A MONTE CARLO CALCULATION FOR NEUTRON RADIOGRAPHY FACILITY USING SEALED-TUBE NEUTRON GENERATOR

• Published in: E-journal of Nondestructive Testing Vol. 12; no. 1
• Main Authors: Bai, Jin-Hyoung, Shin, Myung-Won, Whang, Joo-Ho
• Format: Journal Article
• Language: English
• Published: 01-01-2007
• ISSN: 1435-4934; 1435-4934

Fast neutron radiography (FNR) is a promising non-destructive inspection technique that is especially suitable for non-destructive inspection of industrial products that are too thick or dense to be inspected by conventional thermal neutron radiography. In this study, shielding structures were designed and built within a limited space (that was part of an existing building) in order to protect both operators and nearby residents as well as the sensitive CCD-detection system. The scattering effects caused by the shields were assessed by the detector as well. A sealed-tube neutron generator was used as the neutron source. A Monte Carlo calculation was done using MCNP4C code which is capable of solving the coupling transport problem for neutrons and gamma rays. With the calculation, neutrons were emitted isotropically (14MeV) from a point-like source, and the history of the quantity was determined to discern a relative calculation error within 10%. The dose conversion factor (DCF) from ICRP74 was applied to convert the flux of neutrons and gamma rays. From the calculation results, the highest dose rate was 8.2mrem/week. However, due to the complexity of the shielding structures, there was a possibility that some noise could affect the imaging process. The performance and characteristics of each component was analyzed; the mirror, lens, scintillator and the cooled CCD camera. It was determined that the scattered neutrons together with the shielding structures were both able to cause some distortion within the detector system. For the future, we recommend that a Monte Carlo simulation be done to better determine the optical behaviour of scintillation detectors in order to improve detection efficiency.