Garry Phillips – “ A Primer on the Detection of Nuclear and Radiological Weapons”
p. 5-8
- Nuclear weapons have the greatest potential to destruct of all weapons of mass destruction.
- Ex: the bomb dropped on
- Human effects of radiation fall into two categories: a) acute physical effects (these occur at high doses and lead to debilitation or death) and b) longer term low-dose effects (like cancer or genetic effects, which can lead to birth defects).
- Effects of acute exposure vary depending on which organs were exposed (possible effects = temporary sterility in men, increase in cataracts, and red bone marrow damage, as well as gastrointestinal and nervous system damage at higher doses).
- Type of radiation also matters à short-range alpha particles are stopped by the dead skin layer (and are not harmful), but when ingested or inhaled can cause leukemia or lung cancer.
- Beta radiation can penetrate the skin and cause burns.
- Gamma rays and neutrons can damage internal organs at high doses.
- Hereditary effects of radiation are hard to quantify (especially with cancer).
**Characteristics of Nuclear and Radiological Weapons
- The first nuclear weapons developed during WWII were fission and relied on Uranium or Plutonium through a) gun assembly where an explosive charge propels two subcritical masses together and b) implosion, where a shaped charge is used to compress a subcritical mass into a supercritical condition.
- The two most common used fissile materials are 235U and 239PU, which are fissionable by neutrons of all energies. To be used in a weapon, Uranium must be highly enriched.
- It then goes on to describe the details of how nuclear decay works, but I don’t think we need to know the technical parts.
p.16-17
- It is unlikely, but still possible that a terrorist group or rogue state could get a hold of a nuclear weapon.
- Obstacles would include: a) security measures at nuclear facilities and storage sites, b) smuggling the weapon or material to a safe site, c) actually building the weapon, d) smuggling the weapon into the desired attacking place and e) successfully setting off the weapon.
- What is more likely is the possibility of an attack with a “dirty bomb” (or a radiological weapon), which would combine a chemical explosive with radioactive material.
- In most cases, the exposed population could be evacuated before receiving a lethal dose.
Can Terrorists Build Nuclear Weapons?
--Carson Mark, Theodore Taylor, Eugene Eyster, William Maraman, Jacob Wechsler
Notes by: Allison Meade + Maggie Curme
Two options for nuclear devices: crude design and sophisticated design
Crude: one in which the gum type or implosion type is applied
Gun type: subcritical piece of fissile material (projectile) is fired into another subcritical piece (the target)
Implosion type: near-critical piece of fissile material is compressed by a converging
shock wave resulting from the detonation of a surrounding layer of high explosive and becomes subcritical because of its increase in density.
Small, sophisticated: one with a diameter or 1 or 2 feet and a weight
of one hundred to a few hundred pounds so that it is readily transportable. Size and weight comparable to that of a crude design.
Finished implosion device Critical mass of uranium or Plutonium, or uranium oxide (UO2) or plutonium oxide (PuO2) needed
Small sophisticated design: Similar amount of fissile material needed as in finished implosion device. Oxide powder might be used as is, although terrorists might choose to go through the chemical operation of
reducing it to metal. Such a process would take a number of days and
would require specialized equipment and techniques.
The terrorists would need something like a critical mass of the
material they propose to use.
2 obvious dilution cases:
1) Nuclear weapons CAN be made with reactor-grade plutonium because the effect of the Pu-240 on the neutron source in the material is likely to be more important than its effect on the critical mass.
2) uranium at enrichments lower than 94 percent - Here the effect on
critical mass, and consequently on the
amount of material that must be acquired and moved by the assembly
system, is quite appreciable.
For a crude design, terrorists would need something like 5 or 6 kg of
plutonium or 25 kg of very highly enriched uranium (and more for a gun-type device), even if they planned to use metal. They would have to
acquire more material than is to go into the device, since with metal
considerably more material is required to work with than will appear in the finished pieces. For terrorists there are formidable barriers to overcome.
CRUDE DESIGNS
-Schematic drawings of fission explosive devices of the
earliest types showing in a qualitative way the
principles used in achieving the first fission explosions are widely
available. However, the detailed design
drawings and specifications that are essential before it is possible
to plan the fabrication of actual parts are not
available.
-It is unlikely that any single individual, could equip himself
to proceed in each part of this diverse range of
necessary knowledge and skills
-Team would be required, yet the necessary attributes would be
quite distinct from the paramilitary capability most often supposed to typify terrorists.
- If a group equipped for this role existed, the time needed to
get ready poses a problem.
-The period would depend on a number of factors, such as the
form and nature of the material acquired and the form in which the terrorists proposed to use it; the most important factor would be the extent of the preparation and practice that the group had carried out before the actual acquisition of the material.
-To achieve a minimum turnaround time, the terrorists would,
before acquisition, have to decide whether to use the material as is or to convert it to metal.
-For the first option---using oxides without conversion to
metal---the terrorists would need accurate
information in advance concerning the physical state, isotopic
composition, and chemical constituents of the
material to be used. They would save time by avoiding the need for
chemical processing, but one disadvantage
is the requirement for more fissile material than would be needed were
metal to be used. This larger amount of
fissile material would require a larger weight in the assembly
mechanism to bring the material into an explosive
configuration.
- As to the second option---converting the materials to
metal---a smaller amount of fissile material could
be used. However, more time would be needed and quite specialized
equipment and techniques. The necessary chemical operations, and the methods of casting and machining the nuclear materials is most unlikely to proceed smoothly unless in the hands of someone with experience in the particular techniques involved, and even then substantial problems could arise.
CONCLUSIONS concerning the likelihood of terrorists successfully making a crude device nuclear weapon based on early design prociples.
- Essentially, it is not very likely—possible but not very likely. They would have to
- have a higher skill level than the average terrorist in the field of nuclear power plants (in order to steal nuclear material),
- have been doing all the prep work for months in order to have a quick turnaround time
- Have to be really strong/have great machinery because the final weapon will be very heavy
- Use metal instead of oxide powder because if they were to use powder, the density of powder they can get is not crystal density…so they would need a compressor but that is basically impossible to get without attracting attention
- Worry about the threat of pre-detonation which weakens the affects of the bomb once finally detonated for real—lots of complicated ways by which this could happen
- Worry about accidentally setting off the bomb on themselves
- All these worries stem from “home-grown” terrorists. It is possible that another country could sponsor such an attack, in which case specialists would likely be involved and these worries would not be such an issue.
MORE SOPHISTICATED DEVICES
- Highly unlikely that a terrorist could look at the released qualitative designs of a sophisticated model and make a nuclear weapon smaller enough to be easy to transport/conceal
- Much knowledge concerning the science around nuclear material and weapon making is necessary to construct a sophisticated device
- Must use plutonium metal to make weapons as small/light as possible—this is the most effective form of fissile material
- Certainly not possible with out months of planning-even more planning than the crude device, likely
MAIN CONCERN (with respect to terrorists) should be focused on those in a position to build, and bring with them, their own devices, as well as on those able to steal an operable weapon à as opposed to homegrown terrorists who probably don’t know
Nuclear Radiation Detection --Gary Phillips et al, pg. 27, 52-54
Discusses the technology of how to detect and locate a nuclear device
A detection technology needs to take advantage of one of the attributes of a nuclear device; either physical, chemical, or biological
Difficult to design a technically secure device at an acceptable cost—inevitable trade-offs with design and performance
Important to minimize complexity of the operation of the device and the amount of training needed to use the device
There are two “classes” of nuclear detection:
a. Finding and exploiting a sign that indicates radioactive/nuclear material
b. Images that reveal nuclear material (using high energy x-rays to reveal contents of a truck or ship)
Summary and Conclusions
The power and devastation nuclear weapons are immense
Materials of nuclear weapons are mainly uranium and plutonium, as well as industrial, medical, and chemical explosives. Clean up is costly.
Gamma rays and neutrons from nuclear material are not observable by high-flying aircrafts or satellites
Gamma ray imaging detectors are used to locate nuclear weapons
Plutonium weapons are detectable by their neutron emissions
Nuclear detectors have to be rather large
Need a range of nuclear detectors in order to be fully protected, including scanning cargo at ports of entry and suspicious packages
Monitors in populated areas would provide warning of an attack and time to evacuate the area. False alarms would be costly and time consuming, so proper training and calibration of the technology would be required to avoid this.
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