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Is possible some elements absorb neutrons, without any nuclear reaction?

  1. May 2, 2008 #1
    Is possible some elements (like Cadmium or Bohr) absorb neutrons, without any nuclear reaction in their atomic nucleus? If the answer is YES, then why there isn't any nuclear reaction?
  2. jcsd
  3. May 2, 2008 #2
    A free neutron decays is about 15 minutes, right ? Besides, neutrons almost don't interact electromagnetically (their total electric charge being zero). If you want to call a material "neutron absorber", most probably you are refering to the ability of this material to stop and store free neutrons, and most probably this happens because of nuclei absorbing the neutrons, thus becoming new isotopes of the element they correspond to. Cadmium-113 for instance does just that in nuclear plants. This does involve nuclear reaction.
  4. May 2, 2008 #3
    There isn't any nuclear reaction happening after the absorption of neutron? (I am talking about Cadmium-113)
  5. May 2, 2008 #4
    But the absorption itself is a nuclear reaction. It involves a change in isotope, a re-arrangement of the nucleons in the nucleus, and a gamma-ray emmision.
  6. May 2, 2008 #5
    Yes, sorry. But is there any explosion and release of other neutrons, like in fission?
  7. May 3, 2008 #6
    What is their period of decay, after receiving the neutron? Are control rods inside nuclear power plants often replaced because of this?
  8. May 10, 2008 #7
    There is no explosion after Cadmium-113 recieves the extra neutron, this is the precise reason they use them to slow nuclear fission, because it allows the scientists to slowly pull them out, thus slowly increasing the rate of fission
  9. May 10, 2008 #8


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    As humanino indicated the absorption of a neutron is the nuclear reaction, and most often it is accompanied by gamma emission. Only a few isotopes are fissile, e.g. isotopes of Th, U, Pu, and heavier elements.

    Cadmium, silver, indium, 10B, hafnium (Hf), gadolinium (Gd), dysprosium (Dy), erbium Er) and some other rare earths are good neutron absorbers.

    In Boiling Water Reactors (BWRs), 10B in the form of B4C and Hf are the preferred absorbers for Control Rod which reside incore for reactivity control (and power distribution) during reactor operation. Gd in the form of gadolinia (Gd2O3 is a burnable (meaning it depletes during irradiation) absorber used in the fuel, and is mixed in with the UO2.

    In Pressurzed Water Reactors (PWRs), control rods contain Ag-In-Cd, Hf, Dy, or B4[/sup]C, although Hf has a problem with hydrogen absorption, so it's use is problematic and for the most part, isn't used these day. Usually control rods are withdrawn above the core in PWRs. Some PWRs use grey rods using Ni-alloys to tailor the neutron flux (power distribution) during operation.

    PWRs use boric acid in the reactor coolant water to control reactivity during operation, and this solution is buffered with KOH or LiOH.

    PWR fuel may incorporate burnable absorbers such as Gd (gadolinia), Er (erbia), or 10B in the form of ZrB2. The objective is to select a burnable absorber with low residual. There are also clusters (removable) that can be inserted into the guide tubes of a PWR fuel assembly, similar to control clusters, that contain boron-containing pyrex, and are sometimes called discrete burnable absorbers.
  10. May 10, 2008 #9
    Hydrogen absorb a neutron to become deuterium. Alot of elements can absorb neutron and not undergo nuclear reaction. Most cases neutron acts as glue for the nucleus. If you notice, the heavier the atom the ratio of neutron/proton goes up. I'm assuming nucleus have stability geometry.
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