Noboru Kasai

Aquaculture of Uranium in Seawater by a Fabric-Adsorbent Submerged System

Abstract The total amount of uranium dissolved in seawater at a uniform concentration of 3 mg U/m3 in the world’s oceans is 4.5 billion tons. An adsorption method using polymeric adsorbents capable of specifically recovering uranium from seawater is reported to be economically feasible. A uranium-specific nonwoven fabric was used as the adsorbent packed in an adsorption cage 16 m2 in cross-sectional area and 16 cm in height. We submerged three adsorption cages in the Pacific Ocean at a depth of 20 m at 7 km offshore of Japan. The three adsorption cages consisted of stacks of 52 000 sheets of the uranium-specific non-woven fabric with a total mass of 350 kg. The total amount of uranium recovered by the nonwoven fabric was >1 kg in terms of yellow cake during a total submersion time of 240 days in the ocean.

Low temperature gamma-ray irradiation effects of polymer materials on mechanical property

Abstract A low temperature γ-ray irradiation equipment was constructed for the evaluation of the radiation resistance of polymer materials used in low temperature environment. The change of mechanical property by irradiation at 77 K was studied for glass fiber reinforced plastic (GFRP), poly(methyl methacrylate) (PMMA) and poly(tetra fluoroethylene) (PTFE), and compared with that by irradiation at room temperature. The decrease in flexural strength or in elongation at break showed a big difference between 77 K and room temperature irradiation. The ratio of dose at half strength or half elongation by 77 K and room temperature irradiation was 25 for GFRP, 17 for PMMA and 5 for PTFE. For GFRP the annealing effect at room temperature after irradiation at 77 K was observed scarcely by the flexural strength measurement at 77 K, which means that the degradation on mechanical property depends mainly on the temperature during irradiation.

Low temperature gamma-ray irradiation effects on polymer materials—3. Gas evolution and change of molecular weight

Abstract Gas analysis was carried out after gamma-irradiation at room temperatures (RT) and 77K for poly(methyl methacrylate) (PMMA) and glass fiber reinforced plastic (GFRP). The yield of hydrogen from irradiated PMMA and GFRP was nearly the same at RT and 77K. The yield of CH 4 , CO and CO 2 , however, was much less at 77K than at RT; these results were in good accordance with results of mechanical properties. Changes in molecular weight and network structure were also studied. The radiation degradation mechanism and its temperature dependence is discussed.

Studies on the immobilization of biofunctional components by radiation polymerization and their applications

Abstract The recent progress on the studies of immobilization of various biofunctional components mainly by mean of radiation polymerization as well as their practical applications to biomedical and biochemical fields were reviewed. The immobilization of drugs for the controlled release and targetting, the immobilization of antigens and antibodies for the immunodiagnosis, and the immobilization of microorganisms and tissue cells for the cell culture and the biomass conversion were the main topics in this review. The new findings on the enhanced immobilization methods and the polymeric carriers for immobilization were also attached.

Evaluation and Analysis of Thermal Control Materials under Ground Simulation Test for Space Environment Effects

Thermal control materials such as white paint comprising silicone resin matrix (NASDA-1049/101-S), black paint comprising urethane resin matrix (NASDA-1049/201-U-I), aluminized polyimide adhesive tape (Sheldahl G408810) and silver-backed fluorinated ethylene propylene (silvered FEP) adhesive tape (Sheldahl G402500) were exposed to electron beam (EB), proton (H+), iron ion (Fe5+), ultraviolet (UV) and atomic oxygen (AO) radiation with ground simulation test facilities. Combined irradiation of EB → UV and another combined irradiation of EB → AO, where EB was irradiated at first and then UV or AO was irradiated, were also examined for white paint and black paint. Irradiation energies were 0.5 and 1.9 MeV for EB; 1, 3 and 10 MeV for H+; 15 MeV for Fe5+; equal to or larger than 3.1 eV for UV; and 5 eV for AO. Fluences of EB, H+ and Fe5+ were selected to simulate the environment of geostationary orbit (GEO) for 10 years. UV irradiation was equal to 300 equivalent solar days. AO fluence corresponded to the environment of low Earth orbit (LEO) for about 1 year. The solar absorptance (αS) and normal infrared emittance (εN) of the examined materials both before and after irradiation were acquired. The durability of the materials against each irradiation treatment was judged by evaluating the changes in αS and εN. White paint and black paint were strongly affected by AO, EB → UV, EB → AO and UV irradiation. White paint was also affected by EB and weakly by H+ and Fe5+. Aluminized polyimide and silvered FEP were degraded most by AO and EB. EB had a stronger effect than ions (H+,Fe5+) in all the samples, the reason for which can be explained by the larger absorbed dose with EB compared with ions. The mass loss caused by the irradiation treatment was also measured for white paint and black paint. Analytical techniques such as scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR) were applied to identify morphology and composition of the materials to obtain a deeper understanding of the mechanism of space environment effects on the materials.

Low temperature gamma-ray irradiation effects on polymer materials—2. Irradiation at liquid helium temperature

The low temperature gamma-ray irradiation induced degradation of poly(tetrafluoroethylene), butyl rubber and poly(ethylene) was studied by following changes in mechanical properties. The decrease of tensile strength and elongation at break against dose were nearly the same for 4 and 77K irradiations. The changes of molecular weight or networks in polymers were also the same for both irradiation temperatures.

Low temperature gamma ray irradiation effects on polymer materials (4)-gas analysis of GFRP and CFRP

Abstract Gas analysis was carried out at RT after gamma-irradiation at room temperature and 77K for glass fiber reinforced plastic (GFRP) and carbon fiber reinforced plastic (CFRP) having the same epoxy resin matrix. Gas yield from CFRP was less than that from GFRP at RT, but comparable at 77 K. The yields of CO and CO 2 showed a large dependence on the irradiation temperature, i.e. they were much less at 77 K. Radiation resistance of GFRP and CFRP towards 77 K irrdiation is expected to be higher than that towards RT irradiation.

Effects of Gamma-Ray Irradiation on Cellulase Secretion of Trichoderma reesei

Trichoderma reesei was irradiated with gamma rays to investigate the effects of different dosages on cellulase production. Doses above 0.7 kGy induced cell lysis. Cell growth began to be obstructed at 2.0 kGy. As a result, the cells irradiated at 2.0 kGy secreted 1.8 times as much cellulase as the untreated cells.

Immobilization of microbial cell and yeast cell and its application to biomass conversion using radiation techniques

Abstract The recent results of immobilization of cellulase-producing cells and ethanol-fermentation yeast by radiation were reported. The enzyme of cellulase produced by immobilized cells was used for saccharification of lignocellulosic wastes and immobilized yeast cells were used for fermentation reaction from glucose to ethanol. The wastes such as chaff and bagasse were treated by γ-ray or electron-beam irradiation in the presence of alkali and subsequent mechanical crushing, to form a fine powder less than 50 μm in diameter. On the other hand, Trichoderma reesei as a cellulase-producing microbial cell was immobilized on a fibrous carrier having a specific porous structure and cultured to produce cellulase. The enzymatic saccharification of the pretreated waste was carried out using the produced cellulase. The enhanced fermentation process to produce ethanol from glucose with the immobilized yeast by radiation was also studied. The ethanol productivity of immobilized growing yeast cells thus obtained was thirteen times that of free yeast cells in a 1:1 volume of liquid medium to immobilized yeast cells.

Pulverization of chaff pretreated by radiation

Abstract The pulverization of lignocellulosic materials such as chaff pretreated by radiation was studied. The fragility of irradiated chaff was evaluated by the measurement of the fraction of powder below 250 mesh-powder yield. The enzymatic hydrolysis reaction of irradiated chaff was enhanced by pulverization of the chaff. The powder yield increased with increasing irradiation dose and rotation speed of the wings during pulverization. The powder and glucose yield in irradiated chaff increased with repeated pulverization. The powder requirement and pulverizing capacity in non- and irradiated chaff were examined as a function of the number of repeated pulverizations.