Effect of gamma and neutron irradiation on properties of boron nitride/epoxy resin composites

The Advancement of Neutron-Shielding Materials for the Transportation and Storage of Spent Nuclear Fuel

In this paper, the mechanism of neutron absorption and common reinforced particles is introduced, and recent research progress on different types of neutron-shielding materials (borated stainless steels, B/Al Alloy, B4C/Al composites, polymer-based composites, and shielding concrete) for transportation and wet or dry storage of spent fuel is elaborated, and critical performance is summarized and compared. In particular, the most widely studied and used borated stainless steel and B4C/Al composite neutron-absorption materials in the field of spent fuel are discussed at length. The problems and solutions in the preparation and application of different types of neutron-shielding materials for spent fuel transportation and storage are discussed, and their research priorities and development trends are proposed.

Experimental and Theoretical Study of Gamma Radiolysis and Dose Rate Effect of o-Cresol Formaldehyde Epoxy Composites

Gamma radiolysis behaviors and mechanisms of silica-filled o-cresol formaldehyde epoxy are studied at 2.20 × 10^-5 to 1.95 × 10^-1 Gy/s. The radiolysis-induced changes in chemical structures do not severely affect its thermostability. The slightly deteriorated mechanical strength at temperature exceeding 100 °C is accompanied by the declining glass transition temperature (from 185.9 to 172.2 °C) and enhanced damping ability. The gas yields of hydrogen, methane, and carbon dioxide manifest a remarkable dose rate effect. Based on the Schwarzschild law, their yields at an extremely low dose rate are accurately predicted by the established master curves. Besides, the latent radiolysis of gas products and postradiation effect are found with caution. The radiation-caused residual spin species are proved to be composed of silica defects and a phenoxy-type free radical with a tert-butyl group, according to the experimental results, theoretical calculations, and spectra simulations. The lower vertical ionization potential (7.6 eV) and adiabatic ionization potential (7.1 eV) are primarily due to the ionization of the benzene ring moiety with the tert-butyl group, which is likely to suffer from radiolysis. The calculated bond dissociation energy (260.8-563.5 kJ/mol) of the typical chemical bonds of epoxy is consistent with its radiolytic vulnerability and degradation mechanisms.

Gamma Irradiation and the Radiation Shielding Characteristics: For the Lead Oxide Doped the Crosslinked Polystyrene-b-Polyethyleneglycol Block Copolymers and the Polystyrene-b-Polyethyleneglycol-Boron Nitride Nanocomposites

This work aimed to research the efficiency of gamma irradiation and shielding characteristics on the lead oxide (PbO) doped the crosslinked polystyrene-b-polyethyleneglycol (PS-b-PEG) block copolymers and polystyrene-b-polyethyleneglycol-boron nitride (PS-b-PEG-BN) nanocomposites materials. The crosslinked PS-b-PEG block copolymers and PS-b-PEG-BN nanocomposites mixed with different percentage rates of PbO were used to research gamma-ray shielding characteristics. The synthesis of the copolymer was done by emulsion polymerization methods. The characterization and morphological analyses of irradiated samples were explored handling with the Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), and Scanning Electron Microscope (SEM) methods. The gamma-rays that were emitted from the E 152u source were observed with a High Purity Germanium (HPGe) detector system and examined with a GammaVision computer program. Our samples, including the different percentage rates of the PS-b-PEG (1000, 1500, 10,000), BN, and PbO, were irradiated in various gamma-ray photon energy regions (from 121.78 keV to 1408.01 keV). Then, Linear-Mass Attenuation Coefficients (LACs-MACs), Half-Tenth Value Layer (HVL), Mean Free Path (MFP), and Radiation Protection Efficiency (RPE) values of the samples were calculated. Via crosschecking the acquired data from samples with and without PbO and BN, it was observed that, if the different percentage rates by weight nano-powder of PbO and BN are added in the polymer mixture, it can be used as a convenient shielding material against gamma rays.