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Review Test

Review Test. We have done the review test. We will discuss it later. Please study the review tests of last years. http://nuclear.bau.edu.jo/Reactors/Notes/2007/ReviewTest.ppt. http://nuclear.bau.edu.jo/Reactors/Notes/2008/ReviewTest.pdf. Nuclear Fission. Asymmetry.

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Review Test

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  1. Review Test • We have done the review test. • We will discuss it later. • Please study the review tests of last years. http://nuclear.bau.edu.jo/Reactors/Notes/2007/ReviewTest.ppt http://nuclear.bau.edu.jo/Reactors/Notes/2008/ReviewTest.pdf Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  2. Nuclear Fission Asymmetry • Remember neutron excess. • (A,Z)  (A,Z+1) or (A-1,Z). Only left side of the mass parabola. Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  3. Nuclear Fission  165 MeV average kinetic energy carried by fission fragments per fission. • 235U + n  93Rb + 141Cs + 2n • Q = ???? • What if other fragments? • Different number of neutrons. • Take 200 MeV as a representative value. 66 MeV 98 MeV Light fragments Heavy fragments miscalibrated Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  4. Nuclear Fission •  neutrons emitted per fission. •  depends on fissioning nuclide and on neutron energy inducing fission. India? Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  5. Nuclear Fission • Mean neutron energy  2 MeV. •  2.4 neutrons per fission (average)   5 MeV average kinetic energy carried by prompt neutrons per fission. • Show that the average momentum carried by a neutron is only  1.5 % that carried by a fragment. • Thus neglecting neutron momenta, show that the ratio between kinetic energies of the two fragments is the inverse of the ratio of their masses. Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  6. Nuclear Fission Enge Distribution of fission energy Krane sums them up as  decays. Lost … ! Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  7. Nuclear Fission Segrè Distribution of fission energy a b c Lost … ! • How much is recoverable? • What about capture gammas? (produced by -1 neutrons) • Why c < (a+b) ? Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  8. Fission Products •  and  emissions from radioactive fission products carry part of the fission energy, even after shut down. • On approaching end of the chain, the decay energy decreases and half-life increases. Long-lived isotopes constitute the main hazard. • Can interfere with fission process in the fuel. Example?(poisoning). • Important for research. • -decay favors high energy  ~20 MeV compared to ~6 MeV for . • Only ~ 8 MeV from -decay appears as heat. Why? Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  9. Fission Products f - (n,) A-1, Z j A, Z i A, Z-1 k - (n,) A+1, Z A, Z+1 dNi/dt = Formation Rate - Destruction rate - Decay Rate Ni saturates and is higher with higher neutron flux, larger “fission yield” and longer half-live. ! Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). 9

  10. Fission Products HW 7 Investigate the activity, decay and gamma energies of fission products as a function of time. Comment on consequences (e.g. rod cooling). • Shutdown HW 8 Investigate both and giving full description for the buildup and decay of fission fragment i. Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). 10

  11. Fission Products per watt of original operating power. T = time of operation. Fission product activity after reactor shutdown? Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). 11

  12. Nuclear Fission • The fission gamma radiation • Prompt with average energy of 0.9 MeV. •  delayed gammas. • Investigate how prompt • gammas interact with • water, uranium and lead. HW 9 Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). 12

  13. Nuclear Fission HW 10 The experimental spectrum of prompt neutrons is fitted by the above equation. Calculate the mean and the most probable neutron energies. Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  14. Nuclear Fission • Recoverable energy release  200 MeV per 235U fission. • Fission rate = 2.7x1021P fissions per day. P in MW. • 3.12x1016 fissions per second per MW, or 1.2x10-5 gram of 235U per second per MW (thermal). • Burnup rate: 1.05 P g/day. P in MW. • The fissioning of 1.05 g of 235U yields 1 MWd of energy. • Specific Burnup = 1 MWd / 1.05 g  950000 MWd/t (pure 235U !!). • Fractional Burnup = ??? • Thermal reactor loaded with 98 metric tons of UO2, 3% enriched, operates at 3300 MWt for 750 days. •  86.4 t U. Specific burnup  28650 MWd/t. • Not all fissions from 235U. • Fast fission of 238U. • 238U converted to plutonium  more fission. Actually much less (all heavy material). Work it out. Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  15. Nuclear Fission • Capture-to-fission ratio: • Consumption rate: 1.05(1+) P g/day. • Read all relevant material in Lamarsh Ch. 4. We will come back to this later. • Two neutrinos are expected immediately from the decay of the two fission products, what is the minimum flux of neutrinos expected at 1 km from the reactor. 4.8x1012 m-2s-1 Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh).

  16. Nuclear Fission • 3.1x1010 fissions per second per W. • In thermal reactor, majority of fissions occur in thermal energy region,  and  are maximum. • Total fission rate in a thermal reactor of volume V • Thermal reactor power (quick calculation) Crude Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). 16

  17. Nuclear Fission It is necessary to evaluate the potential hazards associated with an accidental release of fission products into the environment. It is required to determine a proper cooling time of the spent fuel (before it becomes ready for reprocessing) that depends on the decay times of fission products. It is necessary to estimate the rate at which the heat is released as a result of radioactive decay of the fission products after the shut down of a reactor. The poisoning is needed to be calculated (the parasitic capture of neutrons by fission products that accumulate during the reactor operation). Some technicalities, so far! Nuclear Reactors, BAU, 1st Semester, 2007-2008 (Saed Dababneh). Nuclear Reactor Theory, JU, Second Semester, 2008-2009 (Saed Dababneh). 17

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