Warning Devices - hdbk110997

DOE-HDBK-1109-97

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

Student's Guide

There are independent analyses for each component to derive an acceptable shield

thickness.

For example, the calculation used for the primary X-ray beam depends on:

- Peak voltage.

- The maximum permissible exposure rate to an individual.

- The workload of the machine expressed in mA min/wk.

- The use factor: the fraction of the workload during which the useful

beam is pointed in a direction under consideration.

- The occupancy factor that takes into account the fraction of time that

an area outside the barrier is likely to be occupied by a given

individual.

- The distance from the target of the tube to the location under

consideration.

The calculation uses conservative values and derives a value (K) that is used with

graphs to determine shield thickness of a given type of material (e.g., lead or

concrete).

WARNING DEVICES

Operators should be aware of the status of the X-ray tube. Indicators that warn of X-ray

production typically include:

A current meter on the X-ray control panel.

A warning light labeled X-RAYS ON near or on the control panel.

Warning light labeled X-RAYS ON near any X-ray room door.

These warning lights or indicators are activated automatically when power is available

for X-ray production.

For X-ray systems with an open beam in a shielded room, evacuation warning signals and

signs must be activated at least 20 seconds before X-ray production can be started. Any