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The basic precautions are used in order to reduce contamination and personnel exposure. The basic precautions can be divided into laboratory design and equipment, and auxiliary equipment and services.

Laboratory Design and Equipment

• General Working Conditions

Laboratories and equipment specially designed for the purpose of radioactive isotopes are used. No work should be undertaken in these rooms other than that concerned with the application of radioactive isotopes.

• Size of Radioactive Laboratory

The size of a radioactive laboratory is important and suitable provision for adequate floor space should be made. A laboratory designed for one scientist working alone should have a total floor area of 200 sq.ft.

• Floors

The floors should have a smooth, continuous surface, as far as possible, such as stainless steel, painted concrete, or linoleum. Absorbent floors, such as those made of wood, should be avoided. Asphalt tile and similar materials can also be used. The ease of replacement of sections of tile floor compensates for the hazard of crack contamination. Floors should be cleaned daily by wet mopping, or by the use of moist compound. Dry sweeping should be avoided as it may lead to an active dust hazard.

• Walls, Ceiling and Woodwork

Walls, ceiling and woodwork should be finished with a non-porous washable surface, which may be cleaned to remove accumulation of radioactivity. A plastic paint, such as Tygon, is particularly useful as it may be easily removed with acetone if necessary.

• Ventilation

All laboratory operations should be conducted in hoods which will be provided with forced ventilation sufficient to keep the beta active content of the room air below 10-_ curies per cu. m. or 3,700 disintegrations per sec. per cu. m. Experience has shown that the minimum air flow which is sufficient for an efficient cabinet is 150 linear ft. per min., with the cabinet front open 1 ft. Specially hazardous operations, such as handling long-lived bone-seeking isotopes in injection or inhalation studies on animals, should be conducted by personnel wearing suitable respirators or supplied-air masks. Hoods with individual filter systems for the exhaust air are highly recommended. Multiple hood systems are dangerous because reverse air currents may occur. Personnel outside the laboratory must be protected from the radioactive material forced out of the vent from the hoods and careful consideration should be given to this when designing a radioactive laboratory.

• Equipment

Special equipment suitable for the type and level of activity being used should be provided for each type of operation. This should include handling tools such as tongs, forceps: trays and mechanical holders. Long handled tools may provide adequate protection by distance where millicurie amounts of beta or gamma activity are encountered. When the isotopes concerned are chiefly beta emitters, efficient use can be made of transparent plastic shields fitting closely around the equipment to a low close handling with good visibility. Containers for the active material should incorporate the necessary shielding as close to the source as possible. Containers for liquid samples should always be reinforced by an outer, unbreakable container.

• Hoods and Benches

Laboratory furniture should be portable and should not have drawer or cupboards which tend to collect dust and unnecessary apparatus. Portable tables and cabinets are adequate for radioactive laboratories. All work with radioactive material should be done in fume cabinets and experience has shown that the sloping front design is more convenient for continuous work than a straight front. Portable laboratory tables should be painted with Tygon or some other plastic covering. The table tops should be covered with linoleum or glass. The most practical method for covering benches is by means of sheet lead. Services and controls should be outside the cabinet on the bench. This procedure enables one to make complete and thorough clean-ups with a minimum of waste and expense. The purpose of the absorbent paper is to catch minor spills, and it is advisable to change this paper after each laboratory experiment. The work bench should be equipped with papers for the prompt removal of spills. Drawers in work benches should be washable and have removable liners.

• Storage Facilities

Radioactive materials should be stored at a safe distance from all personnel in the building, if possible. If storage at a safe distance cannot be arranged, a small "castle" built of lead bricks should be placed under the storage bin, as well as around it. A heavy lead cover should be secured for the bin.

• Counting room

Counting equipment and other radiometric apparatus should be set up in a nearby room. It is as a rule, not desirable to have counting units in the radioactive laboratory because of the possibility of contamination. The walls of the counting room should furnish shielding against radiation from sources in nearby laboratories. Much care is needed to make sure that the counting room does not become contaminated by very small amounts of radioactive material which do not constitute a health hazard but will hinder a precise measurement.

• Auxiliary Equipment and Services

The chief auxiliary equipment and services required in the operation of a radioactive laboratory, handling quantities of material from one to 100 mc are as follows:

1. Health instruments.

2. Film monitoring.

3. Special laboratory clothing.

4. Special cleaning services.

5. Disposal of radioactive waste materials.

· Health Instruments

For all work with millicurie amounts or greater, the laboratory should have an electroscope or portable ionization chamber with direct current amplifier reading directly in dosage rate (mr. per hr.). This instrument should be capable of measuring dosage rates at least from 6 mr. per hr. to 100 mr. per hr. A removable cover on the ion chamber making it sensitive to beta particles is useful. Portable Geiger counter probe monitors are indispensable for locating and checking sources and monitoring the cleaning up of spills. This instrument is useful in checking shoes, clothing and hands for contamination and it may be used to make measurements in certain experiments.

Film Monitoring

Monitoring films should be worn by all laboratory personnel. Films should be developed and read every week and all over-exposures reported immediately to the director of the laboratory. The use of films makes certain that personnel are not receiving an unreasonable amount of gamma radiation. Pencil chambers and special films worn on the fingers or wrist should be used by personnel when working in comparatively high radiation fields. Special Laboratory Clothing the degree of protection required is a function of the activity used. Even tracer amounts should be handled with laboratory coats protecting normal attire. In a biological laboratory where routine work is done with radioactive materials, it is good practice to have special laboratory coats or coveralls, rubbers or special shoes, and even special trousers and shirts, which are kept for use in the laboratories only. Rubber gloves should be worn while handling active materials which may give rise to contamination of the hands.

Special Cleaning Services

The laboratories should be kept very clean at all times and the equipment used by the janitor. Mops and pails should be used for the active laboratory only and not for other parts of the building. Spills of solution containing radioactive materials should be cleaned up at once by the scientist who was responsible for the accident. He should wear rubber gloves and take proper precautions. When he considers the area to be clean, it should be carefully monitored with a sensitive detector. Careful cleaning up of all spills will help to keep the laboratory free from contamination.

Disposal of Radioactive Waste Materials

Solid Active Materials: The laboratory should have a closed and clearly labeled garbage can, with a moisture proof disposable liner, to hold the discarded absorbent bench paper, wiping papers and other solid active materials. Regular collections of this active waste material should be made. The eventual disposal of such items depends upon the half-life and toxicity of the isotopes used. In the case of isotopes with short half-lives, holding the materials in a controlled place until their residual activity is very small, is a good method. With a long-lived isotope, the best method is burying in a special disposal area. Special care should be given to dry waste which might dust.

Active Solutions: Radioactive waste solutions should only go into ordinary sewers if the amounts of radioactive material are low enough to constitute no possible hazard. Whenever possible, the principal activity in the waste solution should be precipitated, and disposed of as active solid material. Urine from isotope-injected animals or patients, and liquors from

equipment or clothing decontamination, may require attention as radioactive solutions.

The following precautions apply to "safe" amounts as well as to larger quantities of radioactive isotopes.

Protection of Hands

Every precaution should be taken to avoid getting radioactive isotopes on the hands. The hands should be kept at a safe distance from sources as even small sources will cause burns if close to the skin. The hands should be protected by rubber gloves or paper when handling radioactive materials. After working with radioactive materials, the hands should be thoroughly washed for two or three minutes using plenty of soap. A check of the hands should be made with a monitoring instrument after washing and the hands should be washed again if necessary.

Cleaning of Glassware

Scrupulous care in the cleaning of glassware is necessary. All vessels should be marked after use and placed apart from other equipment so that it can be given special attention in cleaning. Even after cleaning, glassware should be kept separate from other equipment. Adsorption of active materials on glassware is a very common phenomenon.

Handling Solutions

Isotopes should be used in solution of possible. Of course, all spills of radioactive material must be cleaned up immediately and thoroughly and the area should then be checked with a monitoring instrument to ensure that no significant activity remains. Radioactive solutions should never be pipette by mouth, some other device should be used. All operations should be done over surfaces covered with paper. If possible, stainless steel trays lined with blotting paper should be used. Experience has shown that a glass container should never be trusted and a secondary container, preferably stainless steel, should always be used. Pipettes, stirring rods, capillary tubes and similar equipment should never be placed on the bench after use but should always be put in small trays lined with blotting paper. Hot plates should be protected with asbestos paper in case a solution boils over.