Measurement of the shape in the radioactive area by ultrasonic wave sensor

The HANARO (High-flux Advanced Neutron Application Reactor) has been operated since 1995. The Cold Neutron (CN) hole was implanted in the reflector tank from the design stage. Before a vacuum chamber and a moderator cell for the cold neutron source are installed into the CN hole, it is necessary to measure exactly the size of the inside diameter and thickness of the CN hole to prevent the interference problem. Due to inaccessibility and high radiation field in the CN hole, a mechanical measurement method is not permitted. The immersed ultrasonic technique is considered as the best way to measure the thickness and the diameter of the CN hole. The 4-Axis manipulator was designed and fabricated for locating the ultrasonic sensors. The transducer of an ultrasonic sensor having 10 MHz frequency leads to high resolution as much as 0.03mm. The inside diameter and thickness of 550 points of the CN hole were measured using 2 channel ultrasonic sensors. The results show that the thickness and inside diameter of the CN hole is in the range of 3.3 - 6.7mm and 0 156-165mm, respectively. This data will be a good reference for the design of the cold neutron source facility.     

Residual stress analysis of an aircraft landing gear part using neutron diffraction

The residual stress of a landing gear part of a fighter jet that has a frequent practice of takeoff and landing was evaluated for the safety. The sample was a cylindrical steel bar with a 22.2 mm diameter and 55 mm length used to fix the main landing gear to the aircraft body. For a deep measurement up to 6 mm, we used a neutron beam. From the measurements, the tensile and compressive strain in the axial direction were observed around one side of the pin hole which was across the steel bar vertically with an 8 mm diameter. The strain distribution along the length of the bar presented a similar tendency through the thickness and a larger value on the surface. The maximum value of the residual stress around the pin hole was about 100 MPa. However, there was no strain on the opposite side of the pin hole. From the results, it may be surmised that the steel bar received a steady force in one direction around the pin hole, however the force was weak and affected a small limited area and thus not influence on the steel bar on the whole.     

Detecting Internal Hot Corrosion of In-service Turbine Blades Using Neutron Tomography with Gd Tagging

Neutron tomography with Gd tagging has been developed for application to in-service turbine blades to ensure theirs maintainability. Hot corrosion was detected in the air channels of 13 % of in-service blades. Hot corrosion occurs in clusters of about 15 mm in diameter. The size of individual hot corrosion features was determined to be in the range of 0.8–2.81 mm by neutron tomography. Turbine blades with indications of flaws were crosscut with a wire for internal verification. Scanning electron microscopy revealed that hot corrosion occurs in scattered groups with multiple pits of about 150 \(\upmu \) m in size in the channels. The analyzed oxygen content of the corroded surface was over 30 wt% higher when compared with new turbine blades by energy dispersive X-ray spectroscopy. These findings may play a pivotal role in curtailing in-service turbine blade failure due to internal corrosion of cooling channels. Applying these results with neutron tomography on in-service turbine blades can lead to more reliable determinations of condemnation.     

Strong convergence of subgradient extragradient method with regularization for solving variational inequalities

The paper concerns with the two numerical methods for approximating solutions of a monotone and Lipschitz variational inequality problem in a Hilbert space. We here describe how to incorporate regularization terms in the projection method, and then establish the strong convergence of the resulting methods under certain conditions imposed on regularization parameters. The new methods work in both cases of with or without knowing previously the Lipschitz constant of cost operator. Using the regularization aims mainly to obtain the strong convergence of the methods which is different to the known hybrid projection or viscosity-type methods. The effectiveness of the new methods over existing ones is also illustrated by several numerical experiments.