The Application of Non-Destructive Techniques in the Quality Control, Inspection and Testing of Fuel Materials for the Dragon Reactor Experiment. Dragon Project Report

The O.E.C.D. High Temperature Gas Cooled Reactor Experiment, Dragon, is graphite moderated and helium cooled and employs fission product retaining fuel of the coated particle type. The development and use of this new type of fuel have required the application of a variety of non-destructive techniques for quality control, inspection and testing. This paper describes certain of the methods which are employed in the inspection of fuel materials both in the development phase and subsequently in production. Physical methods of analysis are used for control of the chemical analysis of fuel cartridges and assessment of fuel contamination of fuel particle coatings and particular gamma spectrometric and alpha scintillation counting techniques are described. The general quality of coated particles is assessed and metrology of coatings performed by means of micro-radiography with the X-ray projection microscope; the procedure is outlined and typical results are presented. Fuel cartridges which consist of fuel particles in a graphite matrix are inspected for homogeneity of fuel distribution and freedom from defects by fluoroscopy and panoramic slit-scanning radiography. Colour radiography is also employed to a limited extent and the various techniques are presented together with illustrative examples of the results obtained. The fuel elements are fabricated almost entirely from various grades of graphite and eddy current non-destructive testing techniques are being developed to permit inspection of raw materials and finish machined components for freedom from significant defects. A brief description of these techniques is given. (author)