SENTINEL™ Selenium-75
Industrial Radioisotopes

SENTINEL Se-75 in Gamma Radiography

QSA Global, Inc.’s SENTINEL Se-75 radioisotope sources are double-encapsulated and sealed using laser welding for superior quality and safety. Radioisotope sources contain a quasi-spherical metallic pellet for the smallest possible focal dimension which minimizes Source-Film-Distance (SFD) and heightens sensitivity on fixed geometries.

Safety is our top priority. QSA Global, Inc. radioisotope sources are made of a patented vanadium-selenium metal alloy producing the highest possible thermal stability combined with physical strength and durability compared to commonly used elemental Se-75.

Our SENTINEL Se-75 radioisotope sources are available in maximum focal sizes ranging from 1.4 mm to 3.9 mm and nominal activities up to 90 Ci. (3.33 TBq).

SENTINEL Se-75 is designated for use within the steel thickness range of 0.20 in-1.57 in (5 mm-40 mm) per ISO 5579:2013.

SENTINEL Se-75 in Gamma Radiography

QSA Global, Inc.’s SENTINEL Se-75 radioisotope sources are ideal for controlling the size of the exclusion zone during radiographic exposures at congested work sites. SENTINEL Se-75 radioisotope sources are used on off shore oil rigs and at power generation plants during outages to reduce non-occupational worker exposure.

MaterialApproximate Material DensityApproximate Half-Value Thickness
Aluminum2.65 g/cm31.100 in (27.0 mm)
Steel7.80 g/cm30.315 in (8.0 mm)
Lead11.34 g/cm30.039 in (1.0 mm)
Tungsten17.80 g/cm30.032 in (0.8 mm)
Gamma Energy Range 66-401 keV
Steel Thickness0.20 in-1.57 in (5 mm-40 mm)
Aluminum / Titanium1.4 in-4.7 in (35 mm-120 mm)
Selenium-75 Half-Life120 days
Special Form Certifications

USA/0502/S-96, USA/0335/S-96

SENTINEL Se-75 Gamma-Ray Source Projectors

Small, light-weight SENTINEL Se-75 exposure devices can be used in difficult to access locations that x-ray generators cannot go due to their size, weight, and power requirements. 

SENTINEL Se-75 is the preferred isotope for our SCAR exposure devices to enable the safety exclusion zone at worksites to be minimized during radiographic exposures in congested areas.

QSA Global, Inc.’s SENTINEL Se-75 radioisotope sources

SystemAssembly NumberSpecial Form CertificateMax Capacity


View Certificate81 Ci (3.00 TBq)


View Certificate150 Ci (5.55 TBq)
A424-25WView Certificate150 Ci  (5.55 TBq)
A424-25WView Certificate80 Ci (3.00 TBq)
SENTINEL 959M SCARX540/1View Certificate81 Ci (3 TBq)
SENTINEL 989 SCARX540/1View Certificate20 Ci (740 GBq)

Loading & Unloading

QSA Global, Inc. offers a variety of options for SENTINEL Se-75 source changes to minimize downtime of your assets.  QSA Global, Inc. and our authorized distributors can reload your SENTINEL Se-75 device at local facilities around the world by trained technicians or sources can be delivered directly to your facility for reload by your trained technicians.

Transporting Isotopes

QSA Global, Inc. distributes radioisotope sources worldwide by utilizing the industry’s largest fleet of source changers.  Source changers are available to deliver a single source up to ten sources in a container for device reloads at your facility or at one of QSA Global, Inc.’s authorized service centers.

Isotope Disposition

Radioactive materials that are no longer required must be transferred to a licensed recipient for final disposition. QSA Global, Inc. provides a one for one exchange on SENTINEL Se-75 radioisotope sources