[en] Runaway electrons are a good probe of magnetic turbulence. They suffer very rare collisions and are little sensitive to electrostatic turbulence, therefore their transport is mainly governed by magnetic structure. The modification of this one by magnetic turbulence will influence the runaway electron confinement and the rate of runaway production. Experimental results on runaway confinement time are conflicting: In some tokamaks, runaway confinement time, τ_r, is about thermal electron confinement time and in other ones is many times longer. These discrepancies can be explained in terms of magnetic turbulent transport if the dependence on energy of the diffusion coefficient is considered. In the TJ-I tokamak, runaway confinement time has been deduced from HXR spectra measured by an NaI(Tl) detector, using a simple dynamic model; the intensity spectra are fitted by a single slope between the lowest detected energy and energies with sufficient statistics. Results are obtained under very different plasma conditions, and τ_r at the maximum of plasma current ranges from 0.2 to 2.5 ms. (author) 5 refs., 2 figs