Mobile Neutron Radiography System for Aircraft Inspection

Abstract

A Mobile Neutron Radiography System (MNRS) has been designed and fabricated for the inspection of naval aircraft for hidden corrosion in aluminum structures. The MNRS is comprised of an accelerator-based thermal neutron source, near real-time neutron imaging system, robotic positioner and manipulator for the source/imager, control trailer housing system control electronics and digital image processing system, mobile dark room for film processing, a self contained electrical power source and a radiation safety system. For insitu aircraft inspection, the Robotic Scanner is programmed (in a teach-learn mode) to scan a region of the components, using a control pendant.

The thermal neutron source consists of a Kaman A-711 neutron generator using the deuterium-tritium (D,T) reaction and an optimized moderator/collimator assembly. The sealed-tube neutron generator produces about 1 × 10¹¹ 14 MeV neutron/sec which is projected to produce a thermal neutron flux of about 5 × 10⁴ thermal n/cm²/sec at the image plane for an L/D = 24. The neutron imaging system uses a 9-inch diameter neutron-sensitive Thomson CSF Image Intensifier tube coupled to a television camera and a user-oriented digital image processing system. With a thermal flux of only 6 × 10³ n/cm²/sec and L/D = 30, the system easily resolves 11 holes (Modified Type A Penetrameter) and detects 6 layers, of Scotch “Magic Tape” (0.012 inches) with 8 sec integration.

MNRS, when delivered to the North Island Naval Air Rework Facility (San Diego) in late 1986, will provide the first opportunity to demonstrate the effectiveness of neutron radiography for in situ inspection of aircraft in a realistic aircraft overhaul environment.