Purpose of Air Monitoring - doe-std-1136-20040074

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

b. Prevention of internal exposure is often more feasible and successful than prevention of external

exposure. Contained radioactive material may continue to produce external penetrating fields of

radiation, but no internal exposure potential. Portable protective devices (respiratory protection

equipment) can minimize internal exposure when containment is not practical.

c. Recommendations of the ICRP in formulating a dose equivalent limit system have resulted in

combining internal and external dose. Again, the difficulty and time del y of internal dosimetry

make elimination of significant internal exposure an economic incentive.

In facilities that process large quantities of uranium, however, there may be situations in which

exposure to work-place airborne activity at low levels occurs daily. The fact that tons of material are

handled, rather than gram quantities, and that the material is less toxic (on a mass basis because of low

specific activity), make total containment impractical.

4.1.2 Purpose of Air Monitoring

The goal of the air monitoring program is to identify, evaluate, and control internal dose received by

workers from routine occupational exposure to airborne radioactive materials, to confirm that source

controls are functioning properly, and to assess the exposure resulting from an unusual event. There are two

general aspects of air sampling that must receive equal consideration in a properly executed monitoring

program. The first involves the methods and equipment by which a sample is collected and analyzed to

yield an accurate measurement of the specific radionuclides. The second is the protocol of sampling

location, duration, and frequency that focuses on determination of the radionuclide exposure in

the work area.

Air monitoring should include both active and passive air samplers. A continuous air monitor (CAM)

provides for immediate alarm, warning workers of an unusual release of high levels of airborne

radioactive material. This active monitoring is needed for high hazard and high potential areas to provide

immediate and timely protective response, while passive sampling provides high-sensitivity activity

records, trends, continuous documentation, etc. Three types of air samplers are used to accomplish the air

monitoring: general area sampling (GAS), breathing zone sampling (BZS), and personal air sampling

(PAS).

The CAM continuously draws air through a sampler that has an active radiation detector. The

sampled air is automatically monitored for an increase above normal or background levels of

contamination. When airborne activity exceeds the alarm level, workers are warned of the potential

problem and prompted to follow alarm procedures. This type of monitor is usually practical only for

stationary samplers (GAS or BZS). It is important that a CAM be placed to sample air that accurately

represents the most likely area of material release. This will protect most workers from a worst-case

exposure and minimize total work-force exposure.

4-2