Chapter 14
Difficulties of Radiological and Nuclear
Interdiction
Unfortunately, there is much more to radiological and nuclear interdiction than simply
putting a large number of detectors into the field and waiting for results to come in.
Radioactive sources can be shielded, and even sources of moderate activity will have
a detection radius that represents only a tiny fraction of the area of a major city or
an area to be searched.
Consider the 500 GBq Ir-192 source discussed earlier in this book; we calculated
a detection radius of slightly less than 900 m. If we assume a detection radius of
1 km to make the calculations easier; the area in which this source (if unshielded) is
detectable is about 3.14 km
2 . The area of New York City is about 785 km
2 ; the area
in which this source can be detected is a relative pinpoint on a map of New York
City and those trying to locate the source are attempting to find that pinpoint. If the
source is shielded or does not emit gamma radiation then the detection radius is even
smaller and the source is correspondingly more difficult to find.
14.1 Challenges to Radiological Interdiction
Detecting an unshielded gamma-emitting source can be challenging, especially if the
source has a relatively low activity, if it emits a low-energy photons, or if it emits a
type of radiation (neutron, alpha, or beta) that has a very short range in air. But even
higher-activity sources can be difficult to detect and/or to identify. Some factors that
can make a source challenging to detect and identify include:
• The random nature of radioactive decay, natural radiation, and radiation detection
• The use of shielding
• Emission of alpha, beta, or neutron radiation
• Presence of nuclides with similar gamma energies.
© Springer Nature Switzerland AG 2021
P. A. Karam, Radiological and Nuclear Terrorism,
Advanced Sciences and Technologies for Security Applications,
https://doi.org/10.1007/978-3-030-69162-2_14
147
Difficulties of Radiological and Nuclear
Interdiction
Unfortunately, there is much more to radiological and nuclear interdiction than simply
putting a large number of detectors into the field and waiting for results to come in.
Radioactive sources can be shielded, and even sources of moderate activity will have
a detection radius that represents only a tiny fraction of the area of a major city or
an area to be searched.
Consider the 500 GBq Ir-192 source discussed earlier in this book; we calculated
a detection radius of slightly less than 900 m. If we assume a detection radius of
1 km to make the calculations easier; the area in which this source (if unshielded) is
detectable is about 3.14 km
2 . The area of New York City is about 785 km
2 ; the area
in which this source can be detected is a relative pinpoint on a map of New York
City and those trying to locate the source are attempting to find that pinpoint. If the
source is shielded or does not emit gamma radiation then the detection radius is even
smaller and the source is correspondingly more difficult to find.
14.1 Challenges to Radiological Interdiction
Detecting an unshielded gamma-emitting source can be challenging, especially if the
source has a relatively low activity, if it emits a low-energy photons, or if it emits a
type of radiation (neutron, alpha, or beta) that has a very short range in air. But even
higher-activity sources can be difficult to detect and/or to identify. Some factors that
can make a source challenging to detect and identify include:
• The random nature of radioactive decay, natural radiation, and radiation detection
• The use of shielding
• Emission of alpha, beta, or neutron radiation
• Presence of nuclides with similar gamma energies.
© Springer Nature Switzerland AG 2021
P. A. Karam, Radiological and Nuclear Terrorism,
Advanced Sciences and Technologies for Security Applications,
https://doi.org/10.1007/978-3-030-69162-2_14
147