NORM = naturally occurring radioactive materials.

Everything that is natural is considered "source" material by the NRC.
Everything un-natural or man-made is considered a "byproduct material".

In nature there are many different radioactive substances, but all come from
only a few parent sources.

Nuclear decay is the process by which a radioactive element sheds radiation and
in the process, spawns a new, lighter, different element. That element may or
may not be radioactive, depending how far down the decay chain it lies.

The parent elements, namely Uranium 235, Uranium 238, and Thorium have a whole
long list of elements produced by the decay process, and this long list is
called a decay CHAIN. Isotopes are nuclides that have the same atomic NUMBER but
differing atomic WEIGHTS because they have a have a different number of
neutrons. U 235 and U 238 are examples of isotopes of Uranium.

A very nice graphic representation of the 3 natural decay chains can be seen
here*:
http://www.oversight.state.id.us/ov_library/Contaminant_Fact_Sheets/DecaySeries_\
FactSheet_ANL.pdf

Only Alpha, Beta (B- and B+) and neutron radiations contribute to decay,as these
are particles. Gamma radiation is an electromagnetic wave, an adjustment of
excess energy, and does not lessen the weight of an isotope, merely its total
energy status. Charged particles travel for short distances before being
absorbed by air or other materials. Alphas only go a few inches in air, and
cannot even penetrate a piece of paper. Betas go further, about 10 feet per MeV
of energy, but still have limited penetrating ability. Gammas have no limit on
their range so in a vacuum would go on forever. In air, many hundreds of feet
are possible before random collisions with molecules absorb them. Therefore
Gammas ( when present) are the best "long-distance" clue to the *location* of a
source, and Alphas and Betas are used to help *identify* that source.

X-Rays and Gamma rays are identical, but differ in the origination location.
Gammas come from within the nucleus, whereas X-Rays are generated external to
the nucleus, in the electron shell area of an atom. Because of this difference,
X-Rays are *generally* of weaker energy than Gammas, but not always> there can
be weak Gammas and strong X-Rays.

When we think of Radium, Radon, Polonium etc. these are elements, but they exist
as creations or daughters from the decay chains, not all by themselves and are
usually still in a mixture with all the original parents and subsequent
daughters, called "equilibrium". Sometimes an isotope can be separated from its
matrix, as in the case of the gas Radon. Most Radon remains in the matrix
however, and soon turns into Polonium, a solid. All decay chain elements
eventually wind up as stable lead at the last step. Not all lead was once
Uranium, but all Uranium will eventually become lead.

A piece of natural Uranium therefore contains U-235 ( less than 1% of the total
U ) U-238, and all their daughters, Radium, Radon, Polonium, Bismuth etc. in
equilibrium.

Other than the 3 decay chains, you will also find radioactive Potassium, K-40 in
nature. As a matter of fact it is everywhere. Even in the bones inside your own
body. About 1/3 of a person's total annual radiation load comes from their own
body. Regular Potassium is very abundant on earth, and .0117 percent of it is
radioactive K-40.

More info on this subject here*:
http://www.nukeworker.com/study/hp/rct/pdf/core_1-06.pdf


*= printout and save these valuable references.

Have Fun

Geo








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