Abstract
The super heavy element (SHE) Tennessine (Ts, Element 117) was discovered in 2016 by corporation of US and Russian scientists vis bombardment reaction of 249Bk + 48Ca --> (117)Ts, while the target element 249Bk (half-life 330d) was produced and provided by the Radiochemical Engineering Development Center (REDC), Oak Ridge National Laboratory (ORNL). The production of 249Bk at REDC, ORNL requires a multi-step chemical process of irradiated curium feedstock target to remove all fission product (FP) elements and to separate 249Bk from other actinide (An) elements (Am, Cm, Cf, Fm and Es), including: Caustic Dissolution, Acid Dissolution, Cleanex, two LiCl Anion Exchanges, LiOH Precipitation, Cation Exchange with AHIB, and with Bk Finishing as the final Bk purification step. The major product of this campaign is 252Cf, while 249Bk is one of important by-products. The current Cf campaign for recovery of c.a. 15 mg of 249Bk per campaign (not including the time for Finishing of Cf, Fm and Es) takes 6 or 7 months, including ~3 months spent on Bk Finishing.
Bk Finishing includes two major processes: (1) BERKEX, operated inside a hot cell with two cycles of batch solvent extraction (SX) using di-2-ethylhexyl phosphoric acid (HDEHP) as the extractant for tetravalent 249Bk from an 8 M HNO3-0.3 M NaBrO3 solution; and (2) Cation Exchange (CX) with AHIB (α-Hydroxy isobutyric acid), operated inside a glove box laboratory. Entire Bk Finishing takes five SX, more than five column runs and several drying down processes for aqueous solutions including one from 500 mL to 1 mL for volume reduction. To shorten the Bk Finishing period and simplify the Bk purification operation steps, possibilities of using other resin columns were explored.
Recent trials using columns of either LN resin or MP-1 anion exchange resin adsorbing the tetravalent 249Bk4+ in 8 M HNO3-0.5 M NaBrO3, followed by eluting impurities (e.g. Ce4+,Cf3+) and stripping 249Bk resulted in a new Dual Column Method of selectively separating 249Bk from other trans-plutonium elements and fission product (FP) impurities. This new method is proposed to replace the current Bk Finishing and provide increased Bk purification effeciency and a shorter processing period of 4 to 5 months (less decay loss for higher 249Bk productivity). This TM Report discusses the trial experimental results, describes the dual column method with relevant chemistry issues and possibilities being used in further process steps ahead of the Bk Finishing.
