On-Site Non-Destructive Inspection of Bridges Using the 950 keV X-Band Electron Linac X-ray Source

Abstract

Regular diagnosis of the structural health of infrastructure, such as bridges, is indispensable to ensure safety and reliable operation of the society. Non-destructive tests based on X-ray imaging are powerful tools to inspect the inside of a concrete structure in detail. Establishing a diagnostic method of bridges based on X-ray visualization is required to examine the internal conditions and helps in the rationalization of maintenances. We demonstrated our 950 keV X-band electron linac based X-ray source for on-site actual bridge inspection and visualized the inner structure of a bottom floor slab. For the more precise inspection of the conditions of wires and rods, we applied three-dimensional image reconstruction methods for bridge mock-up samples. Partial angle computed tomography and tomosynthesis gave cross section images of the samples with 1 mm resolution. We are planning to investigate another part of the bridge, with the 950 keV X-ray system in the near future.

Highway PC Bridge Inspection by 3.95 MeV X-Ray/Neutron Source

“…We use X-band (9.3 GHz) linac based 3.95 MeV X-ray sources for the inspection of the actual bridge [1][2][3]. The systems are shown in Figure 4.…”

“…The calculated neutron yield in the neutron source is approximately ~10 7 n/s (neutrons/second), which is more intense than ~10 6 n/s of 252 Cf (1 μg) moister detector used for NDE in chemical plants. The distribution of neutron energy produced is measured by 3 He gas detector and TOF (Time of Flight) method, as shown in Figure 7.…”

“…However, they are available for thinner concrete than 200 mm. On the other hand, 950 keV / 3.95 MeV X-ray sources can be used for transmission testing for thick concrete of 200-400 mm and 200-1,000 mm based on the calculation and our experience so far [1][2][3][4]. We think that only the 950 keV/3.95 MeV X-ray sources can enable transmission imaging of PC structures in 200-1,000 mm thick concrete within minutes.…”

“…But, practically it is difficult to evaluate PC in thicker concrete than 200 mm. We have developed portable 950 keV/3.95 MeV electron linac (linear accelerator)-based X-ray / neutron sources and applied them to inspection of PC concrete thicker than 200 mm within reasonable measuring time of seconds -minutes more than 10 times so far [1][2][3][4]. Major poor-construction and degradation of PC bridges to be detected by X-rays and neutrons are unfilled grout, rainwater intrusion, corrosion and thinning and disconnection of PC wires.…”

On-Site Bridge Inspection by 950 keV/3.95 MeV Portable X-Band Linac X-Ray Sources

“…We have developed X-band electron linear accelerator (linac)-based portable X-ray sources with high maximum energies of 950 keV and 3.95 MeV and have been demonstrating X-ray inspection of infrastructures using these sources [4][5][6][7]. We have successfully conducted ten on-site inspections using these X-ray sources to date, and we are also working on technology development in laboratories using samples from dismantled bridges.…”