Contamination Control - doe-std-1136-20040073

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

4.0 CONTAMINATION CONTROL

Contamination control is an important part of the overall radiological control program. There are three

main aspects to this: 1) control of the release of contamination into the work-place environment; 2) control

of personnel exposure to the contamination that does get into the work place; and 3) protection of personnel

from intake of contaminants. Effective control of personnel exposure to uranium and its decay products is

accomplished mainly by controlling the potential for inhalation and ingestion of radioactive materials.

Monitoring provides an indication of the effectiveness of physical design features and administrative

controls in controlling exposure to radioactive material.

This chapter addresses the basic features of an effective contamination control program and the

technical considerations of implementing the program. A release of radioactive material from containment

typically results in surface contamination and airborne dispersion. Airborne contaminants are continuously

cleared from the work place by ventilation. Strategic air sampling detects the release of an airborne

contaminant and provides the means for control, minimization of personnel exposure, and evaluation of

inhalation exposure. Considerations for design of an air monitoring program are followed in this chapter by

a section on surface contamination control. Finally, protection of personnel from contaminant intake is

accomplished with protective clothing and respiratory protection.

4.1 AIR MONITORING

The most common route of uranium intake for workers is by inhalation. Airborne particles deposit

throughout the respiratory tract. Some of the deposited particles are swallowed, contributing to ingestion,

requiring that both inhalation and ingestion be considered with an exposure to airborne material. The

particle size distribution that determines deposition in the respiratory tract is affected by the mechanism of

dispersion and the nature of the source material. Characterization of inhalation exposure should make use

of all available information about the chemical and physical form of airborne material. This information,

along with spatial and temporal distribution, provides the basis to minimize personnel exposure for air

contamination control.

4.1.1 Internal Versus External Dose Philosophy

The widespread application of methods to contain uranium in DOE facilities has resulted in a history

of relatively minor internal exposures. The methods used to control internal dose have been developed for

a varie ty of reasons:

a. The assessment of internal dose requiring bioassay is difficult, imprecise, time-consuming, and

offensive to personnel as compared to external dosimetry. For example, an accidental internal

uptake may require the subject to submit dozens of biological samples over the span of many

months, as well as requiring extensive analytical support for measurement of sample content,

considerable time of trained professionals to analyze data and calculate the internal dose, and long

lapses before dose estimates are available, thus handicapping the assessment of the occupational

exposure status and treatment of the worker.

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