Development of monitoring technique for the confirmation of spent fuel integrity during storage

A method is developed to monitor integrity of spent fuels stored in a canister that is sealed by weld. To achieve the monitoring, Kr-85 gas was newly adopted as a kind of probe. In the case of a fuel rod defect, Kr-85 gas of the fuel rod is leaked in the canister. By detection of gamma ray (514 keV) emitted from Kr-85 outside of the canister, defected rods can be detected without unsealing the canister. The monitoring technique was developed using small-scaled mock-up experiments and simulated calculation. The result showed that Kr-85 gas leakage of about 10¹¹ Bq is detectable under the noise gamma rays by using the detection system with collimator, which is about 10% of Kr-85 inventory in a fuel rod. Therefore, this monitoring technique is considered as an inspection method prior to transportation of spent fuel from an interim storage facility to a reprocessing plant.     

Oxygen potential of hypo-stoichiometric Lu-doped UO2

Oxygen potentials of hypo-stoichiometric Lu-doped UO₂, (U_0.80Lu_0.20)O_2−x, were experimentally investigated by thermogravimetric analysis using H₂O/H₂ gas equilibria at 1173, 1273 and 1473 K. The oxygen potentials of (U,Lu)O_2−x were higher than those of other forms of rare earth-doped UO₂, specifically (U,Nd)O_2−x, (U,Gd)O_2−x, and (U,Er)O_2−x. Slope analyses for plots of oxygen potential versus deviation from stoichiometry indicated that (U_0.80Lu_0.20)O_2−x had a similar defect structure to that of the other forms of rare earth-doped UO₂. A relationship between the effective ionic radii and oxygen potentials was found for the hypo-stoichiometric rare earth-doped UO₂.     

Simultaneous Position Estimation and Omnidirectional Camera Parameter Calibration for Multiple Mobile Robots

This paper proposed an algorithm on simultaneous position estimation and calibration of omnidirectional camera parameters for a group of multiple mobile robots. It is aimed at developing of exploration and information gathering robotic system in unknown environment. Here, each mobile robot is not possible to know its own position. It can only estimate its own position by using the measurement value including white noise acquired by two omnidirectional cameras mounted on it. Each mobile robot is able to obtain the distance to those robots observed from the images of two omnidirectional cameras while making calibration during moving but not in advance. Simulation of three robots moving straightly shows the effectiveness of the proposed algorithm.     

Free-form curves cutting using flexible circular saw

A flexible circular saw, which can be used in a novel machining process for high-speed carbon fiber-reinforced plastic (CFRP) plate cutting, was developed. In this process, the saw is deflected like a bowl-like shape. A cross-section of the saw body then forms a circular arc. A curved line can therefore be cut without interference by the bowl-like deflection. In addition, the radius of the cross-section of the saw body can be controlled by adjusting the deflection. This process therefore allows curves to be cut with a varied radius using a single saw. This process can carry out high-speed curved-line cutting with a feed rate of 3 m/min on a CFRP plate. However, it is difficult to cut free-form curves using a flexible circular saw. Therefore, in this research, a new technique that can cut free-form curves using a flexible circular saw was proposed. Then, a cutting test applying the technique was carried out.     

Dickey–Fuller, Lagrange Multiplier and Combined Tests for a Unit Root in Autoregressive Time Series

In this paper we investigate (augmented) Dickey–Fuller (DF) and Lagrange multiplier (LM) type unit root tests for autoregressive time series through comprehensive Monte Carlo simulations. We consider two sorts of null and alternative hypotheses: a unit root without drift versus level stationarity and a unit root with drift versus trend stationarity. The DF-type coef ficient tests are found to show the best overall performance in both cases, at least if the sample size is sufficiently large. How ever, it is also found that the DF and LM tests are roughly complementary with regard to their finite-sample power. We therefore consider combining these two types of unit root tests to obtain ( ad hoc 'but') 'robust' test procedures. Critical values for the proposed tests are provided     

Fully automated two-dimensional electrophoresis system for high-throughput protein analysis

We developed a fully automated electrophoresis system for rapid and highly reproducible protein analysis. All the two-dimensional (2D) electrophoresis procedures including isoelectric focusing (IEF), on-part protein staining, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and in situ protein detection were automatically completed. The system comprised Peltiert devices, high-voltage generating devices, electrodes, and three disposable polymethylmethacrylate (PMMA) parts for IEF, reaction chambers, and SDS-PAGE. Because of miniaturization of the IEF part, rapid IEF was achieved in 30 min. A gel with a tapered edge gel on the SDS-PAGE part realized a connection between the parts without use of a gluing material. A biaxial conveyer was employed for the part relocation, sample introduction, and washing processes to realize a low-maintenance and cost-effective automation system. Performances of the system and a commercial minigel system were compared in terms of detected number, resolution, and reproducibility of the protein spots. The system achieved high-resolution comparable to the minigel system despite shorter focusing time and smaller part dimensions. The resulting reproducibility was better or comparable to the performance of the minigel system. Complete 2D separation was achieved within 1.5 h. The system is practical, portable, and has automation capabilities.     

Effects of photoirradiation in UV and VUV regions during plasma exposure to polymers

Interactions between photons irradiated from Ar-O₂ mixture plasmas and polymer surfaces were investigated on the basis of depth analyses of chemical bonding states in the nano-surface layer of polyethylene terephthalate (PET) films via hard X-ray photoelectron spectroscopy (HXPES) and conventional X-ray photoelectron spectroscopy (XPS). The PET films were exposed to photons from the Ar-O₂ mixture plasmas by covering the PET samples with MgF₂ and quartz windows as optical filters for evaluation of photoirradiation effects in ultraviolet (UV) and vacuum ultraviolet (VUV) regions. The HXPES results indicated that the degradation of the chemical bonding states due to photoirradiation in regions was insignificant in deeper regions up to about 50 nm from the surface. Whereas, conventional XPS analysis showed that CO bond, OCO bond and CO bond increased after photoirradiation in UV and VUV regions. These results suggest that the increase in oxygen functionalities (CO bond, OCO bond and CO bond) may be attributed to chemical reactions and/or terminations of scissed bonds via photodecompositions of the polymer with oxygen and/or OH species (oxygen molecules and radicals during plasma exposure and/or oxygen molecules and moisture after taking the PET samples out of the plasma reactor to the ambient air) in the vicinity of the sample surface.     

Manipulation of small particles utilizing electrostatic force

We developed electrostatic system for manipulating small particles with diameters in the range of several micrometers to 100 μm. The electrostatic manipulation probe consists of a monopole pin electrode. When voltage is applied to the electrode, a dielectrophoresis force generated in the nonuniform electrostatic field is applied to the particle near the tip of the electrode. The particle is captured with the application of voltage, and then it is released from the probe by applying a high voltage of the opposite polarity. It is possible to manipulate not only insulative but also weakly conductive particles. A three-dimensional field calculation and a measurement of the adhesion force were conducted to evaluate the force balance for the capture and release of a particle. On the basis of these investigations, we demonstrated the manipulation of actual lunar dust returned by the Apollo 11 lunar surface mission.