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Portable radiation survey instruments |
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|  Radiological Safety Training for Plutonium Facilities
DOEHDBK11452001
Student's Guide
3. Portable radiation survey instruments
Alpha
Because alpha particles travel only a short
distance in air (typically less than 1 inch),
surveying for alpha radiation is more difficult
than for beta or gamma radiation. Proper
survey techniques require that the probe be
held close to the surface (approximately
one-fourth of an inch). The survey speed
has to be slow (1-2 inches per second).
Alpha radiation can be shielded with a thin
film of water or dirt; therefore, care must be
taken when performing surveys. Because of
possible water shielding, personnel must not
be perspiring and material must be dry.
Beta
One type of portable survey meter is
designed to measure both beta and gamma
radiations. A sliding shield is used to
differentiate between them (closed for
gamma measurements). Like alpha
counting, the distance at which
measurements is made is important.
Gamma
Because of the low energy of the gamma
radiation, not all dose rate instruments can
be used. Due to the low energy, radiation
levels may drop off rapidly in a short
distance, causing these instruments to have
readings lower than the actual surface dose
rate.
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