Radioactivity units

DOE-HDBK-1130-98

Module 1: Radiological Fundamentals

Instructor's Notes

Radioactivity units

Radioactivity is measured in the number of disintegrations

radioactive material undergoes in a certain period of time.

a. Disintegrations per minute (dpm)

b. Disintegrations per second (dps)

c. Curie (Ci)

One curie equals:

2,200,000,000,000 disintegrations per minute (2.2x1012 dpm),

37,000,000,000 disintegrations per second (3.7x1010 dps), or

1,000,000 microcuries (1x106 uCi).

EO3 Identify the units used

to measure radioactivity and

contamination.

Radioactive half- life

Radioactive half- life is the time it takes for one half of the

radioactive atoms present to decay.

EO2 Define radioactive

half- life.

Radioactive contamination

Radioactive contamination is radioactive material that is

uncontained and in an unwanted place. (There are certain places

where radioactive material is intended to be.)

EO2 Define radioactive

contamination.

Contamination is measured per unit area or volume.

dpm/100 cm2

uCi/ml

uCi/g.

EO3 Identify the units used

to measure radioactivity and

contamination.

Ionization

Ionization is the process of removing electrons from neutral atoms.

Electrons will be removed from an atom if enough energy is

supplied. The remaining atom has a positive (+) charge. The

ionized atoms may affect chemical processes in cells. The

ionizations may affect the cell's ability to function normally.