In what situation would you use radiography instead of ultrasonic testing on a steel bridge?

Radiography would be used instead of ultrasonic testing on a steel bridge when a permanent record of the inspection is required, or when access is limited to only one side of the component being inspected. Radiography, using X-rays or gamma rays, produces an image on film or a digital detector that provides a permanent record of the internal structure of the steel, including any defects such as cracks, voids, or inclusions. Ultrasonic testing, while sensitive to internal flaws, typically does not provide a permanent image and requires access to both sides of the component for optimal results. Radiography is also better suited for detecting volumetric defects, while ultrasonic testing is more effective for detecting planar defects like cracks. However, radiography requires strict safety precautions due to the use of ionizing radiation.