The Effect of Pellet Geometry on The Specific Activity of Ni-63

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 (σ_th [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.