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.
Definition
Co-60 emits two gamma rays at 1.17 and 1.33 MeV — much higher than Ir-192 — giving deep penetration suitable for thick-walled pressure vessels and large castings. Its 5.27-year half-life means slower decay and longer source life.
What it is
Cobalt-60, a gamma source with photon energies around 1.17 and 1.33 MeV and a half-life of roughly five and a quarter years. The high energy gives penetration through thick steel that lower-energy sources cannot reach.
Correct use
Chosen for heavy wall sections where iridium cannot deliver adequate density. The penalty is contrast: high energy reduces subject contrast, so sensitivity on thin material is poor and shielding requirements are substantially greater.
Governing standards
ASME Section V Article 2 governs its use in radiographic examination and constrains material thickness ranges by source; transport and licensing follow national regulation and IAEA transport provisions.
The usual mistake
Using it on thin sections because it is what is in the camera. Energy must match thickness; an oversized source on thin wall produces a flat, low-contrast image that will not meet IQI requirements.
Where Cobalt-60 fits in an inspection programme
A term is only useful when it connects to a decision. Cobalt-60 appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.
Related terms
- 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.
- 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.
- 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.
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.