On-site Real-Time Inspection System for Pump-impeller using X-band Linac X-ray Source

Abstract

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 resolution. We can especially evaluate corroded pipes of petrochemical 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 resolution. This 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 electric 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@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.