Development of fast-neutron radiography technique

Neutron radiography is one of effective nondestructive methods for investigation of defects in the specimen. It has a capability to detect a light element, especially hydrogen, while other radiography cannot. In this study, the technique of fast neutron radiography using the (n, p) reaction has been developed. The (n, p) reaction is the nuclear reaction that converts fast neutron particles into proton particles. The recoiled proton produces from hydrogen-rich materials by the (n, p) reaction using the 14 MeV fast-neutron generator. To confirm the existence of (n, p) reaction, the experiment on the track-etching on CR-39 with proton particles is performed. The conditions of track etching are 6 N NaOH, a temperature of 60 °C, etching time of 4.5 hours. The X-ray image plate, BAS-MS type produced by FUJIFILM attached with a converter screen made by hydrogen-rich material (a cloth tape), is irradiated by 14 MeV of fast-neutron about 30 minutes. The results show that the range of particle track size from 5.214 μm to 17.962 μm. The proton particles is confirmed. To find an optimum converter screen condition for the radiography, several types of hydrogen-rich materials (cloth tapes, acrylic plates) with various thickness between 0.81 cm to 3 cm are irritated with 14 MeV neutron produced by a fast-neutron generator. The X-ray image plate BAS-MS type is again applied to record the charge particle effect on a radiography screen. For each test condition, The Photo-Stimulated Luminescence (PSL) is used to determine the quality of images, including the parameters of the image contrast and unsharpness. According to the test results, a cloth tape with 0.81 mm of thickness is selected as an optimum converter screen condition which provides a high PSL of 154.9 PSL/mm2, and relatively high contrast with acceptable unsharpness parameters.