Here's a Radioisotope I've Never Seen Used Before: Scandium-46.

[NNadir]

Scandium is an element in the periodic table about which I seldom think. Older literature I had laying around led me to believe that only a few kg of the metal had been prepared, but looking into the Wikipedia page, I discovered that a few tens of tons of the metal are produced each year.

I was surprised therefore to come across this paper, which caught my eye because of my love for radioactive things:

Solid Flow Mapping at the Bottom Section of a Pilot-Plant Scale Riser with the Help of a Radioactive Particle Tracking Technique Trilokpati Tribedi, Pankaj Tiwari, Harish Jagat Pant, and Rajesh Kumar Upadhyay Industrial & Engineering Chemistry Research 2023 62 (45), 19133-19144

The issue was to study aspects of the flow in a chemical engineering tool known as a circulating fluidized bed. It's described briefly in the text:

Circulating fluidized beds (CFB) have attracted enormous interest in large-scale process industries like metallurgy, petrochemicals, and energy. (1) The CFBs have been widely used in combustion, catalytic cracking, and synthesis due to their benefits, including good heat and mass transfer performances, high efficiency in gas–solid contact, and status as a classic gas–solid contact reactor. In 1922 Winkler first used fluidized bed for coal gasification. The number of fluidized beds and circulating fluidized bed reactors has increased manifold over the past century. (2) In a reactor similar to a circulating fluidized bed, the structure of the gas–solid flow affects heat, mass, momentum transfer, and particle residence time. These variables directly affect the reaction rate and yield while also regulating the overall performance of the reactor. When the solid particles are distributed evenly, the overall efficiency of the riser is increased. However, most of the CFB operates at a high solids circulation rate and low gas flow rate, which causes both axial and radial uniformity of solid concentration. (3) Gas–solid flow in a riser can have distinct radial and axial flow structures based on gas flow rate, solid flux, and riser geometry. In general, axial flow structures are described as having a dense bottom region, a diluted upper section, and a transition region in between them. Based on the exit geometry of the riser, a relatively dense region can occasionally be seen at the top.

Most of the solid velocity data are reported in the literature (4−10) at the middle section or fully developed section of the riser. Some researchers (11−14) have investigated the influence of the outlet configuration on the flow pattern in CFBs using computational fluid dynamics (CFD). De Wilde et al. (13) have reported that strong restrictions on outlet geometry can alter flow patterns throughout the riser. The exit effect, however, is only visible in the immediate proximity of the outlet section in no-restricted outlet configurations...

To study the behavior of this widely used but not entirely understood device, the authors inserted glass beads impregnated with Sc⁴⁶ among the solid particles and followed their locations by the use of scintillation detectors:

...Detailed experimental setup configuration has been presented already in previously published (9,19) works for the middle section and residence time distribution (RTD) measurements. The radioactive particle tracking (RPT) technique is used to track the motion of the solid phase. In the current experiment, a tracer particle made of the high-energy 46Sc isotope is doped in a glass bead of the same size as the bed material used as the solid phase. Ten scintillation (NaI) detectors are installed strategically around the riser’s bottom section from 30 to 80 cm. Details of detector positions are provided in the Supporting Information section, Table S1...

Sc⁴⁶ has a half-life of around 84 days.

Reference 9 is this one: Measurements of Solid Velocity in a Pilot-Scale Geldart’s Group B Circulating Fluidized Bed Using a Radioactive Particle Tracking Technique Trilokpati Tribedi, Premsagar Pillajetti, Roushni Kumari, Harish Jagat Pant, Pankaj Tiwari, and Rajesh Kumar Upadhyay Industrial & Engineering Chemistry Research 2022 61 (25), 9110-9121

I seem to have overlooked that paper last year during my regular reads of this journal. Possibly I was distracted by writing this post about other radioactive stuff more commonly available:

Defective TiO2/CdS for the Photochemical Reduction of CO2; the Capture of Radioactive Cesium.

Have a happy Thanksgiving.