Y. Nagame

Production of 95mTc with proton bombardment of 95Mo

Abstract Formation cross sections of 95m Tc and 95g Tc via the 95 Mo (p, n) reaction have been measured to evaluate the production yield of 95m Tc which is expected to be a useful radiotracer of technetium isotopes. It was found from the cross section data that for incident proton energies above 15 MeV, the thick-target yield of 95m Tc was more than 20 μCi/μAh at the end of bombardment and the 95g Tc contamination was less than 1% after 12 d cooling. To examine the separation and purification of 95m Tc from target, we have carried out a test production of 95m Tc using a thick 95 Mo-enriched target. Other reactions of producing 95m Tc are compared and discussed in terms of the production yield and amounts of contaminants.

Two deformation paths in proton-induced fission of 232Th☆

Abstract Velocities of complementary fission fragments have been accurately measured by a double velocity time-of-flight method in the proton-induced fission of 232 Th with incident energies from 12.0 to 14.7 MeV. The results experimentally demonstrate for the first time the correlation among the threshold energy, the total fragment kinetic energy, and the mass division mode in fission: one type of the fission process has a lower threshold energy and leads to a compact scission configuration with reflection asymmetry, and the other type has a higher threshold energy and leads to a symmetric elongated scission configuration.

Ion source development for the JAERI on-line isotope separator

Abstract In accordance with the JAERI-KEK joint radioactive nuclear beam (RNB) project, we have installed a forced electron beam induced arc discharge (FEBIAD) type integrated-target–ion source in the JAERI-ISOL to produce heavy neutron-rich RNBs with particle-induced fission of 238 U. In the present ion source, a 2.6-g 238 UC 2 target is directly attached to a plasma chamber. RNBs of 8 Li, 18 F and 20 F are also planned to be used for the study of thermal diffusion in materials in the joint project. Release profiles of 7 Li have been studied using a cavity type thermal ion source. For mass-separation of F atoms, the molecular ion formations have been examined using the FEBIAD ion source.

Production and characterization of actinide metallofullerenes

We have, previously, reported on the HPLC elution behavior of the Th, Pa, U, Np, and Am metallofullerenes and the UV/vis/NIR absorption spectra of the Th@C84 and U@C82 species. In this paper, the followings are reported: (1) Pu metallofullerenes were produced and their HPLC elution behavior was investigated using a radiotracer technique. The HPLC chromatogram of this metallofullerene was found to be almost the same as that of the Np and Am metallofullerenes. (2) The oxidation states of Th@C84 and U@C82 produced in macroscopic quantities were examined by XANES (X-ray absorption near edge structure) measurements. The oxidation state of the U atom in the C82 fullerene cage was estimated to be 3+ with the formal charge of the ionic molecule being U3+@C823-.

Pre-equilibrium process in 3He-induced reactions on 59Co, 109Ag, 181Ta and 209Bi

Abstract Excitation functions and mean projected recoil-ion ranges of radioactive nuclei produced in the 3 He-induced reactions were measured for the targets of 59 Co, 109 Ag, 181 Ta and 209 Bi. Most of the excitation functions showed characteristic features of the pre-equilibrium process. We proposed a new method, based on the hybrid model, for evaluation of the initial exciton number n 0 from the slope of excitation function for the reaction in which only a single neutron is emitted. With the deduced n 0 for ( 3 He, n) reaction, the observed excitation functions were compared with the theoretical calculations of the equilibrium and the pre-equilibrium model. The shape of the observed excitation functions for ( 3 He, n) reactions with four kinds of targets was compared and discussed in connection with the n 0 values.

Performance of the multiple target He/PbI2 aerosol jet system for mass separation of neutron-deficient actinide isotopes

Abstract A multiple target He/PbI2 aerosol jet system coupled with a thermal ion source was installed in the isotope separator on line (JAERI-ISOL) at the JAERI tandem accelerator facility. The neutron-deficient americium and curium isotopes produced in the 233,235 U( 6 Li, xn) and 237 Np( 6 Li, xn) reactions were successfully mass-separated and the overall efficiency including the ionization of Am atoms was evaluated to be 0.3–0.4%. The identification of a new isotope 237 Cm with the present system is reported.

Mass separation of neutron-rich isotopes using a gas-jet coupled thermal ion source

A gas-jet coupled thermal ion source was installed in the isotope separator on line at the JAERI tandem accelerator. It was used for separation of neutron-rich isotopes produced in the reaction 238U(15 MeV-p, fission). The separation efficiencies of the whole system were measured to be 3.3% for 140Cs (T12 = 63.7 s), 2.0% for 144La (T12 = 40.8 s), 2.2% for 148Pr (T12 = 2.0 m), 1.2% for 156Pm (T12 = 26.7 s) and 1.0% for 160Eu (T12 = 44 s). A long sticking time of La atoms on the ionizer surface gave a low efficiency of about 0.1% for 148La (T12 = 1.05 s). The first observation of a new isotope 166Tb was carried out using its monoxide ions from this ion source: T12(166Tb) = 21±6 s.

Chemical states of tritium in solid lithium compounds irradiated with neutrons

Chemical states of tritium existing in neutron-irradiated solid lithium compounds were analyzed using a radiometric method. Nearly 100% of tritium was found in the T+ state in LiOH, Li2O2 and Li3N, while the T− state predominated in LiH, Li7Pb2 and Li2C2. Tritium incorporated in Li2O, Li2S, LiF, LiCl, LiBr and LiI was distributed over the T+, T− and T0 states. In Li2O crystals, the distribution of tritium in the T+ state increased from 58% to 81% with increasing neutron fluence from 2.5×1016 cm−2 to 6.3×1017 cm−2.

First successful ionization of Lr (Z = 103) by a surface-ionization technique

We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI2 gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s (256)Lr produced in the (249)Cf + (11)B reaction.

Test Production of Tritium in 3 TBq Level from Neutron-Irradiated 6Li-AL Alloy Targets

Equipments were constructed for the development of tritium production technology. Gaseous tritium in a level of 3 TBq (∼80 Ci) was extracted from neutron-irradiated 6Li-Al alloy by heating at 1,073 K under vacuum and collected in an activated-uranium getter. The recovery of the tritium was 90% or more and the isotopic purity of the product was about 50%. Throughout the production experiment, no release of tritium out of the equipments to the environment was observed.