Interlocks - hdbk110997

DOE-HDBK-1109-97

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

Student's Guide

INTERLOCKS

Fail-safe interlocks should be provided on doors and access panels of X-ray devices so that X-

ray production is not possible when they are open. A fail-safe interlock is designed so that

any failure that can reasonably be anticipated will result in a condition in which personnel are

safe from excessive radiation exposure.

Guidance from the ANSI standards is that interlocks should be tested by the operating group at

least every six months. The interlock test procedure may be locally specified, but typically is

as follows:

Energize the X-ray tube.

Open each door or access panel one at a time.

Observe the X-ray warning light or current meter at the control panel.

Record the results in a log.

(Insert facility-specific information, as appropriate.)

SHIELDING

Analytical Systems.

For analytical X-ray machines, such as X-ray fluorescence and diffraction systems, the

manufacturer provides shielding in accordance with ANSI N43.2. However, prudent

practice requires that any device or source that involves radiation should be surveyed to

determine the adequacy of the shielding.

Enclosed beam systems have sufficient shielding so that the dose rate at 5 cm from its

outer surface does not exceed 0.25 mrem per hour under normal operating conditions.

The dose rate may be difficult to evaluate. According to ANSI N43.2, this requirement