Analysis of Production Mechanisms for Several Radioisotopes and Isomers, and Analysis of Radiation from a Bulk Emitter

Author(s):

Jarrod C. Marsh, James J. Carroll, and Christopher J. Chiara

Abstract:

The ARL Nuclide Science Team analyzed potentially useful isotopes, including those with metastable isomeric states, for a heat source and their production methods, and radiation outputs are discussed. Production pathways for various candidates were analyzed using cross sections extracted from the literature. ^242mAm is the easiest to produce using current neutron-capture techniques assuming steps are taken to minimize burnup in the reactor before sample extraction. ¹⁷⁰Tm and ^242mAm have similar production rates. Dose rates were estimated using Geant4 simulations of radiation emitted within a simple volume of radioactive material to examine self-shielding estimates related to the external dose rate. The simulations confirm nonlinear scaling between the physical size of the radioactive source and the external dose. This demonstrates that the thermal output can be improved by increasing the size of the source without significantly increasing the external dose.