Concealed radioactive sources e.g. in commercial scrap are measured by a radiation detector (10) with a detector surface (12) which is moved past the object (20) and which is surrounded on the side facing th object by a screen surround (16) which may be in the form of a frame. A screen (14) covers the detector on the side away from the object. the screen surround may be replaced by a grid-like cover. The surround or cover consists of a material providing a shield to radioactive radiation and the detector is pref. a scintillation detector.
