Environmental Engineering Reference
In-Depth Information
supplies and water treatment, storage, or distribution systems because radia-
tion emitted from radionuclides in water systems can affect individuals
through several pathways—by direct contact with the contaminated water
or by ingestion of, inhalation of, or external exposure to the contaminated
water. Radiation can occur naturally in some cases due to the decay of some
minerals, but the intentional or unintentional release of manmade radionu-
clides into water systems is also a realistic threat.
Threats to water and wastewater facilities from radioactive contamination
could involve two major scenarios. First, the facility or its assets could be
contaminated, preventing workers from accessing and operating the facil-
ity. Second, at drinking water facilities, the water supply could be contami-
nated, and tainted water could be distributed to users downstream. These
two scenarios require different threat reduction strategies. The first scenario
requires that facilities monitor for radioactive substances being brought on-
site; the second requires that water assets be monitored for radioactive con-
tamination. The effects of radioactive contamination are basically the same
under both types of threats, but each of these threats requires different types
of radiation monitoring and equipment.
Radiation Detection Equipment for Monitoring Water Assets
Most water systems are required to monitor for radioactivity and certain
radionuclides and to meet maximum contaminant levels for these contami-
nants to comply with the Safe Drinking Water Act. Currently, the USEPA
requires drinking water to meet MCLs for beta/photon emitters (includes
gamma radiation), alpha particles, combined radium 226/228, and uranium;
however, this monitoring is required only at entry points into the system.
In addition, after the initial sampling requirements, only one sample is
required every 3 to 9 years, depending on the contaminant type and the
initial concentrations. This is adequate to monitor for long-term protection
from overall radioactivity and specific radionuclides in drinking water, but
it may not be adequate to identify short-term spikes in radioactivity, such as
from spills, accidents, or intentional releases. In addition, compliance with
the SDWA requires analyzing water samples in a laboratory, which results in
a delay in receiving results. In contrast, security monitoring is more effective
when results can be obtained quickly in the field. In addition, monitoring
for security purposes does not necessarily require that the specific radionu-
clides causing the contamination be identified. Thus, for security purposes,
it may be more appropriate to monitor for non-radionuclide-specific radia-
tion using either portable field meters, which can be used as necessary to
evaluate grab samples, or online systems, which can provide continuous
monitoring of a system.
Ideally, measuring radioactivity in water assets in the field would involve
minimal sampling and sample preparation; however, the physical properties
of specific types of radiation combined with the physical properties of water
