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Information Directory

Reference Directory

Contamination Control

What is “contamination”?
When we’re speaking about radioactivity, contamination simply means the presence of radioactivity where it doesn’t belong. The sparks that fly out of a burning fire in a fire place are a good analogy of contamination . . . bits of the burning fuel from the fire that jump out to areas where they don’t belong. Although it is not only possible but typical for facilities who work with radiation and radioactivity to have contamination somewhere within them, it is important that the amount and distribution of contamination be controlled.

What is the purpose of a contamination control program?
A contamination control program is a structured program designed to reduce internal as well as external radiation exposures that result from the presence of contamination on surfaces of buildings, equipment and other areas. The goal of a contamination control program is not necessarily to eliminate contamination but to control its spread.

What are the components of a contamination control program?
An effective contamination control program contains several components including procedural requirements, worker training, the ALARA philosophy, and a Quality Assurance (QA) plan to assure verification.

What are some of the more important elements in a contamination control program?
One key element is classifying and labeling or posting areas with respect to the presence or magnitude of contamination, and whether it is “fixed” or “removable”.

What does “fixed” and “removable” contamination mean?
As the words imply, “fixed” contamination means radioactive materials that are “stuck” onto the surface such that typical handling and touching of that surface does not dislodge the radioactivity. On the other hand, “removable” contamination is radioactivity that can be easily dislodged or transferred.

Why is classification and posting necessary?
Areas are often classified according to their contamination levels. The level of contamination control practiced in that area is dependent on the type and amount of contamination present. Typical designations include “controlled area”, “contaminated area”, “highly contaminated area”, “airborne radioactivity area”, and “radioactive materials” area. Areas having (or likely to have) loose, i.e., removable or transferable surface contamination in excess of specified limits, should be posted as noted above or in another appropriate fashion. Barriers and signs should also be placed at entrances and perimeters around the area to warn personnel of any inherent hazards. The requirements for entering the area should also be posted. Proper posting, followed by training all workers in the meaning of the signs and entrance requirements, goes a long way toward limiting the spread of contamination and reducing personnel exposures to radiation.

Are there other ways of preventing the spread of contamination?
One way is to employ covering techniques. Contamination of clean areas can be minimized by covering those areas with materials such as plastic, paper or strippable coatings. Slightly contaminated areas can be prevented from becoming highly contaminated areas through the use of protective coverings.

How does one select the proper covering?
Safety hazards are often a factor when selecting a particular type of covering. Polyethylene materials, for example, become very slippery when moisture is present. Flammability is an issue with cloth and polyethylene materials. Coverings placed in high traffic areas can promote slipping if not securely fastened to the floor. Consideration must be given to all the safety hazards associated with these covering techniques to reduce the need for excessive decontamination while at the same time minimizing cost, time and excessive exposures.

Are there other covering considerations?
Yes. The amount of preparation required to protect an area can vary greatly. Consideration of the type of work and degree of contamination present will determine the appropriate type of covering and the number of layers required. Covering techniques, however, should be balanced against the volume of radioactive waste generated, i.e., the use of unnecessary amounts of plastic, paper, etc., leads to waste disposal problems.

Are there other contamination control methods?
Yes. Another widely used method is to “confine” the contamination to the greatest extent practical. Confinement techniques should be considered in those instances when work is going to be performed on objects that have very significant levels of contamination or could generate considerable airborne contamination. These techniques include, but are not limited to, the use of fumehoods, glove boxes, glove bags, tents, and portable ventilation systems.

Previously, you said contamination control was important for controlling internal exposures. Why is it important?
Control of internal exposures is a prime objective at sites that use radiation and radioactivity for several reasons. For one, assessing internal exposures is a much more difficult process than assessing external exposures. In addition, the analysis and interpretation of the results is time consuming, especially because of regulatory requirements and a relatively new dose reporting system where both internal and external exposures are summed and reported as one value. The worker’s reluctance to furnish necessary biological samples for an adequate exposure assessment is a practical factor which can not be overlooked. Each of these considerations should serve to encourage both worker and line management to minimize internal exposures by controlling the amount and spread of contamination.

Are there regulations for the control of internal exposures?
Yes, both the Department of Energy (DOE) and the Nuclear Regulatory Commission (NRC) require facilities to keep exposures from sources of radiation inside the body below a given dose limit. In addition, they also require internal exposures be kept As Low As is Reasonably Achievable, or “ALARA”.

Are there specific contamination control methods that will minimize internal exposures?
Absolutely. To reduce the possibility of internal contamination, eating, chewing, drinking and/or smoking should be allowed only in designated areas. Such areas include uncontrolled areas or designated clean areas (permanent/temporary) within controlled areas. Basic contamination control practices dictate that before any individual eats, drinks or smokes, he or she must (1) remove all protective clothing, (2) perform a personal contamination survey and initiate decontamination efforts if necessary, and (3) follow common personal hygiene practices (e.g. washing hands).

What are some other ways of reducing internal exposures?
The design of a facility, with consideration for proper engineering controls, goes a long way toward controlling contamination and reducing internal exposures. Engineering controls are those that are built into the design of the facility. These include things like ventilation systems with associated filters for trapping particulates and gases. Fume hoods and glove boxes, remote handling devices, and shielding may also be employed as confinement and containment devices. When these fail on occasion or become ineffective, respiratory protection may be required.

Are there other engineering controls?
Of course restricting entry to contaminated areas only to those that need to be there, and posting these areas appropriately goes a long way. In addition, detection and alarm systems can alert people to changes in the levels of airborne radioactivity, signifying possible loss of contamination control.

Why is “removable” contamination such an important issue?
Contamination on surfaces such as floors, tools and equipment can be tracked to different locations, spreading the contamination and increasing the possibility of worker exposure. In certain instances, transferable contamination on floors can become airborne through resuspension (the contamination is removed from the floor surface in some fashion, such as “kicking” or simply walking on the floor, and gets into the air).

What are hot particles and why is contamination control for these particles important?
Hot particles are microscopic particles formed from degraded nuclear reactor fuel (fuel “fleas”) or bits of metal that are made radioactive when they are carried by water into the core of a nuclear reactor. Their origin indicates that they pose the greatest concern for operating nuclear reactors. Their small size and high radioactivity demands special contamination controls because they are difficult to detect, yet effective in delivering radiation exposure when they land on the skin.

How is hot particle contamination controlled?
Control of hot particles in the workplace includes both specific procedures tailored to this particular type of contaminant, and significant job pre-planning before doing any work in areas where hot particles are known to exist. In addition, special monitoring devices and survey techniques are used to identify and retrieve particles. Controlling their spread by restricting movement of people and equipment into hot particle areas is also important. In addition, optimum use of special filters, vacuuming, and wet towel wiping of internal valves and floor surfaces are effective in reducing the number of hot particles.

Please explain what a “contamination control point” is.
Gladly.  Contamination control points are special areas at nuclear facilities that are equipped with personal clothing racks or lockers, bins stocked with protective clothing, tape, benches, barrels for contaminated trash and protective clothing, step-off-pads, and personnel survey stations (friskers) or personnel contamination monitors. A properly located and equipped control point is useful for contamination control. They are typically positioned in such a manner as to have a clear view of the entire work area and positive control of all activities within the area. In addition, the location is chosen so that the flow of personnel and equipment entering or exiting a contamination area can be easily monitored and regulated.

You mentioned step-off pads. What are these?
Step-off-pads provide an effective method of contamination control by serving as the boundary between the contaminated area and the contamination control point. Generally, step-off-pads are considered clean (uncontaminated). They should not be located in areas where a safety hazard may result, such as in stairwells or elevators.

When I take equipment out of a contaminated area, how do I keep from spreading contamination?
Equipment used in or removed from contaminated areas should be prepared to minimize the spread of contamination. One or more of the following methods may be used: (1) tape (a method for use on small items such as flashlights or the wheels of a hand cart); (2) sheet material (this would include plastic or paper and would be used to cover large or bulky items); (3) sleeving for hoses and cables; (4) polyethylene bags (a good method to protect items such as portable survey instruments); (5) strippable coating; and (6) sealing of exposed surfaces. Before removal from a contaminated area, most small items should be placed in plastic bags until surveys are performed.

What do you mean by “decontamination”?
During the operation of any nuclear facility, contamination is inevitable; hence, the need exists to properly remove it from tools, equipment, plant surfaces, and personnel. Each decontamination effort must be evaluated on an individual basis and the techniques varied to meet the specific conditions.

What methods can be used for decontaminating tools, equipment and surfaces?
Decontamination of contaminated tools, equipment and surfaces before work commences in an area will reduce both the potential for spreading contamination and the exposure to the worker. A typical scenario includes: Frisking with an acceptable survey instrument; determining whether the contamination is “fixed” or “removable” by smear techniques; and applying detergents or other agents to the area of interest and scrubbing with a hard bristle brush. If the effort is successful, the tools and equipment can be released to “uncontrolled” areas, and the postings and barriers around a contaminated area can be removed. If unsuccessful, the tools and equipment can either be discarded as radioactive waste or placed in a specific area with appropriate controls and postings.

Is decontaminating a person different from decontaminating a piece of equipment?
Yes. In cases of personnel decontamination, the method used should be chosen not only on the basis of the effectiveness of removing the contamination, but also on the effect the method will have on the individual.

What are the most important considerations when decontaminating people?
There are three primary objectives of personnel decontamination: to reduce radiation exposure, minimize the absorption of radionuclides into the body, and prevent localized contamination from spreading.

Is there some general guidance on how one should proceed when decontaminating people?
Yes.  The following general steps should be followed when personnel decontamination is required:

  1. Survey the individual over the skin, hair, clothing, etc., using an appropriate instrument.
  2. If the contamination is widespread, the individual should shower with soap and water. After drying off, the survey should be repeated, hopefully showing the contamination has been reduced to a localized portion of the body. Superficial contamination should always be removed by first washing the affected area with lukewarm water and mild soap. Scrubbing with soft bristle brushes should be done only when absolutely necessary. Hard bristle brushes should not be used because excessive irritation can lead to a loss of integrity of the skin barrier. Hot water which opens pores such that contamination can enter or cold water which closes pores around contamination should be avoided if possible. In addition, when showering, care should be taken to prevent contaminating body orifices with contaminated runoff.
  3. Localized areas can often be decontaminated by taping a surgeon’s glove, plastic bag, etc. over the affected area. The contamination is removed by sweating through the skin.
  4. Contamination present in the eyes, mouth and wounds should be handled by flushing the areas with copious amounts of water and relying on trained medical personnel for further decontamination efforts. Possible evidence of internal contamination can be determined by taking nasal swipes with cotton swabs and counting each swab in a GM counter. Based on the preliminary findings, the individual may be asked to blow his/her nose repeatedly; additional nose swabs are then taken and recounted.
  5. Decontamination efforts should be repeated several times for a given procedure. If after up to four attempts, the contamination levels are not being reduced significantly, additional measures should be employed. These include applying mixtures of corn starch or cornmeal with detergent to the affected area. Only if these physical methods fail should the use of chemical agents be considered. (Note: Chemical agents, such as potassium permanganate, act by removing outer skin layers. These agents should not remain on the skin for very long.)
  6. In cases of gross contamination over the entire body surface (which might be encountered if someone were sprayed with contaminated water), whole body counting should be performed only after the surface contamination is removed. This facilitates locating the existence of any material swallowed or assimilated into the body.
  7. Detailed records should be maintained which include the initial level and extent of contamination, removal methods, skin condition, and final contamination levels.

What do you mean by protective clothing?
Protective clothing is worn by people working or entering contaminated areas to prevent contamination on their clothes or skin. It provides personnel with an easily removed outer “skin” so that if contamination is present on the clothing, the wearer is no longer exposed after the clothing is removed. In addition, protective clothing may provide some shielding for beta radiation. The amount of protection gained by wearing protective clothing depends to a large degree on how the clothing is worn and used by personnel.

What are some examples of protective clothing?
Several types of protective clothing are used depending on the work activity, associated levels of contamination, and whether the contamination is in a dry or wet state. These include lab coats, coveralls (e.g., cotton or tyvek), plastic suits, gloves, shoe covers (ranging from cotton to plastic to rubber overshoes), and head gear (e.g., surgeon’s caps and hoods)

How do I know how to pick the right protective clothing?
Paperwork associated with the work to be performed (such as a Radiation Work Permit) should be reviewed to determine the required protective clothing. Protective clothing specified by a Radiation Work Permit or procedure is typically selected by personnel from control points or storage areas. Used protective clothing should not be worn in clean areas because, even after laundering, it can be slightly contaminated.

Are there other things to keep in mind when selecting protective clothing?
Yes. Protective clothing must be selected to assure that it will fit properly. Clothing that is too large for the wearer makes work more difficult and may drag along the floor spreading contamination. Clothing which is too small for the wearer does not give adequate protection, because as the wearer moves, the joints where the clothing meets (i.e., points where coverall sleeves meet gloves) can separate, exposing skin to possible contamination. Protective clothing should be comfortable and provide sufficient mobility for the wearer. An improper fit reduces worker efficiency and could result in increased exposure from increased stay times.

How does one use protective clothing?
Prior to donning, each article of protective clothing should be inspected for contamination, holes, torn seams, missing buttons, broken zippers, etc. If defects are found, the item should be marked for repair or discarded, and another article selected. When using rubber gloves, check for small holes to ensure that the glove will not leak. Inflate the glove (not by blowing) to check for air leaks. When selecting gloves, be sure the style used is suitable for the type of work being performed. For example, if “finger tip” type work is to be performed, surgeons gloves would be the logical choice. Rubber gloves, which are large and bulky, would not be suitable.

Is there some practical advice you can give me on the use of protective clothing?
Be glad to.  Here are some things to keep in mind when donning protective clothing.  However, it is important to note that every facility instructs their workers in different ways regarding the use of protective clothing, so this listing is provided only as an example.

  1. Only underwear, shorts, or bathing suits; socks, and shoes should be worn under a full set of protective clothing. Wearing personal items (rings, chains, knives, keys, etc.) should be avoided as they can become contaminated and/or lost.
  2. Areas between articles of protective clothing (such as the leg of a coverall and a shoe cover, or a sleeve of a coverall and a glove) should be taped closed to assure a complete seal of clothing and protection of skin and personal clothing. Also, when wearing two sets of shoe covers, tape both the outer and inner shoe cover around the ankle to prevent the shoe covers from slipping off.
  3. When sealing openings (taping shoe covers, gloves, etc.), do not use an excessive amount of tape because it is difficult to remove. (About 1 1/2 turns around the opening provides an adequate seal.) Care must be taken that this tape is not wrapped too tightly or the clothing will tend to be uncomfortable during the wearing period. Tape should always be tabbed so that it can be easily removed.
  4. Transfer dosimetric devices to the protective clothing from your street clothes.
  5. Small, light items (such as pens, dosimeters, etc.) should be taped to protective clothing. In some areas of a nuclear facility, all items MUST be taped to prevent them from being dropped.
  6. When using a respirator, a hood can be worn over the respirator to protect the head area.

Is there a special way of getting out of protective clothing?
Protective clothing must be removed carefully to prevent contamination of the skin or personal clothing. The following general techniques are some examples:

  1. The more highly contaminated articles of clothing, such as rubbers, outer gloves and the outer pair of coveralls (when two pair are worn) are removed first. (Note: Exercise caution during protective clothing removal to prevent contaminating clean areas, such as the step-off pad, from loose contamination which may be present on the protective clothing. Removable contamination can be shaken off while undressing. Control your movements such that any contamination is directed toward the contaminated area.)
  2. All tape is removed from the clothing and discarded.
  3. Clothing is removed in a manner designed to prevent contamination of underlying clothing or skin. (Clothing is essentially turned inside out as it is removed.) When removing contaminated gloves, loosen one glove so that it can fall off the hand when shaken, yet still be used to aid in removing the other contaminated glove. (This technique prevents the inner clean gloves from becoming contaminated.) When removing coveralls, unbutton or unzip them first, and then step out of them while verifying that the shoe covers are still in place. Remove personnel monitoring devices before discarding protective clothing. (Note: When removing shoe covers, maintain your balance so that you don’t fall!)
  4. A general rule-of-thumb to follow when removing protective clothing is “touch contaminated with contaminated and touch clean with clean”.
  5. If respiratory equipment is worn, highly contaminated clothing is removed before respiratory equipment to prevent ingesting material present on the clothes.
  6. After removing protective clothing, discard all items to their appropriate location (single use items as trash, and cloth and rubber protective clothing as laundry, etc.).

Are there some precautions I should take when I wear protective clothing?
To avoid contaminating your exposed skin and hair, remove your outer contaminated gloves first or request assistance when scratching an itch, wiping sweat from your face, or checking a personnel monitoring device. If a tear, broken zipper, etc. is noticed while wearing protective clothing, work should be stopped and a determination should be made as to whether the skin or personal clothing of the worker is contaminated. If so, decontamination should proceed, and defective clothing should be replaced before the job continues.

Are there any other issues about protective clothing that should be kept in mind?
Yes. A storage area should be provided near the main access control point. In addition, only radiation protection personnel should be responsible for shipment of dirty clothing for off-site laundering and receipt of laundered clothing. In the event that an on-site laundry is provided, this operation should be closely monitored by radiation protection personnel.

Where can I obtain more information about contamination control?
There are a number of excellent references that discuss contamination control methods in great detail. Quite a few of them are listed in the “Bibliography” that is located in this web page’s “Tool Box”. If you don’t find the information you need there, please don’t hesitate to “Ask a CHP”.