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Analysis of an Energy Tuning Assembly for Simulating Nuclear Weapon Environments at the National Ignition Facility

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Journal Article - Embargoed Full-Text

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Air Force Institute of Technology Wright-Patterson Air Force Base United States

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An energy tuning assembly ETA was developed to spectrally shape the National Ignition Facility NIF deuterium-tritium D-T fusion neutron source to a notional thermonuclear and prompt fission neutron spectrum TNPFNS to approximate a boosted nuclear device. The spectrally shaped neutron environment can be used to create realistic synthetic post-detonation weapon debris that contain spectrally accurate fission products across all mass chains to enhance U.S. technical nuclear forensics capabilities for nuclear weapon attribution and device reconstruction. This research performed nuclear data covariance analysis through stochastic sampling techniques to predict the performance of an ETA to create the objective TNPFNS, assess anticipated experimental outcomes, and determine the expected fission products to be produced in a highly enriched uranium foil in the sample cavity. It was found that the nuclear data covariance affected the neutron fluence energy distribution by less than 5 percent for neutron energies above 1 keV in the sample region. The foil activation resulting from the perturbed fluence distribution was found to generally vary on the order of 35 but was as high as 20. The range of foil activation outcomes was used to show that neutron-flux unfolding techniques provided broad spectral agreement between the ETA and objective spectrum and resulted in an 80 probability of successful unfolding using STAYSL given the range of expected foil activities. This energy distribution was achieved at a total fluence of 4.9 x 1011 n cm-2 or - 1.4 in a 10-shake neutron pulse. More than 1 billion fissions, approximately of the order collected in nuclear forensics ground samples, were generated with a cumulative fission product distribution that matched the objective within current predictive capabilities.

Subject Categories:

  • Radioactivity, Radioactive Wastes and Fission Products
  • Test Facilities, Equipment and Methods

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