Fragmentation of Coated Particle Fuel Using Welding Techniques

This paper provides results of small-scale feasibility tests concerning fragmentation of HTR fuel particles in view of their reprocessing and/or separation from their coatings to reduce the waste volume. Tests were performed on small amounts of surrogate fuel particles originally received from CEA France for characterization purposes. Experiments were successfully carried out using standard TIG welding equipment. An acetylene torch test was also conducted. The investigated parameters included: AC/DC, voltage, current, exposure time, electrode type, electrode size, crucible shape etc. In most tests, only 20 new surrogate particles were submitted to an electric arc. After exposure, the intact particles, intact kernels and debris were counted and the number of broken particles was used as performance indicator. Conditions were identified, which fragmented 100% of the treated particles. The energy consumption of the process is small. Three failure mechanisms are suspected, namely thermomechanical fragmentation of the SiC coating followed by oxidation of the graphite coatings, and eruption of molten kernel material from a particle. The process would require some further work to qualify it for higher material streams and other aspects of industrial relevance. These tests cannot currently be performed due to the unavailability of sufficient amounts of surrogate particles. (author)