Determination and Simulation of the Neutron Spectrum of Nuclear Detonations and Surrogate Sources
Technical Report,01 Oct 2019,01 Mar 2020
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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This research determined a methodology for characterizing the Fast Beam Facility FBF at The Ohio State University Nuclear Reactor Laboratory to test the response of photovoltaic arrays to nuclear weapon radiation. Additionally, this research developed neutron and gamma nuclear weapon output spectra of two environments for comparison to the FBF spectrum. A Bonner sphere spectrometer BSS, coupled with the unfolding program Maximum Entropy Deconvolution MAXED, was employed as a means of determining the energy spectrum of neutrons. Using the ISO 8529 americium beryllium AmBe source as the a priori default spectrum, MAXED was used to unfold the spectrum of neutrons detected using the BSS from a 500 mCi AmBe source. An MCNP model of the experiment was created with the ISO 8529 spectrum used as the neutron source spectrum. The resulting unfolded neutron spectrum has similar characteristics to the ISO 8529 reference spectrum, with peaks located at 3.1 and 4.7 MeV corresponding to the peaks of the reference spectrum. Spectral deviations from the ISO 8529 reference spectrum caused by low-energy, non-neutron interaction events or neutrons thermalized through interactions in the experimental environment are accounted for in the model and reflected in the final unfolded neutron spectrum. Next, the neutron and gamma ux received at a fixed photovoltaic array from two detonation scenarios were modeled with MCNP6 a ground-only and a single building model for various height-of-bursts and yields. Thermalization due to neutron interaction and scattering of gamma rays with environmental materials is observed in the spectrum of resulting radiation incident on the photovoltaic array.
- Nuclear Instrumentation