Neutron radiographic detection limits of fluids in metal pipes

Thermal neutron radiography has been used to image thin films of various fluids in thick-walled high-pressure process pipes. A 3,500,000 n/(sq cm/sec) thermal neutron beam and standard transfer imaging techniques were used to provide radiographs of the fluid bearing pipes. In addition, a computer graphics procedure was developed which simulated the neutron radiographs; this method permitted examination of some fluid-pipe configurations not studied experimentally. Actual pipe outer dia ranged from 1/4 to 9/16 in. (OD/ID equals 3), but the graphics method was used for some cases outside this range. Fluids in the thermal cross section range 0.29/cm less than or equal to SIGMA/sub th/sup f/ less than or equal to 3.47/cm were examined for pipes with 0.099/cm less than or equal to SIGMA/sub th/sup p/ less than or equal to 1.15/cm.