Radiographic testing (RT) is one of the core methods of non-destructive testing (NDT). It uses X-rays or gamma rays to see inside a part — a weld, casting, composite panel, circuit board or battery — without cutting it open. The physics is the same as security screening, but the goal is different: instead of finding a threat among unknown contents, NDT looks for defects in a known part and judges them against an acceptance standard.
Main system types
Cabinet X-ray systems
Self-shielded enclosures in which the part is placed for inspection. Used for castings, small components, electronics and quality-control sampling. In the US, cabinet X-ray systems are regulated by the FDA under 21 CFR 1020.40, the same performance standard that covers baggage X-ray cabinets.
Film, computed and digital radiography
- Film radiography remains in use and is still the reference method in many codes.
- Computed radiography (CR) uses reusable phosphor imaging plates read by a laser scanner; it replaces film in many field applications.
- Digital radiography (DR) uses flat-panel or line detectors that give an image within seconds, allowing real-time inspection and automated defect recognition on production lines.
Industrial computed tomography (CT)
The part is rotated in front of the source and hundreds or thousands of projections are reconstructed into a 3D volume. CT shows the size and position of internal features, can measure internal dimensions (metrology) and compare a part with its CAD model. It is slower and more expensive than 2D radiography but gives far more information. Microfocus and nanofocus tubes allow very high resolution on small parts.
Field and high-energy radiography
Pipeline welds and large structures are often inspected on site with portable X-ray tubes, pipeline crawlers or gamma sources (iridium-192, selenium-75, cobalt-60). Very thick sections, such as large castings or rocket motors, are inspected with MeV linear accelerators in shielded bunkers. See portable X-ray.
What radiography finds
- Welds: porosity, slag inclusions, lack of fusion or penetration, cracks (depending on orientation), undercut and burn-through.
- Castings: shrinkage, gas porosity, inclusions, cold shuts.
- Composites: voids, foreign objects, some delaminations (CT is better than 2D for planar defects).
- Electronics: solder voids in BGAs, bridging, misaligned components, wire bond defects.
- Assemblies: missing or misplaced parts, foreign object debris.
Radiography is less sensitive to thin planar flaws, such as cracks or laminations, that lie perpendicular to the beam; ultrasonic testing is often used alongside it for that reason.
EV batteries and welded joints
Electric-vehicle manufacturing has become a major use of X-ray NDT. Typical applications include checking electrode alignment and overhang in cylindrical, prismatic and pouch cells, detecting foreign particles, and inspecting welds between cell tabs and busbars (laser or ultrasonic welds) for porosity, cracks and incomplete bonding. Inline 2D/2.5D systems are used for high-volume checks, and CT for process development and failure analysis. Weld integrity in battery packs is commonly verified with a combination of X-ray/CT, electrical resistance measurement and destructive sampling. Commercially available systems come from industrial X-ray suppliers such as Waygate Technologies (Baker Hughes), Comet Yxlon, Nikon, Zeiss, North Star Imaging and a number of Asian manufacturers specialising in battery inspection.
Standards and codes
| Standard | Scope |
|---|---|
| ISO 17636-1 / -2 | Radiographic testing of fusion-welded joints with film / digital detectors |
| ISO 10675 | Acceptance levels for radiographic testing of welds |
| ASME BPVC Section V, Article 2 | Radiographic examination for boiler and pressure-vessel work |
| ASTM E94 / E1742 | Guide and practice for radiographic examination |
| ASTM E1570 | Practice for fan-beam computed tomography examination |
| API 1104 | Welding of pipelines, including radiographic acceptance criteria |
The applicable standard is set by the product code or customer contract; always use the current edition.
Personnel qualification
NDT results are only as good as the people who perform and interpret them. Common schemes:
- ASNT SNT-TC-1A — a recommended practice under which the employer writes a written practice and certifies its own Level I, II and III personnel; widely used in the US.
- ANSI/ASNT CP-189 — a standard (rather than a recommended practice) for employer-based qualification.
- ISO 9712 — third-party, central certification of NDT personnel, common in Europe and internationally.
- NAS 410 / EN 4179 — aerospace-specific qualification and certification requirements.
Separately from NDT certification, radiographers working with gamma sources or open X-ray installations need radiation safety training, and in the US industrial radiographers using sealed sources must meet NRC 10 CFR Part 34 or Agreement State requirements.
Radiation safety
Cabinet systems are designed so that leakage outside the enclosure stays below regulatory limits, with interlocks that cut the beam when doors open. Open installations and field radiography rely on shielded rooms, controlled areas, warning signals, survey meters and personal dosimetry. See shielding and facility layout and radiation safety.
Frequently asked questions
What is an NDT X-ray inspection system?
It is equipment that uses X-rays to image the inside of a part — such as a weld, casting or electronic assembly — to find defects without damaging it. Systems range from shielded cabinets to digital radiography lines and industrial CT scanners.
What is the difference between digital radiography and CT in NDT?
Digital radiography produces a single 2D projection quickly; CT combines many projections into a 3D volume, showing defect position and size and allowing internal measurement, at the cost of time.
How are EV battery welds inspected?
Tab-to-busbar and other battery welds are commonly checked with inline X-ray or CT for porosity, cracks and incomplete bonding, combined with electrical resistance testing and destructive sampling during process qualification.
Which certification do NDT radiographers need?
Common routes are employer certification under ASNT SNT-TC-1A or ANSI/ASNT CP-189, third-party certification under ISO 9712, and NAS 410 / EN 4179 in aerospace, plus radiation safety qualifications.
Sources
- eCFR — 21 CFR 1020.40, Cabinet X-ray systems
- ASNT — Certification and SNT-TC-1A
- ISO 9712 — Qualification and certification of NDT personnel
- IAEA SSG-11 — Radiation safety in industrial radiography
Last reviewed on 2026-10-04.