1 Indication of a manufacturer's name does not constitute endorsement of the instrument nor deny the superiority of other makes. 2 For beta-gamma instruments, the gamma rays are quoted. Calibrations for beta radiation may depend on the energy of the particles and the geometrical distributions of the source.

4. Dust, Gas, and Vapor Samplers

(a) Dust Samplers

Dust or spray may be sampled by drawing air through a filter, or by electrostatic precipitation. The filtration method is reliable, provided that leaks around the edge of the collection paper are eliminated. The activity on the sample paper is measured on standard laboratory counting equipment. Complications are introduced when the halflife of the collected material is short or comparable with the collection time. The electrostatic precipitation method permits the precipitation onto an aluminum surface which is a suitable source for the evaluation of range and energy of the deposited particles.

(b) Gas and Vapor Samplers

One type of sampler draws air through an ion chamber and measures the ion current with a suitable electrometer circuit. A continuous record of the activity in the atmosphere may be obtained in this manner. The method is unsuitable at low levels because of the difficulty of avoiding disturbance to the chamber insulators by friction, etc. Another method involves the collection of samples in evacuated containers which can be returned to a central location for sampling. In special cases, chemical or adsorption methods are available for specific gases or vapors.

V. Hazard Monitoring

1. Inspection of Personnel

The monitoring of personnel with respect to incident radiation is achieved by the use of pocket ion chambers and/or film badges worn on the person. It is standard practice to process the pocket chambers daily, and the films weekly. Where experience has shown continued low exposure, films read every 2 weeks give an adequate exposure index. Similarly, self-reading pocket chambers may be worn for an extended period if the casual leakage is insignificant. Finger film should be processed at least weekly.

In general, each individual using radiosotopes should be responsible for monitoring himself against contamination. The inspection should include qualitative tests for contami

nation of the clothing, hands, and other parts that may be contaminated. Hand checks shall be mandatory before leaving the work area for lunch or termination of the work day. In those cases where the risk of absorption of the isotopes through an open cut is important, hands should be inspected by the supervisor or laboratory leader at the beginning of the work day, and injured persons excluded from the program.

Prompt removal of contamination, when found, is a necessary corollary of the inspection.

2. Inspection of Work Areas

The beta- and gamma-ray exposures at points habitually occupied by workers should be determined periodically by properly designed ionization or counter devices, operated by qualified personnel. An instrument, or instruments, should be available to cover the range from 1 mr/hr up to 2 r/hr. Other meters for the qualitative detection of small amounts of active contamination should be available. Under laboratory conditions, each person in the laboratory should be responsible for maintaining an adequate frequency of inspection in his own work area. In larger organizations, it may be expedient to employ personnel specifically for these inspections. Continuous monitoring equipment, which nay have an alarm feature, is very desirable for locations handling "curie" amounts of radioisotopes. Such meters, and many portable survey meters, give an inadequate indication of the hazard arising from contaminated surfaces. Such surfaces may give a direct contact exposure hazard, or offer a means of transfer to the body.

The instrument response corresponding to a permissible level of beta contamination is a function of the active materials involved, and each laboratory should properly evaluate these levels for its own purpose. In general, if a Geiger counter of flat-plate area about 2 square inches is passed with a normal hand motion over a suspected surface, contamination is present in undesirable amounts if there is an obvious instrument response. This policy will result in the cleaning of some areas which were not specifically dangerous to personnel. This in general is offset by the easier definition of this particular limit, and the benefits arising from the maintenance of an extremely clean work area. Care must be

taken to ensure that the test instrument used is reasonably responsive to radiations emitted by the available isotopes (for example, if C11 is used, rather specialized search equipment may be necessary).

The amount of activity in the form of gas, vapor, dust, or spray in the air must be determined routinely in the laboratory if the activities used are compatible with the production of an inhalation hazard.

3. Inspection of Protective Clothing

The first inspection of protective clothing should be made by the wearer prior to removal. Very active items should be discarded as active solid waste, in closed containers. The remaining items should be washed and monitored under controlled conditions. Special laundry facilities should be used by all groups regularly engaged in radioisotope work. Preferred solvents for laundry rinses depend on the chemistry of the isotopes used. Where miscellaneous isotopes may be present, dilute acetic or citric acid is recommended. Dilute nitric acid may be used on rubber items. Before contaminated garments are considered for release to public laundry service, the extent of hazard shall be very carefully evaluated.

4. Inspection of Wastes

Laboratory personnel is responsible for the inspection of the disposable containers for solid waste. Tests for emitted beta and gamma radiation, and in some cases for radioactive contamination of surrounding air, are required. Radiation monitoring of the assembly of these containers at a central depot may be necessary.

Monitoring and segregation of active liquid waste is similarly required. The inspection of gaseous and dust effluents, etc., is mandatory in the larger installations where such effluents may be hazardous. Tests for possible deposition and accumulation beyond the confines of the laboratory may be required. Detection methods sufficiently sensitive to give large-scale deflections when subjected to natural radioactive contamination in air, water, or soil, are required, because the maximum permissible additional contamination is of this same order of magnitude.

5. Management of Radiation Accidents

(a) External Radiation

A person presumed significantly overexposed to external radiation should be removed promptly from the hazardous area. Such a person should not be allowed to return to work involving radiation unless it is evident that radiation damage will not result. If investigation indicates that the overexposure may be serious, the exposed person should be referred to a physician qualified to ascertain the extent of the radiation injury, if any.

(b) Ingestion

Persons swallowing radioactive solutions should be treated as for poisoning. The material should be removed by an emetic or by stomach pump, and the residue rendered insoluble to reduce absorption. Addition of carrier element may be indicated. Blood samples and subsequent urine samples should be analyzed to compute the body content of contaminant. Where this approximates the maximum permissible load, radical corrective procedures are indicated. Similar protocol applies to other forms of potential intake described below.

(c) Surface Contamination

Persons splashed with active solutions should wash the affected parts immediately, and if still contaminated, apply recognized decontaminating agents. Where the chemistry of the active solution is not immediately known, an application of titanium dioxide paste, or a saturated solution of potassium permanganate followed by a 5-percent sodium bisulfite solution rinse, is frequently effective. Care should be taken to ensure that no activity is left under the fingernails.

When the hand is known to be contaminated with a small spot of high specific activity, it is better not to wash the hand, as this unnecessarily spreads the contamination. Such spots are removed by masking off the surrounding areas, and by cleaning the affected part with cotton applicators dipped in suitable decontaminants. Care should be taken not to scratch or erode through the epidermal skin layer when scrubbing the body to remove surface contamination.