Glass transition temperature(Tg) of 20BaO·10Fe2O3·xWO3·(70−x)V2O5 glasses showed a step-by-step increase from 339 to 470°C when x was increased from 0 to 50, together with a concordant increase in crystallization temperature(Tc) from 406 to 531°C. Plot of Tg against quadrupole splitting(Δ) of FeIII in the Mössbauer spectra yielded a straight line with a slope of 680K(mm s−1)−1. This indicates that FeIII atoms constitute distorted FeO4 tetrahedra and play a role of network former in the 3D-glass network. Dissolution of vanadium ions from vanadate glass into boiling water was suppressed from 34 to 2mg L−1 when x was modified from 0 to 50, reflecting that introduction of WO3 into the 3D-network of vanadate glass is effective in the improvement of water resistivity. A gradual decrease of Δ was observed from 0.82 to 0.76mm s−1 after isothermal annealing of vanadate glass(x＝20) at 500°C for 240min, indicating structural relaxation of the glass network, and a marked increase in conductivity (σ) from 3.9×10−6 to 2.1×10−3 S cm−1 was observed at room temperature.
A compact accelerator mass spectrometry(AMS) system was installed at Yamagata University in 2010 with the aim of developing technologies for the radiocarbon dating of environmental samples and microdosing clinical tests using radiocarbon. With the installation of this AMS system, we also installed a new automatic sample preparation system comprising an elemental analyzer(EA), an isotope ratio mass spectrometer(IRMS), and a glass vacuum line(GVL). This automatic system can automatically collect CO2 from samples, measure the stable isotope ratio, quantify the amount of CO2 and H2 introduced for reduction, and treat 20 samples in approximately 12.5hrs, thus enabling the preparation of 60 samples per week.
It has been reported that γ-ray irradiation on ceramic materials causes deterioration of the dissipation factor and the electrostatic capacity due to the secondary electrons generated by the photoelectric or Compton effects. The authors have measured space charge around the Al2O3 sample during low level γ-ray irradiation, and have confirmed the phenomenon of repetition of electron-hole polarization and recombination on the surface of Al2O3 samples.
Air absorbed dose rates evaluated from uranium, thorium and potassium contents in rock samples have been compared with SiO2 and K2O data in order to understand lithologic characteristics of terrestrial γ-ray dose rate levels in igneous rock terrains. The comparison showed that the dose rate increased with increasing SiO2 or K2O content of rock. The models of partial melting of rock and crystallization differentiation of magma were used to analyze this trend quantitatively. As a result, a semi-empirical formula could be derived for expressing the dose rate as a function of K2O content of rock.
At present, a bulky import product, 99Mo supplied in Japan is produced by a nuclear fission method which enables to produce a generator system with no need of commercially preparing 99mTc-labeled radiopharmaceuticals due to its high specific activity. However its usage of enriched uranium target leads to avoiding the fission method from the option of domestic production. In order to secure the domestic supply of 99Mo/99mTc, the neutron activation method, aiming to meet about 20% of domestic demand, is under development along with the re-start program of JMTR. Development of various production methods using accelerators are also in progress. In those non-fission methods with reactors or accelerators, rapid and effective procedures for concentration and refinement of 99mTc solution eluted from 99Mo of low specific activity are the subjects to be considered for attaining the stable labeling performances.