RADIOLOGICAL HAZARDS AND THEIR CONTROL

http://www.usace.army.mil/publications/armytm/tm5-801-10/app-b.pdf

B- I. Types of ionizing radiation
penetrating than either alpha or beta radiation and may be
At any facility which produces, processes, uses, or stores
radioactive materials, radiological hazards will be present
to some degree. The basic hazard associated with radioactive
material is the emission of ionizing radiation.
Radioactive material, whether naturally occurring or
manmade, is unstable and is constantly seeking a stable,
atomic configuration through a process called radioactive
decay. As radioactive material decays to stable,
nonradioactive material, or to other types of radioactive
material, ionizing radiation is emitted. This ionizing
radiation will be emitted in either particle or
electromagnetic waveform. The four basic types of
radiation of concern are alpha radiation (particles), beta
radiation (particles), gamma radiation (electromagnetic
waves), and neutron radiation (particles).
a. Alpha Radiation. Alpha radiation is composed of
positively charged particles. Each particle is composed of
two neutrons and two protons, making an alpha particle
identical to the nucleus of a helium atom (24He). Alpha
radiation is less penetrating than either beta or gamma
radiation and may be completely stopped by a sheet of
paper. Alpha radiation is not a hazard external to the
body but becomes a hazard if the alpha-emitting
radioactive material gets inside the body. Alpha radiation
is denoted by the Greek letter a.
b. Beta Radiation. Beta radiation is composed of
negatively charged particles. Each particle is identical to
an electron (-10e). Beta radiation is more penetrating than
alpha but less penetrating than gamma radiation and may
be completely stopped by a thin sheet of metal such as
aluminum. Beta radiation is an external hazard to the skin
of the body and to the eyes, and is also an internal hazard
if the beta-emitting radioactive material gets inside the
body. Beta radiation is denoted by the Greek letter $.
c. Gamma Radiation. Gamma radiation is high energy,
short wavelength electromagnetic radiation, frequently
accompanying alpha and beta radiation. Gamma radiation
is much more penetrating than either alpha or beta radiation
because of its wave form. Gamma is similar in form
and energy to K-radiation. Gamma radiation is not
entirely stopped by materials but can be almost
completely attenuated by dense materials like lead or
depleted uranium, and with greater thicknesses of
materials such as water or concrete. Because of its
penetrating power, gamma radiation is a hazard to the
entire body, whether or not the gamma emitting
radioactive material is inside or outside the body. Gamma
radiation is denoted by the Greek letter
d. Neutron Radiation. Neutron radiation is composed
of particles with no electrical charge (10n). Neutron radiation
is less penetrating than gamma radiation, but more penetrating
than either alpha or beta radiation and may be
completely stopped by an appropriate thickness of a
hydrogenous material like water or concrete. Neutron
radiation has the unique property of being able to convert
nonradioactive material to radioactive material. Neutrons
are external hazards. They are emitted by machines such
as nuclear reactors. They could be an internal hazard if a
source emitting neutrons enter the body. Neutron
radiation is denoted by the small English letter n.

B-2. Types of radiological hazards
The radiations described above are hazards because each
has the ability to ionize, either directly or indirectly, cells
which make up body organs and structures. This exposure
can be either internal or external. If the body is exposed
to large doses of ionizing radiation, cell damage may be
sufficient to interfere with normal body functions and can
cause undesirable biological effects, both in the
individuals exposed and in the future offspring of these
individuals. During the decommissioning process,
radiological hazards may be present in the form of
radiation only, or in the form of radiation together with
the radioactive material emitting the radiation. These
hazards may be grouped as external radiation, surface
radioactive contamination, airborne radioactive
contamination and waterborne radioactive contamination.
a. External Radiation.
External radiation hazards to
an individual are those presented by exposure to
emissions from radioactive sources and contaminants that
are external to the person. External radiation can be
emitted from contained or partially contained sources.
Examples include sealed radioactive sources and
radioactive material contained in a closure such as a pipe,
equipment, or a system component of some type. External
radiation hazards may also be posed by surface
contamination, airborne contamination, or waterborne
contamination. Radiation dose to individuals must be
measured to show compliance with regulatory limits. This
measurement is accomplished by film badges,
thermoluminescent dosimeters (TLDs). direct-reading
dosimeters, or a combination of the three. Radiation dose
rates are measured by portable and fixed instruments to
quantify the external radiation hazard. Individuals may be
protected from external radiation, or at least have their
radiation dose minimized, by three methods: time,
distance, and shielding.
(1) Time. Minimizing time spent in areas where external
radiation is present minimizes radiation dose.
(2) Distance. The greater the distance from a source
of radiation, the less the dose rate.
(3) Shielding. Installing materials such as lead or
concrete around a source of radiation will reduce the dose
rate.

b. Surface Radioactive Contamination.
c. Airborne Radioactive Contamination.
d. Waterborne Radioactive Contamination.

For more, see the link. This is all related to
FUSION radiation (think it's safe NOW???)