I believe this is an old beamstop which is placed here until its residual radioactivity has decayed to a safe level. The outside is only mildly radioactive. As this is not a public area, warning notices cautioning persons against loitering within a metre of so of the beamstop are sufficient precaution. Beamstops are placed at the end of the main beamlines to catch any particles that are not used in experiments mounted on the secondary beamlines.
