Progress toward a new production reaction and purification procedure for americium-240

Paul Ellison, University of California, Berkeley


Due to its role in nuclear forensics and stockpile stewardship science, it is desirable 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. This poster summarizes my recent efforts to investigate a new nuclear reaction for the production and purification of americium-240 on the 10-100 nanogram scale.

I have been working to investigate a new production reaction for americium-240 that involves the bombarding of plutonium-242 with protons at an energy that maximizes the evaporation of three neutrons of the compound nucleus. Over the past year, I have made major improvements to our experimental apparatus and procedures for studying this nuclear reaction. Improvements have been made to the process of producing the plutonium-242 targets for irradiation. Also, several improvements are being made to the cyclotron to allow for more safe and reliable cross section measurements of these targets to be made. Once a few more measurements are made, we will be able to assess the feasibility of producing americium-240 on the 10-100 nanogram scale using this new nuclear reaction.

A second part of my work involves investigating a method for the isolation of the americium-240 produced in the above-discussed reaction. Because the amount of americium-240 produced will be very small compared to the amount of plutonium-242 (10^7 times less), the separation procedure
must be very efficient at chemically separating americium from plutonium. Over the past year, we have made significant progress toward developing such a procedure. By combining several anion exchange and extraction chromatography steps, we have experimentally performed small scale separations similar to the large scale separation of an irradiated plutonium-242 target.

Abstract Author(s): P.A. Ellison, L. Stavsetra, Z. Dvorakova, H. Nitsche