Some Pentagon planners hope the end of the Cold War will signal the start of a new era — the age of “mini-nukes,” small nuclear weapons that might be used in future Third World conflicts.
Among the gleams in the nuclear planners’ eyes is a “micro-nuke” with the explosive power of just 10 tons of TNT, an item that might be suitable for jobs like blasting Iraqi dictator Saddam Hussein out of his Baghdad bunker.
A request to fund research into the new generation of small atomic weapons is included in President Clinton’s 1994 budget proposal for the Department of Energy.
Not surprisingly, the idea has sparked a blast from nuclear foes.
“Nuclear zealots couldn’t care less that the Cold War is over,” Bill Arkin, a nuclear researcher with the environmental group Greenpeace, complained yesterday. “What is shocking, though, is that the Clinton administration tolerates, and even supports, these new programs.”
Mr. Arkin described the fledgling program in a report in the July-August issue of the Bulletin of Atomic Scientists. White House and Pentagon officials acknowledged yesterday that such work is under way, but they would not comment further.
In April, Gen. Lee Butler, commander of the Pentagon’s nuclear forces, told Congress that he “is working with selected regional commands to explore the transfer of planning responsibilities for employment of nuclear weapons in theater conflicts.”
And two of the nation’s pre-eminent nuclear research labs — the Lawrence Livermore Lab in California and the Los Alamos Lab in New Mexico — want to press ahead with development of what the Clinton budget proposal calls a “precision, low-yield warhead.”
The proposed 10-ton “micro-nuke,” would pack a punch 10 times the size of the largest non-nuclear bombs dropped by U.S. forces during the Persian Gulf War. It would be 1/500th the size of the B-61, currently the smallest nuclear warhead in the Pentagon inventory.
The labs also are weighing development of a “mini-nuke,” with the explosive power of 100 tons of TNT, to destroy nuclear, biological and chemical warheads in flight, according to Los Alamos documents.
A third warhead — known as the “tiny-nuke” — would have the power of 1,000 tons of TNT and might be used against enemy ground troops. The Army, which in recent years gave up all of its battlefield nuclear weapons, had nuclear artillery shells about this size.
The Los Alamos documents declare that “any long-term nuclear stockpile should include several hundred low-yield nuclear weapons systems.”
Mr. Arkin’s report traces the growing support for these weapons among the military, which is a key element in gaining Pentagon support for their production.
The small nukes would “protect U.S. deployed forces” while denying “sanctuary to nuclear-armed leadership” of Third World nations, it said.
The weapons, according to the Los Alomos documents, also would “discourage proliferation” by deterring “future Third World nuclear states.”
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The first approach to lowering the yield of a nuclear explosion is based on how high you compress the fissile material.
It is well known that the critical mass of a fissile material is inversely proportional to the square of its density. Thus the more you compress it the less you need or the more that you compress it the bigger the bang.
At very high compression levels of 1.6 and above. There is no limit on the minimum amount of fissile material required to construct a nuclear weapon. 1 gram of fissile material will be equal to 1kilogram or more of TNT.
Therefore mini nukes with explosive yields in the several ton range will only require fissile material in the 100’s of grams range or less. This is only limited by current implosion technology. In the future Electro-Magnetic, Microwave and L.E.D. Laser compression will eventually replace simple chemical implosion systems.
The second approach is called the fizzle effect.
In the fizzle mode you simply pre-initiate the nuclear chain reaction in the fissile material while it is in a super critical state. As a result the yield of the explosion is reduced compared to it’s normal detonation value. All nuclear weapons will have a non zero fizzle value no mater what size. There are two types of nuclear weapons composed of fast and slow implosion systems.
Depending on the waiting time between the start of criticality and the moment of optimal condition. The fizzle effect is more probable in a slower gun type compression system with a fissile material with a higher level of neutron self emission (spontaneous fission).
Therefore a very small nuclear device using a single gun type compression system can be made out of reactor grade or weapons grade Plutonium. The fizzle effect is of a statical nature where the main concern would be at the moment of neutron occurrence during the waiting period just before criticality occurs.
Natural fizzle yields of up to 10 to 20 tons have been estimated for a high speed compression system that combines two sub-critical masses of plutonium at about 300 meters per second. A yield of about 5 times lower would be expected at a speed of 100m/s. 2 to 5 tons. With a 5KG mass of plutonium accelerated at 100 meters per second, its kinetic energy would be equal to 25 KJ of energy.
The energy if provided by TNT would be about 4 MJ/kg. So the amount of explosives needed to properly compress the Plutonium into a critical mass would be far less than 1KG of TNT. Simply by using a greater amount of high explosives for the same amount of plutonium, (5KG) it will produce higher velocities and compression rates that would create an even bigger yield in the 100 ton and up to the low kiloton range. 5KT max.
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It was not long before the scientists realized that in creating the tiny “core weapon” for the hydrogen bomb, they had also created a relatively lightweight micro nuclear weapon that could be carried by a single soldier for various uses against high value targets, including hydroelectric power stations and bridges. Less than two years later, the first of the SADM [Special Atomic Demolition Munition] series shown at the top of this page was pressed into operational service.
The “standard” SADM that evolved would eventually have a core of Plutonium 239 encased in a thin shell of non-fissile Uranium 238 known as a “neutron reflector”. Plutonium and Napalm flash burns – but can you tell which are which?
When the 10-ton TNT equivalence SADM went critical, it obviously created far less radiation than the huge and inappropriately named “Little Boy” at Hiroshima, but still produced dangerously high levels of residual radiation. Most of this came from SADM’s very “dirty” Uranium 238 reflector, which along with its Plutonium 239 core, exploded into millions of particles at the point of criticality.
This same non-fissile Uranium 238 material still causes serious illnesses today, after being fired by American tanks and aircraft as sub-critical Depleted Uranium [DU] shells or missile warheads. Ask anyone in southern Iraq and Kosovo how sick this stuff can make you.
The years rolled by and top-secret projects were initiated in America and Israel to replace the old SADM with its heavy weight and excess radioactivity, culminating in the successful development and testing at Dimona during 1981 of the “new” micro nuclear device. Using advanced nuclear physics, the scientists found a way of detonating the new “suitcase” bomb without the use of a Uranium 238 reflector, and further refined the Plutonium 239 in its core to 99.78%. These measures resulted in a weapon considerably smaller and lighter than SADM, which also had another enormous advantage.
The new Dimona micro nuke was the very first critical weapon that could be used in “stealth” mode. Gone was the dirty Uranium 238 reflector, and up went the purity of the smaller Plutonium 239 core. Plutonium emits only alpha radiation, which is for all practical purposes “invisible” to a standard Geiger counter. In direct contrast with its more deadly cousins beta and gamma, alpha can travel only a few feet and is incapable of penetrating human skin.
Remember that this micro nuke is a tiny weapon in terms of critical mass, with its limited number of particles distributed over a very wide area. You will have to be within five feet to detect a single particle. Though the alpha particles cannot penetrate the skin, such radiation is extremely hazardous if inhaled because Plutonium is the most toxic substance known to man. If you breathed in a mouthful immediately after the blast you would be dead in less than an hour, perhaps within minutes.
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Smallest fissile material mass which under fixed conditions (type of fissile material, geometry, moderated/immoderate system, etc.)
initiates a self-perpetuating chain reaction.
The table contains the minimum critical mass for some nuclides under certain conditions. Note in a non compressed form.
| Isotope |
Smallest critical mass in spherical shape for aqueous solution at optimum moderation |
Smallest critical mass in spherical shape for metal (fast systems) |
||
|
Unreflected |
Water-reflected |
Unreflected |
Steel- |
|
| U-233 |
1.080 |
0.568 |
15.8 |
6.1 |
| U-235 |
1.420 |
0.784 |
46.7 |
16.8 |
| Np-237 |
– |
– |
63.6 |
38.6 |
| Pu-238 |
– |
– |
9.5 |
4.7 |
| Pu-239 |
0.877 |
0.494 |
10.0 |
4.5 |
| Pu-240 |
– |
– |
35.7 |
19.8 |
| Pu-241 |
0.511 |
0.246 |
12.3 |
5.1 |
| Am-241 |
– |
– |
57.6 |
33.8 |
| Am-242 |
0.042 |
0.020 |
8.8 |
3.0 |
| Cm-243 |
0.280 |
0.127 |
8.4 |
3.1 |
| Cm-244 |
–
|
–
|
26.6 |
13.2 |
|
Cm-245 |
0.116 |
0.054 |
9.1 |
3.5 |
| Cm-247 |
4.060 |
2.180 |
6.9 |
2.8 |
| Cf-249 |
0.129 |
0.060 |
5.9 |
2.4 |
| Cf-251 |
0.048 |
0.025 |
5.5 |
2.3 |
Smallest critical masses for some fissile material under certain boundary conditions
(Continues in Part II and III)
By Knight-Ridder Newspapers
This makes the case for such weapons.
www dot reuters dot com/article/2014/08/18/us-iraq-security-yazidis-idUSKBN0GI1QK20140818?