High-Temperature Irradiation Experiments on Plutonium-Bearing Coated Particle Fuel

Plutonium-bearing coated particle fuel is being developed by the Dragon Project for use as a feed fuel in a feed and breed system for high-temperature reactors. To demonstrate the feasibility of irradiating this type of fuel in the Dragon Reactor a series of irradiation experiments on small representative fuel specimens have been conducted in purged capsule reactor loops at Studsvik, Sweden. These fuels have operated satisfactorily up to 37% fifa burn-up at temperatures in the reactor-operating range of 1200 to 1450°C at present envisaged, as well as up to 20% fifa burn-up at temperatures of 1850°C which represent credible accident conditions. Particular attention has been paid to the measurement of the release rates of fission products of importance in high-temperature reactor technology as well as to the possible release of plutonium from the fuel which under reactor conditions might lead to contamination of the primary coolant circuit. With fuel temperatures of 1450°C the highest release fractions measured were for 133Xe and 85mKr, and were about 5 X 10-5. Maximum release fractions for short-lived gases were in the region of 1 x 10-1. With fuel temperatures of 1850°C the release fractions o 133Xe were in the region of 10-2 . Solid fission product releases were at worst two orders of magnitude less than 133Xe. No evidence of plutonium release from the coated particles was detected in post-irradiation examination gamma-ray spectrometry. Post-irradiation metallographic examination showed excellent mechanical behaviour of the particles. (author)