[en] This study was undertaken to investigate the long-term performance of elemental iron as reactive material for the removal of uranium in passive groundwater remediation systems. By using ²³⁷U as a radioindicator it was possible to track the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and iron was found to be 1:(1390±62). The reaction between iron and uranium is of pseudo first-order kinetics and the rate constant was measured to be (1.1±0.09)x10^-3 s^-1. These data enable the calculation of ideal lifetime for permeable reactive barriers (PRB) using iron for uranium removal neglecting hydrological factors that may impair the function of PRBs