Measuring Radioactive Contamination

DOE-HDBK-1106-97

Lesson Plan

Instructor's Notes

EO3: IDENTIFY the

Because radioactive contamination is radioactive material,

units used to measure

the units are the same, e.g., disintegrations per minute

radioactive

(dpm).

contamination.

When measuring the amount of radioactive contamination

(material) on a surface, the units most commonly used are

disintegrations per minute per 100 centimeters squared

(dpm/100 cm2).

Direct reading

Contamination monitors measure radiation emitted by

the radioactive material. The units are normally

counts (as seen by the monitor) per minute (cpm).

Discuss counts per minute (cpm) versus

disintegrations per minute (dpm).

Explain counter

There is a direct relationship between the counts

efficiency.

recorded and the actual activity (disintegrations)

present. The counter efficiency (expressed as the

ratio of cpm/dpm) is divided into the measured cpm

to obtain the activity.