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The purpose of this work is to estimate shape of plutonium assemblies using new signatures acquired by passive NMIS measurements (no external source). Applications include identification of containerized regular shapes of plutonium, identification by shape without template, verification of shape for template initialization, and potential utility for estimating shape of holdup in plutonium processing facilities. To illustrate the technique and test its feasibility, laboratory measurements have been performed with californium spontaneous fission sources as a surrogate for plutonium. Advantages of the technique include the following: passive (requires no external source for plutonium measurements), stationary (no scanning of the assembly is required), penetrative (shape is estimated from neutron emissions), obscurable (spatial resolution can be deliberately degraded by changing detector size and/or timing resolution), inexpensive (majority of NMIS components are commercial products), portable (detection system is transported to the item, not vice versa). It is concluded that passive NMIS measurements can infer the mass of plutonium assemblies: NMIS correlations scale directly with spontaneous fission rate (Pu-240); NMIS correlations scale with fissile mass (Pu-239) and multiplication. New third-order correlations can estimate the shape of fission sources (Pu-240 & Pu-239) from passive measurements. Surrogate measurements of californium spontaneous fission sources have demonstrated the feasibility of this concept. Measurements of various shapes of plutonium are necessary to continue the development of this technique

PASSIVE NMIS MEASUREMENTS TO ESTIMATE SHAPE OF PLUTONIUM ASSEMBLIES (SLIDE PRESENTATION)