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Nuclear Fission energy for war and peace

Nuclear Fission energy for war and peace. Nuclear fission is a process, by which a heavy nuclide splits into two or more pieces Nuclear fission reactions release a lot of energy. Nuclear energy has been used for peace and for war. Discovery of Induced Nuclear Fission.

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Nuclear Fission energy for war and peace

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  1. Nuclear Fission energy for war and peace Nuclear fission is a process, by which a heavy nuclide splits into two or more pieces Nuclear fission reactions release a lot of energy. Nuclear energy has been used for peace and for war. Nuclear Fission

  2. Discovery of Induced Nuclear Fission * O. Hahn, L. Meitner, and F. Strassmann in Berlin * F. Joliot and I. Curie in Paris * Enrico Fermi in Rome All three groups thought the reactions to be 238U (n, ) 239U92 (, ) 239E93 (, ) 239E94 Nuclear Fission

  3. Discovery of Induced Nuclear Fission Hahn (chemist), Meitner (physicist), and F. Strassmann (analytical chemist) used H2S to precipitate the radioactive products. The half-life measurements indicated to them that not one but many elements were produced. Meitner used barium ions, Ba2+, as a carrier and precipitated the radioactive products from the neutron bombardment. Nuclear Fission

  4. Discovery of Induced Nuclear Fission Atomic weight of Ba2+ is 137 Neutron induced uranium nuclear fission reactions Nuclear Fission

  5. Induced Nuclear Fission A simplified view of neutron induced fission: n + 235U  xxxEyy + uuuEww + 3 n Nuclear Fission

  6. Discovery of Induced Nuclear Fission The Official History of the Manhattan Project: Dr. Meitner brought the discovery of neutron induced fission to Copenhagen as she, a non-Aryan, exiled from Germany in 1938. She told Frisch, who told N. Bohr and Bohr told Fermi Fermi fond out only 235U underwent fission, for example: 235U + n 142Cs55 + 90Rb37 + 4n neutrons are releases Nuclear Fission

  7. Nuclear Fission Energy Fission Energy Nuclear Fission

  8. Nuclear Fission Energy Problem: If a 235U atom splits up into two nuclides with mass number 117 and 118, estimate the energy released in the process. Nuclear Fission

  9. Nuclear Fission Energy If a 235U atom splits up into two nuclides with mass number 117 and 118, estimate the energy released in the process. From handbooks Stable nuclides with mass numbers 117 and 118 are 117Sn50, and 118Sn50 and masses are given below the symbols 235U 117Sn50 + 118Sn50 235.043924 = 116.902956 + 117.901609 + Qfe Qfe= 0.2394 amu (931.5 MeV) / (1 amu) = 223 MeV. Discussion: The fission reaction equation is over simplified. Usually, neutrons are released too. Nuclear Fission

  10. Nuclear Fission Energy Assume the neutron induced fission reaction to be, 235U + n 142Cs55 + 90Rb35 + 4 n. explain the results and estimate the energy released. Solution: The neutron-rich fission products are beta emitters: 142Cs 142Ba +  (~1 min) 90Rb 90Sr +  (half-life, 15.4 min) 142Ba 142La +  (11 min) 90Sr 90Y +  (27.7 y) 142La 142Ce +  (58 min) 90Y 90Zr (stable) +  (64 h) 142Ce 142Pr +  (51015 y) 142Pr 142Nd (stable) +  (19 h) Nuclear Fission

  11. Nuclear Fission Energy – cont. Assume the neutron induced fission reaction to be, 235U + n ® 142Cs55 + 90Rb35 + 4 n. explain the results and estimate the energy released. Solution – cont. For the energy, consider the reaction and mass balance: 235U92142Nd60 + 90Zr40 + 3 n + Q235.04924 = 141.907719 + 89.904703 + 3x1.008665 + Q Q = (235.043924 - 141.907719 - 89.904703 - 3x1.008665) = 0.205503 amu (931.4812 MeV/1 amu) = 191.4 MeV per fission(1.6022e-13 J / 1 MeV) = 3.15e-11 J Nuclear Fission

  12. Nuclear Fission Energy Estimate the energy released by the fission of 1.0 kg of 235U. Solution From the results of the previous two examples, energy released by 1.0 kg uranium-235 is estimated below: (3.15e-11 J) 1000 g = 8.06e13 J (per kg). 1 mol235 g 6.023e231 mol Discussion This is a large amount of energy, and it is equivalent to the energy produced by burning tones of coal or oil. Nuclear Fission

  13. Nuclear Fission Energy Energy (MeV) distribution in fission reactions Kinetic energy of fission fragments Prompt (< 10–6 s) gamma () ray energy Kinetic energy of fission neutrons Gamma () ray energy from fission products Beta () decay energy of fission products Energy as antineutrinos (ve) 167 MeV 8 8 7 7 7 Nuclear Fission

  14. The Cyclotron and Fission Research Particle acceleratorsmachines to speed up particles Linear accelerators Cyclotrons Nuclear Fission

  15. The Cyclotron and Fission Research 7Li (p, n) 7Be3T (p, n) 3He1H (t, n) 3He2D (d, n) 3He2D (t, n) 4He3T (d, n) 4He Fusion reactions studied using the cyclotron Nuclear Fission

  16. The Cyclotron and Fission Research Threshold* Energy range (keV) Reaction energy(keV) narrow-energy neutron 51V (p, n) 51Cr 2909 5.6-52 45Sc (p, n) 45Ti 1564 2.36-786 57Fe (p, n) 57Co 1648 2-1425 __________________________________ * The threshold energy is the minimum energy of proton required for the reaction. Neutrons of desirable energy is required for fission research. Nuclear Fission

  17. The Cyclotron and Fission Research For neutron sources from the cyclotron, energy can be varied. Energy dependence of neutron induced fission studied. The cross section data enabled nuclear reactor design. fast neutrons - 10 MeV to 10 KeV) slow neutrons - 0.03 to 0.001 eV for neutron induced fission Nuclear Fission

  18. The Synthesis of Plutonium Short notations238U (n, ) 239U ( , ) 239Np ( , ) 239Pu or238U (n, 2) 239Pu Fast neutrons provided the reactions: 238U + n 239U + 239U 239Np +  (t1/2 23.5 min) (t1/2 2.35 d) 239Np 239Pu +  Nuclear Fission

  19. Nuclear Fission

  20. Uniting Political and Nuclear Power Neutron induced fission reactions release energy and neutrons, thus it is possible to start a chain reaction for nuclear power. Dictator Hitler (political power in 1933) made many scientists in Austria, Hungary, Italy and Germany uncomfortable and they came to the U.S.A. Hitler invaded Poland, Hungary, Slovak and other European countries. Nuclear fission was discovered in Germany, and nuclear power threatens the world. Leo Szilard, Eugene Wigner, and Edward Teller drafted a letter and Einstein signed the letter for president Roosevelt of U.S. to use political power for nuclear power. Nuclear Fission

  21. Uniting Political and Nuclear Power F.D. Roosevelt (Einstein’s address omitted) . . . . . . . (address omitted) Sir: Some recent work by E.Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. Certain aspects of the situation which has arisen seemto call for watchfulness and, if necessary, quick action on the partof the Administration. I believe therefore that it is my duty to bring to your attention the following facts and recommendations: . . . . (middle part omitted) . . . .I understand that Germany has actually stopped the sale of uranium from the Czechoslovakian mines which she has taken over. That she should have taken such early action might perhaps be understood on the ground that the son of the German Under-Secretary of State, von Weizsäcker, is attached to the Kaiser-Wilhelm-Institut in Berlin where some of the American work on uranium is now being repeated. Yours very truly, Nuclear Fission

  22. Thermal Neutrons Experiment: Neutron bombarded samples surrounded by water, wood, and paraffin are more radioactive - Fermi’s group discovered Conclusion:Slow neutrons (0.03 to 0.001 eV) are more effective for inducing fission of 235U Fast neutrons (10 MeV to 10 KeV) favours neutron capture reaction of 238U Light atoms are effective moderators Nuclear Fission

  23. Thermal Neutrons - Moderators Light atoms are effective moderators Nuclear Fission

  24. Thermal Neutrons Cross Sections Cross section () a measure of reaction probabilityThermal neutron cross sections (c)Thermal neutron cross section for fission (f) 1H 2H 12C 14N 16O 113Cd  c /b 0.33 0.00052 0.0034 1.82 0.0002 19,820 Moderators: H2O vs. D2O vs. C Fermi’s avoided N2 in his first nuclear reactor and used Cd for emergency Nuclear Fission

  25. Thermal Neutrons Cross Sections Uranium for Fission Fuel in Nuclear Reactor 113Cd 233U 235U 238U  c /b 19,820 46 98 2.7 f /b 530 580 2.7×10-6 t1/2/y 1.6×105 7×108 4.5×109 Nuclear Fission

  26. Thermal Neutrons Cross Sections Plutonium Isotopes 236Pu 237Pu 238Pu 239Pu 240Pu 241Pu 242Pu f 150 2100 17 742 0.08 1010 0.2 t1/2 2.9y 45 d 88 y 24131y 6570 y 14y 3.8×105y Neutrons Capture Cross Sections of Cadmium Isotopes 106Cd 108Cd 110Cd 111Cd 112Cd 113Cd 114Cd  c / b 1 1 0.1 24 2.2 19,820 0.3 Abundance/% 1.25 0.89 12.45 12.80 24.13 12.22 28.37 Nuclear Fission

  27. Fission Productsnuclides produced in nuclear fission Data on fission products are required for reactor design, operation, and accident responses. The study of fission products requires the separation, identification, and quantitative determination of various elements and isotopes. Fission products emit  particles until they are stable. Mass number range: 40 - 170 Elements range: all the elements in the 4th, 5th, and 6th periods. including the lanthanides. Nuclear Fission

  28. Fission Products Fission yield is the relative amounts of nuclides formed in fission reactions. The fission yield curve shown here shows most fission reactions split fission atoms into two unequal fragments. Nuclear Fission

  29. Nuclear Fission Products Fission-product and their decay data are needed for social and environmental concerns, and for the management of used fuel. Fission nuclides usually have very short half lives. Typical medium-life fission products: 85K 10.7 y, 90Sr 29 y, 137Cs 30 y,Typical long-life fission products: 126Sn 1.0e5 y, 126Tc 2.1e5 y, 91Tc 1.9e6 y, 135Cs 3.0e6 y, 107Pd 6.5e6 y, and 129Tc 1.6e7 y. Xenon poisoning: 115Xe, c = 2,640,000 b, and t1/2 = 9.2 h Nuclear Fission

  30. First Fission Nuclear Reactor Fermi’s group assembled natural uranium into an atomic pile to test the feasibility of a sustained chain fission reaction. Key elements: fuel, neutron moderator, control rod, neutron detector, and radioactivity detector Dec. 2, 1942, Fermi achieved sustained chain reaction, and the first fission reactor provided data for future design of nuclear reactors. Today, more than 400 power nuclear reactors provided energy world wide, more than 100 of them in the US. Nuclear Fission

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