Gamma Source

A gamma source is a sealed radioactive isotope used in industrial radiography to produce penetrating gamma rays for inspecting thick or remote components without an external power supply.

Definition

A gamma source is a sealed radioactive isotope housed in a shielded exposure device (camera). Common industrial isotopes are Iridium-192, Cobalt-60, and Selenium-75. Unlike an X-ray tube, a gamma source cannot be turned off and decays continuously, requiring strict ALARA handling.

Technical Context

Activity is measured in Curies (Ci) or Becquerels (Bq). Source strength determines exposure time; energy spectrum determines penetration. Gamma radiography offers portability and high penetration in field conditions.

Related terms

Iridium-192 (Ir-192) — Iridium-192 is the most common industrial radiography isotope, providing gamma energies around 0.3–0.6 MeV and a 74-day half-life, suitable for inspecting steel between approximately 10 mm and 75 mm.
Cobalt-60 (Co-60) — Cobalt-60 is a high-energy gamma source (1.17 and 1.33 MeV) with a 5.27-year half-life, used for radiography of thick steel sections from approximately 50 mm to 200 mm where Ir-192 cannot penetrate.
Selenium-75 (Se-75) — Selenium-75 is a low-energy gamma isotope (average 0.22 MeV, 120-day half-life) used for radiography of thin steel sections from approximately 5 mm to 30 mm, offering better contrast than Ir-192 on light wall material.
Half-Value Layer (HVL) — The half-value layer (HVL) is the thickness of a specified material required to reduce the intensity of a beam of radiation by half, used to characterize radiation penetration and design shielding.
ALARA (As Low As Reasonably Achievable) — ALARA is the regulatory principle requiring that radiation exposures be kept "as low as reasonably achievable", applied through the trinity of time, distance, and shielding controls to minimize dose to workers and the public.
Radiation Safety Officer (RSO) — A Radiation Safety Officer (RSO) is a designated person responsible for ensuring the safe use of radioactive materials and X-ray devices within an organization, including ALARA compliance, training, dose monitoring, and regulatory liaison.

More equipment terms

Calibration Block · Transducer · Dual-Element Probe · Angle-Beam Probe · Normal-Beam Probe · Couplant · Reference Reflector · Side-Drilled Hole · Flat-Bottom Hole · Notch Reference

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.