TM 5-801-10

B-1

APPENDIX B

RADIOLOGICAL HAZARDS AND THEIR CONTROL

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 radioac-
tive 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 (2 He). Alpha

4

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 (-1 e). Beta radiation is more penetrating than

0

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 ener-

gy, short wavelength electromagnetic radiation, frequently
accompanying alpha and beta radiation. Gamma radiation
is much more penetrating than either alpha or beta radia-
tion 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 (1 n). Neutron radia-

0

tion is less penetrating than gamma radiation, but more

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 ex-

ternal 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.

TM 5-801-10

B-2

b.

Surface Radioactive Contamination. 

Surface con-

c. Airborne Radioactive Contamination. 

Airborne

tamination occurs in two basic forms: fixed and

contamination may result from several situations; for ex

removable. Fixed contamination is that which tightly

ample, disturbing surface contamination by walking

adhered to a surface. The hazard is from radioactive

through a contaminated area or working in a

material emissions. Removable contamination is readily

contaminated area, performing an operation such as

spreadable. It poses an external hazard through exposure

welding or grinding on a contaminated surface, or the

to its emissions and is available to be taken inside an

release of radioactive material from a system during

individual by ingestion, inhalation, through the skin, or

operation. Airborne contamination is usually only a minor

through open wounds. Surface contamination can be

external radiation hazard but can pose a serious internal

caused in many ways; for example, opening a system

radiation hazard because the contamination is easily

containing radioactive material for maintenance, leakage

inhaled by an individual.

from a sealed source, or an accidental spill of radioactive

(1)

Individuals are protected against the inhalation of

material during a process of some type. It can also be

airborne contamination by the use of respiratory protec-

transported from contaminated to uncontaminated areas

tive equipment. This equipment may be a filter respirator

by the movement of individuals and equipment or by air

or an air-supplied respirator depending on the concentra-

movement through the HVAC system. Protection and

tion of radioactive material in the air.

removal procedures are as follows:

(2)

Airborne contamination can be minimized, or

(1)

Individuals are protected against skin con-

prevented, by the use of ventilation through filtration and

tamination by removable surface contamination through

by performing airborne producing operations in contained

the use of protective clothing which protects from head to

areas.

foot. This clothing is removed before leaving a contain-

d.

Waterborne Radioactive Contamination. 

Water-

mated area, thus preventing the spread of surface con-

borne contamination may result from such sources as

tamination.

leaks from systems containing contaminated water and

(2)

Any items removed from a contaminated area are

water used for surface decontamination. If contaminated

put in appropriate containers to prevent the spread of

water dries, surface contamination results. Waterborne

contamination.

contamination is usually only a minor external radiation

(3)

Removable surface radioactive contamination

hazard but can pose a more serious internal radiation

can be removed from walls, floors, items, even skin much

hazard if the water is ingested.

in the same manner that dirt is removed from these sur-

(1)

Individuals are protected against waterborne

faces, by the use of soap and water and other routine

contamination by the use of plastic clothing and, if neces-

cleaning techniques.

sary, respiratory protective equipment.

(4)

Fixed contamination can be dislodged from a

(2)

Contaminated water must be handled and dis-

surface and become removable contamination by proces-

posed of in a controlled manner.

ses such as scrubbing a surface with a wire brush, filing
on the surface, flame cutting, welding, and grinding.