A radiation monitor based on a cast polystyrene scintillator with wavelength-shifting optical fibers is described, which has a large aperture; the dimensions of the active part of the detector are 100 × 200 × 5 cm. The monitor also includes a sensor for the presence of a monitored object and a television camera, united by a single control system. The monitor is designed to control transportation of radioactive materials. The operating experience is described.