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Shielding

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Shielding

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    1. Shielding Biological shielding Reactor shielding

    2. Build-up factors Attenuation is easy because you assume that the g-rays disappear with each interaction Where m is the total attenuation coefficient at E0

    3. What really happens Compton effect - the photon is scattered with a loss of energy Pair production incident photon is absorbed x-rays are produced Photoelectric effect - 0.511 keV (annihilation radiation is inevitable)

    4. The shield Before After

    5. So here comes the fudge Ok it’s not really a fudge factor. Several very talented scientist solved the really ugly problem for several materials and geometries to get Bm(ma) - build-up factor

    6. Build-up flux Planar (mono) source Point (isentropic) source

    7. Definitions fb- build-up flux fu- uncollided flux f0 - initial flux Bm(ma) or BR(mR) - build-up factor Table 10.1 for a plane Table 10.2 for isotropic point source

    8. Biological shield Exposure rate mR/hr

    9. Other geometries Infinite planar Disc Line Internal source - results from neutron activation of the shield Multilayered shields

    10. Reactor shielding Slow the fast neutrons down to an energy where the absorption cross sections is larger Coolant activation Gamma rays Point water kernel Removal cross section Half thickness Mean free paths thick Radiation streaming

    11. Why is it so so hard Many energies Every direction In the real world Nuclear engineers use MONTE CARLO

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