This Week. Production, Usage and Distribution of Energy. 8/4/2017 Physics 214 Fall

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1 This Week Fission and fusion What made our world Atomic and Hydrogen bombs Big bangs in small packages Nuclear power plants The solution to the energy problem? Enrichment What does it mean and why is it necessary? Toxic Disposal Radiation in everyday life Limit your exposure Fusion: The Holy Grail Maybe in your lifetime Production, Usage and Distribution of Energy 8/4/2017 Physics 214 Fall

2 Fission and fusion If we make an atom from it s constituents energy is released. This is called the binding energy. Iron is the most tightly bound so if we can make elements up to Iron by the fusion of light elements energy is released. Similarly if we can break a very heavy atom into lighter elements we also have energy release. E = mc 2 Mass is another form of energy a nucleus is lighter than the sum of the constituent particle masses Fusion processes are how the sun produces energy and fission processes are how nuclear reactors produce energy 8/4/2017 Physics 214 Fall

3 The Sun Every second the sun turns 600 million tons of hydrogen into 596 million tons of helium (with 4 million tons transformed into luminous energy via E=mc 2 ). 8/4/2017 Physics 214 Fall

$The process produces 3 neutrons which can then cause 3 more atoms to undergo fission. Without control this chain reaction produces an enormous amount of energy in a fraction of a second.$

4 Chain reaction If a U 235 atom is broken into two lighter elements energy is released. This is accomplished using a neutron. The process produces 3 neutrons which can then cause 3 more atoms to undergo fission. Without control this chain reaction produces an enormous amount of energy in a fraction of a second. It is an atomic bomb. U 235 This process was first observed by Enrico Fermi in a laboratory under the Chicago University football stadium 8/4/2017 Physics 214 Fall

In order for a bomb to work there had to be sufficient Uranium but it could not be in one piece because it

5 Manhattan project and the bomb In the early forties all the top scientists were taken to Los Alamos to design the atomic bomb. In order for a bomb to work there had to be sufficient Uranium but it could not be in one piece because it fission would spontaneously occur. The main challenges were to obtain enough U 235 and to design a system to bring the uranium together with a neutron source when the bomb was dropped. 8/4/2017 Physics 214 Fall

The hydrogen (fusion) bomb Fusion gives a much bigger energy release than fission Hydrogen bombs are designed to use an atomic bomb to provide the

6 The hydrogen (fusion) bomb Fusion gives a much bigger energy release than fission Hydrogen bombs are designed to use an atomic bomb to provide the temperature and pressure so that fusion takes place. There is a central core of light elements surrounded by plutonium or uranium. 8/4/2017 Physics 214 Fall

$Enrichment Naturally occurring uranium is nearly all U 238 U 235 is the fissionable material. Complicated processes have been developed to increase the fraction of U 235, this is enrichment.$

7 Enrichment Naturally occurring uranium is nearly all U 238 U 235 is the fissionable material. Complicated processes have been developed to increase the fraction of U 235, this is enrichment. For a reactor the final fraction of U 235 is about 3.5%. For the original bomb several kilograms were required. In a reactor some of the U 238 is turned into plutonium which is also a fissionable material that is used in atomic bombs. Plutonium is produced and can be obtained from the spent fuel rods 8/4/2017 Physics 214 Fall

Nuclear reactors In order to produce energy we need to have controlled fission.

down and not let them escape. Control rods are used to absorb neutrons.

including shutting the reactor off completely.

8 Nuclear reactors In order to produce energy we need to have controlled fission. Fuel rods are inserted into a moderator, which is used to slow the neutrons down and not let them escape. Control rods are used to absorb neutrons. The control rods can be moved in and out to set the level of energy production including shutting the reactor off completely. The energy is taken out with a circulating liquid and steam is generated to drive a turbine. 8/4/2017 Physics 214 Fall

9 Toxic disposal Most of the elements produced in the fission process are highly radioactive. All materials inside the containment vessel also become highly radioactive. Disposal of this toxic nuclear waste is a very big problem since it must not enter the environment. There is controversy over a proposed waste disposal site at Yucca mountain. In 1986 operator error at the Chernobyl nuclear plant caused an uncontrolled chain reaction. The resulting release of radiation had effects over almost all the northern hemisphere and thyroid cancer rates have increased 10 fold in the Ukraine 8/4/2017 Physics 214 Fall

10 Radiation in everyday life We are exposed to radiation at low levels from a number of sources Cosmic rays Radon and other natural radioactivity Medical imaging Consumer products fire alarms Radiation is also used to treat cancer PET scans All kinds of medical tracers e.g. radioactive iodine Used in industry to control thickness of rolled steel and paper Sterilization of food 8/4/2017 Physics 214 Fall

To emulate the sun we need extremely high temperatures and pressures to squeeze light elements together.

11 Fusion as an energy source Every second the sun turns 600 million tons of hydrogen into 596 million tons of helium (with 4 million tons transformed into luminous energy via E=mc 2 ). To emulate the sun we need extremely high temperatures and pressures to squeeze light elements together. Livermore National lab has tried to do this using high power laser beams to compress pellets of deuterium and tritium. There is a new international effort based in France called ITER to try and produce controlled fusion. 8/4/2017 Physics 214 Fall

accelerating voltage is typically 30,000 volts and X rays are

12 Summary of Chapters 18 and 19 n # electrons 1 (2L+1) x 2 = 2 L = 0 2 (2L+1) x 2 = 8 L = 0 or 1 3 (2L+1) x 2 = 18 L = 0 or 1 or 2 The accelerating voltage is typically 30,000 volts and X rays are produced as the beam hits the screen 8/4/2017 Physics 214 Fall

13 Periodic table The nucleus Decay Chain reaction E = mc 2 8/4/2017 Physics 214 Fall

14 Our World 8/4/2017 Physics 214 Fall

15 Technology, Energy, and Society are Inextricably Intertwined Today s Energy Technologies and Infrastructures are Firmly Rooted in the 20 th Century 40 U.S. Energy Consumption by Source U.S. Energy Consumption by Source Petroleum Quadrillion Btu Hydroelectric Power Natural Gas Coal Nuclear Incandescent Four-stroke Electric lamp, combustion Power 1870s engine, 1870s Wood Watt Steam Engine, Rural Electrification Act, /4/2017 Physics 214 Fall nd water wood animals Intercontinental Rail System mid 1800s Eisenhower Highway

U.S. and World Energy Consumption Today World 446 Quads U.S. Share of World, 2004 15.

6% China United States Population Energy Production Energy Consumption 100 Quads

100 Quads) 8/4/2017 Physics 214 Fall 2017 16 100.

16 U.S. and World Energy Consumption Today World 446 Quads U.S. Share of World, % 22.5% 4.6% China United States Population Energy Production Energy Consumption 100 Quads Russia Some equivalent ways of referring to the energy used by the U.S. in 1 year (approx. 100 Quads) 8/4/2017 Physics 214 Fall quadrillion British Thermal Units (Quads) U.S. & British unit of energy exa Joules (EJ) Metric unit of energy terawatt-years (TW-yr) Metric unit of power (energy/sec)x(#seconds in a year) 16

Three Largely Separate Grids Distribute the Power; High-voltage electrical transmission lines in the United States are divided into three separate grids that

17 Three Largely Separate Grids Distribute the Power; High-voltage electrical transmission lines in the United States are divided into three separate grids that make up the national power grid. The grids operate independently but are connected in a few places by direct-current lines. 8/4/2017 Physics 214 Fall

18 Where does the sunlight go? 8/4/2017 Physics 214 Fall

19 There is an Historic Correlation between CO2 Concentration and Temperature Note dramatic increase in recent years. 8/4/2017 Note that Physics total 214 temperature Fall 2017 change across 19 several ice ages was only about 12 o C or about 22 o F

20 Solar/wind Power Solar is about 12% efficient Wind is about 25% efficient 8/4/2017 Physics 214 Fall

21 Worked Questions and Problems 8/4/2017 Physics 214 Fall

22 Questions Chapter 18 Q11 Assuming that cathode rays are a beam of charged particles, how could you demonstrate that these particles are negatively charged? By deflection in a magnetic field Q13 Would you expect X rays to be produced by a television picture tube? Yes the accelerated electrons hitting the screen do produce X rays 8/4/2017 Physics 214 Fall

23 Q14 If the electron beam in a television tube is striking just one point on the screen at a time, how can we get a full picture? Because the beam sweeps over the screen 30 times/second and we do not see this motion because of the speed and persistence of vision. Q20 What role did Rutherford s scattering experiment play in our developing understanding of atomic structure? Rutherford discovered the nucleus made up of protons and neutrons surrounded at a large distance by electrons. The atom was not of uniform density like a marshmallow 8/4/2017 Physics 214 Fall

24 Q23 Does the spectrum of hydrogen consist of randomly spaced wavelengths or is there a pattern to the spacing? There is unique pattern corresponding to the allowed energy levels. This allows the observation of hydrogen in deep space and the exansion of space by the shift to the red in the pattern 8/4/2017 Physics 214 Fall

25 Ch 18 E 6 How many electrons are required to produce 1 microcoulomb of negative charge? e = 1.6 x C 1 microcoulomb = 10-6 C = ne n = 10-6 /(1.6 x ) = 6.25 x electrons 8/4/2017 Physics 214 Fall

26 Ch 18 E 10 Suppose a photon has wavelength λ = 520 nm a) What is frequency of photon? b) What is photon s energy in Joules? a) c = fλ, f = c/λ = (3 x 10 8 )/(520 x ) = x Hz b) E = hf = (6.626 x )(5.769 x ) = x J 8/4/2017 Physics 214 Fall

27 Ch 18 E 12 An electron in the hydrogen atom jumps from an orbit in which the energy is 1.89 ev higher than the energy of the final lower-energy orbit. a) What is the frequency of photon emitted in this transition? (h = 4.14 x evs) b) What is the wavelength of emitted photon? a) } E = 1.89 ev E = hf, f = E/h = 1.89/(4.14 x ) = x Hz b) c = λf, λ = c/f = (3 x 10 8 )/(4.565 x ) = 6.571nm 8/4/2017 Physics 214 Fall

28 Ch 18 CP 4 An electron (m = 9.1 x kg) moves with velocity v = 1500m/s a) What is the electron s momentum? b) What is the electron s debroglie wavelength? c) How does this wavelength compare to visible light? a) P = mv = (9.1 x )(1500) = x kg.m/s b) λ = h/p = (6.626 x )/(1.365 x ) = nm c) Blue light has λ = nm. Electron has the same wavelength as blue light. 8/4/2017 Physics 214 Fall

29 Questions Chapter 19 Q1 In 1919, Rutherford bombarded a sample of nitrogen gas with a beam of alpha particles. A. In addition to alpha particles, what other particle emerged from the nitrogen gas in this experiment? B. What conclusion did Rutherford draw from this experiment? Explain. Q3 Is it possible for two atoms of the same chemical element to have different masses? Yes by adding or subtracting neutrons e.g. C 12 and C 14 8/4/2017 Physics 214 Fall

30 Q4 Is it possible for atoms of the same chemical element to have different chemical properties? No the chemical properties are determined by the electrons Q5 Which number, the mass number or the atomic number, determines the chemical properties of an element? The atomic number gives the number of electrons Q7 In a nuclear reaction, can the total mass of the products of the reaction be less than the total mass of the reactants? Yes. E = mc 2 and mass can be turned into energy 8/4/2017 Physics 214 Fall

31 Q13 In a time equal to two half-lives of a radioactive isotope, would you expect all of that isotope to have decayed? NO. In one half life ½ decay so in two half lives ¼ would be left Q15 Chemical reactions and nuclear reactions can both release energy. On the average, would you expect the energy released per unit of mass in a chemical reaction to be greater than, equal to, or less than what is released in nuclear reaction? Chemical reactions involve changes in the electron energy levels and these are very low energy compared to nuclear reactions 8/4/2017 Physics 214 Fall

32 Q17 Suppose that you light a match to a mixture of oxygen and hydrogen, which then reacts explosively to form water. Is this a chemical reaction or a nuclear reaction? It is a chemical reaction in which two hydrogen atoms and one oxygen atom join. Q18 The most common isotope of uranium is uranium-238. Is this the isotope that is most likely to undergo fission? NO U 235 8/4/2017 Physics 214 Fall

33 Q19 What property of the fission reaction leads to the possibility of a chain reaction? The emittance of more than one neutron. Q21 Do the control rods in a nuclear reactor absorb or emit neutrons? They absorb neutrons 8/4/2017 Physics 214 Fall

34 Q22 If you wanted to slow down the chain reaction in a nuclear reactor, would you remove or insert the control rods? Insert Q28 How does nuclear fusion differ from nuclear fission? Fission is breaking a very heavy element into two lighter elements Fusion is joining two very light elements into on heavier element Both produce energy. Fusion produces the most and is cleaner but much more difficult 8/4/2017 Physics 214 Fall

35 Q29 Is nuclear fission the main process involved in the energy generated in the sun? No, the process is fusion. Q31 Which can produce larger yields of energy, a fission weapon or a fusion weapon? A fusion weapon. The original bomb was a fission bomb. The hydrogen bomb uses a fission bomb to trigger a fusion bomb. 8/4/2017 Physics 214 Fall

36 Ch 19 E 2 94Pu 239 is an isotope of Plutonium produced in nuclear reactors. a) How many protons in the nucleus of the isotope? b) How many neutrons in the nucleus of the isotope? a) Atomic number = # of protons = 94 b) Mass number = # of protons + # of neutrons = 239 # of neutrons = mass number - # of protons = = 145 8/4/2017 Physics 214 Fall

37 Ch 19 E 6 The fission fragment of iodine 131 undergoes negative Beta Decay. Complete the reaction equation and identity the daughter nucleus. unknown 53I 131 a X m + -1 e + o -- Conserve mass number: 131 = m , m=131 Conserve atomic number: 53 = , a = 54 54X 131 = 54 Xe 131 8/4/2017 Physics 214 Fall

38 Ch 19 E 10 How many half lives must go by for radioactivity of a give isotope to drop to: a) one-sixteenth its original value? b) one-sixty fourth its original value? a) In one half life, radioactivity drops by ½. 1/16 = 1/2 1/2 1/2 1/2 four half lives b) 1/64 = 1/2 1/2 1/2 1/2 1/2 1/2 six half lives 8/4/2017 Physics 214 Fall

39 Ch 19 E 12 Suppose two deuterium nuclei ( 1 H 2 fuse in a reaction that emits a neutron. Complete the reaction equation and identify the resulting nucleus. 1H H 2 a X m + o n 1 Conserve mass number = m + 1, m = 3 Conserve atomic number = a + 0, a = 2 2X 3 = 2 He 3 8/4/2017 Physics 214 Fall

40 Ch 19 CP 4 Nuclear power has been a source of controversy over the last few decades. Although the use of nuclear power has grown during this time, we still get more than half our power by burning fossil fuels. Discuss the different environmental & economic impacts of these power sources: a) Burning fossil fuels produces CO 2 as a natural byproduct, a gas that contributes to the greenhouse effect and to global warming. Is this a problem with nuclear power? b) What environmental problems are associated with nuclear power that are not present in the burning of fossil fuels? c) What environmental problems are associated with burning fossil fuels that are not present with nuclear power? d) If alternatives were not available, which power source would you choose to develop further? 8/4/2017 Physics 214 Fall

41 CH 19 CP 4 cont. a) No. CO 2 is not created in the nuclear reaction associated with the fission of Uranium. b) Disposal of nuclear wastes. Reactor safety. Depleted uranium fuel rods must be buried as they are still radioactive. Complex processes associated with nuclear reaction and reactor stability lend nuclear reactors to events like that at Chernobyl! c) Availability of fossil fuels. Green house gasses and other pollutants. d) Nuclear power. 8/4/2017 Physics 214 Fall

This Week. 3/23/2017 Physics 214 Summer

This Week. 3/23/2017 Physics 214 Summer This Week Fission and fusion What made our world Atomic and Hydrogen bombs Big bangs in small packages Nuclear power plants The solution to the energy problem? Enrichment What does it mean and why is it