DOE OSTI2013
The 'Apres ORIENT' research program, recently initiated in 2011, will deal with the transmutation of radioactive fission products (FP) to create rare metals / rare earth (RE) elements (NRM) by neutron capture on the FP followed by beta- decay. Target are radioactive FP and any created NRM should be more valuable and non-, or significantly less, radioactive than the initial FP. In the case of transmutation of radioactive Ba (i.e., non RE element) to La (i.e., light RE), the yield of {sup 139}La was low (< 3.5 %) with 5 years irradiation at thermal neutron energy conditions. However, by neutron irradiation in the fast reactor blanket region corresponding to a resonance energy range of 10 - 100 keV with an expected cross section, σ{sub γ}=0.27 b, of {sup 139}Ba a higher transmutation rate of more than 12 % over 5 years is obtained when the neutron flux is 1.0*10{sup 15} n/cm{sup 2}*s. Created La will be non-radioactive (< 0.001 Bq/g) despite natural La is slightly radioactive ca. 1 Bq/g. To facilitate Ba/La separation various kinds of crown ether (CE) resins were tested. The highest separation of Ba{sup 2+}/La{sup 3+} was obtained by a newly synthesized Benzo-18-Crown-6 (BC18) -substituted resin indicating SF(Ba/La) > 1,000 at 5 mol/l HCl medium. To confirm the scientific feasibility on such new program, actual irradiation tests by various target materials in a test reactor and separation/analysis of the products are required. While the test reactor available at the University of California Irvine has a steady state flux in the order of 10{sup 12} n/cm{sup 2}*s which is at least 2 orders of magnitude lower than a conventional power reactor, proof-of-concept investigations will be carried out since the production of nuclides should scale up linearly with the neutron flux. (author)
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗