Characterization of Controls

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

c. Material with high intrinsic hazard is usually well contained, but if it is moved over wide areas in

process flows, there is a potential for release at any point. The effectiveness of containment, in the

process flow at locations where workers have access, is a major factor when considering use of

PASs.

When evaluating risks associated with direct handling of radioactive materials, the variation in

techniques employed by different workers to perform the same task must also be considered. No two

workers perform the same operation in exactly the same manner. Aerosol production may depend on

how each individual performs the operation (i.e., rate, accuracy, operating temperatures, etc.).

Characterization of Controls

For the purpose of evaluating work-place controls, work sites can be characterized as either "tightly

controlled" or "loosely controlled." Tightly controlled work areas are preferred in all cases, but there are

situations where good control is difficult or not reasonably achievable. PAS monitoring can help define

those operations that pose the greatest radiological control problems and thus facilitate decisions to

improve specific work situations.

Significant exposure incidents in highly controlled (i.e., tightly controlled) areas usually are the

result of isolated and unforeseeable events, which are complete departures from the normal material-

processing routine. These events usually include loss of containment. In tightly controlled areas, PAS

can serve as a means of detecting a failure of containment because work locations may be located near

potential release points, and inadequate physical controls may be apparent only during an operation

performed by a worker.

4.2 SURFACE CONTAMINATION CONTROL

Uranium contamination on plant surfaces, such as floors and walls, does not present a significant risk

to personnel unless the uranium becomes airborne by resuspension and is inhaled. The probability of

significant airborne concentrations resulting from resuspension of uranium as a result of normal activities

(such as walking) is low; however, any activity that vigorously disturbs the surface (such as floor

sweeping) increases the probability of significant airborne concentrations of uranium. Resuspension is a

function of both the chemical and physical forms of the uranium contamination. External exposure

hazards from surface contamination can become an important concern when uranium decay products

and/or fission products accumulate on surfaces. In some instances, efforts to decontaminate uranium

compounds may leave behind insoluble uranium and decay product compounds which could present an

external exposure hazard. Good industrial housekeeping practices and normal standards of personal

hygiene will usually ensure that uranium surface contamination does not present a significant exposure

hazard. However, even if the probability of resuspension is low, surface contamination on floors can result

in contamination of shoes and thereby result in the potential for tracking of contamination into

uncontrolled areas. Thus, contamination on surfaces must also be adequately controlled to prevent transfer

of contamination above acceptable levels.

Several other contamination control objectives can be accomplished by a program of monitoring

and control of surface contamination:

The program can be designed to provide information to detect containment failures or departures

from good operating practices.

4-14