5. 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 provide adequate protection by distance where millicurie amounts of beta or gamma activity are encountered. Semiremote-control sampling and stirring devices should be included. Operations with larger amounts require the use of specially designed, remote-control equipment including a shielded optical system (e. g., a periscope or mirror arrangement). When the isotopes concerned are primarily beta emitters, efficient use can be made of transparent plastic shields fitting closely around the equipment to allow 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.

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6. Hoods and Benches

Laboratory benches should be free from cracks, crevices, or sharp corners. Suitable surfaces for work tables are stainless steel, Monel metal, plate glass, and some smooth-surfaced plastics. The work surface should be covered with absorbent paper to catch minor spills, and this paper should be changed after each laboratory experiment. The work in hoods should similarly be performed over an inner washable tray covered with the absorbent paper. The work bench should be equipped with wiping papers for the prompt removal of spills. Drawers in work benches, if provided at all, should be washable and have removable liners.

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7. Disposal of Contaminated Wastes &

(a) Absorbent Papers, Wipes, etc.

Waterproof disposable containers to hold the discarded absorbent bench paper and wiping papers should be provided at each laboratory station. Regular collections of these dis

See appendix 1 for thickness.

A "diaper" paper is available that has a waterproof backing to reduce penetration of spills to the work surface.

8 This subject will be covered more extensively in the report of the Subcommittee on Waste Disposal and Decontamination.

posal vessels from the laboratory should be made. The eventual disposal of such items is conditioned by the half-life and toxicity level of the isotopes involved. With short halflives, retention of the materials in a controlled area, until their residual activity is insignificant, is a preferred method. With long-lived isotopes, the laboratory management is committed to a prevention of contamination of the public domain. The association of groups of laboratories to provide a single controlled and economical disposal area may be feasible.

(b) Active Solutions

The disposal of active solutions to the public sewers can only be considered safe when the possible subsequent chemical, physical, and biological concentrations will still leave the materials at safe concentrations. Disposal to a water system should include consideration of the accumulation of activity in soil or mud, and in algae and similar organisms. Concentration of the order of 100,000 fold may occur. Whenever possible, the principal activity in the waste solution should be removed, and discarded as active solid material.

Excreta from isotope-injected animals or patients, and liquors from equipment or clothing decontamination, may require attention as active solutions.

(c) Tools

Tools and other miscellaneous equipment used in handling radioisotopes should be regarded as contaminated, and should not be released for other work until proven otherwise.

8. Protective 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. Where routine radiochemical or biological work is done, coveralls or other clothing that completely clothes the body shall be worn and must be restricted to this operation. Rubber gloves should be worn while handling active materials which may give rise to contamination of the hands. If the material may be spilled on the floor, special cloth or rubber overshoes should be used. In some cases, the provision of shoes to be used only in the laboratory is preferable.

Good protective practice in many respects is similar to, but usually less stringent than, that employed in the manipulation of virulent bacteriological organisms.

IV. Hazard Instrumentation

1. Personnel Meters

(a) Pocket Ion Chambers

Each radiation worker should wear a pocket ionization chamber throughout the course of his work. The chamber should be effective in the range up to 200 mr. Daily measurements of the integrated gamma-ray dose should be recorded. It has been found preferable in many cases to wear two identical pocket chambers, in which case the lower of the two readings is considered valid. This eliminates casual errors due to accidental discharge of one chamber. The usual chambers are not sensitive to beta radiation. Where the isotopes used do not emit gamma rays, specially constructed beta chambers should be provided.

(b) Film Badges

Pocket chambers should be supplemented by a film badge that contains film partially covered by a suitable metallic filter, such as 1 mm. of silver or cadmium. Blackening of the film in the shielded area is then approximately independent of the energy of the gamma radiation (above 80 Kev). Blackening of the unshielded portion may be caused by beta or gamma radiation, especially low-energy gamma radiation. Such film badges give a sufficiently quantitative record of the integrated weekly gamma-ray dose. The beta-ray dose can be obtained quantitatively when exposure to soft gamma radiation is excluded. Special film packets containing two films of different sensitivity are available for badge monitoring. Sensitive film is effective in the range 25 mr to about 5 r. The insensitive film is effective up to about 40 r, and is read only in the event of a major exposure.

(c) Finger Rings

Workers who manipulate radioactive solutions or handle sources should wear film rings or other suitable devices on

the fingers to estimate the hand exposure. Rings which include the metal shield with open window can be used. In many cases, a simple film disk covered with thin rubber is an effective substitute, which introduces very little inconvenience in handling laboratory tools. Strictly quantitative results are obtained only when calibrations can be made with the particular isotopes used in the laboratory.

2. Beta-Gamma Survey Meters

These meters fall into two classes:

1. Sensitive detection instruments primarily used for qualitative estimation of contamination. Whenever contamination is found, it is customary to remove it, and there is consequently no need to determine the exposure, quantitatively. Geiger counters in various circuit combinations are frequently used for this purpose. The "Zeuto" survey meter is also convenient for detection purposes.

2. Quantitative survey meters consisting of ion chambers with suitable indicating circuits, for the measurement of radiation transmitted through shields, or in other cases where it is necessary to evaluate the potential radiation exposure. When properly designed, the response of these chambers is independent of the wavelength of the incident radiation over a wide range. The chambers are made optionally sensitive to both beta and gamma radiations or to gamma radiation only. This is effected by provision of a removable shield over a thin window on the chamber. Table 3 includes some of the currently available radiation meters.

3. Beta-Gamma Hand Counters and Shoe Counters

The small laboratory can use the simple Geiger counter equipment for the detection of contamination on the hands and shoes of workers. Where the procedure is economically justified, it is preferred to use combinations of G. M. tubes assembled so as to register the activity on both sides of the hands and on the shoes. Ten-tube combinations are available for this purpose. Registration may be either by scaler and registers, or by multiple counting-rate meters. Whenever it is required to make a permanent record of the hand and shoe counts, the scaler-register combination is more effective, and can be made on an automatic printing basis.