Accuthera, Inc.

The methods of nondestructive testing (NDT) are generally ultrasonic, neutron, eddy-current and X-rays, NDT by using X-rays, in particular, is the most useful inspection technique having high resolutionWe can especially evaluate corroded pipes of petrochem. complex, nuclear and thermal-power plants by the high energy X-ray NDT system.We develop a portable X-ray NDT system with X-band linac and magnetron.This system can generate a 950 keV electron beam.We are able to get X-ray images of samples with 1 mm spatial resolutionThis system has application to real time impeller inspection because linac based X-ray sources are able to generate pulsed X-rays.So, we can inspect the rotating impeller if the X-ray pulse rate is synchronized with the impeller rotation rate.This system has application in condition based maintenance (CBM) of nuclear plants, for example.However, 950 keV X-ray source can only be used for thin tubes with 20 mm thickness.We have started design of a 3.95 MeV X-band linac for broader X-ray NDT application.We think that this X-ray NDT system will be useful for corrosion wastage and cracking in thicker tubes at nuclear plants and impeller of larger pumps.This system consists of X-band linac, thermionic cathode electron gun, magnetron and waveguide components.For achieving higher elec. fields the 3.95 MeV X-band linac structure has the side-coupled acceleration structure.This structure has more efficient acceleration than the 950 keV linac with alternating periodic structure (APS).We adopt a 1.3 MW magnetron for the RF source.This accelerator system is about 30 cm long.The beam current is about 150 mA, and X-ray dose rate is 10 Gy[at]1 m/500 pps.In this paper, the detail of the whole system concept and the electromagnetic field of designed linac structure will be reported.(c) 2009 American Institute of Physics.

We have developed porTable 950 keV/3.95 MeV X-band (9.3 GHz) electron linear accelerator (LINAC)-based X-ray sources and conducted onsite prestressed concrete (PC) bridge inspection in the last 10 years. A T-shaped PC girder bridge with a thickness of 200–400 mm and a box-shaped PC girder bridge with a thickness of 200–800 mm were tested. X-ray transmission images of flaws such as thinning, fray, and disconnection caused by corrosion of PC wires and unfilled grout were observed. A three-dimensional structural analysis was performed to estimate the reduction in the yield stress of the bridge. In this study, we attempted to evaluate the unfilled grout quantitatively because it is the main flaw that results in water filling and corrosion. In the measured X-ray images, we obtained gray values, which correspond to the X-ray attenuation coefficients of filled/unfilled grouts, PC wires (steel) in a sheath, and concrete. Then, we compared the ratio of the gray values of the filled/unfilled grouts and PC wires to determine the stage of the unfilled grout. We examined this quantitative evaluation using the data obtained from a real T-shaped PC girder bridge and model samples to simulate thick box-shaped PC girder bridges. We obtained a clear quantitative difference in the ratios for unfilled and filled grouts, which coincided with our visual perception. We synthesized the experience and data and proposed a quantitative analysis for evaluating the unfilled grout for subsequent steps such as structural analysis and destructive evaluation by boring surveys.