The Atom and Radiation

Nuclear Radiation

Goals: To answer the following questions

What is radiation?Are there different types?Are all forms (equally) dangerous?

Where is radiation found?Is all radiation man-made?

What is radiation used for?Are there benefits to some types?

How long is something radioactive for?

The Discovery of Radioactivity

The German physicist W.K. Roentgen “accidentally” discovers a mysterious source of radiant energy that can pass through low density shields (like card board). He calls this mysterious energy X-rays.

Further research showed that X-rays cannot pass through everything, particularly high density materials like lead and bone.

Roentgen takes the first X-rays of his wife’s hand to present to his colleagues.

Hand X-ray, December 22, 1895

The Discovery of Radioactivity

The French physicist Henri Becquerel takes interest in Roentgen's X-rays in 1896. He investigated whether certain minerals could emit X-rays. He experiments with Uranium and a photographic plate (develops upon exposure to light).

Another accident happens…Becquerel becomes frustrated with his research, wraps the photographic plate in black paper (to prevent light exposure), throws it in his desk drawer with a piece of Uranium on top and closes it up.

What do you know??? A few days later, Becquerel discovers that the photographic plate has been exposed while sitting in his dark drawer.

The Discovery of Radioactivity

What Becquerel inadvertently discovered was radioactivity, the spontaneous emission of nuclear radiation.

Soon after (in 1898,) Becquerel's colleagues, Marie Curie and her husband Pierre discover two other radioactive elements: polonium and radium.

What is Radioactivity?

Radioactivity: the spontaneous emission of nuclear radiation.

We now know that there are two categories of radiation: Non-ionizing radiation – low-energy radiation that

transfers energy to matter usually only harmful in large amounts

Ionizing radiation – high-energy radiation that can eject electrons from atoms/molecules to form highly reactive ions and can cause serious cell damage

exposure should be limited.

Concerns…..

But radiation is all around us…the question is, should we be concerned about our safety?? Are we in danger of serious exposure to radiation? Can we use radiation?

Forms of Radiation

Radiation comes in several forms as shown in the electromagnetic spectrum below; but not all forms are represented here

Types of Radiation

Three main types (from the 2 categories) :1. Non-ionizing electromagnetic radiation

RadioMicroInfraredVisiblelow energy UV

2. Ionizing electromagnetic radiation High UVX-rays Gamma rays

3. Ionizing atomic particle radiation radioactive elements

Why are some elements radioactive? To answer this question, you must understand a little about atomic structure.

All matter can be broken down into atoms:

Isotopes (cont.)

Some isotopes are stable and others are unstable. This is where radioactivity comes in.

A stable isotope is not radioactive, but an unstable isotope is!

Ex. 12C is stable 13C is stable 14C is radioactive Radioactive elements will emit radiation until

they become a stable isotope.

Every Element has Isotopes – the amount of each isotope is fixed

Ex. Uranium

Which isotope of Uranium is used to make an atomic bomb?

Mass Abundance238 99.28%235 0.71%234 0.0054%

Emitted radiationThis emitted radiation can be one of these

types:Alpha ( 4 α or 4 He )

heavy particle radiation easily blocked because its so bigthe most dangerous particle

Beta ( 0 β or 0 e) particle radiation smaller than alpha and negative

in charge

22

-1 -1

Emitted radiationThis emitted radiation can be one of these

types:Positron (0 β or 0 e )

positive beta particle

Gamma ( 0 γ ) high energy radiation

0

1 1

Alpha and Beta emission cause radioactive elements to change to a new element.

Gamma causes no change in the radioactive element.

Emitted radiation

Ionizing Radiation

alpha particle

beta particle

Radioactive Atom

X-ray

gamma ray

Radiation Exposure

Naturally occurring radioisotopes provide a constant small dose of radiation

Radioactive isotopes constantly decay, releasing alpha, beta and/or gamma radiation.

This constant, inescapable radiation is called background radiation.

Natural background radiation:

- Outer spaceAll forms of electromagnetic radiation

- Ground water, rocks, soil contain Uranium and Thorium

- Atmosphere contains radon

- Food and Environmentlike C-14 and potassium

Radon

Produced as Uranium in the soil decays. Uranium decays to produce radon gas:

When this gas is inhaled, it further decays in your lungs into Polonium, Bismuth and Lead (these heavy metals cannot be exhaled).

The resulting alpha radiation is being released into your body, causing cell damage.

Manmade background radiationFallout (nuclear weapons testing)Airplane flightsReleased from

burning fossil fuels nuclear power plantsminingmaking

cement concrete sheet rock

Commonly Used Radioisotopes

Americium-241= Diagnose thyroid disorders, smoke detectors.

Cesium-137= Cancer treatment. Iodine-125,131= Diagnosis & treatment

liver, kidney, heart, lung and brain.Technetium-99=Bone and brain imaging;

thyroid and liver studies; localization of brain tumors.

Americium-241= Diagnose thyroid disorders, smoke detectors.

Cesium-137= Cancer treatment. Iodine-125,131= Diagnosis & treatment

liver, kidney, heart, lung and brain.Technetium-99=Bone and brain imaging;

thyroid and liver studies; localization of brain tumors.

Medical Applications

Medical uses of radioisotopes fall into two categories.Diagnostic

Therapeutic

Diagnostic

A standard x-ray cannot produce an image of an organ like the heart, liver, pancreas, blood vessels, etc.

To illuminate the targeted region, a radioisotope is injected into the body.

Radioisotopes used are low dosages with a short half-life.localized 0.1 to 50 rem doses are common

CAT & PET scans

A computerized tomography scan is an enhanced x-ray machine using multiple beams capable of producing a 3D image.

A positron emission tomography scan uses a positron emitter to generate a 3D image.

CAT & PET scans

MRI

In magnetic resonance imaging, a powerful magnetic field is used along with low energy radio frequency to generate an image.

Based on the premise that hydrogen atoms have “spin.”

In a powerful magnetic field, these hydrogen atoms can be made to flip between the two spin states.

THIS IS NOT NUCLEAR RADIATION

MRI

Therapeutic

In radiation therapy, radiation is used to target cancer cells.

Radiation levels are in very high dosages.localized 4000 – 6000rem doses are common

Cyberknife treatment uses computer technology to aim 100’s of x-ray beams precisely at a tumor.

Measuring RadiationMainly, two units are used to measure

radiation:RAD = radiation absorbed dosage

1 RAD = 1.0 x 10-2 J / kg of body tissueRBE = a multiplier for each type of

radiation.alpha = 20; protons, neutrons = 10; betas,

positrons, and gammas = 1.REM = radiation equivalent in humans

REM = RAD x RBE There are several other units out there; we are not going to worry about those.

Biological Effects

Alpha particles cannot penetrate our skin, yet internally they can cause massive damage on soft tissues like the lungs and intestinal linings.

Beta particles can cause a burn on the outer portion of the skin.

Gamma particles penetrate completely and if exposed to large quantities is deadly.

Biological Effects

Radiation affects those cells in our body that undergo rapid cell division like bone marrow, intestinal lining, and the skin.

Radiation tends not to affect cells that remain unchanged like our brain, liver, muscles, etc.Doesn’t mean it CAN’T, it just is less likely

How It Works…

When radiation hits a molecule like water, it ionizes.

This water molecule reacts with another water molecule.

1 -2 2H O radiation H O 1e

OH OH OH OH 132

12

How It Works…

The “dot” on the OH is an odd electron.Molecules with an odd electron are called

free radicals.Free radicals are electron scavengers and

interfere with electron transfer reactions – many of which are vital in the function of the body.

How much is safe? Ionizing radiation breaks bonds in

molecules within the body. At low exposure levels, your body can fix the minimal damage. Higher exposure levels that your body cannot fix will lead to damaged DNA, causing mutations (tumors and birth defects)

Average U.S. individual receives 0.360 rem per year.

About 0.300 rem of this is from natural sources

U.S. limit for background radiation in a given area is 0.500 rem.

U.S. safe exposure in the work environment is 5.000 rem.

Dose Response Relationships

0-15 rem—No or minimal symptoms15-40 rem—Moderate to severe illness40-80 rem—Severe illness deaths start

above 50 remAbove 80 rem—Fatal

***Acute whole body doses

Your Annual ExposureActivity Typical DoseSmoking .280 rem/year

Radioactive materials use  in a UM lab

<.010 rem/year

Dental x-ray .010 rem per x-ray

Chest x-ray  .008 rem per x-ray

Drinking water  .005 rem/yearCross country round trip by air 

.005 rem per trip 

Coal Burning power plant 0.000165 rem/year 

Radiation Protection

Decrease Time

Increase Distance

Increase Shielding

Measurement and Detection

A Geiger tube is often used to detect radiation.

Consists of a metal tube filled with a gas like Argon.

When radiation enters the tube, it ionizes the gas.

The ions are attracted to a negative charged wire and the electrons are then counted.

Measurement and Detection

Animation: http://www.dlt.ncssm.edu/tiger/Flash/nuclear/GeigerTube.html

AlphaRadioactive isotopes decay until a stable

nucleus can be formed. What happens when radioactive isotopes decay?

Many elements release alpha radiation:

226 Ra 4 He + 222 Rn

(radium) (alpha particle) (Radon)

As these radioactive isotopes decay, an alpha particle is released and a new element is formed.

86288

• Alpha Particles: 2 neutrons and 2 protons

• They travel short distances, have large mass

• Only a hazard when inhaled or formed in the lungs• because they

can’t pass through skin)

Alpha Particles

Beta

Many elements release beta radiation:

222 Rn 0 e + 222 Fr

(radon) (neg. beta particle) (Francium)

As these radioactive isotopes decay, a beta particle is released and a new element is formed.

86 -1 87

Beta

Many elements release beta radiation:

222 Rn 0 e + 222 At

(radon) (pos. beta particle) (Astatine)

As these radioactive isotopes decay, a beta particle is released and a new element is formed.

86 1 85

Beta ParticlesBeta Particles: Electrons or positrons having small mass and variable energy. Electrons form when a neutron transforms into a proton and an electron or

1 0 10 -1 1 + H n e

Gamma

In addition to releasing a radiation particle (alpha or beta), most radioactive decay is accompanied by the release of gamma radiation too. Remember, gamma radiation is just energy; it is not a particle, so it does not cause the element to change its identity.

Gamma Rays

Gamma Rays (or photons): Result when the nucleus releases

Energy, usually after an alpha, beta or positron transition

X-Rays

X-Rays: Occur whenever an inner shell orbital electron is removed and rearrangement of the atomic electrons results with the release of the elements characteristic X-Ray energy

NeutronsNeutrons: Have the same mass as protons but are uncharged

They behave like bowling balls- they wreck things when they hit them

- Identify the starting element and write the symbol.

- Identify the type of radiation released.- Subtract the two upper left numbers to find

the mass of the new element formed.- Subtract the two lower left numbers to find

the atomic number of the new element formed.

- Look up the new atomic number on the periodic table to find the new element made.

How do you determine the new element made after radioactive decay?

In a completed nuclear equation, the sum of the mass numbers of the unstable

isotope and the products are equal sum of the atomic numbers of the

unstable isotope and the products are equal Sum of Mass Numbers

251 = 251251Cf 247Cm + 4He

98 96 2

98 = 98 Sum of Atomic Numbers

57

Completing Nuclear Equations

58

Guide to Completing a Nuclear Equation

Write an equation for the alpha decay of 222Rn.STEP 1 Write the incomplete equation: STEP 2 Determine the mass number: 222 – 4 =

218STEP 3 Determine the atomic number: 86 – 2 =

84

STEP 4 Determine the symbol of element: 84 = Po

STEP 5 Complete the equation:

59

Equation for Alpha Decay

84 Po

85 At

86 Rn

42 He

222 218 4 86 84 2Rn Po + He

222 4 86 2Rn ? + He

STEP 1 Write an equation for the decay of K42 (potassium-42), a beta emitter.

STEP 2 Mass number: (same) = 42

STEP 3 Atomic number: 19 + 1 = 20STEP 4 Symbol of element: 20 = Ca

STEP 5 Complete the equation:

60

Equation for a Beta Emitter

19 K

20 Ca

42 0 19 -1K ? + e

42 42 0 19 20 -1K Ca + e

0-1e

Write the nuclear equation for the beta decay of

Co-60.

61

Learning Check

beta particle

62

Solution

60 60 0 27 28 -1Co Ni + e

In positron emission, a proton is converted to a neutron and a

positron

the mass number of the new nucleus is the same, but the atomic number decreases by 1

63

Positron Emission

1 1 01 0 +1H n e

49 49 0 25 24 +1Mn Cr + e

In gamma radiation, energy is emitted from an unstable

nucleus, indicated by m following the mass number

the mass number and the atomic number of the new nucleus are for the same element

64

Gamma Radiation

99m 99 0 43 43 0Tc Tc +

Summary of Types of Radiation

65

Changes in Mass and Atomic Numbers

66

Nuclear Reactions

Decay/Emission◦ particle is given off (is a

product)

◦ Typically seen with: alpha beta gamma positron

Capture/Bombardment◦ particle is picked

up/added (is a reactant)

◦ Typically seen with: neutron bombardment electron capture

What radioactive isotope is produced when a neutron bombards 59Co?

68

Learning Check

59 1 4 27 0 2Co + ? + He n

Sum of mass numbers

60 = 60

27 = 27Sum of atomic numbers

69

Solution

59 1 56 4 27 0 25 2Co + Mn + He n

Energy and Atomic StructureThere is energy associated with holding

the parts of an atom togetherRemember that the protons repel each

otherThere is no electrostatic attraction that

holds the neutrons together, nor holding them to the protons

But…. The nucleus still stays together despite the repulsion and lack of attraction

It is held together by what we call “strong force” or nuclear force.

Stability of Nuclei and EnergyRemember that all things like to be at the

lowest energy level possible.Forming a nucleus releases energy, putting

the particles in a lower energy state than when alone as p+, n0, and e- alone

Some nuclei are inherently more stable than others so building a bigger nucleus isn’t the final answer in getting lower in energyDecay stabilizes the nucleus, getting to an

arrangement of protons and neutrons that is favorable for that element

So, what makes some nuclei radionuclides?

If the correct proton to neutron ratio is not present for that atom, it will spontaneously give off radiation (decay) in order to achieve a more stable nucleus that has a more favorable proton to neutron ratio for that element The proper ratio ISN’T NECESSARILY 1:1

For most elements over 18, there are more neutrons than protons in the stable isotope(s)

All nuclides that with a mass number (A) ≥ 83 are inherently unstable, but lighter elements can be unstable, too

Radioactive atoms give off radiation (decay) spontaneously, but at a constant, predictable rate for that radionuclide

This is the half-life of the radionuclide

http://library.thinkquest.org/3659/nucreact/stability.html

The Odd-Even RuleIn the odd-even rule, when the numbers of neutrons and protons in the nucleus are both even numbers, the isotopes tends to be far more stable than when they are both odd. Out of all the 264 stable isotopes, only 5 have both odd numbers of both, whereas 157 have even numbers of both, and the rest have a mixed number.

This has to do with the spins of nucleons. Both protons and neutrons spin. When two protons or neutrons have paired spins (opposite spins), their combined energy is less than when they are unpaired.

The Magic Numbers

Another rule of nuclear stability is that isotopes with certain numbers of protons or neutrons tend to be more stable then the rest. These certain numbers are called the magic numbers, and they are, for reasons too detailed to explain here, 2, 8, 20, 28, 50, 82, and 126. When a nucleus has a number of protons and neutrons that are the same magic number, it is very stable. For example: 4

2He, 168O, and 40

20Ca. One stable isotope of lead, 208

82Pb, has 82 protons and 126 neutrons.

http://library.thinkquest.org/3659/nucreact/stability.html

• Band of Stability: The area of stable nuclei (here, the middle of the dots)

• Based upon location near the band, the type of radiation emitted is predictable

Radionuclides emit radiation until a stable

nuclei is reached

Half-Life

Radioactive isotopes change what they are as they decay and release radiation.

Scientists call the amount of time it takes for half of a radioactive sample to decay a half life.

14C has a half life of 5,730 years.

This means that if we started with 100 grams of 14C, only 50 grams of 14C would remain after 5,730 years have passed. The other 50 grams will have turned into 14N as a beta particle is released.

Half-Life

How long does it take for a radioactive sample to decay?

Although it is not possible to predict when any individual isotope will decay, this question can be answered for an entire radioactive sample by the half-life of each radioisotope.

The half-life of radioisotopes varies greatly, but is constant for a particular radioisotope. So constant and reliable, it could be used to keep time.

How long does it take for a radioactive sample to decay?

Why would anyone want to know this?

It’ very useful to know how long a radioisotope used in medicine will remain radioactive within the body, to plan how long hazardous nuclear wastes must be stored and to estimate the age of ancient organisms, cavitations or rocks (fossils).

Half Life Equations

Ae = Ao x .5 t/t½

Ae = amount of substance left Ao = original amountt = elapsed timet ½ = the half-life

Learning Check

The isotope Cr-51 has a half-life of 28 days. How much of a 160.mg sample would remain after 112 days?

A patient is injected with N-13, which has a half-life of 10 minutes. If the original activity of the sample is 40 mCi, what activity would be remain after 40 minutes?

The amount of F-18 decreases from 40.mg to 10.mg in 220 minutes. What is the half-life of this radioisotope?

Learning Check

The isotope Cr-51 has a half-life of 28 days. How much of a 160.mg sample would remain after 112 days? 10mg

A patient is injected with N-13, which has a half-life of 10 minutes. If the original activity of the sample is 40 mCi, what activity would be remain after 40 minutes? 2.5 mCi

The amount of F-18 decreases from 40.mg to 10.mg in 220 minutes. What is the half-life of this radioisotope? 110 minutes

Fusion

Fusion involves taking two or more smaller nuclei and fusing them together.

Once again, mass is converted to energy.This is the process by which all stars work.

All elements lighter than Fe have formed in stars via fusion reactions

β2 He H H H H 01

42

11

11

11

11

FusionOn our planet, fusion has been achieved.

The temperatures required are extremely high.

Currently, more energy is required to achieve fusion than we get back from the reaction.

Research continues as this represents the “holy grail” of energy.

n He H H 10

42

31

21

Learning Check

In one possible fission reaction for U-235, the U-235 is bombarded with a neutron producing Kr-91, three neutrons, and another nuclei. What is the unidentified nuclei?

FissionNuclear fission is the process by which a

larger nuclei is split into two smaller ones.During this process, a small percentage of

the mass is converted to energy as predicted by Einstein.

E = mc2 ; where c = speed of light. 1 x 10-3 g “lost” can generate 9.0 x 1010 kJ

of energy.Only two fissionable isotopes are known.

U-235 and Pu-239

Nuclear Fission

How much energy ??? The fission of uranium-235 produces 26 million times more energy than the combustion of methane.It releases the nuclear binding energy

How does nuclear fission work???

1n + 235U —> 93Kr + 140Ba + 3 1n + ENERGY Bombarding a uranium atom with one neutron

produces two smaller atoms and two more neutrons, free to collide with other uranium atoms. This causes a chain reaction to occur.

Animation U-235 Fission

Animation 2- moderation v unmoderatied

Fission

Begins when a neutron strikes a U-235 atom.

The products are numerous – below is just one example.

On average, three new neutrons are produced.

Each new neutron can split another U-235.

energy n 3 Kr Ba n U 10

9436

13956

10

23592

Since not all of the neutrons produced will hit and split a uranium nucleus, a minimum amount of uranium is necessary. The more uranium present, the more likely the produced neutrons will hit and split another uranium nucleus.

This minimum amount of uranium is called its critical mass. It is the minimum amount of fissionable material required to sustain a chain reaction.

Fission

In a nuclear weapon, a ____________ of U-235 is imploded producing an uncontrolled chain reaction.

Fission

In a nuclear power plant, the quantity of U-235 cannot sustain a chain reaction.

Control rods absorb excess neutrons.Waste products, with long half-life’s, from

spent fuel rods are stored in large pools at the power plant.

Cooling System Reactor Animation

Uranium

Mined from the ground as Uranium Oxide U3O8

Two isotopes1. Uranium-235

- natural abundance = 0.720%

- used for fission in nuclear reactions and

weapons

2. Uranium-238

- most abundant = 99.275%

Enrichment

Must have between 1 to 3% U-235 for fission

2 ways to enrich U-235 1. Change U3O8 into UF6 gas

- needs to be done about 1200 times- get 4% u-235

2. Use lasers- excite electrons of lighter isotope (U-

235)- collected using magnetic fields- works in 1 try

Decay Series of Uranium

Mass Defect

Difference between the mass of an atom and the mass of its individual particles.

4.00260 amu 4.03298 amu

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Nuclear Binding Energy

Energy released when a nucleus is formed from nucleons.

High binding energy = stable nucleus.

E = mc2

E: energy (J)m: mass defect (kg)c: speed of light

(3.00×108 m/s)

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Nuclear Binding Energy

U-238

10x108

9x108

8x108

7x108

6x108

5x108

4x108

3x108

2x108

1x108

Fe-56

B-10

Li-6

H-2

He-4

00 20 40 60 80 100 120 140 160 180 200 220 240

Mass number

Bin

ding

ene

rgy

per

nucl

eon

(kJ/

mol

)

Unstable nuclides are radioactive and undergo radioactive decay.

A nucleus will become more stable if a reaction brings it closer to the iron peak

Nuclei heavier than iron do this by breaking up into smaller nuclei via Fission

Nuclei lighter than iron do this by joining together via Fusion reactions

Mass Defect and Nuclear Stability

2 protons: (2 x 1.007276 amu) = 2.014552 amu

2 neutrons: (2 x 1.008665 amu) = 2.017330 amu

2 electrons: (2 x 0.0005486 amu) = 0.001097 amu

Total combined mass: 4.032979 amu

The atomic mass of He atom is 4.002602 amu.This is 0.030366 amu less than the combined mass.

This difference between the mass of an atom and the sum of the masses of its protons, neurons, and electrons is called the mass defect.

= 4.002602 amu

Nuclear Binding EnergyWhat causes the loss in mass?

According to Einstein’s equation E = mc2

Convert mass defect to energy units

0.030377 amu1.6605 x 10-27 kg

1 amu = 5.0441 x 10-29 kg

The energy equivalent can now be calculated

E = m c2

E = (5.0441 x 10-29 kg) (3.00 x 108 m/s)2

E = (4.54 x 10-12 kg m2/s2) = 4.54 x 10-12 J

This is the NUCLEAR BINDING ENERGY, the energy released when a nucleus is formed from nucleons.

Binding Energy

1) Calculate mass defect

3) E = mc2

protons: 1.007276 amu

neutrons: 1.008665 amu

electrons: 0.0005486 amu

2) Convert amu kg

1 amu________ amu1.6605 x 10-27 kg

= _______ kg

c= speed of light = 3.00 x108 m/s

Li7

3

Li - 7

atomic number(# of protons)

mass number(# of protons + neutrons)

Binding Energy per Nucleon

1) Calculate mass defect

3) E = mc2

4) Divide binding energy by number of nucleons (p+ and n0, here =7 )

protons: 1.007276 amu

neutrons: 1.008665 amu

electrons: 0.0005486 amu

2) Convert amu kg

1 amu________ amu1.6605 x 10-27 kg

= _______ kg

c= speed of light = 3.00 x108 m/s

Li7

3

Li - 7

atomic number(# of protons)

mass number(# of protons + neutrons)

The Energy of Fusion: Making Bigger Atoms

The fusion reaction releases an enormous amount of energy relative to themass of the nuclei that are joined in the reaction. Such an enormous amountof energy is released because some of the mass of the original nuclei is con-verted to energy. The amount of energy that is released by this conversioncan be calculated using Einstein's relativity equation E = mc2.

Suppose that, at some point in the future, controlled nuclear fusion becomes possible. You are a scientist experimenting with fusion and you want to determine the energy yield in joules produced by the fusion of one mole of deuterium (H-2) with one mole of tritium (H-3), as shown in the following equation:

First, you must calculate the mass that is "lost" in the fusion reaction. Theatomic masses of the reactants and products are as follows: deuterium (2.01345 amu), tritium (3.01550 amu), helium-4 (4.00150 amu), and a neutron (1.00867 amu).

2.01345 amu 3.01550 amu 4.00150 amu 1.00867 amu

5.01017 amu5.02895 amu

Mass defect:

5.02895 amu 5.01017 amu

-0.01878 amu

n He H H 10

42

31

21

According to Einstein’s equation E = mc2

Convert mass defect to energy units

0.01878 amu1.6605 x 10-27 kg

1 amu = 3.1184 x 10-29 kg

The energy equivalent can now be calculated

E = m c2

E = (3.1184 x 10-29 kg) (3.00 x 108 m/s)2

E = (2.81 x 10-12 kg m2/s2) = 2.81 x 10-12 J

This is the NUCLEAR BINDING ENERGY, for the formation of a single Helium atom from a deuterium and tritium atom.

Mass defect = 0.01878 amu

Therefore, one mole of helium formed by the fusion of one mole of deuterium and one mole of hydrogen would be 6.02 x 1023 times greater energy.

2.81 x 10-12 J

6.02 x 1023

1.69 x 1012 J of energy released per mole of helium formed

The combustion of one mole of propane (C3H8), which has a mass of 44 g, releases 2.043 x 106 J. How does this compare to the energy released by the fusion of deuterium and tritium, which you calculated?

C3H8 + O2 H2O + CO2 + 2.043 x 106 J (unbalanced)

44 g

1,690,000,000,000 J2,043,000 J

4 g He44 g C3H8

Fusion produces ~1,000,000 x more energy/mole

x

1,690,000,000,000 J

Mass Defect

If you add up a certain number of neutrons and protons and put them together in a nucleus you end up with less mass than you started with!

The ‘missing mass’ is known as the Mass Defect and we can use

that mass change to determine the energy released by using E=mc2

How do we detect that energy?

That energy is released as heat and/ or lightThat light does not need to be visible

light, but can be any form of electromagnetic radiation, or EMR

The heat is what we harness in nuclear power plants that use fission

The following information is

F.Y.I

Nuclear Weapons

Fission Bomb (a.k.a. Atom Bomb)1. 2 non-critical masses

2 portions of U-235 are propelled into each other – make 1 critical mass

1 neutron then starts fission, then…BOOM!

2. 1 critical massUsually PlutoniumCompressed to get explosion

Nuclear Weapons

Fusion Bomb (a.k.a. H-Bomb)Uses Lithium Hydride

High temperatures create fusionFusion: 2 different isotopes fuse togetherReleases more energy (100x)

Nuclear Power There are many benefits in using nuclear

technology to create electricity, but this must be carefully regulated. If the reactor reaches temperatures that are too high, the danger of a meltdown occurs.

A nuclear meltdown can occur when temperatures inside the reactor reach levels that are too high. The materials used to construct the reactor actually melt. If this happens, the chain reaction is no longer contained and dangerous radioactive material can be expelled into the environment.

Animation Animation 2

How does it work?

When the steam from the generator is cooled by water from nearby water sourcesWhen the steam from

the generator is cooled by water from nearby water sources

Cooling Tower

Nuclear Power has reached dangerous conditions three times.

Three Mile Island Chernobyl 1979, Pennsylvania 1986, Russia

the reactor reached dangerous temperatures, but no meltdown

occurred

the reactor reached temperatures high enough to cause the core to

melt

caused by both equipment failure and human error

caused by both poor plant design and improper operation

while some radioactive material was expelled into the atmosphere, no damage sustained by people or

environment

radiation spewed into the atmosphere and spread over the

entire Northern Hemisphere

caused government to create stricter regulations over nuclear

power plants

an estimated 75 million people exposed

Fukushima Daiichi

http://www.youtube.com/watch?v=BdbitRlbLDc

The Chernobyl incident happened April 26, 1986 in Ukraine.

The Chernobyl accident was a result of a flawed reactor design that was operated with inadequately trained personnel and without proper regard for safety.

When the operator went to shut down the reactor from it’s unstable condition arising from previous errors, a peculiarity of design caused a dramatic power surge.

3 mile island is located in Harrisburg PA

The 3 mile island is a nuclear generating station

What Happened?

Occurred on 4:00 a.m. March 28, 1979

Problem in secondary, non-nuclear section of the plant

The main water pump failed and prevented steam generators from removing heat that the radioactive material was producing

The pressure in the primary system (nuclear part of plant) increased

What Happened?

The relief valve on top of the pressurizer did not close when the pressure decreased

Workers reduced the flow of coolant which made the fuel overheat

Half of the long metal tubes which held the nuclear fuel pellets ruptured and the pellets started to melt

Future Technology…

Nuclear Fusion - the joining of two smaller nuclei to create a large nucleus and tremendous energy release.Produces more energy per atom than fission Requires tremendous heat and pressure!Technology does not yet exist that allows

more energy to be produced than must be put in.