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The evaluated spectroscopic data are presented for known nuclides of mass 249 (Cm, Bk, Cf, Es, Fm, Md, No). {sup 249}No has not been identified as yet. Significant amounts of new data have been added since the last evaluation of A=249 nuclides. This work supersedes earlier full evaluations of A=249 published by 1999Ar21.
Berkelium-249 ( 249 Bk) and einsteinium-254 ( 254 Es) are isotopes of great importance for the investigation of berkelium and einsteinium chemical properties and super heavy element research. Therefore, it is necessary to be able to isolate acceptable, pure quantities of both isotopes to further research capabilities. These isotopes, along with californium-252 ( 252 Cf), are synthesized through the irradiation of mixed-curium targets in the High Flux Isotope Reactor (HFIR), which has the highest continuous thermal neutron flux in the world. Once irradiated, the targets are transferred to the Radiochemical Engineering Development Center for further chemical processing and final purification to separate 249 Bk and 254 Es from the remainder of isotopes present. Several methods of separation, such as the Berkex batch solvent extraction along with cation-exchange and alpha-hydroxy-isobutyrate (AHIB) columns, are employed to achieve a clean separation of the isotopes. Production Campaigns 74–77 are discussed in depth for 252 Cf, 249 Bk, and 254 Es production and isolation of 249 Bk and 254 Es. An attempt to isolate 257 Fm in Campaign 77 is discussed as well. Table 1 summarizes the total amount of material isolated in each campaign.
Quasifission is the primary reaction mechanism that limits the formation of superheavy nuclei and consequently an important ingredient for choosing the best target-projectile combinations for the heavy element searches. Quasifission is characterized by nuclear contact-times that are much longer than those found in deep-inelastic reactions, resulting in a substantial mass and charge transfer. In this manuscript we employ the fully microscopic time-dependent Hartree-Fock (TDHF) theory to study quasifission. New results are presented for the {sup 48}Ca+{sup 249}Bk system.
Using multi-dimensional Langevin equations for the probability distribution of the distance between the surfaces of two approaching nuclei, we have studied the formation of superheavy elements via calculation of evaporation and fission cross sections of these elements. Evaporation residue cross sections have been calculated for the 1n, 2n, 3n, 4n, and 5n evaporation channels using one and four dimensional Langevin equations for the {sup 48}Ca+{sup 226}Ra, {sup 232}Th, {sup 238}U, {sup 237}Np, {sup 239,240,242,244}Pu, {sup 243}Am, {sup 245,248}Cm, {sup 249}Bk, and {sup 249}Cf reactions. Our results show that with increasing dimension of Langevin equations the evaporation residue cross section is increased. Also, obtained results based on fourdimensional Langevin are in better agreement with experimental data in comparison with one-dimensional model.
The evaporation residue (ER) cross sections for 3n and 4n evaporation channels in the {sup 50}Ti + {sup 249}Bk reaction leading the formation of {sup 296}119 and {sup 295}119 isotopes are evaluated by means of a modified fusion-by-diffusion model. In the model, the dynamic evolution from dinucleus to mononucleus is taken into account with the two-dimensional coupled Langenvin equations. The calculated maximum ER cross sections in 3n and 4n evaporation channels of the {sup 50}Ti + {sup 249}Bk reaction are 0.17 and 0.57 pb, respectively. The cross section of 0.57 pb is close to the present experimental limit for the registration of the evaporation residual nuclei. Therefore, superheavy element 119 may be the most hopeful new element with Z>118 to be synthesized under somehow improved experimental conditions in the near future.
Purification of berkelium-249 ( 249 Bk) at Oak Ridge National Laboratory requires a multi-step process with Bk Finishing as the final step. The current multi-process takes 6–7 months, including ~ 3 months spent on Bk Finishing. Recent trials of using columns of either LN resin or MP-1 anion exchange resin adsorbing the tetravalent 249 Bk4+ in 8M HNO 3 -0.5M NaBrO 3 , followed by eluting impurities (e.g. Ce 4+ , Cf 3+ ) and stripping 249 Bk resulted in a new dual column method of selectively separating 249 Bk from other trans-curium elements and fission product impurities, which is proposed to replace the current Bk Finishing with higher Bk purification efficiency and shorter processing period. This paper displays the experimental results and describes the dual column method with relevant chemistry issues.
In the late 1980s, the DOE Defense Programs identified a need to recover special isotopes of americium, curium, and plutonium (Am/Cm/Pu) from Mark-42 (Mk-42) targets that had been irradiated at the SRS. Eighty Mk-42 target segments were transferred from SRS to ORNL for recovery of these special isotopes. Approximately 65% of the target materials has been processed and converted to solids. The remaining Mk-42 materials are either targets stored in their irradiated forms or target material stored from various stages of processing. The Pu, Am-243 and Cm-244 in these targets are valuable materials; for example, the Am/Cm materials are potential feedstocks for production of heavy actinides (Cf-252, Bk-249, etc.). Although the isotopes in the Mk-42 materials have value, there is continual pressure to look at de-inventorying material in storage to only retain the most valuable materials needed to meet mission needs and to allow other materials to be added to the inventory as they become available. Evaluations are underway for potential disposition options for the Mk-42 materials. (authors)
In the late 1980's, the DOE defense programs identified a need to recover special isotopes of americium, curium, and plutonium from Mark-42 (Mk-42) targets that had been irradiated at the SRS. Eighty Mk-42 target segments were transferred from SRS to ORNL for recovery of these special isotopes. Approximately 65% of the target material has been processed, and the recovered material converted to solids. The remaining Mk-42 materials are stored either as targets in their irradiated forms or as target material from various stages of processing. The Pu, Am-243 and Cm-244 in these targets are valuable materials; for example, the Am/Cm materials are potential feedstocks for production of heavy actinides (Cf-252, Bk-249, etc.). In addition, rare long-lived fission product (LLFP) isotopes present in the targets in much smaller quantities, such as Zr-93, also have value to the research community. Although the isotopes in the Mk-42 materials have value, there is continual pressure to de-inventory the material in storage and only retain the most valuable materials needed to meet mission needs and provide inventory space for other materials to be added as they become available. Evaluations are underway for potential disposition options for the Mk-42 materials. Previous studies have included identification and evaluation of disposition options for the various Mk-42 materials in storage at ORNL [1]. Evaluations have included options for recovering the major isotopes and evaluating the waste that would be sent to disposal facilities. This paper summarizes the next steps in the evaluation process to develop an optimum path forward for the disposition of the Mk-42 materials. It includes an evaluation of the future programmatic need for the materials, the impact of storage on facility operations, and additional evaluations of options for dispositioning the materials. In addition to recovery of the major isotopes previously evaluated, it also looks at the potential to recover rare LLFP isotopes present in the targets in small quantities. (authors)
The reaction of 249 Bk(OH) 4 with iodate under hydrothermal conditions results in the formation of Bk(IO 3 ) 3 as the major product with trace amounts of Bk(IO 3 ) 4 also crystallizing from the reaction mixture. The structure of Bk(IO 3 ) 3 consists of nine-coordinate Bk III cations that are bridged by iodate anions to yield layers that are isomorphous with those found for Am III , Cf III , and with lanthanides that possess similar ionic radii. Bk(IO 3 ) 4 was expected to adopt the same structure as M(IO 3 ) 4 (M = Ce, Np, Pu), but instead parallels the structural chemistry of the smaller Zr IV cation. Bk III –O and Bk IV –O bond lengths are shorter than anticipated and provide further support for a postcurium break in the actinide series. Photoluminescence and absorption spectra collected from single crystals of Bk(IO 3 ) 4 show evidence for doping with Bk III in these crystals. In addition to luminescence from Bk III in the Bk(IO 3 ) 4 crystals, a broad-band absorption feature is initially present that is similar to features observed in systems with intervalence charge transfer. However, the high-specific activity of 249 Bk ( t 1/2 = 320 d) causes oxidation of Bk III and only Bk IV is present after a few days with concomitant loss of both the BkIII luminescence and the broadband feature. The electronic structure of Bk(IO 3 ) 3 and Bk(IO 3 ) 4 were examined using a range of computational methods that include density functional theory both on clusters and on periodic structures, relativistic ab initio wave function calculations that incorporate spin–orbit coupling (CASSCF), and by a full-model Hamiltonian with spin–orbit coupling and Slater–Condon parameters (CONDON). Some of these methods provide evidence for an asymmetric ground state present in Bk IV that does not strictly adhere to Russel–Saunders coupling and Hund’s Rule even though it possesses a half-filled 5 f 7 shell. Multiple factors contribute to the asymmetry that include 5 f electrons being present in microstates that are not solely spin up, spin–orbit coupling induced mixing of low-lying excited states with the ground state, and covalency in the Bk IV –O bonds that distributes the 5f electrons onto the ligands. These factors are absent or diminished in other f 7 ions such as Gd III or Cm III .
An example of a 249 Bk 3+ phosphine oxide complex has been prepared to examine and quantify the effects of the inverse trans-influence (ITI) on a late actinide complex. This has been accomplished through a comparison of cis and trans Bk-ligand bonds in the meridional berkelium(III) complex, BkBr 3 (OPCy 3 ) 3 (OPCy 3 = tricyclohexylphosphine oxide). A detailed bond metric analysis was completed that includes the shortest published distance for a Bk 3+ −O bond, attributed to the smaller coordination number of Bk 3+ of six in mer-BkBr 3 (OPCy 3 ) 3 . ITI calculations of the trans Bk 3+ −O bond provide an ITI value (98.5(2)%) comparable to that of mer-AmBr 3 (OPCy 3 ) 3 (98.2(2)%) and indicate a small 5f orbital contribution to bonding. This effect is discussed in the context of the isomorphous lanthanide(III) series where the ITI is calculated to be higher for mer-BkBr 3 (OPCy 3 ) 3 than in most Ln 3+ analogues.
The merging of small-scale syntheses and rapid crystallization methods have provided access to crystalline samples of berkelium (Z=97) and californium (Z=98) coordination complexes and compounds that can be interrogated with a suite of spectroscopic tools and structural elucidation approaches that have come online over the last 20 years. The combination of this experimental data with relativistic theoretical methods that capture the effects of spin-orbit coupling and scalar relativistic effects have allowed us to understand the electronic structure of berkelium and californium compounds at a level of detail that was not previously possible. The harbinger of this new era of post-curium chemistry was the synthesis and characterization of [Cf{B 6 O 8 (OH) 5 }]. This compound possesses a structure type that is distinct from earlier actinide borates, a reduction in coordination number for californium, contracted Cf-O bond lengths, a substantially reduced magnetic moment with respect to the calculated free-ion moment and, most importantly, vibronically coupled broadband photoluminescence. Ligand-field analysis also showed that the splitting of the ground state was larger than typically found in the f-block elements, and when taken together places its overall electronic structure as a hybrid of d- and f-block components. The discovery of the unusual properties of this compound has led to the development of large families of 4f and 5f coordination complexes, in an effort to uncover the underlying origin of the electronic structure oddities, and whether there really is a sharp onset of these changes at californium. This in turn pushed the development of far more challenging berkelium chemistry (from a radiologic standpoint) because the half-life of the isotopes decreases from 351 years for 249 Cf to 330 days for 249 Bk. This short review details some of the chemistry that has been reported over the last 15 years, and its consequences for understanding the periodic table.
The super heavy element (SHE) Tennessine (Ts, Element 117) was discovered in 2016 a collaboration of US and Russian scientists vis bombardment reaction of 249 Bk + 48 Ca $\rightarrow$ 117 Ts, while the target element 249 Bk (half-life 330d) was produced and provided by the Radiochemical Engineering Development Center (REDC), Oak Ridge National Laboratory (ORNL). The production of 249 Bk at REDC, ORNL requires a multi-step chemical process of irradiated curium feedstock target to remove all fission product (FP) elements and to separate 249 Bk 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 252 Cf, while 249 Bk is one of important by-products. The current Cf campaign for recovery of c.a. 15 mg of 249 Bk 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 249 Bk from an 8 $M$ HNO 3 -0.3 $M$ NaBrO 3 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 249 Bk 4+ in 8 $M$ HNO 3 -0.5 $M$ NaBrO 3 , followed by eluting impurities (e.g. Ce 4+ ,Cf 3+ ) and stripping 249 Bk resulted in a new Dual Column Method of selectively separating 249 Bk 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 249 Bk 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.
In 1957 Glenn T. Seaborg conceived and advocated for the construction of the High Flux Isotope Reactor (HFIR) and the Transuranium Processing Plant (since then renamed the Radiochemical Engineering Development Center, or REDC) at Oak Ridge National Laboratory. There, heavily shielded hot cells, glove boxes, and laboratories allow recovery of transuranium elements produced in substantial quantities. Seaborg’s vision of HFIR and REDC producing milligram quantities of berkelium, californium, and einsteinium has been fulfilled beginning in 1966 through May 2019 with 78 production campaigns yielding a cumulative totals of 1.2 g of 249 Bk, 10.2 g of 252 Cf, 39 mg of 253 Es, and 15 pg of 257 Fm. Notably, 252 Cf is a neutron source used in many industrial applications including oil exploration; process control systems for the cement industry, coal analysis, and power production; sources to start nuclear reactors and perform nondestructive materials analyses; homeland security and national defense detection devices; and medical research. Isotopes made available through transplutonium production at HFIR/REDC have enabled scientists to study the nuclear properties and reactions, chemical properties, optical properties, and solid-state properties of transplutonium elements. Long-lived isotopes have served as targets in heavy ion accelerators to produce heavier elements leading to the discovery of 104 Rf, 105 Db, 106 Sg, 113 Nh, 114 Fl, 115 Mc, 116 Lv, 117 Ts, and 118 Og. This paper reviews the evolution of the processing flowsheets to produce, separate, and purify transplutonium isotopes, which have evolved over 50 years of operation at HFIR and REDC, and summarizes directions of future work to improve the efficiency of the production operations.
Detailed level schemes, decay schemes, and the experimental data on which they are based are presented for all nuclei with mass number A=248. The experimental reaction and decay data are evaluated; inconsistencies and discrepancies are noted; and adopted values are given for various level properties (including spin and parity, halflife, and configuration), γ properties (including energy, intensity, and multipole character) and α properties (including energy, intensity, and hindrance factor). This evaluation replaces the A=248 evaluation published by A. Akovali in Nuclear Data Sheets 87, 249 (1999)
Element 117 (tennessine) joined the periodic table in November 2016. Two tennessine isotopes were synthesized by bombarding 249 Bk from Oak Ridge National Laboratory with 48 Ca ions at the Joint Institute of Nuclear Research, Russia, and 11 new heaviest isotopes of odd-Z elements were observed in subsequent decay chains. These isotopes exhibit increasing lifetimes as the closed nuclear shell at neutron number N = 184 is approached, providing evidence for the “island of stability” for super-heavy elements. Here, this article summarizes recent super-heavy element research with a focus on element 117, the role of actinide targets, and opportunities to synthesize elements 119 and 120.