A beam shaping assembly (10) used in a neutron capture system and capable of changing an irradiation range of a neutron beam. The beam shaping assembly includes: a beam inlet (11), a target (12), a moderator (13) adjoining the target (12), a reflector (14) surrounding the moderator (13), a thermal neutron absorber (15) adjoining the moderator (13), a radiation shield (16) arranged inside the beam shaping assembly (10), and a beam outlet (17). The beam shaping assembly (10) further includes replacement components (21, 22) that can be attached to and detached from the beam shaping assembly (10) to change the irradiation range of the neutron beam.
