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Copyright 2004 Questions or Comments:
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Survey and Detection of Clandestine
WMD
Mobile Detection Systems hitchhiking
a ride on Taxicabs
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Abstract
This Web Page will describe a novel approach to "WMD Hunting,"
using techniques similar to Uranium Prospecting. We will introduce the
novelty of hitching a ride on taxicabs and/or similar fleet vehicles. Although
this approach is applicable to Chemical and Biological WMD detection, this
page will mainly cover Radiological weapons.
Review of the fundamentals of radiological survey (prospecting)
and the obstacles to be overcome. Existing detection technology as well
as emerging technology. Also a typical survey instrumentation platform,
including detectors, data gathering, storage and transmission, as well
as centralized analysis for "connecting the dots."
Finally, refreshers on some of the pertinent technology
with historical perspectives on uranium prospecting techniques. |
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Overview:
One of America's first lines of defense against nuclear terrorism is
the Nuclear Emergency Search Team (NEST). NEST consist of a force of 1,000
civilians, most of whom come from the nuclear-weapons industry. Aware of
what such weapons can do, they have been selected to find and deactivate
nuclear bombs and materials in the hands of terrorists.
These weapons could be anywhere; from a shipping container to someone's
basement.
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Proposed:
A method for discovering Clandestine Weapons of Mass Destruction (CWMD)
by hitchhiking sensors on existing Fleet Vehicles.
This system would utilize fleet vehicles such as commercial taxicabs,
police cars, mail trucks, and other similar ubiquitous, high mileage, fleet
vehicles.
Such vehicles would be equipped with an array of sensors for the detection
of chemical, biological, and radiological weapons or materials.
Information gathered, along with GPS location data, is transmitted in
real, or near real-time, via cellular radio or satellite, to a central
authority for rapid analysis.
The unique feature of such a system is the random nature of its coverage
and the high mileage covered in a relativity short time, as well as the
diversity of sensing vehicles; all for "free."
Statistically, there are two components of this type of random search:
temporal and spatial sampling. In the case of taxis and police cars, both
dimensions are at play; where as, mail trucks would be only temporal--same
routes, at regularly scheduled sampling times.
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Factors influencing Detection
of Nuclear Radiation
Detecting clandestine nuclear materials is not unlike prospecting for
Uranium deposits in the western desert. In both cases there are several
factors which influence detection:
1)_ Intensity of the radioactive source.
2)_ Attenuation of radiation due to Shielding. The amount and
type of shielding material, e.g., to attenuate the radiation by half requires:
Lead = 0.49", Steel = 0.87", Concrete = 5.0".
3)_ Detector types, and their dimensions.
4)_ Background radiation (background count).
Background (natural radiation) radiation is caused by cosmic rays,
naturally occurring radiation from soil, plants, nuclear fallout, etc.
It is a matter of Signal to Noise (SNR).
5)_ The Distance between the source and detector reduces radiation
intensity--in air--according to the Inverse Square Law function,
i.e., the amount of radiation at a given distance from the source
is inversely proportional to the square of that distance, e.g., if the
exposure rate at 1 meter equals 100 mR/hr then the exposure rate at 2 meters
will be 25 mR/hr. see fig
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Some typical vehicles used by system; note GPS antennas---more
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-Uranium
Prospecting-
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Using Geiger Counter
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Using Scintillation Counters
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Vehicular survey covers more area---more
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Arial survey covers much more area
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Basic Survey Instruments
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Geiger Counter with Probe
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Scintillation Counter
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Geiger Muller Tube
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Scintillation Counter Front End
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| The Geiger Muller tube is filled with Argon gas, with ~ 900 Volts D.C.
applied to the thin wire in the center. When a particle enters the tube,
it pulls an electron from an Argon gas atom. The electron is attracted
to the central wire, and as it rushes towards the wire, the electron will
knock other electrons from Argon atoms, causing an "avalanche". Thus one
single incoming particle will cause a number of electrons to arrive at
the wire, creating a pulse which is amplified and counted. |
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Scintillation Detectors work by the radiation striking a suitable
material called the Scintilator (such as Sodium Iodide), produces a very
short flash of light. This light falls on the end of a very sensitive "Photomultiplier
Tube" which results in a burst of electrons large enough to be detected.
Scintillation detectors form the basis of the hand-held instruments used
to monitor contamination in nuclear power stations. They detect Alpha,
Beta, Gamma, X-ray, and Nutron radiation. |
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In the case of a nuclear bomb, radiation detectors
will be chiefly looking for Neutrons and Gamma Rays; both of which,
Uranium U235 and Plutonium Pu235 emit.
However, so called "Dirty Bombs" may use other radioactive
isotopes such as depleted Uranium, depleted Plutonium, medical isotopes,
etc. |
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There may be a requirement to to
detect Alpha and Beta particles using 'sniffer' technology similar to Chemical
and Biological sensors. [1] |
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[1] Alpha
and Beta particles are difficult to detect, e.g., Alpha particles can be
blocked by a sheet of paper. |
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-Riding
piggyback in the trunk: sensing, collection, and communication units -
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System block diagram-
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Detection Sensitivity is a function of Inverse Square Law:-
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The radiation field decreases with distance from the source as a function
of the Inverse Square Law, which states that the amount of radiation at
a given distance from a source is inversely proportional to the square
of that distance.
more info |
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Residential neighborhood overlayed with tracking and sensor data (3
vehicles).
Note the green circle is the approximate geometrical center of interest--"hot
spot." |
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Detector Shadowing
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The red line indicates the "shadowing" boundry,
notice the vehicle sensor package is at a severe
disadvantage, especially if the package is located
in the trunk. |
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Car Top Sensor Package
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A possible location for Sensor Package
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Vehicle mounted GPS and Cellular modem Antennas;
Satellite data links can be used in place of Cellular modem. |
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Various Terror Scenarios
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| One chilling aspect of the danger al Qaeda poses is the possibility
of their having suitcase Nukes!
A few of those strategically placed and all going off at the same instant
could bring down this country so easily; and think of all our enemies "piling
on" is that event; we would all have to take up speaking Russian, French,
German, Arabic, Farsi and pig latin ...
Anyway, I was thinking about how to detect clandestine nukes, something
NEST is charged with doing.
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It occurred to me that because detecting that kind of target is like
prospecting
for Uranium deposits in the western states.
Survey Vehicle
Prospecting for surface deposits of Uranium
That is, a survey in a grid pattern (raster) back and forth logging
sensor data
to be analyzed in its entirety looking for subtle trends.
When I went prospecting for uranium in the 'Four Corners" area back
in 1958; I
used a Scintillation Counter stuck inside a 75 lb lead shield which
was mounted
in a hole on the passenger side of my pickup truck--with an opening
facing the
ground.
-----Field Portable Gieger Counter
Attached to the Scintillation counter was a strip recorder of my own
design (a
rubber bladdered fountain pen, attached to a swing arm that was driven
by a
modified DC relay--sans core--as the 'meter movement,' all powered
by two KT66
audio power tubes. All of this powered by a vibrator 12 Volt to 120
VAC
inverter).
-----Field Portable Scintillation Counter
The strip chart was 3" adding machine tape. That damn thing actually
worked!
Anyway--again, the idea was to drive in a raster pattern over the terrain
of
interest, collecting data, and later analyzing the strips laid out
in rows
replicating the survey pattern.
Sadly I didn't find any deposits, but it was quite an adventure for
a 19 year
old preparing to go into the service. |
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LINKS:
----Glossary
----Isotopes
----Depleted
Plutonium and depleted Uranium
----Nuclear
Materials Management & Safeguards System (NMMSS)
----Nuclear
Primer
----GammaCamTM
Radiation Imaging System
----Technical
Aspects of Nuclear Proliferation .pdf ~2MB
----Weapons
Primer
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----"Suitcase
Nukes:" Permanently Lost Luggage 2/13/2004
--------"Suitcase
Nukes": A Reassessment 9/23/2002
----Chemical
& Biological Weapons Resource Page
----Pattern
Recognition and Intelligent Sensor Machines Laboratory
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----Preparedness
for CBR Attack
----Chemical/Biological/Radiological
Incident Handbook
----http://www.radrisk.com/detectors.htm#survey
----Cardinal
Surveys Company
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Terms:
----CBR
Chemical, Biological, Radiological
----NBC
Nuclear, Biological, Chemical
----WMD
Weapons of Mass Distruction
----W
----W
----W
----W |
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Appendix
Detection Distances |
Inverse Square Law:
Inverse Square Law: The radiation field decreases with distance from
the source. When considering a point source in air, the decrease
will follow the inverse square law, which states
that the amount of radiation at a given distance from a source
is inversely proportional to the square of the distance.
I/i = d2/D2
or
I x D2 = i x d2
(Where I = intensity at a distance (D) from a point source, and i =
intensity at a distance (d) from the same source).
Example: If the exposure rate at 1 meter equals 100 mR/hr then the
exposure rate at 2 meters equals 25 mR/hr.
Exposure Rates VS. Distance - 100 mci Sources
| Radioactive Isotope |
mR/hr @ 3' |
mR/hr @ 6' |
mR/hr @ 9' |
| 192Ir |
61 |
15.25 |
6.8 |
| 131I |
25 |
6.25 |
2.8 |
see fig
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Half-value Layer:
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The half-value layer is the thickness of a substance which reduces the
intensity of a beam of radiation to one-half of its initial value. The
half-value layer is a function of the energy of the gamma and the composition
of the shield or absorber. Examples:
Half-Value Layers
| Radioactive Material |
-Half-Life |
--Lead-- |
--Steel-- |
Concrete |
| Radionuclide |
60Co |
5.27 years |
0.49" |
0.87" |
5.0" |
| Radionuclide |
137Cs |
30.07 y |
0.25" |
0.68" |
2.1" |
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192Ir |
73.831 d |
0.19" |
0.50" |
1.9" |
| Radioiodine |
131I |
8 days |
0.14" |
0.37" |
1.4" |
60Co Cobalt radionuclide halflife 5.27 years.
137Cs Cesium radionuclide
192Ir Iridium
131I Iodine Radioiodine 131I has a half life of 8 days |
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Activity [Curie]:
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The activity of a radioactive substance is often designated by the Curie
[Ci]. The Curie is not a measure of dose; it merely states the amount of
a radioactive disintegrations per unit time. The Curie is a unit of measurement
defined as the activity of a radioactive substance disintegrating
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at a rate of: 3.7 x 1010 disintegrations per second.
Activity Units
| Name |
Definition |
Abreviation |
| Millicurie |
1/1,000 Ci |
[mCi] |
| Microcurie |
1/1,000,000 Ci |
[uCi] |
| Nanocurie |
1/1,000,000,000 Ci |
[nCi] |
| Picocurie |
1/1,000,000,000,000 Ci |
[pCi] |
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Curie:
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Units of measurement. One curie is that quantity of a radioactive nuclide
disintegrating at the rate of 3.700 x 1010 atoms per second.
Units Of Activity
| Units |
Disintegrations / Second |
| microcurie |
3.7 x 104 |
| millicurie |
3.7 x 107 |
| picocurie |
3.7 x 10-2 |
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| Energies in Electron Volts
Room temperature thermal energy of a molecule..................................0.04
eV
Visible light photons....................................................................................1.5-3.5
eV
Energy for the dissociation of an NaCl molecule into Na+ and Cl- ions:.............................................................................................4.2
eV
Ionization energy of atomic hydrogen ........................................................13.6
eV
Approximate energy of an electron striking a color television screen...................................................................................20,000
eV
High energy diagnostic medical x-ray photons...............................200,000
eV (=0.2 MeV)
Typical energies from nuclear decay:
(1) gamma..................................................................................................0-3
MeV
(2) beta.......................................................................................................0-3
MeV
(3) alpha....................................................................................................2-10
MeV
Cosmic ray energies ........................................................................1
MeV - 1000 TeV |
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© Copyright 2004 Questions
or Comments:
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