Year
2013
Abstract
Identification of device characteristics from nuclear fallout shortly after a low-yield nuclear detonation can provide important clues to nuclear forensics investigators. The gamma radiation emitted from this fallout possesses features that can be used to identify the materials used in the construction of the device as well as the type of reaction which powered the detonation. Building upon previous work by Monterial et al. [1], this work identifies characteristics of the short time period gamma spectra emitted by fallout that can be used to determine whether the device was primarily powered by a 239Pu or 235U core and whether the detonation primarily produced a fission neutron spectrum or a high energy spectrum characteristic of fusion. The Defense Land Fallout Interpretive Code (DELFIC) [2] was used to simulate fallout from a 10kt ground burst of U and Pu devices at time periods of one day to one month after the event, when gamma ray characterization is expected to be conducted. These simulations were analyzed to identify distinctive characteristics of each gamma spectra (U vs. Pu, fission vs. fusion) for use in device identification. To check for possible sources of interference in the gamma spectra, 238U fission was also simulated and a detailed soil model was developed to check for the presence of neutron activation products that may be present in the fallout.