Rapid Contamination Survey

The purpose of this survey is to obtain samples required to quickly identify areas having removable contaminants. The wipe sample is useful for detecting the presence of contaminants from a weapon-handling accident (alpha) and/or from fallout (beta-gamma). This survey should be made after any event suspected of contaminating the ship. It should be repeated after known or possible significant changes in the amount or distribution of contamination. An example would be after a decontamination operation or after a suspected scattering of the contaminant through previously clean areas. The survey involves the taking of wipe samples in various areas of the ship.

The procedure for taking wipe samples requires a two-person survey team. These personnel should wear protective clothing when they survey the contaminated areas of the ship or when they attempt to determine the contamination limits. The equipment needed for sampling includes filter papers or absorbent papers such as paper towels (about 3 by 3 inches) for wipes and for beta-contamination samples. You will need an equal number of envelopes to contain the wipes, a pencil and a clip board to mark the envelopes, and a stapler to seal the envelopes. One team member, designated the sampler, will take all the wipe samples. The other team member, designated the recorder, will seal the samples in the envelope after marking the envelope. A sample is taken by wiping the clean piece of absorbent paper lightly over a 16-square-inch area (for example, a 4- by 4-inch area) of the surface being surveyed. Generally, in a rapid contamination survey, wipes are taken only of deck areas. The recorder holds the envelope open, and the sampler drops the sample into the envelope. The recorder then seals the envelope by stapling, taping or folding it closed-never by licking the gummed flap.

To determine the boundaries of the contaminated area, take samples from several types of areas such as the following:

1. Important areas presumed to be clean. Examples are mess halls, the sick bay, living quarters, machinery spaces, the bridge, and so forth.

2. Areas that might be contaminated. These areas would be selected on the basis of the circumstances. They should include areas that had some traffic after the presumed contaminating event. Examples are passageways to the exterior of the ship and compartments that were open or ventilated during the contamination event.

3. Areas presumed to be contaminated. After fallout, these would include selected action stations on the weather deck; after a weaponhandling accident, these would include areas near the accident scene.

Several survey teams might be dispatched- one for each type of area. If only one survey team is available to take samples, the team should take the samples in the order given above and should not mix the samples.

The wipe samples protected by the envelopes should then be taken to a low-radiationlevel area for radiation-intensity measurements. The radiation intensity of samples of fallout contamination should be measured while they are in the envelope. Measure the radiation intensity with a beta-gamma instrument, such as the AN/PDR-27 or AN/PDR-43 radiac. Be sure that the open beta window is in contact with the envelope. Always use the same radiac instrument. Before samples are read, take and record an initial background reading. Subtract this background reading from the gross sample reading to get a net sample reading. The background reading is merely a radiation reading with no sample present and should be taken about every 10 minutes when a series of samples is being analyzed. Figure 8-18 is an example of the data form.

Alpha wipe samples can be read as they are taken. Place the wipe sample on a flat surface with the wiped side facing up. Place the probe within one-eighth inch of the sample's surface. Allow 3 to 5 seconds for the alpha radiac to stabilize before you record the reading.

Personnel-Exposure Survey

The purpose of a personnel-exposure survey is to make a direct estimate of the radiation exposures of ship's personnel. This estimate is made by reading and recording the exposures indicated by the dosimeters worn by one or more persons in each team.

Protective actions, such as personnel rotation, are based in part on personnel dosimeter readings. For this reason, readings of dosimeters must be made quickly to allow adequate planning time. The interval between dosimeter checks will depend on the intensity levels where personnel perform duties, on previous individual exposures, and on the designated planning exposure. The method of

Figure 8-18.-Data form for wipe sample analysis. 8-26

determining the maximum interval between read_{ings is as follows:}

For the above example, the dosimeter should be read and recorded at least every 45 minutes. The dosimeters to be used should be specified. The DT-60/PD personnel dosimeter can be read rapidly with the CP-95/PD radiac computerindicator.

When readings are required on a minute-to-minute basis, use a self-reading dosimeter, such as the IM-143/PD. The exposure of personnel wearing selfreading dosimeters can be monitored in a manner similar to that of the area-exposure monitoring survey. On the other hand, the monitoring of nonself- reading dosimeters is best done at some fixed location, such as at an entrance to a mess hall.