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Production of Co-59 in nuclear reactor.

  1. Apr 23, 2016 #1
    Hi,

    As far as i know, when Co-59 is bombarded with neutron inside the reactor core then Co-60 is produced. What i want to know that what is the origin of the Co-59. Is it one of the products of nuclear fission? if it is so, can you show me the reaction of it. Or is it already exist in the fuel? Since co-59 is a stable isotope, it might be found in the uranium ore and during the enrichment process it may not be extracted..

    Thank you in advance..
     
  2. jcsd
  3. Apr 23, 2016 #2

    mfb

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    2016 Award

    Staff: Mentor

    Cobalt is a component of some steel alloys, but it is also put in deliberately to produce Co-60.

    Alloys
    Deliberate production1, and https://inldigitallibrary.inl.gov/sti/3374760.pdf [Broken]
     
    Last edited by a moderator: May 7, 2017
  4. Apr 23, 2016 #3

    Astronuc

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    Naturally occurring cobalt would come from the same source that produced Fe, Ni, Cr, Cu and other transition elements, i.e., some supernova some billions of years ago.

    USGS publishes summaries of element production. According to the 2016 summary, Import Sources (2011–14): Cobalt contained in metal, oxide, and salts: China, 19%; Norway, 13%; Finland and Russia, 9% each; and other, 50%.
    http://minerals.usgs.gov/minerals/pubs/commodity/cobalt/

    According to the Wikipedia article on cobalt, "the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo, Central African Republic and Zambia yields most of the cobalt mined worldwide." https://en.wikipedia.org/wiki/Cobalt

    An old article in the CRC Handbook of Chemistry and Physics, 68th Edition (1987-1988), production was mainly in Zaire, Morocco and Canada, usually associated with ores of other elements, e.g., nickel, lead, silver, copper and iron. Production will vary around the world according to commodity prices and production costs, and the discovery of deposits.

    Cobalt-59 can be produced from the neutron capture by Fe-58 to produce Fe-59, which would then undergo beta decay to Co-59. However, Fe-58 is a relatively rare isotope of Fe (0.0028).

    Cobalt-58 and -60 is produced in Ni alloys used in core components, by (n,p) reactions, which is why fuel manufacturers have removed Inconel grids from in-core positions in nuclear fuel. Top and bottom grids in PWR are usually Inconel (e.g., 718), while intermediate grids are made of Zr alloy. Co-59 is then produced from neutron capture (n,γ) by Co-58.

    BWR fuel designs have incorporated Zr alloy grids with Inconel (X750) springs, but some designs are all Inconel (e.g., X750).

    GE irradiates Co-59 in two commercial BWRs for Co-60 production.
     
    Last edited: Apr 23, 2016
  5. Apr 23, 2016 #4
    Cobalt-59 is present in Stellite valve seats, and will flake off into the reactor coolant system, pass through the core, and become Cobalt-60. Stellite components are the biggest source of Cobalt-60 in commercial BWRs.

    Also, as Astronuc said, there are two BWRs that have GE-14i fuel assemblies which contain some Cobalt-59 rods where it gets transmuted to Cobalt-60. After enough time in the core, the Cobalt-60 rods get removed and processed for medical or other uses.
     
  6. Apr 23, 2016 #5

    Astronuc

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    Cobalt forms 'hardface' alloys, and over the years, Stellite was a problem for BWRs. EPRI and the industry sponsored a program to develop low activation alloys to replace Stellite. These days, when stainless steel and Inconels are used in fuel, in-core and primary loop components, the alloys have an extra low Co content.
     
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