Re-evaluation of Radiation-Energy Transfer to an Extraction Solvent in a Minor-Actinide-Separation Process Based on Consideration of Radiation Permeability

ABSTRACT

Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process.     

Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH₂) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.     

Radiophotoluminescence phenomenon in copper-doped aluminoborosilicate glass

Radiophotoluminescence phenomena have been widely investigated on various types of materials for dosimetry applications. We report that an aluminoborosilicate glass containing 0.005 mol% copper exhibits intense photoluminescence in the visible region induced by X-ray and γ-ray irradiation. The luminescence is assigned to the 3d⁹4s¹ → 3d¹⁰ transition of Cu⁺. The proportionality of the intensity of the induced photoluminescence to the irradiation dose was confirmed up to 0.5 kGy using ⁶⁰Co γ-ray irradiation. Based on the spectroscopic results, a potential mechanism was proposed for the enhancement of the photoluminescence. The exposure to the ionizing radiation generates electron-hole pairs in the glass, and the electrons are subsequently captured by the Cu²⁺ ions, which are converted to Cu⁺ and emit the luminescence. For the glass containing 0.01 mol% copper, the pronounced enhancement of the photoluminescence was not observed because the reverse reaction, ie, the capture of the holes by the Cu⁺ ions, becomes prominent. The photoluminescence induced by the irradiation was stably observed for the glasses kept at room temperature and even for the glasses heat-treated at 150°C. However, the induced photoluminescence could be eliminated by the heat treatment at a temperature at 500°C, and the glass returned to the initial pre-irradiation state. The Cu-doped aluminoborosilicate glass is a potential candidate for use in dosimetry applications.     

A highly transparent and thermally stable copolymer of 1‐adamantyl methacrylate and styrene

Thermal and optical properties of copolymers of 1‐adamantyl methacrylate (AdMA) and styrene (St) prepared by free radical polymerization in the bulk are investigated. The copolymer forms an azeotrope when the composition is AdMA/St = 55/45 mol%. The glass transition temperature and decomposition temperature of the azeotropic copolymer are 170 and ca 340 °C, respectively. The refractive index increases nonlinearly with St content from 1.522 to 1.591. The light scattering loss at 633 nm is 28.1 dB km^?1, which is less than half of that of polystyrene. The total optical loss including molecular vibrational absorption, which is evaluated using a copolymer‐based optical fiber, is 292–645 dB km^?1 at 500–700 nm. These values correspond to transmittances of 86–93% for a 1 m optical path length. © 2014 Society of Chemical Industry     

Mechanisms of orientational and photoelastic birefringence generation of methacrylates for the design of zero–zero‐birefringence polymers

The intrinsic birefringence Δn⁰ and photoelastic coefficient C of poly(methyl methacrylate), poly(2,2,2‐trifluroethyl methacrylate), poly(phenyl methacrylate), and poly(2,2,3,3,3‐pentafluorophenyl methacrylate) were determined. We categorized these methacrylate polymers into four birefringence‐types, even though their molecular structures differed only by the substituents on the side chains. Based on the results of Δn⁰ and C, novel polymers that exhibit neither orientational nor photoelastic birefringence, i.e., zero–zero‐birefringence polymers, were designed and synthesized by quaternary copolymerization system. Furthermore, we confirmed that the mechanisms of orientational birefringence and photoelastic birefringence generation were different in these methacrylate polymers. The conformation of the repeat unit of the polymers was nearly constant during the generation of orientational birefringence. In contrast, the conformation of the repeat unit of the polymers changed during the generation of photoelastic birefringence in the glassy state. These findings demonstrated the reasonability of evaluating orientational and photoelastic birefringence separately, as well as the adequacy of the classification of polymers into four birefringence‐types. Given these results and the fact that zero–zero‐birefringence polymers could be prepared successfully by four‐birefringence type monomers, we demonstrated the reasonability of the method for designing the zero–zero‐birefringence polymers. POLYM. ENG. SCI., 55:1330–1338, 2015. © 2015 Society of Plastics Engineers     

A 300-MHz 25-/spl mu/A/Mb-leakage on-chip SRAM module featuring process-variation immunity and low-leakage-active mode for mobile-phone application processor

An on-chip 1-Mb SRAM suitable for embedding in the application processor used in mobile cellular phones was developed. This SRAM supports three operating modes - high-speed active mode, low-leakage low-speed active mode, and standby mode - and uses a subdivisional power-line control (SPC) scheme. The combination of three operating modes and the SPC scheme realizes low-power operation under actual usage conditions. It operates at 300 MHz, with leakage of 25 /spl mu/A/Mb in standby mode, and 50 /spl mu/A/Mb at the low-leakage active mode. This SRAM also uses a self-bias write scheme that decreases of minimum operating voltage by about 100 mV.     

Superconductivity in the tetragonal phase of La1.9Bi0.1CuO4+δ annealed under high oxygen pressure

We have investigated the relation between the crystal structure and superconductivity in La_1.9Bi_0.1CuO_4+δ , in which the phase separation observed in La₂CuO_4+δ is suppressed. A phase diagram in theT?δ plane is given for La_1.9Bi_0.1CuO_4+δ with excess oxygen. For very smallδ values, the crystal structure is orthorhombic, and an orthorhombic-tetragonal phase transition occurs markedly atδ ～ 0.03 in the measured temperature range between 13 and 293 K. Superconductivity is observed in the range of 0.04<δ<0.11. This is clear evidence thathigh-T _c superconductivity also appears in the tetragonal phase.     

The role of repeat transurethral resection in stage A1 carcinoma of the prostate

In order to evaluate the significance of repeat transurethral resection (TUR) in differentiating stage A1 prostatic adenocarcinoma from those with stage A2, we performed repeat TUR in 34 patients with an initial diagnosis of stage A1 prostatic adenocarcinoma. It was found that residual adenocarcinoma was present in five cases (14.7%), but the diagnosis was changed from stage A1 to stage A2 in only one case (2.9%). In one patient with final diagnosis of stage A1 carcinoma, bone metastases were detected seven months after the repeat TUR. It was concluded that repeat TUR for stage A1 prostatic adenocarcinoma did not yield clinically significant information.     

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm^-3 FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm^-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe²⁺]² and po₂, exhibiting an activation energy of 51.6 . kJ mol^-1. In another path the reaction rate was proportional to [Fe²⁺]², [SO_4-], and po₂ with an activation energy of 144.6 kJ . mol^-1. A reaction mechanism in which the SO_4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol . dm^-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² and Po₂, and was also affected by [H⁺] and [SO_2- ⁴]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).