We present results of studies of formation mechanism of luminescence centers of the blue range in lithium fluoride crystals. We found that the centers under study are intrinsic defects of crystal lattice formed as a result of a radiation-thermal process in the temperature range much higher than room temperature. Experimental confirmation of simultaneous formation of these centers and F3+ centers, the increase in their concentration during thermal destruction of F3+ centers, and absence of the phonon structure characteristic of R2 centers give basis to attribute the considered centers to a stable configuration of intrinsic radiation defects constituting isomer of F3 center.