Behaviour of radioactive impurities in DFR primary liquid metal coolant

The use of a vented metallic fuel of uranium-molybdenum alloy as the driver charge in DFR has led to the contamination fo the coolant by fission products and fissile material. the design of the reactor has made it difficult to study the behaviour of these impurities to the extent which would be necessary to assemble a detailed picture of their behaviour in the circuit, but by taking advantage of opportunities which have arisen from time to time, some information has been obtained on the longer lived fission products and other radioactive contaminants, associated with components of the primary coolant circuit. This paper outlines this information and discusses the results in relation to the general question of fission product and fissile material behaviour in sodium systems.