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.
Highlights
In recent decades, industrial and medical applications involving the use of radiation sources have been spreading all over the world
The PHITS (Particle and Heavy Ion Transport code System) Monte Carlo computer code was used to compute fluxes and radiation dose rates generated by neutron and gamma radiation from 241Am/Be sources considered as disused sealed radioactive sources (DSRSs) to be disposed of
The investigated geometry forms together with their characteristics are presented in Table I, which are the point-like source, disk source, spherical source, cylindrical source, and rectangular or parallelepiped solid
Summary
Industrial and medical applications involving the use of radiation sources have been spreading all over the world. According to radiation protection principles, manufacturing of these radioactive sources requires geometry optimization in view of minimizing self-absorption To this extent, point-like and disk geometries have proven to be more adequate and economic than other geometry forms. The present study is thereby to investigate the optimizing geometry among the point-like source, disk source, spherical source, cylindrical source, and rectangular or parallelepiped solid available to be used for the disposal of 241Am/Be neutron sources To this extent, the PHITS (Particle and Heavy Ion Transport code System) Monte Carlo computer code was used to compute fluxes and radiation dose rates generated by neutron and gamma radiation from 241Am/Be sources considered as disused sealed radioactive sources (DSRSs) to be disposed of
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