Page 76 - July-August 2012
Basic HTML Version
76
Nuclear Plant Journal, July-August 2012
Alleviating
Tritium
Concern
By Electric Power Research Institute.
During nuclear plant operation,
leaks and spills can occur that lead to
radionuclides such as tritium entering the
soil and groundwater. While the levels of
radioactivity in the soil and groundwater
do not pose a health hazard, detecting and
characterizing these leaks is important
in ensuring public safety and informing
remediation actions.
Nuclear power plants typically
implement groundwater monitoring
programs to understand the amount of
radionuclides in the groundwater, to
assess the extent of the plume, and to
prevent off-site migration. Samples taken
using traditional methods such as low-
flow pumps, however, may take as long
as a week to analyze, resulting in a time
lag between leak occurrence and operator
awareness.
Recognizing this limitation, EPRI has
been investigating supplemental options
for identifying leaks. There currently is
no viable in-situ technology for detecting
the low levels of radioactivity found in
nuclear plant groundwater. Instead, EPRI
has been exploring how technologies for
monitoring other chemical and physical
properties could be used to detect changes
in the groundwater that might indicate
contamination. These properties include
conductivity, pH, dissolved oxygen,
salinity, temperature, and water level.
One type of in-situ probe that
has not been widely used in nuclear
applications is called a sonde, which
is specifically designed for long-term
deployment in groundwater monitoring
wells. Sondes can stay in the monitoring
well between sampling campaigns and
provide information about groundwater
temperature, conductivity, level, and
pressure.
An increase in groundwater
temperature, for example, might indicate
a leak of hot system water from a
particular part of the plant. Using an in-
situ sonde, temperatures can be tracked
over time and subtle shifts could trigger
an investigation to determine whether a
leak had really occurred or if the change
in temperature was a natural occurrence.
In-situ sensors like sondes can detect
minute changes and then alert plant
personnel through telemetry systems
such as radiofrequency or wi-fi networks.
They also can be programmed to trigger
automatic sampling systems when
specified changes are detected. This way,
anomalies can be immediately detected,
sampled, and additional investigations
can proceed.
The advanced technologies addressed
in the EPRI report can enhance existing
groundwater monitoring programs by
capturing critical data between sampling
Example of a downhole water quality
probe. Photo courtesy of YSI Inc.
campaigns. In effect, they can serve as
the proverbial “canary in the coal mine,”
providing early warning of potential
problems. Because the performance
and applicability of these technologies
are
site-specific,
however,
field
demonstration at nuclear power plants
will be needed to fully assess their value
as groundwater protection tools. EPRI
is currently pursuing several such field
demonstrations.
Contact: Brian Schimmoller, Electric
Power Research Institute, 1300 West WT
Harris Blvd., Charlotte, North Carolina
28262; telephone: (704) 595-2576, email:
Example of a downhole water quality
probe. Photo courtesy of YSI Inc.
