Radiation history

RADIATION AND THE HISTORY

SALONI CHAWLA

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CONTENTS • WHAT IS RADIATION ?

• TYPES OF RADIATION

• DISCOVERY OF X RAYS

• DISCOVERY OF RADIOACTIVITY

• RADIUM GIRLS

• NUCLEAR POWER PLANT

• CHERNOBYL ACCIDENT

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RADIATION

• In general , Radiation is the emission and propagation of energy in the form of waves or Particles .

• Eg :Sound ,light, x-rays , UV rays , Heat etc• It can travel through medium or vacuum. • In Physics, we take radiation in the form of

electromagnetic waves or particles. • Eg :light, x-rays , UV rays etc

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EM SPECTRUM

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A TOUCH OF QUANTUM MECHANICS

• The idea of a radiation being a wave or particle became vague when the WAVE PARTICLE theory came into the scene .

• DE BROGLIE hypothesis says that the wave can act as a particle sometimes and also sometimes electrons ,protons etc can behave as waves.

• This can be clearly explained by the PHOTOELECTRIC EFFECT .

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• De Broglie wavelength is given by Lambda=h/p Or h/mv .• λ is indirectly proportional to velocity and

mass • All the macroscopic bodies do have

wavelength associated with them but that is too small to observed.eg football

• Also Heisenberg uncertainty principle says that when we try to find the position its momentum become undefined and vice versa

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MORE ABOUT HEISENBERG

• The uncertainty principle says that we cannot measure the position (x) and the momentum (p) of a particle with absolute precision.

• The more accurately we know one of these values, the less accurately we know the other.

• Multiplying together the errors in the measurements of these values has to give a number greater than or equal to half of a constant called "h-bar".

• This is equal to Planck's constant (usually written as h) divided by 2π.

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• One way to think about the uncertainty principle is as an extension of how we see and measure things in the everyday world.

• You can read these words because particles of light, photons, have bounced off the screen or paper and reached your eyes. Each photon on that path carries with it some information about the surface it has bounced from, at the speed of light.

• Seeing a electron, is not so simple. You might similarly bounce a photon off it and then hope to detect that photon with an instrument.

• But chances are that the photon will impart some momentum to the electron as it hits it and change the path of the particle you are trying to measure. Or else, given that quantum particles often move so fast, the electron may no longer be in the place it was when the photon originally bounced off it.

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CLASSIFICATION Ionizing Radiation

– Higher energy electromagnetic waves (gamma) or heavy particles (beta and alpha).

– High enough energy to pull electron from orbit.

Non-ionizing Radiation– Lower energy electromagnetic waves.– Not enough energy to pull electron from orbit, but

can excite the electron.

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TYPES OF IONISING RADIATION 1.DIRECTLY IONISING RADIATION • Energy > 13.6 ev• Ionisation of an atom • CHARGED• Eg : electrons , protons or alpha ,beta etc 2. INDIRECTLY IONISING RADIATION • Energy <13.6 ev • Two step interaction• UNCHARGED• Eg x rays , gamma rays etc

Can a non ionising radiation be an indirectly ionising one ?

FOOD FOR THOUGHT ...


X RAYS

• Wilhelm Conrad Roentgen , a German physicist discovered X rays on November 8,1895.

• He was investigating the behaviour of cathode rays in high energy cathode ray tube

• It consists of a glass envelope from as much air as possible was evacuated

• He covered the CRT with black paper to ensure that light does not escape and also to block outside light .


• He also darkened the laboratory room .• He found that whenever the cathode ray was

organised the unknown type of ray was produced .

• This ray caused the fluorescence of a small paper coated with barium platinocyanide .


• This could not be electrons from cathode ray • This could not be the light because it is all dark and

cardboard was also there in between them. • There is something that cross the tube when CRT is

organised and also penetrate the cardboard • Excitement increased and he kept different things in

between them replacing cardboard results were different

• Then he held his hand between the tube and the fluorescent screen and the result was ...


RESULT


• The skeleton of his hand appeared on the screen .

• He called it X RAYS, because he was still unknown of this radiation .

• This led him to win NOBEL PRIZE IN 1901



BACKGROUND • HENRI BECQUEREL was a scientist who worked on

minerals and optics .• He belonged to a family of scientist ,Grandfather

discovered piezoelectricity and father phosphoresce.• After discovery of x rays , Becquerel was trying to find

out whether these are related to phosphorescence or not .

• He took Uranium salts and photographic film covered with black paper and thought if the X-rays were coming out from phosphorescent* material it will cross film and form a image provided we need to give a UV radiations ie Sun.


DISCOVERY

• Those days in February , Paris was short of sunshine .• Becquerel had to delay his experiment .He kept the

Uranium minerals and film in the drawer .• After week or so he decided to develop film though

sunshine was not there • He found that the photographic film had an impression • Even when uranium was not phosphorescent .• He was dumbstruck ,seeing it as he hypothesised that

Uranium salts are sources of X-rays .


RESULT


RESEARCH CONTINUES

• To continue the research RUTHERFORD came • His topic of concern was to study the rays given out

by URANIUM • He discovered that the rays by Uranium are not X

rays they are some other rays .• He gave three rays alpha beta and gamma which

comes from some special substance


EXPERIMENT


AND IT DIDNOT STOP! MARIE CURIE : MOTHER OF MODERN PHYSICS

• The term radioactivity was actually coined by Marie Curie, who together with her husband Pierre, began investigating the phenomenon recently discovered by Becquerel.

• She worked on the uranium ore pitchblende and found that it emitted much more radioactivity than the uranium in the mineral could deliver .

• It must contain another highly radioactive element, yet unknown. • In 1898, PIERRE AND MARIE ,discovered two new elements -

polonium and radium. • Polonium was named after Marie's homeland, Poland. Radium got

its name from the Latin word for ray..


RADIUM GIRLS

• There was a factory of radium watches which hired 70 WOMEN to paint RADIUM DIAL .

• Ii was called UNDARK paint made of glue ,water and radium powder .

• Women wee taught to shape paintbrush with mouths to maintain a fine point

• Some painted their nails and teeth too with that paint• Management and scientist kept themselves away from

the exposure but the workers were unaware of it .


• Five Radium Girls sued U.S. Radium in a case that initiated labour safety standards and workers' rights.

• Workers suffered from inexplicable bone fractures, bleeding gums and eventually, necrosis of the jaw.

• The Radium Girls' case was settled in 1928, putting a swift end to shaping paintbrushes with the mouth and open containers of radium paint.


NUCLEAR POWER PLANT • In nuclear power station, electrical power is

generated by nuclear reaction.• Here, heavy radioactive elements such as Uranium

(U235) or Thorium (Th232) are subjected to nuclear fission. This fission is done in a special apparatus called as reactor.

• FISSION : The nuclei of heavy radioactive atoms are broken into two nearly equal parts. During this breaking ,huge quantity of energy is released. This release of energy is due to mass defect. (mass of final products are reduced than initial )


• It is same as steam power station. Only difference is that, instead of using heat generated due to coal combustion , here heat is generated due to fission

• Heat is used to produce steam from water in the boiler. This steam is used to drive a steam turbine. This turbine is the prime mover of the alternator which generates electrical energy.

• Very less amount of nuclear fuel can generate huge amount of electrical energy. This is the unique feature of a nuclear power plant.


• One kg of uranium is equivalent to 4500 metric tons of high grade coal. That means complete fission of 1 kg uranium can produce as much heat as can be produced by complete combustion of 4500 metric tons high grade coal.

• To meet up conventional fuel crisis in present era, nuclear power station can be the most suitable alternatives.


DIFFERENT COMPONENTS OF NUCLEAR POWER STATION

The plant consists of mainly following parts:1 NUCLEAR REACTOR

2 HEAT EXCHANGER

3 STEAM TURBINE

4 ALTERNATOR


WORKING • In nuclear fission, the nuclei of nuclear fuel, such as U235 are

bombarded by slow flow of neutrons.• Uranium is broken, huge heat energy released and also

number of neutrons are emitted during breaking .• These neutrons cause further fission which needs to be

controlled • These neutrons should be removed otherwise explosion can

occur .• Cadmium rods are used because they are good absorber of

neutrons called control rods they are moveable .• There is also moderator to slow down the neutrons .


• Heat Exchanger: The heat carried by sodium metal, is dissipated in water and water is converted to high pressure steam here.

After releasing heat in water the sodium metal coolant comes back to the reactor by means of coolant circulating pump.

• Steam Turbine :In nuclear power plant, the steam drives the turbine in the same way. After doing its job, the exhaust steam comes into steam condenser where it is condensed to water and can be reused.

• Alternator :an electrical generator that converts mechanical energy to electrical energy in the form of alternating current


CHERNOBYL DISASTER The worst manmade disaster in human history

Czech Technical University In Prague23 May 2007

Czech Technical University in Prague 3423 May 2007

WHERE IS CHERNOBYL?


CHERNOBYL ACCIDENT • NUCLEAR power plant is located 11 miles from the city of

Chernobyl• Plant consisted of 4 reactors while 5 and 6 reactors were

under construction each capable of producing 1GW of ELECTRIC POWER

• On Saturday, April 26, 1986, at 1:23:58 a.m. local time, the fourth reactor of the Chernobyl power plant known as Chernobyl-4 suffered a catastrophic steam explosion that resulted in a fire, a series of additional explosions, and a nuclear meltdown.• It is regarded as the worst nuclear accident . It produced radioactive debris that drifted over parts the

western soviet union Scandinavia, UK, and even eastern USA.

WHAT HAPPENED?•Reactor 4 was undergoing a test to test the backup power supply in case of a power loss.•The power fell too low, allowing the concentration of xenon-135 to rise.•The workers continued the test, and in order to control the rising levels of xenon-135, the control rods were pulled out.

WHAT HAPPENED?

• The experiment involved shutting down the coolant pumps, which caused the coolant to rapidly heat up and boil.• Pockets of steam formed in the coolant lines. When the coolant expanded in this particular design, the power level went up.• All control rods were ordered to be inserted. As the rods were inserted, they became deformed and stuck. The reaction could not be stopped.• The rods melted and the steam pressure caused an explosion, which blew a hole in the roof

THE CHERNOBYL REACTOR AFTER THE EXPLOSION.


DIRECT CASUALTIES

• 5.5 million people still live in contaminated areas• 31 people died in 3 months of radiation

poisoning• 134 emergency workers suffered from acute

radiation sickness• 25,000 rescue workers died since then of

diseases caused by radiation• Increased birth defects, miscarriages, and

stillbirths


INDIRECT CASUALTIES

• By the year 2000 there were 1800 case of thyroid cancer in children and adolescent.

• High number of suicide and violent death among Firemen, policemen, and other recovery workers


Bibliography

• www.physicspages.com• www.earthmagazine.com• www.electricals4u.com• Radiation detection and measurement by

SAHA • Christensen book on XRAY PRODUCTION


Education

Radiation history