l26 - Nuclear fusion Nuclear fusion Nuclear weapons The...

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Nuclear fusion Nuclear weapons The curve of binding energy Fission Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Centrifuge enrichment Iran’s centrifuges Example nuclear weapons Proliferation Nuclear fusion The power source of stars, including our sun (see Serway Eq. 14.10): 1 1 H+ 1 1 H 2 1 H+ 0 1 e + + ν 1 1 H+ 2 1 H 3 2 He+ γ 1 1 H+ 3 2 H 4 2 He+ 0 1 e + + ν 3 2 He+ 3 2 He 4 2 He+ 1 1 H+ 1 1 H Net effect: four protons combine to make an alpha particle and two positrons, releasing 25 MeV of energy. Works at high temperature (1 . 5 × 10 7 K) and high pressure in sun’s interior. These reactions are a little easier to drive (work at lower temperature and pressure; Serway Eq. 14.11): D-D: 2 1 H+ 2 1 H 3 2 He+ 1 0 n+3.27 MeV D-D: 2 1 H+ 2 1 H 3 1 H+ 1 1 H+4.03 MeV D-T: 2 1 H+ 3 1 H 4 2 He+ 1 0 n+17.59 MeV Deuterium ( 2 1 H) is cheap; can get 0.12 g from 1 gallon of water for about $0.04. Tritium is hard to get and has t 1 / 2 = 12 . 3 years and is produced mainly in nuclear reactors.
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Nuclear fusion Nuclear weapons The curve of binding energy Fission Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Centrifuge enrichment Iran’s centrifuges Example nuclear weapons Proliferation Nuclear fusion From the curve of binding energy, if we can cause light nuclei to fuse we can release even more energy per nucleon. Requires high density and high kinetic energy(=temperature) to overcome the Coulomb barrier. Fusion products have a short half-life and thus don’t present a long-term nuclear waste problem. However, all reactor materials get flooded with neutrons so just about everything is made radioactive. One approach: extreme heating of a fusion pellet using lasers (interial confinement fusion or ICF). We talked about NIF at Livermore . . . Another approach: magnetically confined plasma (magnetically confined fusion or MCF). The challenges are daunting! “Fusion is thirty years away”—a statement made beginning in the 1950s. “Fusion is the energy source of the future, and always will be.”
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Nuclear fusion Nuclear weapons The curve of binding energy Fission Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Centrifuge enrichment Iran’s centrifuges Example nuclear weapons Proliferation The Lawson criterion Required temperature/density combination for energy breakeven. See also Serway Fig. 14-13.
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Nuclear fusion Nuclear weapons The curve of binding energy Fission Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Centrifuge enrichment Iran’s centrifuges Example nuclear weapons Proliferation TFTR at Princeton Tokamak Fusion Test Reactor. Operated 1982–1997 at Princeton University.
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Nuclear fusion Nuclear weapons The curve of binding energy Fission Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Centrifuge enrichment Iran’s centrifuges Example nuclear weapons Proliferation Joint European Torus Oxfordshire, UK, 1983–1999 with some continued operation. An inside view when “cold” and when operating:
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