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Fuel Depletion

Fuel Depletion. Time scale: Days and months. More depletion  change steady state flux by means of reducing absorbers. For a given fuel isotope For constant flux  0 the solution is For time varying flux. Exponential burnup. Neutron fluence. Solve numerically. Fuel Depletion.

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Fuel Depletion

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  1. Fuel Depletion Time scale: Days and months. • More depletion  change steady state flux by means of reducing absorbers. • For a given fuel isotope • For constant flux 0the solution is • For time varying flux Exponential burnup Neutron fluence Solve numerically. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  2. Fuel Depletion • Constant power. • Power ~ flux only over short time periods during which Nf is constant. • The solution is obviously   Energy released per fission Fission rate Linear depletion!   Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  3. Fuel Depletion HW 31 Do the calculations for different flux and power levels. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  4. Poisoning and Fuel Depletion Infinite, critical homogeneous reactor.    thus  Constant power Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  5. Poisoning and Fuel Depletion Constant Constant • Other fission products (poisons) with less capture cross sections. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  6. Poisoning and Fuel Depletion • Now we know all macroscopic cross sections.    • When there are no absorbers left to remove, we need to refuel. • Absorbers are not only control rods. • All fuel nuclei should be considered. • For each species, all sources and sinks should be taken into account. Until = 0. Solve for t to get upper limit for “core loading lifetime”. Damaged fuel…! • Online loading  environmental. • 3H. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  7. Poisoning and Fuel Depletion Fuel loading Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  8. Poisoning and Fuel Depletion • Some poisons are intentionally introduced into the reactor. • Fixed burnable poisons. • B, Gd. • More uniform distribution than rods, more intentionally localized than shim. • Soluble poisons (chemical shim) with caution. • Boric acid (soluble boron, solbor) in coolant. • Boration and dilution. • Scram emergency shutdown (sodium polyborate or gadolinium nitrate). • Non-burnable poisons. • Chain of absorbers or self shielding. Flatter flux. Power shaping. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  9. Delayed Precursors • For one-group • What about delayed neutrons? Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  10. Delayed Precursors Delayed neutron emitter One of 66 delayed neutron precursors known so far. Data for all precursors are not accurately known. Delayed neutron fraction Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  11. Delayed Precursors Increases with N. Data for thermal neutron induced fission, except for * fast neutron induced fission. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  12. Delayed Precursors (s) 235U  < 0.7% = 0.016 /  Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  13. Delayed Precursors • The multi-group equation now becomes Different energy spectra Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

  14. Delayed Precursors • In steady state Significance of ggg depends on whether we have fine or course energy groups. Nuclear Reactors, BAU, 1st Semester, 2008-2009 (Saed Dababneh).

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