Abstract
Nuclear forensic teams will be deployed to collect and evaluate fallout samples on the ground in the scenario of a low-yield nuclear detonation in a heavily populated area. Quick non-destructive methods of predicting the quality of the sample before it is analyzed in detail are essential for efficient post-event collections. In this work, the process of exporting Defense Land Fallout Interpretive Code (DELFIC) results into Gamma Detector Response and Analysis Software (GADRAS) has been automated within the Fallout Analysis Tool. This coupling allows for the simulation of detector responses to fallout samples with varying degrees of fractionation. The degree to which the samples are fractionated depends on the location of the samples in the fallout field. In the following study, this phenomenon is examined, as its understanding is important to the investigation of debris distribution. The simulated detector spectra from GADRAS can be used to compare peak ratios of volatile-refractory isotope pairs in order to determine the degree of fractionation. Simulated fractionated fallout samples from DELFIC for a 10 kt, pure 235U fission surface burst were modeled for distances ranging to 256 km out from ground zero, and for times up to 1 week from detonation. The fractionation ratios, also known as r values, from isotope concentrations, photon lines and peak areas of four volatile-refractory pairs were calculated and compared. Fractionation prediction via the peak areas method was evaluated for each pair by comparing the results with the simulated radionuclide inventory.
