A bulk material analyser (10) and method of assembly for analysis of bulk material on a conveyor belt (11) passing through the analyser (10) between a radiation source (12) and a radiation detector (13). The analyser (10) includes a generally C-shaped housing (14) extending around an open-sided aperture (15) for passage of the belt (11). The housing (14) is substantially filled with radiation shielding material (17) to provide radiation shielding around the aperture (15). A removable block (18) of radiation shielding material closes the open side of the aperture (15) and provides surrounding radiation shielding of the aperture.