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Nuclear Data Sheets for A = 248

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)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Fusion-fission and quasifission in the reactions with heavy ions leading to the formation of Hs

Mass and energy distributions of binary reaction products obtained in the reactions {sup 22}Ne+{sup 249}Cf,{sup 26}Mg+{sup 248}Cm,{sup 36}S+{sup 238}U and {sup 58}Fe+{sup 208}Pb leading to Hs isotopes have been measured. At energies below the Coulomb barrier the bimodal fission of Hs*, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed. In the reaction {sup 36}S+{sup 238}U the considerable part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier the symmetric fragments originate mainly from fusion-fission process for both reactions with Mg and S ions. In the case of the {sup 58}Fe+{sup 208}Pb reaction the quasifission process dominates at all measured energies. The pre- and post-scission neutron multiplicities as a function of the fragment mass have been obtained for the reactions studied.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Processing and Disposition of Special Actinide Target Materials - 13138

The Department of Energy (DOE) manages an inventory of materials that contains a range of long-lived radioactive isotopes that were produced from the 1960's through the 1980's by irradiating targets in high-flux reactors at the Savannah River Site (SRS) to produce special heavy isotopes for DOE programmatic use, scientific research, and industrial and medical applications. Among the products were californium-252, heavy curium (including Cm-246 through Cm-248), and plutonium-242 and -244. Many of the isotopes are still in demand today, and they can be recovered from the remaining targets previously irradiated at SRS or produced from the recovered isotopes. Should the existing target materials be discarded, the plutonium (Pu) and curium (Cm) isotopes cannot be replaced readily with existing production sources. Some of these targets are stored at SRS, while other target material is stored at Oak Ridge National Laboratory (ORNL) at several stages of processing. The materials cannot be stored in their present form indefinitely. Their long-term management involves processing items for beneficial use and/or for disposition, using storage and process facilities at SRS and ORNL. Evaluations are under way for disposition options for these materials, and demonstrations of improved flow sheets to process the materials are being conducted at ORNL and the Savannah River National Laboratory (SRNL). The disposition options and a management evaluation process have been developed. Processing demonstrations and evaluations for these unique materials are under way. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Formation of Superheavy Elements: Study Based on Dynamical Approach

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.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Combination of DGA and LN Columns: A Versatile Option for Isotope Production and Purification at Oak Ridge National Laboratory

The chromatographic resins DGA and LN have been used sequentially to separate curium, californium, plutonium, and various fission products (FPs) to obtain products with a pure radioisotope or a radioelement with high isotopic purity. This 2-step combination of resins has found applications in the 252 Cf and 238 Pu campaigns performed at Oak Ridge National Laboratory. Experiments have been carried out in glove boxes, shielded caves, and hot cells, demonstrating that these resins are adequate and maintain their performance in highly radiolytic environments. We find that using these resins has led to the recovery of curium highly enriched (>95%) in 248 Cm, the clean separation of 251 Cf for the superheavy element research, and the recovery of 147 Pm from the FP stream obtained during the 238 Pu production campaign while demonstrating that the raffinate post DGA is essentially free of transuranic elements.

07 ISOTOPE AND RADIATION SOURCES↗