NDT Study Guide 2026

The speed of sound in a specific homogeneous material is a fundamental and constant property of that material under given conditions, such as temperature. It does not change with distance from the transducer or other factors during an ultrasonic test. This consistent speed is crucial for accurate distance measurements and flaw location in ultrasonic testing.

An Electronic Personal Dosimeter (EPD), also known as an alarming dosimeter, provides a direct, digital readout of the accumulated dose in real-time. It can be set to alarm at a preset dose or dose rate, providing immediate warning to the radiographer. Film badges, TLDs, and OSLs are passive dosimeters that record the cumulative dose over a period (e.g., a month or quarter) and must be processed by a lab to be read.

Liquid Penetrant Inspection (LPI) relies on the penetrant entering surface-breaking discontinuities. If the part's surface is extremely rough or porous, the penetrant can become trapped in the surface texture itself, leading to false indications or making it difficult to properly wash off excess penetrant. This can obscure actual defects or make interpretation unreliable, hence the need for a relatively smooth, non-porous surface.

In an emergency where a source fails to retract, the first priority is to protect people from exposure. This is achieved by securing the controlled area to prevent anyone from entering the high radiation field. Once the area is secure, the radiographer must notify the RSO for further instructions. Attempting a retrieval without proper assessment and authorization is extremely dangerous and against procedure.

In SNT-TC-1A, 'qualification' refers to the process where an individual demonstrates they have the required training, skills, and experience. 'Certification' is the act of the employer providing written testimony—a certificate—that the individual has successfully met the qualification requirements outlined in the company's Written Practice.

Longitudinal magnetization creates magnetic field lines that run parallel to the long axis of the bar. This orientation is perpendicular to transverse discontinuities, creating the strongest flux leakage and therefore the most detectable indications. A coil is the standard method for inducing a longitudinal field in this type of component.