Fundamental Fission Signatures and Their Applications to Nuclear Safeguards

The Los Alamos Scientific Laboratory is presently involved in a research and development program in the technology of inspection and identification of fissionable material to meet the growing need for more effective national and international controls over nuclear materials. The implementation of an effective nuclear safeguards and materials management system requires direct physical methods of detecting, identifying, and quantitatively analysing fissionable materials in various practical configurations. Practical active interrogation methods are being developed using sources of neutrons to induce fissions in the material under investigation. In these methods, quantitative assay is based on detailed observations of the delayed and prompt neutrons and gamma rays from fission. The characteristic differences in the yields and kinetics of delayed neutrons from the various fission species provide a unique method for analysis of individual fissionable isotopes in unknown mixtures; assay methods using these signatures are described. To investigate fully all possible signatures of individual fissionable isotopes, one must have detailed knowledge of the various emissions associated with the fission process. For this reason, a number of fundamental measurements of these emissions are being performed at Los Alamos. A review of our delayed neutron and gamma-ray work is presented. (author)