[en] A simplified model for radiation-induced second-phase precipitation at point-defect sinks is proposed. The model yields a simple analytical expression for the shift of the solubility limit under irradiation. This shift is a function of the vacancy supersaturation, which includes kinetic parameters and the sink density. Qualitative agreement with the observed behaviour of the solubility limit of Si in Ni under irradiation is obtained. The model is shown to account only for extensions by irradiation of the two-phase fields of the phase diagrams, and points to yet unobserved behaviour of alloys under irradiation. (author)