Nuclear Physics SPH3U – Unit #3 : Energy. SPH3U – Unit #3: Energy – Topic: Nuclear Physics Created by: Mr. D. Langlois - GECDSB Natural Radioactivity

Nuclear PhysicsNuclear PhysicsSPH3U – Unit #3 : EnergySPH3U – Unit #3 : Energy

SPH3U – Unit #3: Energy – Topic: Nuclear PhysicsSPH3U – Unit #3: Energy – Topic: Nuclear PhysicsCreated by: Mr. D. Langlois - GECDSBCreated by: Mr. D. Langlois - GECDSB

Natural RadioactivityNatural Radioactivity Becquerel accidentally discovered that uranium compounds caused Becquerel accidentally discovered that uranium compounds caused

a photographic plate to become fogged. (He was investigating the a photographic plate to become fogged. (He was investigating the relationship between x-rays and fluorescence using crystals of relationship between x-rays and fluorescence using crystals of uranium potassium sulphate.)uranium potassium sulphate.)

RadioactivityRadioactivity is the spontaneous disintegration of an unstable is the spontaneous disintegration of an unstable atomic nucleus and the emission of particles or electromagnetic atomic nucleus and the emission of particles or electromagnetic radiation. radiation.

Pierre and Marie Curie investigated uranium ores using chemical Pierre and Marie Curie investigated uranium ores using chemical separation. They discovered that separation. They discovered that pitchblendepitchblende and and chalcocitechalcocite, , naturally occurring ores, were highly radioactive due to the presence naturally occurring ores, were highly radioactive due to the presence of plutonium and radium.of plutonium and radium.

All naturally occurring elements with atomic numbers greater than All naturally occurring elements with atomic numbers greater than 83, as well as some 83, as well as some isotopesisotopes of lighter elements, are radioactive. of lighter elements, are radioactive.

Based on later work by Rutherford, Soddy, Villard, and others, three Based on later work by Rutherford, Soddy, Villard, and others, three different types of radiation were identified.different types of radiation were identified.


The Alpha, Beta, Gammas of The Alpha, Beta, Gammas of RadiationRadiation

Alpha particlesAlpha particles are helium nuclei, containing two protons and two are helium nuclei, containing two protons and two neutrons. They are deflected slightly in an electric or magnetic field. neutrons. They are deflected slightly in an electric or magnetic field. Their penetrating power is very low, being stoppable by a thin sheet Their penetrating power is very low, being stoppable by a thin sheet of aluminum or paper.of aluminum or paper.

Beta particlesBeta particles are electrons capable of traveling at speeds are electrons capable of traveling at speeds approaching the speed of light. Their low mass allows them to be approaching the speed of light. Their low mass allows them to be deflected greatly in an electric or magnetic field, in the opposite deflected greatly in an electric or magnetic field, in the opposite direction as the deflection of alpha particles. Their high speed gives direction as the deflection of alpha particles. Their high speed gives them greater penetrating power than alpha particles. Some beta them greater penetrating power than alpha particles. Some beta particles can penetrate several centimetres of aluminum. particles can penetrate several centimetres of aluminum.

Alpha particle emissions and beta particle emissions change the Alpha particle emissions and beta particle emissions change the composition of the nucleus.composition of the nucleus.

Gamma raysGamma rays are high energy electromagnetic radiation with short are high energy electromagnetic radiation with short wavelengths. Gamma rays, unlike alpha and beta particles, do not wavelengths. Gamma rays, unlike alpha and beta particles, do not change the composition of the nuclide. They have the highest change the composition of the nuclide. They have the highest penetrating power, being able to penetrate at least 30 centimetres of penetrating power, being able to penetrate at least 30 centimetres of lead.lead.


Testing Penetrating StrengthTesting Penetrating Strength

Radioactive particles videoRadioactive particles video


Characteristics of Radioactive Characteristics of Radioactive MaterialsMaterials

All radioactive nuclides have the following common All radioactive nuclides have the following common characteristics:characteristics:

Their radiations affect the emulsion of photographic film, Their radiations affect the emulsion of photographic film, ionize surrounding air molecules, make certain ionize surrounding air molecules, make certain compounds fluoresce, and have certain special biological compounds fluoresce, and have certain special biological effects.effects.

They undergo radioactive decay.They undergo radioactive decay. Radioactivity is found in naturally occurring sources and Radioactivity is found in naturally occurring sources and

in artificially produced ones.in artificially produced ones. People are constantly being exposed to radiation from a People are constantly being exposed to radiation from a

variety of natural and human-created sources. Exposure variety of natural and human-created sources. Exposure should be minimized, but it can never be reduced to should be minimized, but it can never be reduced to zero.zero.


Nuclear NotationNuclear Notation Some commonly used symbols for subatomic particles are:Some commonly used symbols for subatomic particles are: neutronneutron

protonproton

electron (beta particle)electron (beta particle)

positron positron (A positron is a particle much the same as an electron, but with a (A positron is a particle much the same as an electron, but with a

positive charge. It is an example of "antimatter".)positive charge. It is an example of "antimatter".)

alpha particlealpha particle

gamma ray (photon)gamma ray (photon)


Detecting RadiationDetecting Radiation Radioactivity can not be detected with our senses. Special detectors Radioactivity can not be detected with our senses. Special detectors

are needed. Because it can not be detected by human senses it is are needed. Because it can not be detected by human senses it is particularly dangerous; one may unknowingly be exposed to it for particularly dangerous; one may unknowingly be exposed to it for prolonged periods of time. Radiation has an effect on tissue and on prolonged periods of time. Radiation has an effect on tissue and on genetic material.genetic material.

Several devices have been developed to detect radioactivity, with Several devices have been developed to detect radioactivity, with the earliest being an unexposed photographic plate placed in the the earliest being an unexposed photographic plate placed in the vicinity of a source being detected. Other devices include a Wilson vicinity of a source being detected. Other devices include a Wilson cloud chamber, electroscopes, ionizing chambers, the Geiger-Muller cloud chamber, electroscopes, ionizing chambers, the Geiger-Muller tube, liquid and electronic bubble chambers, scintillation detectors tube, liquid and electronic bubble chambers, scintillation detectors (spinthariscope), and solid state semiconductor devices.(spinthariscope), and solid state semiconductor devices.

DosimetryDosimetry is the measurement of radiation and the study of its is the measurement of radiation and the study of its effects on living organisms.effects on living organisms.


Test YourselfTest Yourself Define the following terms: radioactivity, isotopes, alpha particles, Define the following terms: radioactivity, isotopes, alpha particles,

beta particles, gamma raysbeta particles, gamma rays State how radioactivity was discovered. State how radioactivity was discovered. Develop a generalization based on atomic number regarding Develop a generalization based on atomic number regarding

some radioactive elements. some radioactive elements. State the number of different types of radiation found in nature. State the number of different types of radiation found in nature. Identify the composition of alpha particles, beta particles, and Identify the composition of alpha particles, beta particles, and

gamma rays. gamma rays. Compare the penetrating power, speed, potential danger, and Compare the penetrating power, speed, potential danger, and

other important characteristics of alpha particles, beta particles, other important characteristics of alpha particles, beta particles, and gamma rays. and gamma rays.

Identify common characteristics of all radioactive nuclides. Identify common characteristics of all radioactive nuclides. Suggest some important implications arising from the fact that Suggest some important implications arising from the fact that

radioactivity can not be detected by human senses. radioactivity can not be detected by human senses. Identify one device that can be used to detect radioactivity. Identify one device that can be used to detect radioactivity.


Nuclear FissionNuclear Fission A neutron can be captured by the nucleus of some heavy atoms. The A neutron can be captured by the nucleus of some heavy atoms. The

nucleus then becomes unstable and splits. Other neutrons are released nucleus then becomes unstable and splits. Other neutrons are released when the nucleus splits.when the nucleus splits.

FissionFission is the term used to describe the splitting of a heavy nucleus into two is the term used to describe the splitting of a heavy nucleus into two or more smaller nuclei.or more smaller nuclei.

Slow moving neutrons are more easily captured by the nucleus. A Slow moving neutrons are more easily captured by the nucleus. A moderatormoderator is a medium which causes neutrons to travel more slowly. is a medium which causes neutrons to travel more slowly.

Graphite, heavy water, and beryllium are all excellent moderators, capable Graphite, heavy water, and beryllium are all excellent moderators, capable of slowing neutrons without absorbing them.of slowing neutrons without absorbing them.

The neutrons liberated by fission travel very quickly unless moderated.The neutrons liberated by fission travel very quickly unless moderated. A very large amount of energy is released when an atom undergoes fission. A very large amount of energy is released when an atom undergoes fission.

( 200 MeV or Mega electron volts – a unit of energy commonly used in ( 200 MeV or Mega electron volts – a unit of energy commonly used in subatomic physics. 1.60x10^-19 J = 1 eV)subatomic physics. 1.60x10^-19 J = 1 eV)

In a typical fission reaction, the energy released is distributed as follows: In a typical fission reaction, the energy released is distributed as follows: 170 MeV of kinetic energy of fission fragments, 5 MeV of kinetic energy of 170 MeV of kinetic energy of fission fragments, 5 MeV of kinetic energy of neutrons, 15 MeV of energy beta particles and gamma rays, and 10 MeV as neutrons, 15 MeV of energy beta particles and gamma rays, and 10 MeV as energy of antineutrinos.energy of antineutrinos.


The Mass-Energy InterfaceThe Mass-Energy Interface Mass is not conserved in a nuclear reaction. The products formed Mass is not conserved in a nuclear reaction. The products formed

during nuclear fission have a slightly lower mass, due to the during nuclear fission have a slightly lower mass, due to the nuclear nuclear mass defectmass defect. This nuclear mass defect can be used to determine . This nuclear mass defect can be used to determine the nuclear binding energy which held the heavier nucleus together the nuclear binding energy which held the heavier nucleus together and was released when fission occurred.and was released when fission occurred.

The energy released by a fission can be calculated by finding the The energy released by a fission can be calculated by finding the difference between the mass of the parent atom and neutron, and difference between the mass of the parent atom and neutron, and the masses of the daughter atoms and emitted neutrons, and the masses of the daughter atoms and emitted neutrons, and converting this mass "loss" into energy using E = mc^2, where m is converting this mass "loss" into energy using E = mc^2, where m is the change in mass from the parent to daughter atoms, and c is the the change in mass from the parent to daughter atoms, and c is the speed of light (3.0x10^8 m/s) speed of light (3.0x10^8 m/s)

Neutrons released when an atom undergoes fission are capable of Neutrons released when an atom undergoes fission are capable of causing other nuclei to undergo fission, if the neutrons are slowed causing other nuclei to undergo fission, if the neutrons are slowed down by a moderator.down by a moderator.

A sustained fission reaction caused in this way is called a A sustained fission reaction caused in this way is called a chain chain reactionreaction..


Fission VideosFission Videos


E=mc^2E=mc^2 It is believed that the famous equation E=mc^2 applies to It is believed that the famous equation E=mc^2 applies to

most processes, although the changes are usually far too most processes, although the changes are usually far too small to be measured. small to be measured.

For example, the heat of combustion of coal is approximately For example, the heat of combustion of coal is approximately 3.2x10^7 J/kg. If 1.0 kg of coal is burned, what change would 3.2x10^7 J/kg. If 1.0 kg of coal is burned, what change would the release of energy in light and warmth make in the mass of the release of energy in light and warmth make in the mass of coal compared with the mass of the products of combustion?coal compared with the mass of the products of combustion?

kgsm

J

c

Em 10

28

7

2106.3

)/100.3(

102.3

We can see this is a negligable amount of mass which is not detectable with even the most sensitive electronic balance.


ExamplesExamples

Calculate the energy released when 0.250kg of Calculate the energy released when 0.250kg of Uranium splits into two smaller atoms which Uranium splits into two smaller atoms which each have a mass of 0.121kg. [ANS:7.2x10^14J] each have a mass of 0.121kg. [ANS:7.2x10^14J]

The total energy consumption of Canada is The total energy consumption of Canada is about 9.80x10^18 J. How much mass would about 9.80x10^18 J. How much mass would have to be totally converted into energy to meet have to be totally converted into energy to meet this need. [ANS: 1.09x10^2kg]this need. [ANS: 1.09x10^2kg]

Calculate the energy of a proton in electron Calculate the energy of a proton in electron volts. The mass of a proton is 1.67x10^-27kg. volts. The mass of a proton is 1.67x10^-27kg. [ANS: 939 MeV][ANS: 939 MeV]


Nuclear ReactorsNuclear Reactors Natural uranium ore contains about 0.7% uranium-235. Natural uranium ore contains about 0.7% uranium-235.

To increase the likelihood of sustaining a chain reaction To increase the likelihood of sustaining a chain reaction for uranium, the fissionable isotope of uranium must be for uranium, the fissionable isotope of uranium must be increased in its relative proportion through enrichment. increased in its relative proportion through enrichment.

A A nuclear reactornuclear reactor produces a sustained chain reaction produces a sustained chain reaction at a controlled rate. The heat energy produced by the at a controlled rate. The heat energy produced by the reaction is used to drive turbines, generating electricity. reaction is used to drive turbines, generating electricity.

Control rodsControl rods, made of materials such as cadmium , made of materials such as cadmium which absorb neutrons, are used to control the rate of a which absorb neutrons, are used to control the rate of a chain reaction in a nuclear reactor.chain reaction in a nuclear reactor.

A A critical masscritical mass of fissionable material is the minimum of fissionable material is the minimum mass that will produce a nuclear explosion. To produce a mass that will produce a nuclear explosion. To produce a sustainable nuclear chain reaction requires more sustainable nuclear chain reaction requires more material than the critical mass.material than the critical mass.


The CANDU ReactorThe CANDU Reactor The The CANDU reactorCANDU reactor (Canadian deuterium uranium) (Canadian deuterium uranium)

uses uranium, bundled in the form of uranium oxide fuel uses uranium, bundled in the form of uranium oxide fuel pellets, to produce electricity. (A comparison between pellets, to produce electricity. (A comparison between CANDU reactors and other types of reactors would be CANDU reactors and other types of reactors would be an interesting optional extension topic.)an interesting optional extension topic.)

Saskatchewan has abundant deposits of uranium ore Saskatchewan has abundant deposits of uranium ore which is refined for use in nuclear reactors.which is refined for use in nuclear reactors.

The refined uranium oxide fuel pellets are stacked into The refined uranium oxide fuel pellets are stacked into cylindrical rods. The rods are arranged into a cylindrical rods. The rods are arranged into a fuel fuel bundlebundle which is then ready to be placed in special which is then ready to be placed in special pressure tubes inside the reactor.pressure tubes inside the reactor.

The reactor vessel is called the The reactor vessel is called the calandriacalandria..


What if…?What if…?

Nuclear reactors can not explode like a Nuclear reactors can not explode like a nuclear bomb. Even under a worst-case nuclear bomb. Even under a worst-case scenario, with a core scenario, with a core meltdownmeltdown, a critical , a critical mass of fuel would not be present and the mass of fuel would not be present and the fuel would burn into the ground. (This, of fuel would burn into the ground. (This, of course, would lead to very serious course, would lead to very serious consequences, including possible loss of consequences, including possible loss of life and environmental damage.)life and environmental damage.)


Fuel of a ReactorFuel of a Reactor

Refueling can be done by removing fuel bundles Refueling can be done by removing fuel bundles from the pressure tubes and replacing them with from the pressure tubes and replacing them with new bundles. In a CANDU reactor this can be new bundles. In a CANDU reactor this can be done without having to shut the reactor down.done without having to shut the reactor down.

Heavy waterHeavy water is used as the moderator in a is used as the moderator in a CANDU reactor. Heavy water contains CANDU reactor. Heavy water contains deuteriumdeuterium, an isotope of hydrogen having one , an isotope of hydrogen having one neutron in the nucleus. Heavy water also neutron in the nucleus. Heavy water also transfers heat from the fuel into a heat transfers heat from the fuel into a heat exchanger which heats ordinary water to exchanger which heats ordinary water to produce steam. produce steam.


The ProcessThe Process The steam produced is used to turn turbines The steam produced is used to turn turbines

which are connected to electric generators.which are connected to electric generators. CondensersCondensers change the steam back into water change the steam back into water

so it can be cycled back to the steam generator.so it can be cycled back to the steam generator. Some experts believe that the design of the Some experts believe that the design of the

CANDU reactor makes them safer than other CANDU reactor makes them safer than other types of nuclear reactors.types of nuclear reactors.

If excess heat builds up in the calandria, the If excess heat builds up in the calandria, the heavy water can be drained out. This causes the heavy water can be drained out. This causes the chain reaction to stop, because the moderator is chain reaction to stop, because the moderator is no longer present.no longer present.


Pro’s and ConsPro’s and Cons Supporters of the use of nuclear energy feel that it is a Supporters of the use of nuclear energy feel that it is a

safe and effective way to produce energy. With the safe and effective way to produce energy. With the demand for energy increasing, and the problems demand for energy increasing, and the problems associated with burning fossil fuels, such as acid associated with burning fossil fuels, such as acid precipitation and the greenhouse effect, they regard the precipitation and the greenhouse effect, they regard the use of nuclear energy as being necessary.use of nuclear energy as being necessary.

Nuclear energy avoids some of the problems of Nuclear energy avoids some of the problems of generating hydro-electric power. Flooding land to build generating hydro-electric power. Flooding land to build dams creates environmental and social problems.dams creates environmental and social problems.

The use of nuclear energy may avoid the need for long The use of nuclear energy may avoid the need for long transmission lines. Nuclear plants can be built in transmission lines. Nuclear plants can be built in relatively close proximity to where the power is needed.relatively close proximity to where the power is needed.


Pro’s and ConsPro’s and Cons Nuclear energy produces very small amounts of waste by volume. Nuclear energy produces very small amounts of waste by volume.

The radioactive materials can be concentrated for storage and The radioactive materials can be concentrated for storage and monitoring in one place. Poisonous metals (such as arsenic, lead, monitoring in one place. Poisonous metals (such as arsenic, lead, and mercury), toxic gases, carbon dioxide, and fly ash are not and mercury), toxic gases, carbon dioxide, and fly ash are not released into the atmosphere.released into the atmosphere.

Critics of the use of nuclear energy cite various problems with its Critics of the use of nuclear energy cite various problems with its use. The opposition to the use of nuclear energy has grown so use. The opposition to the use of nuclear energy has grown so strong in recent years, that some reactors have been shut down. strong in recent years, that some reactors have been shut down. Other reactors scheduled for development have been delayed or Other reactors scheduled for development have been delayed or were never completed because of the social and political pressure were never completed because of the social and political pressure exerted by the antinuclear lobby. The debate continues.exerted by the antinuclear lobby. The debate continues.

The Chernobyl nuclear accident lead to a justifiable scepticism The Chernobyl nuclear accident lead to a justifiable scepticism about any claims of the safety of nuclear reactors, particularly if about any claims of the safety of nuclear reactors, particularly if those claims come from spokespersons of the industry, who often those claims come from spokespersons of the industry, who often cite the strict controls and regulations faced by the industry.cite the strict controls and regulations faced by the industry.


Pro’s and ConsPro’s and Cons CANDU reactors need to be built near a large body of water. Fresh CANDU reactors need to be built near a large body of water. Fresh

water is circulated through the condensers. Excess heat is returned water is circulated through the condensers. Excess heat is returned to the source. Raising the temperature reduces the oxygen content to the source. Raising the temperature reduces the oxygen content of the water, creating an environmental stress on many kinds of of the water, creating an environmental stress on many kinds of living organisms. The heated water does, however, offer some living organisms. The heated water does, however, offer some possibilities for commercial aquaculture, allowing for warm-water possibilities for commercial aquaculture, allowing for warm-water species to be harvested in colder regions. The excess heat can also species to be harvested in colder regions. The excess heat can also be used for commercial greenhouses or other applications. Air be used for commercial greenhouses or other applications. Air cooling is possible.cooling is possible.

Critics also suggest that mining safety is an issue with the use of Critics also suggest that mining safety is an issue with the use of nuclear energy. The ore is slightly radioactive. Radon gas is often nuclear energy. The ore is slightly radioactive. Radon gas is often present at the mine site. The disposed present at the mine site. The disposed tailingstailings contain trace contain trace amounts of uranium. Unless they can be disposed of properly, they amounts of uranium. Unless they can be disposed of properly, they can cause ground water contamination and environmental damage can cause ground water contamination and environmental damage to the land on which they are dumped. to the land on which they are dumped.


Nuclear Fuel CycleNuclear Fuel Cycle The entire cycle, from mining the fuel to its eventual The entire cycle, from mining the fuel to its eventual

disposal after use, is called the disposal after use, is called the nuclear fuel cyclenuclear fuel cycle.. Used nuclear fuel is both hot and radioactive. It is stored Used nuclear fuel is both hot and radioactive. It is stored

under water in large cooling pools for up to two years under water in large cooling pools for up to two years after use, until it cools. Some of the used fuel will still after use, until it cools. Some of the used fuel will still remain radioactive for up to several thousand years. This remain radioactive for up to several thousand years. This concerns many people.concerns many people.

The storage of used fuel is a contentious issue for those The storage of used fuel is a contentious issue for those concerned about the protection of the environment. No concerned about the protection of the environment. No ideal solution has yet been developed to dispose the ideal solution has yet been developed to dispose the waste. Current proposals for waste management merely waste. Current proposals for waste management merely offer temporary storage solutions until better methods offer temporary storage solutions until better methods become available.become available.


Nuclear Fuel CycleNuclear Fuel Cycle Storage of waste in underground salt mines offers one possible Storage of waste in underground salt mines offers one possible

solution. Formations in the Canadian Shield offer other possibilities. solution. Formations in the Canadian Shield offer other possibilities. The area being considered as a storage site must be dry and The area being considered as a storage site must be dry and relatively free of earthquake and volcanic activity.relatively free of earthquake and volcanic activity.

DecommissioningDecommissioning of nuclear reactors, once they have completed of nuclear reactors, once they have completed their useful service, is another issue frequently raised by opponents their useful service, is another issue frequently raised by opponents to the use of nuclear energy. to the use of nuclear energy.

One of the waste materials from a nuclear reactor is plutonium. It is One of the waste materials from a nuclear reactor is plutonium. It is known to cause cancer in extremely small quantities. It is also used known to cause cancer in extremely small quantities. It is also used to make nuclear weapons. Some argue against the use of nuclear to make nuclear weapons. Some argue against the use of nuclear reactors because they provide a country with the potential to build a reactors because they provide a country with the potential to build a nuclear weapons arsenal. (An interesting anecdote is that of the nuclear weapons arsenal. (An interesting anecdote is that of the development of India's first atomic bomb, which occurred partially as development of India's first atomic bomb, which occurred partially as a result of their having purchased the rights to the CANDU a result of their having purchased the rights to the CANDU technology from Canada. This occurred in spite of India having been technology from Canada. This occurred in spite of India having been under a contractual obligation not to exploit CANDU reactor under a contractual obligation not to exploit CANDU reactor technology for anything other than peaceful uses.)technology for anything other than peaceful uses.)


How a Nuclear Power Plant WorksHow a Nuclear Power Plant Works

Nuclear Energy Plant VideoNuclear Energy Plant Video


Nuclear WeaponsNuclear Weapons An atomic bomb explodes when two or more sub-critical An atomic bomb explodes when two or more sub-critical

masses of fissionable material are brought together very masses of fissionable material are brought together very rapidly. Chemical explosives are used to implode the rapidly. Chemical explosives are used to implode the sub-critical masses together to form a mass sub-critical masses together to form a mass largerlarger than than the critical mass.the critical mass.

An atomic bomb produces devastating destruction. Its An atomic bomb produces devastating destruction. Its explosive force is measured in terms of the comparable explosive force is measured in terms of the comparable number of megatons of conventional explosives that number of megatons of conventional explosives that would be needed to produce similar results.would be needed to produce similar results.

Nuclear weapons produce radioactive contamination of Nuclear weapons produce radioactive contamination of the environment. For this and other reasons many the environment. For this and other reasons many countries have banned atmospheric testing of these countries have banned atmospheric testing of these weapons.weapons.


History of the Atomic BombHistory of the Atomic Bomb The first atomic bombs, developed and tested by the The first atomic bombs, developed and tested by the

United States during the Manhattan Project in World War United States during the Manhattan Project in World War II, were dropped on the Japanese cities of Hiroshima II, were dropped on the Japanese cities of Hiroshima and Nagasaki in 1945. Over 110 000 people were killed and Nagasaki in 1945. Over 110 000 people were killed and many others suffered from the effects of the and many others suffered from the effects of the explosions for years afterwards. Japan surrendered explosions for years afterwards. Japan surrendered shortly after the atomic bombs were dropped, bringing shortly after the atomic bombs were dropped, bringing the war to an end.the war to an end.

Leo Szilard, one of the developers of the atomic bomb, Leo Szilard, one of the developers of the atomic bomb, recommended that it be tested before an international recommended that it be tested before an international audience of observers prior to being used, offering the audience of observers prior to being used, offering the Japanese a chance to surrender beforehand. Whether or Japanese a chance to surrender beforehand. Whether or not the atomic bomb should have been used is an issue not the atomic bomb should have been used is an issue worthy of debate.worthy of debate.


Today’s Nuclear WeaponsToday’s Nuclear Weapons Today the nuclear arsenals of the superpowers contain such vast Today the nuclear arsenals of the superpowers contain such vast

supplies of nuclear weapons that, according to one scenario, if a supplies of nuclear weapons that, according to one scenario, if a large proportion of them were deployed simultaneously, it would large proportion of them were deployed simultaneously, it would render the planet virtually uninhabitable by humans. Contemporary render the planet virtually uninhabitable by humans. Contemporary societal reactions to this issue are growing.societal reactions to this issue are growing.

Should scientists ultimately help bring about an understanding that Should scientists ultimately help bring about an understanding that nuclear weapons are immoral? Do such weapons threaten the nuclear weapons are immoral? Do such weapons threaten the existence of all forms of life on Earth? These are questions worth existence of all forms of life on Earth? These are questions worth pondering.pondering.

Should a scientifically literate society help to reduce the potential Should a scientifically literate society help to reduce the potential threat of nuclear war? Can nuclear weapons be thought of as a threat of nuclear war? Can nuclear weapons be thought of as a "deterrent" if their destructive capabilities could be so severe that it "deterrent" if their destructive capabilities could be so severe that it may be unreasonable to consider their use for solving international may be unreasonable to consider their use for solving international conflict?conflict?


Test YourselfTest Yourself Define the following terms: fission, moderator, nuclear mass defect, chain Define the following terms: fission, moderator, nuclear mass defect, chain

reaction, enrichment, control rods, nuclear reactor, critical mass. reaction, enrichment, control rods, nuclear reactor, critical mass. Describe what happens during a fission reaction. Describe what happens during a fission reaction. Give an example of a substance which can act as a good moderator. Give an example of a substance which can act as a good moderator. Explain how the neutrons released during a fission reaction can help to Explain how the neutrons released during a fission reaction can help to

sustain the reaction. sustain the reaction. Describe how a nuclear reactor works. Describe how a nuclear reactor works. Identify the type of fuel used in a nuclear reactor. Identify the type of fuel used in a nuclear reactor. Outline the nuclear fuel cycle, from the initial mining of raw materials to Outline the nuclear fuel cycle, from the initial mining of raw materials to

the final storage of waste material. the final storage of waste material. Explain why a nuclear explosion is not possible in a nuclear reactor. Explain why a nuclear explosion is not possible in a nuclear reactor. Identify some of the main features of the CANDU nuclear reactor. Identify some of the main features of the CANDU nuclear reactor. Explain the purpose of using heavy water in CANDU reactors. Explain the purpose of using heavy water in CANDU reactors.


Test YourselfTest Yourself State some of the facts that supporters of the use of nuclear State some of the facts that supporters of the use of nuclear

energy use to substantiate their position. energy use to substantiate their position. State some of the concerns that critics raise regarding the use of State some of the concerns that critics raise regarding the use of

nuclear energy. nuclear energy. Suggest what concerns regarding the environment emerge as a Suggest what concerns regarding the environment emerge as a

result of the use of nuclear energy. result of the use of nuclear energy. Suggest how environmental concerns regarding the use of non-Suggest how environmental concerns regarding the use of non-

nuclear methods of electrical generation might be alleviated with nuclear methods of electrical generation might be alleviated with the use of nuclear energy. the use of nuclear energy.

Using a solid knowledge base of all of the previous outcomes, Using a solid knowledge base of all of the previous outcomes, develop a position which either supports or rejects the use of develop a position which either supports or rejects the use of nuclear energy for peaceful purposes. nuclear energy for peaceful purposes.

Defend a position which either supports or rejects the use of Defend a position which either supports or rejects the use of nuclear energy for peaceful purposes. nuclear energy for peaceful purposes.

Defend a position which either supports or rejects the use of Defend a position which either supports or rejects the use of nuclear energy for military purposes. nuclear energy for military purposes.


Atomic TheoryAtomic Theory Rutherford's gold foil experiment, performed in Rutherford's gold foil experiment, performed in

conjunction with Geiger and Marsden, provided evidence conjunction with Geiger and Marsden, provided evidence for the nucleus due to the scattering of alpha particles. for the nucleus due to the scattering of alpha particles. The repulsion of some alpha particles suggested that the The repulsion of some alpha particles suggested that the nucleus is positively charged, containing protons within nucleus is positively charged, containing protons within the nucleus of the atom.the nucleus of the atom.

The The atomic numberatomic number describes the number of protons in describes the number of protons in the nucleus. For a neutral atom this is also the number of the nucleus. For a neutral atom this is also the number of electrons outside the nucleus.electrons outside the nucleus.

Subtracting the atomic number from the atomic mass Subtracting the atomic number from the atomic mass number gives the number of neutrons in the nucleus.number gives the number of neutrons in the nucleus.


Atomic TheoryAtomic Theory IsotopesIsotopes are atoms of the same element ( are atoms of the same element ( i.e.i.e., ,

they have the same number of protons, or the they have the same number of protons, or the same atomic number) which have a different same atomic number) which have a different number of neutrons in the nucleus. Isotopes of number of neutrons in the nucleus. Isotopes of an element have similar chemical properties.an element have similar chemical properties.

Radioactive isotopes are called Radioactive isotopes are called radioisotopesradioisotopes.. Most of the elements in the periodic table have Most of the elements in the periodic table have

several isotopes, found in varying proportions for several isotopes, found in varying proportions for any given element. any given element.

The average atomic mass of an element takes The average atomic mass of an element takes into account the relative proportions of its into account the relative proportions of its isotopes found in nature.isotopes found in nature.


Binding ForceBinding Force A A nuclear binding forcenuclear binding force holds the nucleus of holds the nucleus of

the atom together. The the atom together. The nuclear mass defectnuclear mass defect, a , a slightly lower mass of the nucleus compared to slightly lower mass of the nucleus compared to the sum of the masses of its constituent matter, the sum of the masses of its constituent matter, is due to the nuclear binding energy holding the is due to the nuclear binding energy holding the nucleus together. nucleus together.

The mass defect can be used to calculate the The mass defect can be used to calculate the nuclear binding energy, with nuclear binding energy, with E = mc^2E = mc^2..

The The average binding energyaverage binding energy per nucleon is a per nucleon is a measure of nuclear stability. The higher the measure of nuclear stability. The higher the average binding energy, the more stable the average binding energy, the more stable the nucleus. nucleus.


Test YourselfTest Yourself Define the following terms: atomic number, isotope, radioisotopes, Define the following terms: atomic number, isotope, radioisotopes,

nuclear binding force, average binding energy, nuclear mass nuclear binding force, average binding energy, nuclear mass defect, nuclear binding energy.defect, nuclear binding energy.

Use the atomic number of an element to determine the number of Use the atomic number of an element to determine the number of protons in a nucleus. protons in a nucleus.

Infer the number of electrons in a neutral atom from the atomic Infer the number of electrons in a neutral atom from the atomic number of an element. number of an element.

Use the atomic mass number and the atomic number to Use the atomic mass number and the atomic number to determine the number of neutrons in the nucleus of an atom. determine the number of neutrons in the nucleus of an atom.

Recognize that isotopes of an element have similar chemical Recognize that isotopes of an element have similar chemical properties, but different physical properties. properties, but different physical properties.

Give an example of an element which contains isotopes and Give an example of an element which contains isotopes and show how those isotopes differ from each another. show how those isotopes differ from each another.


Half-Life & Radioactive DecayHalf-Life & Radioactive Decay TransmutationTransmutation describes a process by which the describes a process by which the

nucleus of a radioactive atom undergoes decay into an nucleus of a radioactive atom undergoes decay into an atom with a different number of protons, until such time atom with a different number of protons, until such time as a stable nucleus is produced.as a stable nucleus is produced.

An alpha particle (An alpha particle (i.e.i.e., a helium nucleus) is released , a helium nucleus) is released during during alpha decayalpha decay of a radioactive substance. An of a radioactive substance. An element with a lower mass is formed.element with a lower mass is formed.

Ex:Ex:


Criteria for Alpha DecayCriteria for Alpha Decay In general, if X is the parent nucleus and Y is the In general, if X is the parent nucleus and Y is the

daughter nucleus:daughter nucleus: For alpha decay:For alpha decay: Alpha decay can only occur if Alpha decay can only occur if Mx > My + MHeMx > My + MHe. The . The

atomic masses of He and Y are atomic masses of He and Y are less thanless than the mass of the mass of the parent atom, X. This "lost" mass is converted into the parent atom, X. This "lost" mass is converted into energy (energy (E = mc2E = mc2) which appears as kinetic energy of ) which appears as kinetic energy of the alpha particle.the alpha particle.


Alpha DecayAlpha Decay Recall that alpha particles have the ability to penetrate Recall that alpha particles have the ability to penetrate

5cm of air and to penetrate a few sheets of paper. They 5cm of air and to penetrate a few sheets of paper. They must therefore possess some kinetic energy. So where must therefore possess some kinetic energy. So where did the energy come from?did the energy come from?

The protons within the nucleus repel one another The protons within the nucleus repel one another through the electromagnetic force. A stable nucleus must through the electromagnetic force. A stable nucleus must therefore be held together by a force that is – at least therefore be held together by a force that is – at least over short distances stronger than the electric force. This over short distances stronger than the electric force. This force is called the force is called the STRONG NUCLEAR FORCESTRONG NUCLEAR FORCE. .

Since the strong nuclear force is attractive, work must be Since the strong nuclear force is attractive, work must be done to break the nucleus apart. done to break the nucleus apart.


ExampleExample

An unstable polonium atom spontaneously An unstable polonium atom spontaneously emits an alpha particle and trasmutes into emits an alpha particle and trasmutes into an atom of some other element. Show the an atom of some other element. Show the process, including the new element, in process, including the new element, in standard nuclear-reaction notation.standard nuclear-reaction notation.


Converting Mass Units to Energy Converting Mass Units to Energy UnitsUnits

Recall that E=mc^2 relates the mass of an object in Recall that E=mc^2 relates the mass of an object in kilograms to the energy of the object in joules.kilograms to the energy of the object in joules.

If the mass of an object is given in atomic mass units (u), If the mass of an object is given in atomic mass units (u), then the following conversion factor can be used:then the following conversion factor can be used:

1 u = 931.4 MeV/c^21 u = 931.4 MeV/c^2 Studies have shown that the mass of an atomic nucleus Studies have shown that the mass of an atomic nucleus

is always less than the sum of the masses of its is always less than the sum of the masses of its constituent neutrons and protons. The energy equivalent constituent neutrons and protons. The energy equivalent of the mass difference is the of the mass difference is the Binding Energy, Binding Energy, or or positive work that would have to be done to break a positive work that would have to be done to break a nucleus apart. nucleus apart.


ExampleExample

Calculate the total kinetic energy, in electron Calculate the total kinetic energy, in electron volts, of the daughter particles released volts, of the daughter particles released when Uranium 236 undergoes alpha decay. when Uranium 236 undergoes alpha decay.

Given:Given:

um

um

um

He

Th

U

002602.4

038051.232

045562.236


Beta DecayBeta Decay

Beta decayBeta decay (beta negative decay) occurs (beta negative decay) occurs when a beta (negative) particle is released when a beta (negative) particle is released from the nucleus (from the nucleus (i.e.i.e., electron)., electron).

i.e.i.e.

In the above example thorium-234 releases a beta particle, forming protactinium-234. Mass is also not conserved in beta decay. Nucleon number is conserved.In beta decay, the beta particle released originated in the nucleus of the atom, not in the electron orbital. A neutron is lost, and in its place a proton and an electron are formed.


Beta DecayBeta Decay

Although to understand Beta decay we are Although to understand Beta decay we are assuming that a neutron is the assuming that a neutron is the combination of a proton and electron, this combination of a proton and electron, this model is incorrect for several reasons. model is incorrect for several reasons.

A better model requires the understanding A better model requires the understanding of the elementary particles called quarks, of the elementary particles called quarks, which is not needed at this time.which is not needed at this time.


Criteria for Beta DecayCriteria for Beta Decay For beta decay:For beta decay: (v is a neutrino) (v is a neutrino) (Actually an antineutrino is produced for beta emission.)(Actually an antineutrino is produced for beta emission.) My < MxMy < Mx The mass deficit appears as kinetic energy of the The mass deficit appears as kinetic energy of the

electron (and energy of the neutrino).electron (and energy of the neutrino). A A neutrinoneutrino was "invented" to maintain conservation of energy, was "invented" to maintain conservation of energy,

linear momentum, and angular momentum in beta decay. It has no linear momentum, and angular momentum in beta decay. It has no mass, no charge, and virtually no interaction with matter. It travels mass, no charge, and virtually no interaction with matter. It travels at the speed of light and carries off energy and momentum.at the speed of light and carries off energy and momentum.


ExampleExample

An atom of Sodium-24 can transmute into An atom of Sodium-24 can transmute into an atom of some other element by emitting an atom of some other element by emitting a beta particle. Represent this reaction in a beta particle. Represent this reaction in symbols and identify the daughter symbols and identify the daughter element. element.


ExampleExample

Calculate the energy released in the Calculate the energy released in the previous example.previous example.

Given:Given:

um

um

Mg

Na

985042.23

990961.23


The Weak Nuclear ForceThe Weak Nuclear Force

Recall that alpha decay was explained Recall that alpha decay was explained with reference to the strong nuclear force, with reference to the strong nuclear force, which binds nucleons together. which binds nucleons together.

It is not the same force which gives an It is not the same force which gives an explanation of beta decay. The force explanation of beta decay. The force which must be overcome for beta decay to which must be overcome for beta decay to occur is the occur is the Weak Nuclear Force.Weak Nuclear Force.


Gamma DecayGamma Decay Gamma decayGamma decay is the release of excess stored energy from the is the release of excess stored energy from the

nucleus. No transmutation occurs. However, gamma decay often nucleus. No transmutation occurs. However, gamma decay often accompanies alpha and beta negative decay in a disintegration accompanies alpha and beta negative decay in a disintegration series. Gamma decay results in the production of photons that have series. Gamma decay results in the production of photons that have zero mass and no electric charge. zero mass and no electric charge.

Gamma decay occurs when an excited nucleus (excited by photon Gamma decay occurs when an excited nucleus (excited by photon or particle bombardment, or it may be a decay product in an excited or particle bombardment, or it may be a decay product in an excited state) returns to the ground state. An excited nucleus is heavier than state) returns to the ground state. An excited nucleus is heavier than the ground state, by a mass equal to the mass/energy equivalent of the ground state, by a mass equal to the mass/energy equivalent of the energy of the emitted gamma ray.the energy of the emitted gamma ray.

(The asterisk indicates an "excited" nucleus.)


Gamma RaysGamma Rays

In reality Gamma rays are very similar to X-rays. In reality Gamma rays are very similar to X-rays. However, they are typically of a higher frequency However, they are typically of a higher frequency and thus higher energy than X-rays, although and thus higher energy than X-rays, although there is some overlap in their frequency ranges. there is some overlap in their frequency ranges.

Physicists distinguish between the 2 based on Physicists distinguish between the 2 based on how they’re produced: X-rays occur when high how they’re produced: X-rays occur when high energy electrons interact with matter, while energy electrons interact with matter, while Gamma Rays are produced within the nucleus. Gamma Rays are produced within the nucleus.


ExampleExample

Give the values of x & y in each of the Give the values of x & y in each of the following equations:following equations:

xPbPo

HeRnRa

ePoBi

yBiPb

xy

xy

x

21182

21584

42

22286

01

21483

21283

212


Decay SeriesDecay Series

A series of nuclear transmutations occurs A series of nuclear transmutations occurs until a stable nucleus results. The series of until a stable nucleus results. The series of steps in the transmutations is called a steps in the transmutations is called a disintegration seriesdisintegration series (or (or decay seriesdecay series).).

Nuclide chartsNuclide charts, with atomic number , with atomic number plotted against neutron number, are used plotted against neutron number, are used in nuclear physics to illustrate a in nuclear physics to illustrate a disintegration series. disintegration series.


Background RadiationBackground Radiation

Background radiationBackground radiation comes from a variety of comes from a variety of radioactive sources. Cosmic rays penetrating the radioactive sources. Cosmic rays penetrating the Earth's atmosphere from outer space usually Earth's atmosphere from outer space usually account for less than 25% of background account for less than 25% of background radiation (but this depends on altitude). radiation (but this depends on altitude).

Minute quantities of naturally occurring Minute quantities of naturally occurring radioactive sources in the surroundings (radioactive sources in the surroundings (e.g.e.g., , soil, air, drinking water, building materials, food, soil, air, drinking water, building materials, food, etc.etc.) also contribute to background radiation.) also contribute to background radiation.


Half-LifeHalf-Life

Some nuclei are more unstable than others and Some nuclei are more unstable than others and therefore more likely to decay in any given therefore more likely to decay in any given period of time.period of time.

The concept of The concept of Half-lifeHalf-life is a useful mathematical is a useful mathematical tool in modeling radioactive decay.tool in modeling radioactive decay.

It is based on the premise that the rate at which It is based on the premise that the rate at which nuclei decay is related to the number of unstable nuclei decay is related to the number of unstable nuclei present. nuclei present.

The time needed for one-half of the unstable The time needed for one-half of the unstable nuclei to decay will always be a constant.nuclei to decay will always be a constant.


Try This!Try This!

Place 40 or so coins in a jar, shake it, then Place 40 or so coins in a jar, shake it, then empty the coins onto your desk. Assume that the empty the coins onto your desk. Assume that the coins showing tails have not yet decays. Record coins showing tails have not yet decays. Record this number and remove the coins which came this number and remove the coins which came up heads from the plate.up heads from the plate.

Put the remaining coins back into the jar and Put the remaining coins back into the jar and repeat the process. Continue until all the coins repeat the process. Continue until all the coins have “decayed”. Graph the results. What type of have “decayed”. Graph the results. What type of relationship exists?relationship exists?


Half-LifeHalf-Life

• The amount of radioactive substance N left The amount of radioactive substance N left after some time t is given by after some time t is given by

2/1)2

1(0

t

t

NN

•Where N0 is the initial quantity and t1/2 is the half life.


Got Math?Got Math?

Recall the following property of logarithms:Recall the following property of logarithms:

xyx y loglog


Example 1Example 1

The half life of carbon-14 is 5730 years. A The half life of carbon-14 is 5730 years. A specimen of peat from an ancient bog specimen of peat from an ancient bog presently contains 800 presently contains 800 μμg of carbon-14.g of carbon-14.

What will be the amount of carbon-14 What will be the amount of carbon-14 remaining after 10,000 years? [ANS: 240]remaining after 10,000 years? [ANS: 240]

At what time will the amount remaining be At what time will the amount remaining be 300 300 μμg? [ANS: 8100 years]g? [ANS: 8100 years]


Rate of DecayRate of Decay Each radioactive nuclide emits radioactivity at its Each radioactive nuclide emits radioactivity at its

characteristic rate, different from that of other nuclides. characteristic rate, different from that of other nuclides. The rate of radioactive decay is related to the energy The rate of radioactive decay is related to the energy change that accompanies the transformation, but it is not change that accompanies the transformation, but it is not a direct relationship.a direct relationship.

The rate of radioactive emissions of a radioactive nuclide The rate of radioactive emissions of a radioactive nuclide is directly proportional to the amount of radioactive is directly proportional to the amount of radioactive material present.material present.

• The activity A, is measured in decays per second (Bq) Becquerel is the SI unit for radioactivity; 1 Bq = 1 s^-1


Rate of DecayRate of Decay

The activity A, after some time t is given The activity A, after some time t is given by:by:

where Awhere A00 is the original activity is the original activity

2/1

2

10

t

t

AA


Example 2Example 2

The half-life of cobalt-60 is 5.2714 years. The half-life of cobalt-60 is 5.2714 years. At a certain medical-supply house At a certain medical-supply house specializing in radiotherapy, a particular specializing in radiotherapy, a particular sample of this isotope currently has an sample of this isotope currently has an activity of 400.00 kBq. How much time will activity of 400.00 kBq. How much time will have passed before the activity drops to have passed before the activity drops to 40.000 kBq? [ANS: 17.511 years]40.000 kBq? [ANS: 17.511 years]


Radioactive DatingRadioactive Dating

If the half-life of a rdioactive isotope, the If the half-life of a rdioactive isotope, the level of radioactivity, and the original level of radioactivity, and the original amount are know, then the age of a amount are know, then the age of a material can be estimated.material can be estimated.

Archaeologists and geologists use Archaeologists and geologists use radioactive dating to estimate the age of radioactive dating to estimate the age of ancient objects (ie: Dinosaurs). ancient objects (ie: Dinosaurs).


Example 3Example 3

A piece of wood from an ancient burial site A piece of wood from an ancient burial site has an activity of 30.0 Bq. The original has an activity of 30.0 Bq. The original activity is estimated to be 240 Bq. What is activity is estimated to be 240 Bq. What is the estimated age of the wood? The half-the estimated age of the wood? The half-life is 5730a. [ANS:1.7x10^4 years]life is 5730a. [ANS:1.7x10^4 years]


Medical Applications of Medical Applications of RadioactivityRadioactivity

CANCERCANCER High energy radioactive particles destroy molecules faster than High energy radioactive particles destroy molecules faster than

replacement copies can be made, killing the cell. Even worse, replacement copies can be made, killing the cell. Even worse, the damage to the cell’s DNA might be such that altered cells the damage to the cell’s DNA might be such that altered cells could survive and continue to divide. Such a condition could lead could survive and continue to divide. Such a condition could lead to one of many forms of cancer.to one of many forms of cancer.

Fortunately, the damaging effects of radiation on living tissue Fortunately, the damaging effects of radiation on living tissue can be put to use on cancer since the processess that kill can be put to use on cancer since the processess that kill healthy cells are even more liable to kill the rapidly growing healthy cells are even more liable to kill the rapidly growing cancerous cells. cancerous cells.

One process localizes the damage by moving the source of One process localizes the damage by moving the source of radiation around the body while directing a thin beam of particles radiation around the body while directing a thin beam of particles at the cancerous tissue. at the cancerous tissue.

A second process localizes the effect by using very small, rice-A second process localizes the effect by using very small, rice-like radioactive particles, embedded close to the cancer. like radioactive particles, embedded close to the cancer.


Test YourselfTest Yourself Define the following terms: transmutation, alpha decay, Define the following terms: transmutation, alpha decay,

beta decay, gamma decay, neutrino, disintegration beta decay, gamma decay, neutrino, disintegration (decay) series, decay constant, half-life (decay) series, decay constant, half-life

Explain why mass is not conserved in a nuclear Explain why mass is not conserved in a nuclear reaction. reaction.

Write equations representing nuclear alpha and beta Write equations representing nuclear alpha and beta decay. decay.

Explain what background radiation is and where it Explain what background radiation is and where it originates. originates.

State the correct units for half-life State the correct units for half-life State the correct unit for the decay constant. State the correct unit for the decay constant.


Nuclear FusionNuclear Fusion Nuclear Nuclear fusionfusion occurs when two small nuclei join together to form occurs when two small nuclei join together to form

a larger nucleus. A large amount of energy is released during a larger nucleus. A large amount of energy is released during fusion. fusion.

Nuclear fusion occurs within the sun and the stars. Nuclear fusion occurs within the sun and the stars. Fusion in the sun is believed to occur in steps. Four protons Fusion in the sun is believed to occur in steps. Four protons

produce one atom, two positrons, and two neutrinos. The first two produce one atom, two positrons, and two neutrinos. The first two steps shown below must occur twice before the third step takes steps shown below must occur twice before the third step takes place:place:


Nuclear FusionNuclear Fusion Fusion in stars produces all of the chemical elements found on Fusion in stars produces all of the chemical elements found on

Earth.Earth. Sunlight is energy released from fusion reactions in the sun.Sunlight is energy released from fusion reactions in the sun. Examining the spectral characteristics of stars may provide a better Examining the spectral characteristics of stars may provide a better

understanding of fusion.understanding of fusion. Fusion is believed to be possible only under extremely high Fusion is believed to be possible only under extremely high

temperatures. For this reason it is referred to as a thermonuclear temperatures. For this reason it is referred to as a thermonuclear reaction.reaction.

The use of nuclear fusion for commercial purposes is currently The use of nuclear fusion for commercial purposes is currently being investigated.being investigated.

One reaction that may eventually be able to produce controlled One reaction that may eventually be able to produce controlled fusion is:fusion is:


Requirements for FusionRequirements for Fusion

Fusion has the potential of providing an Fusion has the potential of providing an abundant supply of energy. The fuel needed for abundant supply of energy. The fuel needed for fusion is readily available.fusion is readily available.

Deuterium must be extracted from water. Deuterium must be extracted from water. (About 0.015% of the hydrogen in water is exists (About 0.015% of the hydrogen in water is exists as deuterium.) Tritium ( ) must be made, since as deuterium.) Tritium ( ) must be made, since it does not occur naturally in sufficient quantities.it does not occur naturally in sufficient quantities.

Tritium is radioactive (a beta emitter), with a half-Tritium is radioactive (a beta emitter), with a half-life of 12.3 years. It is also toxic.life of 12.3 years. It is also toxic.


Fusion HopesFusion Hopes Complete fusion reactions produce no long-life products. Complete fusion reactions produce no long-life products.

Induced radioactivity is produced in the reactor container Induced radioactivity is produced in the reactor container due to neutron flux. Also, tritium is radioactive and quite due to neutron flux. Also, tritium is radioactive and quite toxic. toxic.

Sustaining a fusion reaction may be possible by Sustaining a fusion reaction may be possible by containing the reactants in a high temperature form of containing the reactants in a high temperature form of matter called plasma. Plasma particles can be contained matter called plasma. Plasma particles can be contained within a magnetic field. This principle is referred to as within a magnetic field. This principle is referred to as magnetic confinement. The purpose of magnetic magnetic confinement. The purpose of magnetic confinement is to avoid heat loss, not to prevent the confinement is to avoid heat loss, not to prevent the walls of the confinement vessel from vaporizing, as often walls of the confinement vessel from vaporizing, as often believed. believed.


Fusion ApplicationsFusion Applications

Another possible technique for sustaining Another possible technique for sustaining a fusion reaction is inertial confinement, in a fusion reaction is inertial confinement, in which a fuel pellet containing the fusion which a fuel pellet containing the fusion reactants is bombarded by a high energy reactants is bombarded by a high energy source such as a laser or an electron source such as a laser or an electron beam. beam.

The fusion bomb, developed and first The fusion bomb, developed and first exploded in the early 1950's, was the first exploded in the early 1950's, was the first use of nuclear fusion. use of nuclear fusion.


Test YourselfTest Yourself Define the following terms: fusion, thermonuclear, plasma, Define the following terms: fusion, thermonuclear, plasma,

magnetic confinement, inertial confinement. magnetic confinement, inertial confinement. Describe what happens during a fission reaction. Describe what happens during a fission reaction. Explain that nuclear fusion occurs within the sun and the stars . Explain that nuclear fusion occurs within the sun and the stars . Recognize that scientists believe that nuclear fusion is possible Recognize that scientists believe that nuclear fusion is possible

under extremely high temperatures. under extremely high temperatures. State that fusion reactions produce no long-term waste products. State that fusion reactions produce no long-term waste products. Recognize that the fuel needed for a fusion reaction is abundant. Recognize that the fuel needed for a fusion reaction is abundant. Compare fusion and fission. Compare fusion and fission. Explain one possible way of sustaining a fusion reaction. Explain one possible way of sustaining a fusion reaction. Suggest the potential that fusion has for providing an abundant Suggest the potential that fusion has for providing an abundant

supply of energy. supply of energy.

Documents

Nuclear Physics SPH3U – Unit #3 : Energy. SPH3U – Unit #3: Energy – Topic: Nuclear Physics Created by: Mr. D. Langlois - GECDSB Natural Radioactivity