Ludlum Measurements 2241-2, Manual

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Model 2241-2RK Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-2 July 2012
The Unstable Atom
Radiation comes from atoms, the basic building blocks of matter.
Most atoms are stable; a 12 C atom, for example, remains a 12 C atom forever,
and an 16 O atom remains an 16
When an atom of a radioisotope decays, it gives off some of its excess
energy as radiation in the form of gamma rays or fast-moving sub-atomic
particles. One can describe the emissions as gamma, beta, and alpha
radiation.
O atom forever, but certain atoms eventually
disintegrate into a totally new atom. These atoms are said to be unstable or
radioactive. An unstable atom has excess internal energy, with the result that
the nucleus can undergo a spontaneous change towards a more stable form.
This is called radioactive decay.
Apart from the normal measures of mass and volume, the amount of
radioactive material is given in curie (Ci), a measure which enables us to
compare the typical radioactivity of some natural and other materials.
Radioactivity of some natural and other materials
1 adult human (2.7 X 10 -9 Ci/kg) 1.89 X 10 -7 Ci
1 kg (2.2 lb) of coffee 2.70 X 10 -8 Ci
1kg (2.2 lb) of super phosphate fertilizer 1.35 X 10 -7 Ci
The air in a 100 m 2 (1076 ft 2 ) Australian
home (radon)
8.12 X 10 -8 Ci
The air in many 100 m 2 (1076 ft 2 ) European
homes (radon)
8.12 X 10 -7 Ci
1 household smoke detector (with
americium)
8.12 X 10 -7 Ci
Radioisotope for medical diagnosis 1.89 X 10 3 Ci
Radioisotope source for medical therapy 2702.7 Ci
1 kg (2.2 lb) of 50-year old vitrified high-
level nuclear waste
270.27 Ci
1 luminous Exit sign (1970s) 27.027 Ci
1 kg (2.2 lb) of uranium 675.68 X 10 6 Ci
1 kg (2.2 lb) of uranium ore (Canadian, 15%) 675.68 X 10 6 Ci