[en] The effect of neutron irradiation on cold worked, commercially pure A5 aluminum was investigated, utilizing scanning as well as transmission electron microscopy, and tensile measurements. During irradiation Si precipitates, while the dislocation density decreases suggesting a partial recovery. A threshold fluence of 2x10²¹ thermal neutrons/cm² was observed for nucleation of Si precipitation. No voids could be observed up to fluences of about 8x10²¹ thermal neutrons/cm². After an initial decrease in the ultimate tensile strength both ultimate tensile strength and elongation increase as functions of fluence. This is attributed to a combination of irradiation recovery and Si precipitation hardening. The mechanical properties are independent of the drawing direction. The results are discussed in terms of existing irradiation effect theories. (orig.)