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14 Difficulties of Radiological and Nuclear Interdiction
• Field response tests use a radioactive source of known strength to confirm that
the radiation instrument produces a reading that is within a specified percentage
of the expected reading. For example, a Cs-137 source that is known to give a
reading of 15 µGy hr
−1 when held at a specified distance from the detector should
reliably produce this reading (within acceptable variability) whenever tested. A
field response test can also include checking to confirm that the displayed background radiation dose rates are within acceptable limits. The field response test is
not the same as performing an instrument calibration, but it can verify that instrument readings are reasonably accurate. Field response tests should be performed
annually or semi-annually.
• Calibration is a more detailed process [1] that involves confirming the instrument’s physical condition, testing alarms, checking electrical and electronic
systems as well as confirming the instrument’s response to multiple radiation
dose rates and/or count rates; if the instrument does not respond within acceptable margins then the calibration procedure also includes adjusting the instrument
as necessary. Calibration of instruments used for health and safety or regulatory
compliance purposes is typically performed annually; for instruments used only
for interdiction or for informational purposes calibration is recommended when
the instrument fails its bump or field response checks or every three to five years,
whichever is more frequent.
Instrument calibration can be expensive, costing thousands, tens of thousands,
or even hundreds of thousands of dollars annually depending on the number of
instruments an agency has purchased. In addition to the cost of calibration, the
agency must also collect the instruments, ship them to the calibration facility, and
the instruments cannot be used for up to several weeks—for these reasons it is not
uncommon for agencies to neglect calibration altogether. However, if field response
checks show that an instrument is indicating properly, it might not be necessary to
conduct annual calibrations; calibrating every 3–5 years (or when an instrument fails
a field response check) can reduce costs while still ensuring that an instrument is
operating properly.
In addition, users should perform regular checks on their instruments to confirm
that the instruments are not visibly damaged, to replace depleted batteries, to confirm
the instrument’s calibration status, and to ensure that it is the proper instrument to
use for the mission to be performed.
14.4 Managing Large Interdiction Efforts
Consider the commander of an interdiction mission—the person responsible for
managing and coordinating the efforts of five hundred people on foot, in vehicles,
in the air, and on the water. Four hundred of these personnel are likely carrying
14 Difficulties of Radiological and Nuclear Interdiction
• Field response tests use a radioactive source of known strength to confirm that
the radiation instrument produces a reading that is within a specified percentage
of the expected reading. For example, a Cs-137 source that is known to give a
reading of 15 µGy hr
−1 when held at a specified distance from the detector should
reliably produce this reading (within acceptable variability) whenever tested. A
field response test can also include checking to confirm that the displayed background radiation dose rates are within acceptable limits. The field response test is
not the same as performing an instrument calibration, but it can verify that instrument readings are reasonably accurate. Field response tests should be performed
annually or semi-annually.
• Calibration is a more detailed process [1] that involves confirming the instrument’s physical condition, testing alarms, checking electrical and electronic
systems as well as confirming the instrument’s response to multiple radiation
dose rates and/or count rates; if the instrument does not respond within acceptable margins then the calibration procedure also includes adjusting the instrument
as necessary. Calibration of instruments used for health and safety or regulatory
compliance purposes is typically performed annually; for instruments used only
for interdiction or for informational purposes calibration is recommended when
the instrument fails its bump or field response checks or every three to five years,
whichever is more frequent.
Instrument calibration can be expensive, costing thousands, tens of thousands,
or even hundreds of thousands of dollars annually depending on the number of
instruments an agency has purchased. In addition to the cost of calibration, the
agency must also collect the instruments, ship them to the calibration facility, and
the instruments cannot be used for up to several weeks—for these reasons it is not
uncommon for agencies to neglect calibration altogether. However, if field response
checks show that an instrument is indicating properly, it might not be necessary to
conduct annual calibrations; calibrating every 3–5 years (or when an instrument fails
a field response check) can reduce costs while still ensuring that an instrument is
operating properly.
In addition, users should perform regular checks on their instruments to confirm
that the instruments are not visibly damaged, to replace depleted batteries, to confirm
the instrument’s calibration status, and to ensure that it is the proper instrument to
use for the mission to be performed.
14.4 Managing Large Interdiction Efforts
Consider the commander of an interdiction mission—the person responsible for
managing and coordinating the efforts of five hundred people on foot, in vehicles,
in the air, and on the water. Four hundred of these personnel are likely carrying