Glossary cont'd - hdbk110997

DOE-HDBK-1109-97

Radiological Safety Training for Radiation-Producing (X-Ray) Devices

Instructor=s Guide

Secondary radiation: Radiation (electrons, X-rays, gamma rays, or neutrons) produced by the interaction

of primary radiation with matter.

Shielding: Attenuating material used to reduce the transmission of radiation. The two general types of

shielding are primary and secondary. Primary shielding is material sufficient to attenuate the useful beam

to the required level. Secondary shielding is material sufficient to attenuate stray radiation to the required

level.

Shielded installation: An industrial X-ray installation in which the source of radiation and all objects

exposed to that source are within a permanent enclosure.

Skyshine: Radiation emerging from a shielded enclosure which then scatters off air molecules to increase

radiation levels at some distance from the outside of the shield.

Stem radiation: X-rays given off from parts of the anode other than the target, particularly from the

target support.

Stray radiation: Radiation other than the useful beam. It includes leakage and scattered radiation.

Survey: An evaluation of the radiological conditions and potential hazards incident to the production, use,

transfer, release, disposal, or presence of radioactive material or other sources of radiation. When

appropriate, such an evaluation includes a physical survey of the location of radioactive material and

measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material

present. (10 CFR 835.2(a)).

System barrier: The portion of an X-ray installation that clearly defines the transition from a Controlled

Area to a Radiation Area and provides such shielding as may be required to limit the dose rate in the

Controlled Area during normal operation.

Tenth-value layer (TVL): The thickness of a specified substance that, when introduced into a beam of

radiation, reduces the dose rate to one-tenth of the original value. One TVL is equivalent to 3.3 HVLs.