Report on Work at A.E.R.E. for the Dragon Project. April - October, 1965. Dragon Project Report

A report on the irradiation behaviour of this type of fuel is being published. The behaviour is assessed in terms of the four experimental techniques used for fuel study, viz. metallography, 'in-pile' gas release, 'post irradiation annealing' gas release, and solid fission product release. Results from over seventy fuel compacts examined metallographically have shown that these fuel particles withstand a wide range of irradiation conditions (temperatures 800-1600°C, burn-ups 0.2-10% fima) without any Signs of failure. At higher temperatures, 1900°C, the coating remained mechanically intact but the fuel migrated outwards through the coatings The results on solid fission product release are fewer and scattered, but , show the expected reduction in release of mobile metal products, e.g. Sr, by a factor of 10-100 compared with that from plain pyrocarbon coated particles; long-lived fission gas release from these particles (R/B values) are of the order 10^-5 at 1000°C (10^-4 at 1500°C). Evidence suggests, however, that the actual release from intact particles is considerably lower (10^-6 at 1300°C), and that the observed release comes from approximately 1% of the particles which were broken during either fabrication or handling.