Gamma ray

RADIOLOGICAL FUNDAMENTALS

DOE-HDBK-1079-94

Tritium Primer

A particle is identical to an electron, and its mass and charge are the same as those of an

electron. As in the case of alpha particles, beta particles ionize atoms by removing electrons

from their orbits. This reaction occurs from charged particle interactions or "collisions" with

orbiting electrons.

Beta particles penetrate further than alpha particles of the same energy. A high-energy beta

particle can penetrate a few centimeters of organic tissue. The higher the energy, the greater

the penetrating ability. However, low-energy beta particles of tritium can be shielded by skin,

paper, or only about 6 mm of air.

gamma ray ( )--is emitted when the nucleus of a nuclide releases stored energy without

releasing a particle. Many gamma-emitters are found among the products of nuclear

fission.

During pure emission the nucleus does not emit particles or change its nuclear

structure or chemical characteristics. For instance,

+ AX .

Gamma radiation is in the form of electromagnetic waves (or photons). Gamma rays are similar

to x-rays, but they differ in their origin and energy. Gamma rays originate within the nucleus,

and x-rays originate outside the nucleus.

Gamma rays have a very high penetrating power because they have no charge or mass.

Depending on their energy, a stream of gamma rays may penetrate with gradually diminishing

intensity through several inches of concrete or similar material. They can be shielded effectively

by very dense materials, such as lead and uranium. Gamma rays are a whole-body hazard. That

is, because of their penetrating ability, the damage caused by gamma rays is not restricted to

any particular body organ.

neutron (n)--may be emitted spontaneously by heavy nuclei during fission or may be

emitted during radioactive decay. They are uncharged particles that have mass and a

high penetrating ability.

A neutron has about 2,000 times the mass of an electron, but only one-fourth the mass of an

alpha particle. Neutrons are difficult to stop because they lack a charge. Neutrons mainly

interact with matter by striking hydrogen nuclei or interacting with the nucleus of atoms. These

collisions generally cause charged particles or other radiation to be emitted. These particles

may then ionize other atoms. Collisions between neutronsand hydrogen nuclei (protons) are

effective in stopping or slowing down high-energy neutrons. Neutrons are best shielded by

materials with a high hydrogen content, such as water or plastic (see Figure 6).

Tritium

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