Page 139 - Environmental Control in Petroleum Engineering

126 Environmental Control in Petroleum Engineering

is one tenth the level that causes medically observable changes in
cellular chemistry. The maximum permitted occupational exposure is
one tenth of the maximum recommended exposure level (500 mREM/
yr), while the maximum permitted exposure to the general public is
one tenth of the occupational level (50 mREM/yr). These limits do
not include exposure from natural radiation or medical X-rays.
Radiation exposure limits are governed by the as low as reasonably
achievable (ALARA) concept. Under ALARA, all exposures are kept
to a minimum, even if the exposures are well below the maximum
recommended levels.

3.8.3 Naturally Occurring Radioactive Materials

In most cases, the level of NORM found at a site and the subse-
quent dose from exposure are too low to represent a serious hazard
to employees. At a few sites, however, the potential exists for expo-
sures that exceed the recommended levels after only a few hours. The
largest risk of NORM exposure is probably ingestion or inhalation of
NORM by workers handling and cleaning contaminated equipment.
Care must be taken to prevent buildup of NORM-contaminated scale
on the ground after cleaning out equipment. Because of its long half-
life (1,622 years), Ra-226 contaminated pipe yards could pose a health
threat to future development of the area, particularly in urban areas.
To determine the level of NORM at a site, radioactive assays are
conducted. The concentration of NORM in equipment or scale is
important in determining whether the material is considered radioactive
or not and how it can be disposed. These assays are expensive ($50-
$150 per sample) and can take up to 90 days before the results become
available (Miller et al., 1990).
Because of the cost and time required to assay NORM levels to
determine handling and disposal options, several attempts have been
made to develop a relationship between the specific activity of NORM
to the levels of radiation around the equipment as measured by a hand-
held detector (Carroll et al., 1990; Miller et al., 1990; Smith, 1987),
Additional work in the area is needed, however.

3.9 AIR POLLUTION

The primary impacts of air pollutant from production activities
comes from chronic exposure. For materials, the impact includes