241Am/Be source optimum geometry for DSRS management-based Monte Carlo simulations

Abstract

The geometry form related to 241Am/Be spontaneous neutron sources has been investigated to evaluate the most optimizing geometry for disused sealed radioactive source (DSRS) disposal. Nine source geometries were assessed: point, disk, sphere 1, sphere 2, sphere 3, cylinder 1, cylinder 2, rectangle 1, and rectangle 2. The most radiological optimizing geometries were found to be the disk, followed by the point source, sphere 1, and cylinder 1, while the rectangle or parallelepiped 2 source forms were the worst cases. Neutron and photon generated fluxes were computed, and the parallelepiped 2 source geometry generated the lower value of flux inversely to the effective dose rate computed in the decision-making area, where it was found to be the highest value. The obtained results were in agreement with the as low as reasonably achievable principle for the exposure rate optimization. The obtained exposure dose rates were found to be <∼2 µSv/h (maximum value on horizontal calculation) and 1.75 µSv/h (maximum value on vertical computation), which are lower than the 2.5 µSv/h acceptable limit for the public area. Whenever possible, the DSRSs should be pressed into a disk form (or a cylindrical form with a small height) before embedding them into the Am1 P60 capsule for disposal purposes. The dose profile for the 241Am/Be source obtained, the neutron flux, and the gamma generated from neutron absorption showed agreement with the expected experimental physical data. The supported data contribute to postulate that Monte Carlo methods are effective computational tools that can be used to select the most effective radioactive waste form for disposal purposes.