Date of Award
Master of Science
Ivan Maldonaro, Laurence Miller
63Ni [Nickel-63] is routinely produced at HFIR with a specific activity of ~15 Ci/g [Curies/gram] by irradiating highly enriched stable 62Ni [Nickel-62] (86.31 %) for 2 years. Impurities in the original material are also activated and must also be accounted for, as well as removed through anion and cation exchange columns. The main goal is to investigate if a greater specific activity can be achieved by reducing target thickness axially (i.e. neutron depletion), thus reducing neutron interaction within the target interior. Because of rather high neutron capture cross-section of 62Ni (σth [cross-section] = 14.5 barns, and I0 [resonance integral] =6.6 barns), it is thought that in removing the center of the target, more 63Ni activity can be produced per mass of material. To experimentally test this, three sets of solid 62Ni targets were prepared of varying thickness; a solid pellet with O.D. [outer diameter] of ~6 mm and two targets in form of rings with 6 mm O.D. and 2 and 4 mm I.D. The results obtained from those targets will be presented, along with model calculations of neutron depletion in the targets with a 3D Monte Carlo simulation, part of the SCALE package.
Walsh, Spenser Riley, "The Effect of Pellet Geometry on The Specific Activity of Ni-63. " Master's Thesis, University of Tennessee, 2013.