Managing the Uranium-233 Stockpile of the United States

Development of 225Ac Radiopharmaceuticals: TRIUMF Perspectives and Experiences

“…( 1 ) of the 233 U decay chain). The majority of this 233 U ( t 1 / 2 = 1.6 × 10 5 y) was produced between 1954 and 1970 via neutron irradiation of 232 Th while being investigated for its use in nuclear weapons and reactors that were never fully deployed [15]. Between 1995 and 2005, 229 Th (t 1/2 = 7340 y) generated from 233 U decay was extracted from stockpiles stored at Oak Ridge National Laboratory (ORNL, Oak Ridge, TN).…”

“…While harnessing untapped 229 Th supplies has the potential to more significantly impact 225 Ac availability, in 2005 the U.S. Congress ordered the Department of Energy (DOE) to cease extraction of 229 Th from 233 U stockpiles and to instead begin down-blending (dilution with 238 U to a non-weaponizable 233 U concentration) and permanent disposal of the two tonnes of stockpiled 233 U [15]. Petitions to recover 229 Th before 233 U disposition have been denied [20], and completion of these efforts is scheduled for 2018 [15]. From the high- and intermediate-purity 233 U sources within the inventory [32], this represents the loss of 32.6 g (∼260 GBq or 7 Ci) of 229 Th or a potential 1.5 TBq (40.5 Ci) of annual 225 Ac production.…”

Characterization of Uranium Foil Irradiations at the WSU TRIGA Reactor Using a New Reactor Model in Scale

“…Alongside this reaction, small amounts of 232 U are also produced by competing (n,2n) reactions that can occur on 232 Th, 233 U, or 233 Pa. 232 U has found importance as a laboratory chemical tracer in analyses of other uranium isotopes, but is otherwise considered a contaminant in the production of 233 U. Because 233 U is fissile, its use in both power reactors and as weapons fuel has been thoroughly explored, (Alvarez, 2013) (Ade, et al, 2014) particularly in breeder reactors, which in theory would ultimately produce more fissile material than they consume. While research and development is still ongoing on the thorium fuel cycle and for reactor development, many factors have led to decreased interest in 233 U use, including high gamma dose rates from decay daughters of 232 U produced alongside the 233 U, the unexpected low rise in cost of raw uranium over time, and the fact that reactors using natural or low enriched uranium (LEU) fuels produce less overall power when thorium is added (Kang & von Hippel, 2001).…”

Feasibility of a novel photoproduction of 225Ac and 227Th with natural thorium target

“…The only commercial way to produce 225 Ac is a milking from 229 Th cow which is a decay product of the legacy 233 U stockpile 6 , 7 . It is known that the stockpile was mainly produced in the Th-fuelled nuclear reactors in the 1960s in US and Russia 8 , 9 . Consequently, the 225 Ac supply is rather monopolized and affordable ways are strongly required for progress in the 225 Ac-based TAT.…”