RAPID ASSAY OF TRACE SNM USING SHORT-LIVED FISSION PRODUCT MEASUREMENTS

Quantifying the fissile content of Special Nuclear Material (SNM) is of great importance to the materials management community and has traditionally relied on Destructive Assay (DA) measurements or passive detection of gamma/neutron signatures through Non-Destructive Analysis (NDA). These methods are highly accurate and employed globally as both a nuclear forensics capability and a material accountability measurement. However, common DA techniques rely on sample dissolution, a time-consuming process which can be particularly difficult for certain sample matrices. Likewise, trace quantities of SNM prove difficult to measure using NDA techniques due to relatively low emission rates and potentially activated materials in the sample matrix. Research being conducted at the Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR) aims to establish a fissile material assay method that can address these challenges for trace sample analyses. The Neutron Activation Analysis (NAA) lab at HFIR currently supports the International Atomic Energy Agency’s Network of Analytical Laboratories (NWAL) by characterizing trace quantities of uranium in environmental samples of safeguards interest. Each reactor cycle, the NAA lab analyzes dozens of samples with a reporting time of less than two weeks. The NAA lab has continued to reduce this time of analysis by using HFIR pneumatic transfer tubes with high-resolution gamma spectroscopy at short decay times to evaluate short-lived fission products. The method being currently researched has shown to be capable of analyzing nanogram quantities of uranium and plutonium samples in a time period of less than ten minutes.