Nuclear forensics techniques for attributing material used in a radiological dispersal device event

If a radiological dispersal device (RDD) is detonated in the U.S. or near U.S. interests overseas, it will be crucial that the actors involved in the event can be identified quickly. Law enforcement officials will need information concerning the material used in the device, specifically what type of material it was and from where it originated. This information will then be used to help identify the specific individuals who manufactured the device and perpetrated the event. Texas A&M University and Los Alamos National Laboratory are collaborating on the development of a technique for identifying the material used in a radiological dispersal device. This methodology is currently focused on radiological dispersal devices that make use of spent nuclear fuel as the source material. The methodology developed makes use of both a forward model and an inverse model to identify specific spent fuel characteristics using isotopic composition of RDD debris. The forward model is based on sophisticated reactor physics calculations for the prediction of spent fuel isotopic compositions as a function of fuel type (e.g., PWR, BWR, CANDU, RBMK, etc.), fuel burnup (in MWd/MTHM), fuel age (in years since permanent discharge from the reactor), and operating characteristics (e.g., operating power level, timemore » at power, etc.). These reactor physics calculations are benchmarked to measured data to establish their accuracy in predicting isotopic compositions. The inverse model makes use of a Bayesian inverse method to identify the specific spent fuel assembly (or assemblies) used based on measurements of actinide and fission product isotopic ratios in the RDD debris. A description of both the forward and inverse models, accuracies of the technique, and the results to date are given.« less