Promethee: An alpha low level waste assay system using passive and active neutron measurement methods

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[alpha] (about 50 mug 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 Pu-239 in total active neutron counting, and 0.08 mg of effective Pu-239 coincident active neutron counting, may currently be detected (empty cavity, measurement time of 15 min, neutron generator emission of 1.6 x 10(8) s(-1) [4pi]). 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.