Environmental Engineering Reference
In-Depth Information
Various radionuclides have unique properties, and different equipment is
required to detect the different types of radiation; however, it is impractical
and potentially unnecessary to monitor for specific radionuclides. Instead, for
security purposes, it may be more useful to monitor for gross radiation as an
indicator of unsafe substances. To protect against radioactive materials being
brought on-site, a facility may set up monitoring sites outfitted with radiation
detection instrumentation at entrances to the facility. Depending on the spe-
cific types of equipment chosen, this equipment would detect radiation emit-
ted from people, packages, or other objects being brought through an entrance.
One of the primary differences between the various types of detec-
tion equipment is the means by which the equipment reads the radiation.
Radiation may be detected by direct measurement or through sampling.
Direct radiation measurement involves measuring radiation through an
external probe on the detection instrumentation. Some direct measurement
equipment detects radiation emitted into the air around the monitored object.
Because this equipment detects radiation in the air, it does not require that
the monitoring equipment make physical contact with the monitored object.
Direct means for detecting radiation include using either a walk-through,
portal-type monitor that detects elevated radiation levels on a person or in a
package or a hand-held detector, which would be moved or swept over indi-
vidual objects to locate an radioactive source.
Some types of radiation, such as alpha or low-energy beta radiation, have
a short range and are easily shielded by various materials. These types of
radiation cannot be measured through direct measurement. Instead, they
must be measured through sampling. Sampling involves wiping the surface
to be tested with a special filter cloth and then exposing the cloth to a special
counter; for example, specialized smear counters measure alpha and low-
energy beta radiation.
Reservoir Covers
Reservoirs are used to store raw or untreated water. They can be located
underground (buried), at ground level, or on an elevated surface. Reservoirs
can vary significantly in size; small reservoirs can hold as little as 1000 gal-
lons, and larger reservoirs may hold many millions of gallons. Reservoirs
can be either natural or manmade. Natural reservoirs can include lakes or
other contained water bodies, whereas manmade reservoirs usually consist
of some sort of engineered structure, such as a tank or other impoundment
structure. In addition to the water containment structure itself, reservoir sys-
tems may also include associated water treatment and distribution equip-
ment, including intakes, pumps, pump houses, piping systems, chemical
treatment, and chemical storage areas.
Drinking-water reservoirs are of particular concern because they are poten-
tially vulnerable to contamination of the stored water, through direct con-
tamination of the storage area or via infiltration of the equipment, piping, or
