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.

Definition

Ir-192 is a man-made radioactive isotope with a 74-day half-life and an average gamma energy of about 0.38 MeV. It is the workhorse isotope for industrial field radiography on carbon steel weldments and pipework in the typical 10–75 mm thickness range.

Technical Context

Strength decays to half every 74 days, so exposure times must be recalculated frequently. The HVL in steel is approximately 13 mm.

What it is

Iridium-192, the workhorse gamma source of industrial radiography — energies averaging around 0.35 MeV and a 74-day half-life, suited to steel in the mid-thickness range most piping and vessel work occupies.

Correct use

The short half-life means activity planning is part of scheduling: a source near the end of its working life doubles exposure times. Source changes, transport and bonded storage are regulated activities with real lead times.

Governing standards

ASME Section V Article 2 bounds usable thickness ranges by source; transport under IAEA regulations; possession under national licensing.

The usual mistake

Stretching an aging source with ever-longer exposures. Beyond a point scatter degrades contrast faster than exposure compensates, and the images stop meeting IQI sensitivity even though density looks right.

Where Iridium-192 fits in an inspection programme

A term is only useful when it connects to a decision. Iridium-192 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.
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.

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.