RadioactivitRadioactivityy

1896 Henri Becquerel1896 Henri Becquerel was experimenting with was experimenting with a uranium compound to determine whether it a uranium compound to determine whether it gave off X-rays.gave off X-rays.

• He did prove their existence as well as the He did prove their existence as well as the existence of other particles.existence of other particles.

• Eventually these particles were called nuclear Eventually these particles were called nuclear radiation.radiation.

• Marie Curie (Marya Sklodowska), a Marie Curie (Marya Sklodowska), a Polish scientist (former student of Polish scientist (former student of Becquerel) discovered a new Becquerel) discovered a new radioactive element with her husband radioactive element with her husband Pierre Curie and she named it Pierre Curie and she named it PoloniumPolonium after Poland. after Poland.

• Later, they discovered Later, they discovered RadiumRadium meaning meaning “shining element” which was also “shining element” which was also radioactive. radioactive.

• 1934 Marie Curie would die from 1934 Marie Curie would die from radiation sickness due to the exposure. radiation sickness due to the exposure. Her husband died from cancer in 1901.Her husband died from cancer in 1901.

The Curies…The Curies…

1934

1901

Nuclear StabilityNuclear Stability• Binding energy is needed for the stability of Binding energy is needed for the stability of

a nucleus (associated with the nuclear a nucleus (associated with the nuclear strong forcestrong force• High: stableHigh: stable• Low: unstableLow: unstable• Many elements have radioactive isotopes.Many elements have radioactive isotopes.Ex. Carbon 12: non-radioactive (coal, Ex. Carbon 12: non-radioactive (coal,

diamond, graphite)diamond, graphite)Carbon 14: radioactive (used for carbon Carbon 14: radioactive (used for carbon

dating)dating)*a nucleus that is unstable can become *a nucleus that is unstable can become

stable by undergoing a nuclear reaction stable by undergoing a nuclear reaction or changeor change

RadioactivityRadioactivity The release of The release of

nuclear nuclear radiation in radiation in the form of the form of particles and particles and rays from a rays from a radioactive radioactive elementelement

Alpha ParticlesAlpha Particles• Nucleus of He Nucleus of He

atom. atom. • WeakestWeakest• Positive chargePositive charge• Can burn flesh Can burn flesh

but stopped by but stopped by paperpaper

Beta ParticlesBeta Particles• Electron Electron

formed in the formed in the nucleus when nucleus when a neutron a neutron breaks apart breaks apart

• 10x stronger 10x stronger than alpha than alpha

• Can pass Can pass through 3 mm through 3 mm of aluminumof aluminum

Gamma RaysGamma Rays• Electromagnetic Electromagnetic

wave of high wave of high frequency and frequency and short wave lengthshort wave length

• StrongestStrongest• Can pass through Can pass through

several cm of leadseveral cm of lead

Radioactive DecayRadioactive Decay• The The

spontaneous spontaneous breakdown of breakdown of an unstable an unstable atomic nucleusatomic nucleus

• Emits Emits particles/rays particles/rays to become to become lighter and lighter and more stablemore stable

Alpha DecayAlpha Decay

• Occurs when a nucleus Occurs when a nucleus releases an alpha particlereleases an alpha particle

Beta DecayBeta Decay

• Loses a beta particle causing Loses a beta particle causing the # of protons to go up by 1.the # of protons to go up by 1.

Gamma DecayGamma Decay

• Release of gamma Release of gamma rayray

• Nucleus is not Nucleus is not changed only changed only lowered to a lowered to a different energy different energy levellevel

Radioactive Half-LifeRadioactive Half-Life

Radioactive Half-LifeRadioactive Half-Life

• The amount of time it takes the atoms The amount of time it takes the atoms in a given sample of an element to in a given sample of an element to decaydecay

• Helps determine the age of rocks and Helps determine the age of rocks and fossilsfossils

• Some are only seconds, others are Some are only seconds, others are billions of years of half-lifebillions of years of half-life

• Ex: 5,730 yrs. Ex: 5,730 yrs. Carbon 14Carbon 14 30 sec. 30 sec. Rhodium 106Rhodium 106 4.5 billion yrs. 4.5 billion yrs. Uranium 238Uranium 238

Half-Life

Terminology of Radioactivity• Decay seriesDecay series – the series of steps by – the series of steps by

which a radioactive nucleus decays which a radioactive nucleus decays into a non-radioactive nucleus.into a non-radioactive nucleus.

• TransmutationTransmutation – the changing from – the changing from one element into another after a one element into another after a nuclear reaction has taken place.nuclear reaction has taken place.

• Artificial transmutationArtificial transmutation – the – the changing from one type of element changing from one type of element into another through science (man).into another through science (man).

Decay Series

Transmutation Where one Where one

element element changes changes into another into another as a result as a result of changes of changes in the in the nucleus nucleus (beta decay)(beta decay)

Ernest RutherfordErnest Rutherford• Produced the first artificial Produced the first artificial

transmutationtransmutation• A particle accelerator uses A particle accelerator uses

magnets and electric fields magnets and electric fields to speed up particlesto speed up particles

Now the fun begins!!

Nuclear Nuclear FissionFission

• Splitting of an Splitting of an atomic nucleus into atomic nucleus into 2 smaller nuclei of 2 smaller nuclei of approximately equal approximately equal massmass

Chain Reaction

• Nuclear Chain Reaction – billions of fissions reactions take place every second. The energy produced is extreme and causes a nuclear explosion (the atom bomb).

Nuclear Power PlantsIn a nuclear chain In a nuclear chain reaction billions of reaction billions of fission reactions may fission reactions may take place each secondtake place each second

Ex: current Ex: current operating operating nuclear nuclear plants use plants use fission fission to create to create energy energy in the form of in the form of heat and then heat and then transferred into transferred into electricityelectricity

Atom Bomb

Einstein hatedthat people used his discovery forthis…

Nuclear Fusion• Joining of 2 atomic Joining of 2 atomic

nuclei of smaller nuclei of smaller mass to form a mass to form a single nucleus of a single nucleus of a larger masslarger mass

• Temperature must Temperature must be well over a be well over a million degrees million degrees CelsiusCelsius

• Fusion produces less Fusion produces less radioactive wasteradioactive waste• Ex: the sun Ex: the sun

Tools used to detect radiation• ElectroscopeElectroscope – a simple device that – a simple device that

consists of a metal rod with two consists of a metal rod with two thin metal leaves at one end.thin metal leaves at one end.

• Geiger counterGeiger counter – developed in 1928. – developed in 1928. Consists of a tube filled with a gas Consists of a tube filled with a gas such as argon at reduced pressure. such as argon at reduced pressure. Makes a clicking noise each time Makes a clicking noise each time the nucleus releases a particle or the nucleus releases a particle or energy.energy.

Pictures of the tools used…

Bubble chamber

electroscope

Cloud chamber

Geiger counter

Radioactivity uses

• RadioisotopesRadioisotopes – can be used to – can be used to find leaks or weak spots in metal find leaks or weak spots in metal pipes. Can also be used as a pipes. Can also be used as a tracer in humans to track blood tracer in humans to track blood flow. flow.

• RadiationRadiation – can also be used to – can also be used to destroy unhealthy cells that destroy unhealthy cells that cause cancer. This treatment is cause cancer. This treatment is called radiation therapy.called radiation therapy.

Dangers of radiation

• The same radiation that kills The same radiation that kills cancer can also cause cancer.cancer can also cause cancer.

• Radiation sicknessRadiation sickness – reddening of – reddening of skin, drop in white blood cells, skin, drop in white blood cells, nausea, fatigue, and loss of hair. nausea, fatigue, and loss of hair.

• We are constantly exposed to We are constantly exposed to some radiation through cosmic some radiation through cosmic rays, microwaves, cell phones, x-rays, microwaves, cell phones, x-rays, etc…rays, etc…

Radiation Sickness

•Nausea Nausea •FatigueFatigue•Loss of hairLoss of hair•Cause of Cause of

Marie Marie Curie’s Curie’s death!death!

Radioactive comics.

Sooo…that’s how Rudolph got Sooo…that’s how Rudolph got his red nose.his red nose.

ChernobylChernobyl

http://www.youtube.com/watch?v=3u_8frR0IpE

What caused the Chernobyl Disaster?In the early morning of 26 April 1986, one of

the fourreactors at the Chernobyl nuclear power station

ran outof control while engineers were running safety

tests.Within four seconds, a power surge of 100

times normaloutput led to a violent explosion and fire. The

1,000tonne concrete top of the reactor building was

blownoff and huge chunks of blazing, radioactive

materialwere blasted into the air like a volcanic

explosion. Thereactor burned furiously and highly radioactive

debriswas scattered around and inside the reactor

building.

What caused the Chernobyl Disaster?

The reactor burned for a week, spewing out radiation, andwas eventually put out by helicopters dumping tonnes ofsand, and fire fighters and site works fighting the blaze.

Hundreds of thousands of people, many of them soldiers,were drafted in to clean up the site. They had very little inthe way of protective clothing and were only allowed intothe reactor building for 90 seconds at a time. They were

called the ‘liquidators’. The clean-up work continued for two years as the entire

reactor building was sealed in a huge concrete tomb-likestructure known as the Sarcophagus.

The monument to the “Liquidators” who lost their lives putting out the fires

Where is Chernobyl?Chernobyl is about 1,500 miles from Britain, 60 milesnorth of Kiev, capital of the Ukraine in Eastern Europe.Now an independent country, in 1986 the Ukrainewas part of the Soviet Union. Just to the north is theinternational border with Belarus, then also part of theSoviet Union. Belarus was to be the country worstaffected by the disaster. The nuclear power station wasSoviet designed and built.

What happened to those nearby?Direct casualties of the explosion were rushed off tohospitals as far away as Moscow. Then it became clearthat because of the intense radioactive fallout, all thesurrounding population would have to be evacuated – 14,000 people.Police surrounded Pripyat, the nearest town (2.5kmaway), set up road blocks and prepared to deal with anypanic.

On Sunday 27 April, at 1.50pm, local radio announced thestart of a mass evacuation. At 2pm, 1,100 buses beganto pick up the 40,000 residents. Almost all belongingshad to be left behind. Sunday lunches were left on tables,pets and livestock abandoned. By 4.20pm the town wasempty. In all, more than 110,000 men, women and children were evacuated from surrounding areas.

Illnesses and deathsImmediately after the accident about 30 people died but this was just the beginning of the deaths, illnesses and changes to DNAAlthough it is impossible to say with certainty that a particular cancer has a particular cause, statistics imply that the accident at Chernobyl has had a catastrophic effect on the populations of nearby areas. There had been up to the year 2002 about 4,000 cases of thyroid cancer reported in children and adolescents who were exposed at the time of the accident, and more cases can be expected during the next decades.