Photonuclear activation of pure isotopic mediums.

Grohman, Mark A. ; Lukosi, Eric Daniel

Sandia National Laboratories

关键词: Time Resolution;    Attenuation;    Photons;    Photonuclear Reactions;    Thickness;   

DOI  :  10.2172/993310
RP-ID  :  SAND2010-5430
RP-ID  :  AC04-94AL85000
RP-ID  :  993310

美国|英语

来源: UNT Digital Library

【 摘 要 】

This work simulated the response of idealized isotopic U-235, U-238, Th-232, and Pu-239 mediums to photonuclear activation with various photon energies. These simulations were conducted using MCNPX version 2.6.0. It was found that photon energies between 14-16 MeV produce the highest response with respect to neutron production rates from all photonuclear reactions. In all cases, Pu-239 responds the highest, followed by U-238. Th-232 produces more overall neutrons at lower photon energies then U-235 when material thickness is above 3.943 centimeters. The time it takes each isotopic material to reach stable neutron production rates in time is directly proportional to the material thickness and stopping power of the medium, where thicker mediums take longer to reach stable neutron production rates and thinner media display a neutron production plateau effect, due to the lack of significant attenuation of the activating photons in the isotopic mediums. At this time, no neutron sensor system has time resolutions capable of verifying these simulations, but various indirect methods are possible and should be explored for verification of these results.