Nuclear Fission

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Lecture 14 1 Nuclear Fission

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. and represent just one of many potential outcomes

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Lecture 14 2 Nuclear Fission

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Lecture 14 3 Nuclear Fission

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4 : = 4.029 2 , () 4He nucleus: mass = 4.0015 26 MeV of THIS FUSION IS THE SOURCE OF THE SUN’S ENERGY, 7 (and of energy in thermonuclear hydrogen ) 8

Lecture 14 4 Nuclear Fission

UCSD UCSD Question Nuclear energy in nuclear reactors comes from: A. 238 B. Uranium 235 C. 239 D. Hydrogen E. Both B and C

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Lecture 14 5 Nuclear Fission

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Lecture 14 6 Nuclear Fission

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Plutonium is a little harder; need high : to squeeze Pu close. But is only 10 kg. In fact with better design and reflecting materials critical can be made much smaller (e.g. about 15 kg for 235U and less than 5 kg 239Pu)

Fat boy: (Pu) 13 14

Lecture 14 7 Nuclear Fission

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Lecture 14 8 Nuclear Fission

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Lecture 14 9 Nuclear Fission

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• 1.2GW BWR • 46000 rods (170 tons) • 71 atmospheres pressure • 2.8% enriched U-235 • Emergency core cooling system if control rods fail (adds to not shown are ); back-up water system the control rods that absorb and thereby keep the process from running away

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Lecture 14 10 Nuclear Fission

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Lecture 14 11 Nuclear Fission

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A Z X N

12 €6 C6 14 6C8 235 92U143 238U € 92 146 239 € 94 Pu145 € 23 € 24 €

Lecture 14 12 Nuclear Fission

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Lecture 14 13 Nuclear Fission

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Lecture 14 14 Nuclear Fission

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Lecture 14 15 Nuclear Fission

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Lecture 14 16 Nuclear Fission

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Lecture 14 17 Nuclear Fission

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• Iron (Fe) is at the peak • On the heavy side of iron, fission delivers energy • On the lighter side of iron, fusion delivers energy • This is why normal stars stop fusion after iron • Huge energy step to be gained in going from hydrogen (H) to -4 via fusion

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Lecture 14 18 Nuclear Fission

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Lecture 14 19 Nuclear Fission

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Lecture 14 20 Nuclear Fission

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Lecture 14 21