Neutron radiography with the VPI & SU research reactor

Abstract

A feasibility study to determine the feasibility of neutron radiography with the VPI & SU Research Reactor has been completed. Various experimental facilities of the reactor were tested to determine which gave the best beam parameters. The beam parameters considered were: 1) thermal neutron flux; 2) thermal to fast-flux ratio; 3) gamma vs neutron relative film exposure ratio; 4) collimator length vs diameter ratio. It was found that the north beam port best met the necessary requirements. The direct exposure method utilizing a commercially available gadolinium paint was decided upon for X-ray film exposure. The resolution capabilities of the gadolinium paint converter screen were determined for several screen thicknesses using a cadmium test object. Exposure times and object limitations were found for the combination of the X-ray film, converter screen, and neutron beam of the north beam port. The test devices used were: 1) various thicknesses of acrylic plastic; 2) plywood and white pine test pieces; 3) thorium and natural uranium slugs; 4) enriched uranium fuel plate; 5) used and unused boral control elements; 6) miscellaneous small test objects. The results were, in general, good. Exposure times and limitations were found to be in agreement with other published works. Any significant differences in the technique's capability with other facilities were noted in the discussion of procedures and results. From the results of this work, neutron radiography can be successfully carried out on the VPI & SU reactor with small objects while further development should allow studies to be made of larger objects.