Quality control tests for high-temperature gas-cooled reactor recycle fuel

Inspection of recycle fuel for HTGRs involves a large number of operations which, because of the high radiation level associated with the presence of 232U, must be performed in shielded (5cm of lead) glove boxes containing automated sample-handling and analysis equipment. Equipment for obtaining representative fuel particle samples and for pneumatically transferring particles and fuel rods through long tubes has been developed. Schemes for cross-checking inspection data were devised and shown to be useful for determining the accuracy and precision of several analytical techniques, as well as for detecting occasional errors in analytical data. The density of the particle buffer coating layer was shown to increase significantly during deposition of the overlying coating layer. A method was developed for determining the final buffer density to an accuracy of about 0.05g/cm3 while not requiring sampling at the buffer stage of the coating operation. Methods using high-pressure mercury pycnometry were developed for measuring both the amount of open porosity and the geometric density of low-temperature isotropic (LTI) coatings. With this technique the LTI density can be measured with a precision of about 0.01g/cm3. A 15000C gaseous chlorine leach technique was shown to be useful for measuring defective particle fractions for both loose particles and particles bonded into fuel rods. An automated particle size analyser suitable for glove-box operation was developed with the capability of measuring particles at the rate of 1500/min. Techniques for measuring particle shape and strength were also developed and demonstrated to be useful. (author)