Studies on the Amoeba Effect: Carbon Transport in Coated Fuel Particles under Temperature Gradient

The amoeba effect in coated carbide and oxide fuel particles has been analyzed and proposals for a stabilization of the two types of particles have been made. In a series of out-of-pile measurements, the stabilizing effect of nitrogen doping in UC₂ or substituting of the UC₂ phase by U(C,N) or (U,Zr)(C,N) phase could be demonstrated. In-pile, a number of fuel particles having different kernel composition was- irradiated. The quantitative evaluation of this test has shown that the susceptibility of oxide particles to amoeba attack can essentially be reduced by doping with small amounts of carbide which getters excess carbon monoxide.