The low-field Hall coefficient R0of irradiated aluminium at 4.6 K is independent of the Frenkel defect (FD) concentration, however sensitively dependent of their configuration. Since measurement of R0is not too difficult, rather extensive investigations of FD clustering during irradiation can be performed, but only qualitative interpretations are possible. We have irradiated several pure Al samples with reactor neutrons at 4.6 K up to very high dosestresp. resistivity increments Δρ0(maximum 91% of extrapolated saturation value Δρ0sat≈ 980 nΩcm). Our main results are: