14.2 Complications with Nuclear Interdiction
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14.2 Complications with Nuclear Interdiction
One of the most significant challenges to nuclear interdiction is the fact that nuclear
weapons do not necessarily emit high levels of radiation and are not unequivocally
detectable at anything other than relatively short distances. While specific information about most nuclear weapons tends to be classified, some scientists ([5] and [6])
were permitted to make a series of measurements in close proximity to Soviet SSN-12 “Sandbox” nuclear-armed missiles using both U-235 and Pu-239 as the fissile
material. These measurements indicated that the weapons surveyed would have had
a maximum detection range of about 4–5 m using the instruments available at that
time.
Fetter’s paper was written in 1990, using both Russian and American radiation
detectors of that era and it is natural to wonder if the results and conclusions of this
paper are applicable today. It seems reasonable to conclude that they are for reasons
enumerated below:
• While the radiation instruments used today are considerably different from those
in use in 1990, the detectors themselves have not changed much; many of the
advances in the design of the most common radiation instruments involve the
user interface, adding digital (versus analog) processing and displays, and developing more powerful software for identifying analyzing gamma peaks. However,
the most commonly used detectors continue to use sodium iodide, high-purity
germanium, and a variety of neutron detectors—the same materials used in 1990.
• The instruments used by emergency responders are not the most-advanced instruments that have been developed over the last few decades; the most-advanced
instruments continue to be used by national laboratories, military, and intelligence communities. Instruments used by emergency responders are rugged and
reliable but they are not cutting-edge.
• The weapons surveyed are reported to have had a yield of over 300 kt [3] which
is considerably higher than the anticipated yield of a terrorist group’s improvised
nuclear device. This means that the weapons surveyed almost certainly contained
much more U-235 and Pu-239 than would a terrorist device and, if anything,
would be detectable at a greater distance than an anticipated IND.
• The detection method described in this paper involved detecting specific gamma
energies, which can be detected at a greater distance than less sophisticated means
(e.g. gross count rate, gross radiation dose rate) because narrow energy bands have
a lower background count rate than the energy spectrum as a whole.
For these reasons, it seems reasonable to conclude that the results of this paper
remain relevant today and that a reasonable maximum detection radius for a terrorist
IND is less than 10 m. Thus, nuclear weapons are even more difficult to detect during
interdiction operations than are radiological devices.
Nuclear weapons also emit neutron radiation from the spontaneous fission of
heavy atoms, from an alpha-neutron interaction in which an alpha particle is absorbed
by a heavy atom, prompting the release of a neutron, and from the occasional cosmic
155
14.2 Complications with Nuclear Interdiction
One of the most significant challenges to nuclear interdiction is the fact that nuclear
weapons do not necessarily emit high levels of radiation and are not unequivocally
detectable at anything other than relatively short distances. While specific information about most nuclear weapons tends to be classified, some scientists ([5] and [6])
were permitted to make a series of measurements in close proximity to Soviet SSN-12 “Sandbox” nuclear-armed missiles using both U-235 and Pu-239 as the fissile
material. These measurements indicated that the weapons surveyed would have had
a maximum detection range of about 4–5 m using the instruments available at that
time.
Fetter’s paper was written in 1990, using both Russian and American radiation
detectors of that era and it is natural to wonder if the results and conclusions of this
paper are applicable today. It seems reasonable to conclude that they are for reasons
enumerated below:
• While the radiation instruments used today are considerably different from those
in use in 1990, the detectors themselves have not changed much; many of the
advances in the design of the most common radiation instruments involve the
user interface, adding digital (versus analog) processing and displays, and developing more powerful software for identifying analyzing gamma peaks. However,
the most commonly used detectors continue to use sodium iodide, high-purity
germanium, and a variety of neutron detectors—the same materials used in 1990.
• The instruments used by emergency responders are not the most-advanced instruments that have been developed over the last few decades; the most-advanced
instruments continue to be used by national laboratories, military, and intelligence communities. Instruments used by emergency responders are rugged and
reliable but they are not cutting-edge.
• The weapons surveyed are reported to have had a yield of over 300 kt [3] which
is considerably higher than the anticipated yield of a terrorist group’s improvised
nuclear device. This means that the weapons surveyed almost certainly contained
much more U-235 and Pu-239 than would a terrorist device and, if anything,
would be detectable at a greater distance than an anticipated IND.
• The detection method described in this paper involved detecting specific gamma
energies, which can be detected at a greater distance than less sophisticated means
(e.g. gross count rate, gross radiation dose rate) because narrow energy bands have
a lower background count rate than the energy spectrum as a whole.
For these reasons, it seems reasonable to conclude that the results of this paper
remain relevant today and that a reasonable maximum detection radius for a terrorist
IND is less than 10 m. Thus, nuclear weapons are even more difficult to detect during
interdiction operations than are radiological devices.
Nuclear weapons also emit neutron radiation from the spontaneous fission of
heavy atoms, from an alpha-neutron interaction in which an alpha particle is absorbed
by a heavy atom, prompting the release of a neutron, and from the occasional cosmic