Investigating a new production reaction and purification procedure for americium-240

Paul Ellison, University of California, Berkeley

It is desirable for nuclear forensics and stockpile stewardship science to experimentally measure the neutron-induced fission cross section of americium-240. The smallest amount of material that such a measurement can be performed upon is 10-100 nanograms. Because of its half-life of 50.8 hours, the production of this amount of pure americium-240 is a difficult task. Thus, the goal of my research to develop a production and purification procedure for americium-240 on the 10-100 nanogram scale.

Production of americium-240 on any scale takes place via a nuclear reaction using either a particle accelerator or a nuclear reactor. To produce americium-240 on the 10-100 nanogram scale such a nuclear reaction must be carefully chosen to maximize its production rate. The bombarding of plutonium-242 with protons at an energy that preferentially evaporates three neutrons from the compound nucleus has been predicted to have a high americium-240 production probability (Mashnik, et al., LANL Report LA-UR-05-7321, Los Alamos (2005)). However, this production reaction has not been previously studied experimentally. We are experimentally investigating this reaction and assessing its feasibility to produce 10-100 nanograms of americium-240.

A second part of my research is to develop a procedure for isolating the americium-240 produced in the above nuclear reaction. When producing americium through this method, it is made in quantities much smaller than the plutonium from which it is formed. Thus, to produce a pure americium-240 sample, one must perform an effective separation to isolate the 10 nanograms of americium-240 from hundreds of milligrams of plutonium-242. During the americium-240 production reaction very small quantities of fission products and other undesirable reaction products are being produced that also require separation from the americium.. Several methods including liquid/liquid extraction and extraction chromatography are being investigated to effectively perform these separations.

Abstract Author(s): Paul A. Ellison, Zuzana Dvorakova, Liv Stavsetra, Heino Nitsche