Authors:Ch. He, E. Hamada, T. Suzuki, H. Kobayashi, K. Kondo, V. Shantarovich, and Y. Ito
A new pulsed mono-energetic slow positron beam as well as the conventional positron annihilation lifetime spectroscopy (PALS) have been applied to study the sub-surface and the bulk of epoxy polymer. Significant changes of o-Ps parameters were found at a short distance from the surface. The lifetime of o-Ps was observed to decrease with increasing the positron implantation depth, while its intensity increased. The temperature effect on o-Ps parameters at sub-surface was also investigated. The glass transition temperature for the sub-surface was lower than that for the bulk. Furthermore, the thermal expansion coefficient of the sub-surface was found smaller than that of the bulk.
Authors:J. Wang, Q. Li, M. Wu, G. Xu, Ch. Li, B. Bao, W. Zheng, H. He, and Sh. Zhang
N,N-dimethylhydroxylamine (DMHA) is a novel salt-free reducing reagent used in the separation U from Pu and Np in the reprocessing
of power spent fuel. This paper reports on the radiolysis of aqueous DMHA solution and its radiolytic liquid organics. Results
show that the main organics in irradiated DMHA solution are N-methyl hydroxylamine, formaldehyde and formic acid. The analysis
of DMHA and N-methyl hydroxylamine were performed by gas chromatography, and that of formaldehyde was performed by ultraviolet–visible
spectrophotometry. The analysis of formic acid was performed by ion chromatography. For 0.1–0.5 mol L−1 DMHA irradiated to 5–25 kGy, the residual DMHA concentration is (0.07–0.47) mol L−1, the degradation rate of DMHA at 25 kGy is 10.1–30.1%. The concentrations of N-methylhydroxylamine, formaldehyde and formic acid are (8.25–19.36) × 10−3, (4.20–36.36) × 10−3 and (1.35–10.9) × 10−4 mol L−1, respectively. The residual DMHA concentration decreases with the increasing dose. The concentrations of N-methylhydroxylamine and formaldehyde increase with the dose and initial DMHA concentration, and that of formic acid increases
with the dose, but the relationship between the concentration of formic acid and initial DMHA concentration is not obvious.