a thin sheet of aluminum foil to stop a beta particle.

0 0-1 -1 or eβ

• Beta decay occurs when a neutron changes into a protonand an electron.• The proton stays in the nucleus, and the electron is released.

Example: The beta decay of iodine - 131131 131 053 54 –1

131 131 053 54 –1

I Xe +

I Xe + o

er

β→

→

Beta Decay 0 0-1 -1 or eβ

GAMMA RADIATION:

• Gamma radiation, γ, is a ray of high energy, short-wavelength radiation.

• has no charge and no mass.

• is the highest energy form of electromagnetic radiation.

• Gamma decay results from energy being released from a high-energy nucleus.

60 60 028 28 0Ni Ni + * γ→

Shows unstable nucleus for gamma decay

Often, other kinds of radioactive decay will also release gamma radiation.

Uranium-238 decays into an alpha particle and also releases gamma rays.

238 234 492 90 2U Th + He + 2 γ→

NUCLEAR REACTIONS:

Chemical Reactions

Mass is conserved (doesn’t change)

Small energy changes

No changes in the nuclei

Nuclear Reactions

Small changes in mass

Huge energy changes

protons, neutrons, electrons and gamma rays can be lost or gained

Nuclear reactions are different than chemical reactions

SYMBOLS TO REMEMBER:

NUCLEAR REACTIONS

Two types:

• Fission = the splitting of nuclei• Fusion = the joining of nuclei (they fuse together)

Both reactions involve extremely large amounts of energy

Albert Einstein’s equation E = mc2 illustrates the energy found in even small amounts of matter

1. NUCLEAR FISSION:• Nuclear fission is the splitting of one heavy nucleus into two or more smaller

nuclei, as well as some sub-atomic particles and energy.

• A heavy nucleus is usually unstable, due to many positive protons pushing apart.

When fission occurs:

1.Energy is produced.2.More neutrons are given off.

2. NUCLEAR FUSION• joining of two light nuclei into one

heavier nucleus.• In the core of the Sun, two hydrogen

nuclei join under tremendous heat and pressure to form a helium nucleus.

• When the helium atom is formed, huge amounts of energy are released.

The fusion of hydrogen

nuclei

NUCLEAR EQUATIONS:• are written like chemical equations, but represent changes in the

nucleus of atoms.• Chemical equations represent changes in the position of atoms, not

changes to the atoms themselves.

Remember:1. The sum of the mass numbers on each side of the equation should equal.

2. The sum of the charges on each side of the equation should equal.

FUSION IN THE STARSNuclear fusion produces most of the stars energy and occurs in three steps:Step 1:

• Two Hydrogen nuclei (protons) collide and fuse

• One proton becomes a positron and is emitted resulting in the production of a neutron

• One proton and one neutron

Step 2:

• A proton collides with the proton-neutron pair and produces a rare Helium nuclei

Step 3:

• Collision between two of these nuclei collide and fuse emitting two protons and forming a Helium nuclei with two protons and two neutrons.

At every step energy is released thus the mass is converted into energy.

MASS CHANGING TO ENERGY• The sun is changing about 4 million tons of matter into energy every

second.

• 26 Mev of energy is released in the last step of fusion.

• 240,000,000,000 fusion reactions need to occur to produce 1 Joule

• Neutrinos are emitted from the sun during Fusion and arrive at the Earth 8 minutes after they leave the Sun.

• Studies of Neutrinos prove that hydrogen fusion is taking place in the Sun.

Albert Einstein’s equation E = mc2 illustrates the energy found in even small amounts of matter

HOMEWORK

Radioactive Decay and Nuclear Energy

LESSON 3: TECHNOLOGY AND IMPLICATIONS

TELESCOPES

Telescopes:• are designed to observe space

• detect electromagnetic wavelengths and concentrate it for better observation

• optical telescopes observe visible light, they are either reflecting or refracting

• Invisible electromagnetic radiation can be observed with telescopes. However, the atmosphere acts as a shield against these waves, there for telescopes outside of the atmosphere are most effective.

Fermi Gamma Ray Telescope

Radio Telescope

OPTICAL TELESCOPE – REFRACTION TELESCOPE• Lenses are used to bend light. Refraction is the bending of light.

• Light passes through the lens to a focal point and is magnified by an eyepiece.

Disadvantage:• Different wavelengths of light focus

differently, that is, if an object is in focus in red light than it wont focus in blue light.

• Difficult to build large lenses, the amount of light collected from distant objects is limited by the size of the objective lens

OPTICAL TELESCOPE – REFLECTION TELESCOPE

• Mirrors are used to gather distant light and focus it.

INVISIBLE ELECTROMAGNETIC RADIATION TELESCOPE

RADIOISOTOPE THERMOELECTRIC GENERATORS (RTGS)

SUBMARINES

NUCLEAR ENERGY

INDUCED NUCLEAR REACTIONS

• Scientists can also force ( = induce) nuclear reactions by smashing nuclei with alpha, beta and gamma radiation to make the nuclei unstable

4 14 17 12 7 8 1 + N O + pα →

4 14 17 12 7 8 1He + N O + H→

or

INDUCED NUCLEAR FISSION OF URANIUM-235

• is the origin of nuclear power and nuclear bombs.

• A neutron, , crashes into an atom of stable uranium-235 to create unstable uranium-236, which then decays.

• After several steps, atoms of krypton and barium are formed, along with the release of 3 neutrons and huge quantities of energy.

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CHAIN REACTIONS:

• The neutrons released in the induced reaction can then trigger more reactions on other uranium-235 atoms…causing a CHAIN REACTION

• A chain reaction can quickly get out of control• materials that absorb some neutrons can help to control the chain

reaction.

• Nuclear reactors have complex systems to ensure the chain reaction stays at safe levels.

• An uncontrolled chain reaction can result in the release of excess energy as harmful radiation

• It is on this concept that nuclear bombs are created.

• Nuclear “meltdown” occurs if the chain reactions cannot be controlled

INDUCED NUCLEAR FISSION

• Neutrons are used to make nuclei unstable• It is much easier to crash a neutral neutron than a positive proton

into a nucleus to release energy.

OTHER APPLICATIONS AND IMPACTS OF RADIATION

COMMERCIAL APPLICATIONS

DAILY LIFE

RADIATION SHIELDING

ENVIRONMENTAL AND HEALTH EFFECTSWhat is a millisievert?For ionising radiation (X-rays, gamma-rays, electrons, neutrons etc.) the quantity of absorbed energy is called a "dose" and is measured in sieverts (Sv). A sievert is a very large and extremely unusual dose so more often we talk about thousandths of a sievert - a millisievert.

Ionising radiation can be found in soils, in our air and water, and in us. Because it occurs in our natural environment, we encounter it every day through the food we eat, the water we drink, and the air we breathe. It is also in building materials and items we commonly use. Public Health England and its predecessor organisationshave calculated the exposure of the UK population from naturally occurring and artificial sources of ionisingradiation periodically since 1974.

Dose (rem) Symptoms/Effects< 5 no observable effect

5–20 possible chromosomal damage20–100 temporary reduction in white blood cell count50–100 temporary sterility in men (up to a year)

100–200mild radiation sickness, vomiting, diarrhea, fatigue; immune system suppressed; bone growth in children retarded

> 300 permanent sterility in women

> 500 fatal to 50% within 30 days; destruction of bone marrow and intestine

> 3000 fatal within hours

Table 20.4 The Effects of a Single Radiation Dose on a 70 kg Human

MEASURING RADIATION

RADIATION AND NUCLEAR ENERGY REVIEW