The development of a passive-active neutron assay system for alpha low level waste characterization at the French Atomic Energy Commission is discussed. Less than 50 Bq[] (about 50 g Pu) per gram of crude waste must be measured in 118-l "European" drums in order to reach the requirements for incinerating wastes. Detection limits of about 0.12 mg of effective 239Pu in total active neutron counting, and 0.08 mg of effective 239Pu coincident active neutron counting, may currently be detected (empty cavity, measurement time of 15 min, neutron generator emission of 1.6 × 108 s-1 [4]). The most limiting parameters in terms of performances are the matrix of the drum - its composition (H, Cl...), its density, and its heterogeneity degree - and the localization and self-shielding properties of the contaminant.