Part of the reason I post this is because I still enjoy occasionally (that’s occasionally, not always) reading technical papers. This article exposes a lot of information about what the nuclear development programs were about, and who was involved.
So enjoy the technicals, or, at the very least, send a nuclear “Bomb of Light” into this whole subject.
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VT Flexing Its Nuclear Muscle
From the team that solved 9/11, the ‘nuclear event,’ 11 years ago…
…by Gordon Duff, Senior Editor, and the Members of the Department of Energy 9/11 Investigation Team
“Everything we are told about nuclear weapons, who makes them, how they work and what they do is a lie. If truth is an orphan, perhaps we can supply the needed parental guidance.”… Gordon Duff
“A very small and compact fusion-fission weapon can be made consisting of 1.5 grams of tritium and 660 grams of PU-239. This will produce sufficient neutrons to fission 120 grams of plutonium directly and 660 grams of plutonium indirectly when the secondary neutrons are taken into account. The explosive energy released from a very small fusion-fission weapon design of this size is 0.20 kt or about 200 tons of TNT. In a much larger weapon containing 4.5 kg of plutonium this would release 11.6 kt of energy. Larger total yields and higher efficiency is possible.”
…(submitted by the lead investigator for the Department of Energy’s 9/11 team) …Note: This has been edited for national security reasons. Anyone attempting to play with these formulas we suggest you put your financial affairs in order, write your final letters…and please go way out into the desert somewhere on a holiday.
[Editors Note: Clinton Bastin died earlier this year, taking with him his 40 year career with the Atomic Energy Comission and the Dept. of Energy, that motherload of knowledge him in that we know longer can bried and get briefed by him.
But while he was here we did plenty and we owe him for bringing us up to to speed. And it was convenient with his being right here in Atlanta.
He put us onto how the politicians chose a nuclear policy the created huge ongoing profits via never ending maintenance and safey concerns over one of reusing nuclear fuel over and over which would eliminate the storage problem and the continued purchase of uranium. It seems the weapons producers did not like that approach.
The Iran nuclear weapons program hoax was what we most interested in at the time. He destroyed everything that had been put out to the public both here and in Israel. Not only would it have taken Iran ten years minimum to complete a program, but that we woule be able to tell in a variety of ways right away.
The American people and the world were poorly used here, and the deserve to get some retribution for what they were put through that was all theater used to manipulate us.
Clinton was not in the 911 loop, that came later with those who were his students and proteges. The big hoax we learned there is that nuclear proliferation concerns were also a hoax, as the US had first given Israel long ago all of our Davy Crockett nukes and the material in those warheads was used in more modern designs and eventually found their way into being used in terror bombing blamed on other parties... nasty stuff.
So there have been much betrayl by our ruling class, and also the security orgs that never warned us that these weapons were bascially all over the places, because they wanted to hide who had initiated it all.
And the contemporary boutique weapons designers who had worked to make cleaner, smaller, more specific target use weapons which tremendously reduced collateral damage and and the radiation after effects.
They were not happy to have seen their designs used in terrorist attacks right here in US that only very high officials could have been capable of, and/or with the assistance of a country/countries that we provide nuclear weapons grade material to. The biggest national security threat to us all has been hidden from us because of who it involved.
This information is coming out now because a reknowning is now called for, a hitting of the reset button to review what was supposedly done for our national defense, and what we know now was converted into a domestic terror threat by those within. All are welcome to join in.
After all, it is your lives at stake, your families and future generations. Plus, you have paid for it all, and will continue to do so. Believe you have a right to know, as do do the loyal weapons designers and inspectors who worked to do the right thing, and are trying to do so now… Jim W. Dean ]
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For the first time in American history, high level nuclear scientists have come forward about a massive government coverup. Veterans Today has published key sections of the highly classified 2003 DOE 9/11 Report proving the World Trade Center was destroyed by specialized nuclear munitions originating from stolen American warheads.
For those who have chosen to ignore the inexorable proofs already published, we now, with the cooperation of the DOE investigating team, publish the most comprehensive demonstration of nuclear weapons technology knowledge ever made available.
The original investigators at Ground Zero say they are no longer being silenced, that the current administration has lifted their gag orders. They have also said that their contacts inside the highest levels of the US government’s security apparatus have warned them that many “9/11 activists” are, in fact, running a sting operation, aiding the DHS and other agencies in their illegal surveillance activities.
They cite the largest and best financed groups as not gate keepers but “professional snitches.” With the bulk of 9/11 material either wild speculation or bizarre “gatekeeper” theories, the work below is our way of raising the bar to a point others can never hope to emulate.
When I contacted the DOE team, they had been following the continuing 9/11 cover up, now, according to them, being run by the “Truther” movement itself. Toward that end, “daylight” is the best way of fighting darkness. Many claim to be experts, explosives, engineering and so on. When real experts let loose, angry at the police informants and “sniffer” types, we all benefit.
The document below demonstrates how even reactor fuel can be made into powerful nuclear weapons, supplies historical context for the nuclear weapons technology and walks to the very edge of publishing the highest classified scientific secrets in the history of the world.
Editors Note: Some exact numbers and formulas have been edited for National Security reasons and may not be 100% correct.
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Presentation One: A Small Nuclear Device (don’t do this at home without a trained professional supervising)
In a very small single point compression fusion-fission weapon design. The fissile core is made of plutonium and it is assembled through linear implosion. It is usually made from tungsten and uranium alloys. The use of the tungsten is to provide a high-Z material for the radiation case, and for the fuel capsule pusher/tamper. Uranium may be used simply to provide inertial mass around the core compression system, it also serves in part as the neutron reflector and tamper.
A sketch of the design is given below. The dimensions are in centimeters. They are given along the left hand and lower border of the design. All other information is edited for national security reasons.
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The fissile material mass in this design would be up to 10 kg maximum. For a 750 ton fusion yield it would require at least 10 g of D-T mixture for the fusion fuel. Under high static pressure hydrogen can reach densities of around 0.1 mole/cc (0.25 g/cm^3 for DT).
This indicates a fuel capsule volume of at least 40 cm^3, with a spherical radius of 2.5-3 cm including wall thickness and a 10 cm spherical radius for the outer casing of the weapon. Note: The exact numbers are edited for national security reasons.
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Real Nuclear Weapons; Presentation Two
In the design of nuclear weapons the compression of PU-239 to above normal density (achievable factors range up to 3 or so in weapons) reduces the (critical mass) physical dimensions of the system proportionately.
In computing the effective reactivity of a system we must also take into account the rate at which neutrons are lost by escape from the system. This rate is measured by the number of neutrons lost per collision. For a given geometry, the rate is determined by the size of the core. Put another way, for a given geometry and degree of reactivity, the size of the core is determined only by the parameter C or core compression size. The higher the value of core compression, the smaller the assembly can be.
An indication of the effect of core compression on the size of a critical assembly can be gained by the following table of critical radii for a bare (unreflected) sphere:
Critical Radius (Cr) vs (c )
If the composition, geometry, and reactivity of a system are specified then the size of a system is fixed. Therefor the physical size or scale of the system (measured in centimeters) is inversely proportional to its density. Since the mass of the system is equal to volume*density, and volume varies with the cube of the radius. To double the density of one cubic centimeter of uranium (18.9 grams) 1.7 x 10^12 ergs is required for shock compression.
This is the amount of energy found in 40 grams of TNT, about twice the weight of the uranium. The efficiency of an implosion system at transferring high explosive energy to the core is generally not better than 30%. This allows us to make a good estimate of the amount of explosive required to compress a given amount of uranium or plutonium to high density (a minimum of 6 times the mass of the fissile material for a compression factor of 2).
That is, the critical mass of a system is inversely proportional to the square of the density. C is the degree of compression (density ratio). This scaling law applies to bare cores, it also applies to cores with a surrounding reflector, if the reflectors density has an identical degree of compression. This is usually not the case in real weapon designs, a higher degree of compression generally being achieved in the core than in the reflector. These same considerations are also valid for any other specified degree of reactivity, not just critical cores. These curves also show that very high shock compressions (four and above) are so energetically expensive as to be infeasible.
To achieve a factor of only 3, 7.1×10^11 ergs/g of uranium is required. Factoring implosion efficiency (30%), the high explosive (if it is TNT) must have a mass 56 times that of the material being compressed. Reports of compressions of four and higher can thus be safely discounted. Compression figures for plutonium above 30 kilobars, is not much different from that of uranium. Although there are large density variations from element to element at low pressure, the low density elements are also the most compressible, so that at high pressures (several megabars) the plot of density vs atomic number becomes a fairly smooth function.
This implies that what differences there may be in behavior between U and Pu at low pressure will tend to disappear in the high pressure region. Even in the low pressure region the available information shows that the difference in behavior isn’t all that great, despite the large number of phases (six) and the behavior exhibited by plutonium at atmospheric pressure. The highest density phases of both metals have nearly identical atomic volumes at room pressure, and the number of phases of both metals drops rapidly with increasing pressure, with only two phases existing for both metals above 30 kilobars.
The lowest density phase of plutonium, the delta phase, in particular disappears very rapidly. The amount of energy expended in compression at these low pressures is trivial. The compression data for uranium is thus a good substitute for plutonium, especially at high pressures and high compressions. The shock and isentropic pressures required corresponding to the compression energy curves are shown below. The pressures shown on the X axis are in kilobars, the y axis gives the relative volume change (V/V_0).
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Required Pressure for Shock and Isentropic Compression of Uranium
Since the compression energies of interest vary by many orders of magnitude over compressions ranging up to 3, it is often more convenient to look at logarithmic plots or energy. Figure 4.1.6.2.1-3, below, gives the isentropic curve from 10^7 ergs/cm^3 to 10^12 ergs/cm^3.
Since the energy for shock compression is virtually identical to the isentropic value at small compressions, the curve for shock compression is given for compression energies of 10^10 erg/cm^3 (V/V_0 ~ 0.9)
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Logarithmic Plot of Energy Required for Isentropic Compression of Uranium
Logarithmic Plot of Energy Required for Shock Compression of Uranium
Shock Wave Generation Systems
The only practical means of generating shock waves in weapons is through the use of high explosives. When suitably initiated, these energetic materials support detonation waves: a self-sustaining shock wave that triggers energy releasing chemical reactions, and is driven by the expanding gases that are produced by these reactions. Normally a high explosive is initiated at a single point. The detonation propagates as a convex detonation wave, with a more or less spherical surface, from that point. To drive an implosion, a divergent detonation wave must be converted into a convergent one (or a planar one for linear implosion).
Gun Assembly.
This was the first technique to be used for creating fission explosions, and the first to be successfully developed. The first nuclear weapon to be used in war was the gun-type bomb called Little Boy, dropped on Hiroshima. Basic gun assembly is very simple in both concept and execution. The super critical assembly is divided into two pieces, each of which is sub critical. One of these, the projectile, is propelled into the other, called the target, by the pressure of propellant combustion gases in a gun barrel. Since artillery technology is very well developed, there are really no significant technical problems involved with designing or manufacturing the assembly system.
The simple single-gun design (one target, one projectile) imposes limits on weapon, mass, and efficiency. Gun designs may be used for several applications. They are very simple, and may be used when development resources are scarce or extremely reliability is called for. Gun designs are natural where weapons can be relatively long and heavy, but weapon diameter is severely limited – such as nuclear artillery shells (which are “gun type” weapons in two senses!) or earth penetrating “bunker busters” (here the characteristics of a gun tube – long, narrow, heavy, and strong – are ideal).
Single guns are used where designs are highly conservative (early US weapon, the South African fission weapon), or where the inherent penalties of the design are not a problem (bunker busters perhaps). Double guns are probably the most widely used gun approach (in atomic artillery shells for example).
Single Gun Systems.
A practical limit for simple gun assembly (using a single gun) is a bit less than 2 critical masses, reasoning as follows: each piece must be less than 1 critical mass, if we have two pieces then after they are joined the sum must be less than 2 critical masses. If we hollow out a super critical assembly by removing a chunk from the center like an apple core, we reduce its effective density. Since the critical mass of a system is inversely proportional to the square of the density, we have increased the critical mass remaining material (which we shall call the target) while simultaneously reducing its actual mass.
The piece that was removed (which will be called the bullet) must still be a bit less than one critical mass since it is solid. Using this reasoning, letting the bullet have the limiting value of one full critical mass, and assuming the neutron savings from reflection is the same for both pieces we have: M_c/((M – M_c)/M)^2 = M – M_c where M is the total mass of the assembly, and M_c is the standard critical mass.
The solution of this cubic equation is approximately M = 3.15 M_c. In other words, with simple gun assembly we can achieve an assembly of no more than 3.15 critical masses. Of course a practical system must include a safety factor, and reduce the ratio to a smaller value than this. The weapon designer will undoubtedly surround the target assembly with a very good neutron reflector. The bullet will not be surrounded by this reflector until it is fired into the target, its effective critical mass limit is higher, allowing a larger final assembly than the 3.15 M_c calculated above.
Looking at U-235 critical mass tables for various candidate reflectors we can estimate the achievable critical mass ratios taking into account differential reflector efficiency. A steel gun barrel is actually a fairly good neutron reflector, but it will be thinner and less effective than the target reflector. M_c for U-235 (93.5% enrichment) reflected by 10.16 cm of tungsten carbide (the reflector material used in Little Boy) is 16.5 kg, when reflected by 5.08 cm of iron it is 29.3 kg (the steel gun barrel of Little Boy was an average of 6 cm thick). This is a ratio of 1.78, and is probably close to the achievable limit (a beryllium reflector might push it to 2). we get: M_c/((M – (1.78 M_c))/M)^2 = M – (1.78 M_c) which has a solution of M = 4.51 M_c. If a critical mass ratio of 2 is used for beryllium, then M = 4.88 M_c.
This provides an upper bound on the performance of simple gun-type weapons. Some additional improvement can be had by adding fast neutron absorbers to the system, either natural boron, or boron enriched in B-10. A boron-containing sabot (collar) around the bullet will suppress the effect of neutron reflection from the barrel, and a boron insert in the target will absorb neutrons internally thereby raising the critical mass. In this approach the system would be designed so that the sabot is stripped of the bullet as it enters the target, and the insert is driven out of the target by the bullet. This system was apparently used in the Little Boy weapon.
Using the M_c for 93.5% enriched U-235, the ratio M/M_c for Little Boy was (64 kg)/(16.5 kg) = 3.88, well within the limit of 4.51 (ignoring the hard-to-estimate effects of the boron absorbers). It appears then that the Little Boy design was developed with the use of >90% enrichment uranium in mind. The actual fissile load used in the weapon was only 80% enriched however, with a corresponding WC reflected critical mass of 26.5 kg, providing an actual ratio of 64/26.5 = 2.4. The mass-dependent efficiency equation shows that it is desirable to assembly as many critical masses as possible. Applying this equation to Little Boy (and ignoring the equation’s limitations in the very low yield range) we can examine the effect of varying the amount of fissile material present:
If its fissile content had been increased by a mere 25%, its yield would have tripled.
The explosive efficiency of Little Boy was 0.23 kt/kg of fissile material (1.3%), compared to 2.8 kt/kg (16%) for Fat Man (both are adjusted to account for the yield contribution from tamper fast fission). Use of 93.5% U-235 would have at least doubled Little Boy yield and efficiency, but it would still have remained disappointing compared to the yields achievable using implosion and the same quantity of fissile material.
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Cylindrical and Planar Shock Techniques.
Cylindrical and planar shock waves can be generated using the techniques previously described, making allowances for the geometry differences. A cylindrical shock can be created using the 2-D analog of the explosive lens, a wedge shaped lens with the same cross section as the conical version. A planar shock is simply a shaped shock with zero curvature. A complete cylindrical implosion would require several parallel wedge-shaped explosive lenses arranged around the cylinder axis to form a star shape.
To make the implosion truly cylindrical (as opposed to conical) it is necessary to detonate each of these lenses along the entire apex of the wedge simultaneously. This can be done by using a lens made out of sheets of high explosive (supported by a suitable backing) to create a plane shock. The edge of this sheet lens would join the apex of the wedge. This sheet lens need not extend out radially, it can join at an angle so that it folds into the space between the star points. Some special techniques are also available based on the peculiar characteristics of the 1-D and 2-D geometries. The basic principle for these techniques is the “flying plate line charge”, illustrated below.
A metal plate is covered on one side with a sheet of explosive. It is detonated on one edge, and the detonation wave travels across the plate. As it does so the detonation accelerates the plate, driving it to the right. After the explosive has completely detonated the flying plate will be flat again. The angle between the original stationary plate and the flying plate is determined by the ratio between the detonation velocity, and the velocity of the accelerated plate. When this high velocity plate strikes the secondary explosive charge the shock will detonate it, creating a planar detonation.
As described above, the system doesn’t quite work. A single detonator will actually create a circular detonation front in the explosive sheet, expanding from the initiation point. This can be overcome by first using a long, narrow flying plate (a flying strip if you will) to detonate the edge of wide plate. This wide plate can then be used to initiate the planar detonation. The flying strip approach can also be used to detonate the cylindrical lens system described above in place of the sheet lens.
The flying plate scheme can be easily extended to create cylindrical detonations.
This is a cross section view of a hollow truncated cone covered by a layer of explosives. The wide end of the cone is joined to a sheet of explosives with a detonator in the center.
The single detonator located on the axis causes an expanding circular detonation in the explosive sheet. When the shock wave reaches the perimeter, it continues traveling along the surface of the cone. The cone collapses starting at the wide end. The angle of the cone is such that a cylindrical flying plate is created that initiates a cylindrical detonation in the secondary explosive. Flying plate systems are much easier to develop than explosive lenses. Instrumentation for observing their behavior is relatively simple. Multiple contact pins and an oscilloscope can easily measure plate motion, and well established spark gap photography can image the plate effectively.
Explosives.
The choice of explosives in an implosion system is driven by the desire for high performance, safety, ease of fabrication, or sometimes by special properties like the slow detonation velocity needed in explosive lenses. The desire for high performance leads to the selection of very energetic explosives that have very high detonation velocities and pressures (these three things are closely correlated).
The highest performance commonly known explosive is HMX. Using HMX as the main explosive will provide the greatest compression. HMX was widely used in US weapons from the late fifties on into the 1970s, often in a formula called PBX-9404 (although this particular formulation proved to have particularly serious safety problems – causing eight fatalities in a six month period in 1959 among personnel fabricating the explosive). HMX is known to be the principal explosive in many Soviet weapon designs since Russia is selling the explosive extracted from decommissioned warheads for commercial use. The chemically related RDX is a close second in power. It was the principal explosive used in most early US designs, in the form of a castable mixture called Composition B.
In recent years the US has become increasingly concerned with weapon safety, following some prominent accidents in which HE detonation caused widespread plutonium contamination and in the wake of repeated fatal explosions during fabrication. Many of the high energy explosives used, such as RDX and HMX, are rather sensitive to shock and heat. While normally an impact on the order of 100 ft/sec is required to detonate one these explosives, if a sliding or friction-producing impact occurs then these explosives can be set off by an impact as slow as 10 ft/sec (this requires only a drop of 18 inches)! This has led to the use of explosives that are insensitive to shock or fire. Insensitive explosives are all based on TATB, the chemical cousin DATB lacks this marked insensitivity. These explosives have very unusual reaction rate properties that make them extremely insensitive to shock, impact, or heat. TATB is reasonably powerful, being only a little less powerful than Comp B. A composition known as PBX-9504 has been developed that adds 15% HMX to a TATB mixture, creating a compromise between added power and added sensitivity. Another very strong explosive called PETN has not been used much (or at all) as a main explosive in nuclear weapons due to its sensitivity, although it used in detonators.
Fabricating explosives for implosion systems is a demanding task, requiring rigid quality control. Many explosive components have complex shapes, most require tight dimensional tolerances, and all require a highly uniform product. Velocity variations cannot be greater than a few percent. Achieving such uniformity means carefully controlling such factors as composition, purity, particle size, crystal structure, curing time and curing temperature.
Casting was the first method used for manufacturing implosion components since a very homogenous product can be produced in fairly complex shapes. Unfortunately the most desirable explosives do not melt, which makes casting of the pure explosive impossible. The original solution adopted by the US to this problem was to use castable mixtures of the desired explosive and TNT. TNT is the natural choice for this, being the only reasonably powerful, easily melted explosive available. Composition B, the first explosive used, typically consisted of 63% RDX, 36% TNT, and 1% wax (cyclotol, a mixture with a higher proportion of RDX to TNT, was used later). Great care must be taken to ensure that the slurry of solid explosive and melted TNT is uniform since settling occurs.
Considerable attention must be paid to controlling the particle size of the solid explosive, and to monitoring the casting, cooling, and curing processes. Mold making is also a challenging task, requiring considerable experimentation at Los Alamos before an acceptable product could be made. Pressing is a traditional way of manufacturing explosives products, but its inability to make complex shapes, and problems with density variations and voids prevented its use during WWII. Plastic explosives (that is – soft, pliable explosives) can be pressed into uniform complex shapes quite easily, but their lack of strength make them unattractive in practical weapon designs. During the forties and fifties advances in polymer technology led to the creation of PBXs (plastic bonded explosives).
These explosives use a polymer binder that sets during or after fabrication to make a rigid mass. The first PBX was developed at Los Alamos in 1947, an RDX-polystyrene formulation later designated PBX 9205. Some early work used epoxy binders that harden after fabrication through chemical reactions, but current plastic binders are thermosetting resins (possibly in combination with a plasticizer). Explosive granules are coated with the plastic binder and formed by pressing, usually followed by machining of the billet.
The desire for maximum explosive energy has led to the selection of polymers and plasticizers that actively participate in the explosion, releasing energy through chemical reactions. Emphasis on this has led to undesirable side effects – like sensitization of the main explosive (as occurred with PBX-9404), or poor stability.
In the 1970s the W-68 warhead, the comprising large part of the U.S. submarine warhead inventory, developed problems due to decomposition of the LX-09 PBX being used, requiring the rebuilding of 3,200 warheads. LX-09 also exhibited sensitivity problems similar to PBX-9404, in 1977 three men were killed at the Pantex plant in Amarillo from a LX-09 billet explosion. Normally the explosive and polymer binder are processed together to form a granulated material called a molding powder. This powder is formed using hot pressing – either isostatic (hydrostatic) or hydraulic presses, using evaluated molds (1 mm pressure is typical).
The formed material may represent the final component, but normally additional machining to final specifications is required. PBXs contain a higher proportion of the desired explosive, possess greater structural strength, and also don’t melt. These last two properties make them easier to machine to final dimensions. Plastic bonding is very important in insensitive high explosives (IHEs), since mixing the insensitive explosives with the more sensitive TNT would defeat the purpose of using them.
PBX was first used in a full-scale nuclear detonation during the Redwing Blackfoot shot in June 1956. PBXs have replaced melt castable explosives in all US weapons. The PBX compositions that have been used by the U.S. include PBX-9404, PBX-9010, PBX-9011, PBX-9501, LX-04, LX-07, LX-09, LX-10, LX-11. Insensitive PBXs used are PBX-9502 and LX-17.
Explosive Compositions Used In U.S. Nuclear Weapons
Baratol: 76% barium nitrate, 24% TNT (typical)Low velocity castable explosive used in early explosive lenses.
Boracitol: 60% boric acid, 40% TNT (typical)Low velocity castable explosive used in later explosive lens designs.
Composition B: 63% RDX, 36% TNT, 1% wax (typical)High velocity castable main explosive used in early nuclear weapons
(e.g. Fat Man; Mks 4, 5 and 6), also MK 28 and MK 53 (latter warhead
still in service).
Cyclotol: 75% RDX, 25% TNTHigh velocity castable main explosive, basically just Comp B with a
higher RDX content for higher performance. Used in MK 28 and MK-53
(latter warhead still in service). Substituted for PBX-9404 when
unacceptable sensitivity problems arose.
LX-04: 85% HMX, 15% Viton AHigh velocity PBX main explosive. Used in W-62 and W-70.
LX-07: 90% HMX, 10% Viton AHigh velocity PBX main explosive. Used in W-71.
LX-09: 93% HMX, 4.6% pDNPA, 2.4% FEFOHigh velocity PBX. Main explosive used in the W-68 warhead. Withdrawn
from use due to aging problems (binder/plasticizer exudation). Serious
safety problems.
LX-10: 95% HMX, 5% Viton A; and LX-10-1: 94.5% HMX, 5.5% Viton AHigh velocity PBX main explosive. Replaced LX-09 in W-68. Also used in
W-70; W-79; and W-82.
LX-11: 80% HMX, 20% Viton AHigh velocity PBX main explosive. Used in W-71.
LX-17: 92.5% TATB, 7.5% Kel-F 800High velocity insensitive PBX. One of two IHEs in use. Used in B-83;
W-84; W-87; and W-89. Stockpile-monitoring of the W87 warhead shows
some evidence of stiffening with age, perhaps due to an increase in the
crystallinity of the binder.
PBX-9010: 90% RDX, 10% Kel-FHigh velocity PBX main explosive. Used in MK 43 and W-50.
PBX-9011: 90% HMX, 10% EstaneHigh velocity PBX main explosive. Used in MK 57 Mods 1 and 2.
PBX-9404: 94% HMX, 3% NC, 3% CEFHigh velocity PBX main explosive. Widely used – MK 43; W-48; W-50;
W-55; W-56; MK 57 Mod 2; MK/B 61 Mods 0, 1, 2, 5; and W-69. Serious
safety problems.
PBX-9501: 95% HMX, 2.5% Estane, 2.5% BDNPA-FHigh velocity PBX main explosive. Used in W-76; W-78; and W-88.
PBX-9502: 95% TATB, 5% Kel-FHigh velocity insensitive PBX. Principal IHE in recent US weapon
designs, currently being backfitted to earlier warheads replace other
plastic bonded explosives. Used in B-61 Mods 3, 4, 6-10; W-61; W-80;
W-85; W-90; and W-91.
Plumbatol: 70% lead nitrate, 30% TNT (typical)The use of this low velocity castable explosive in US nuclear weapons
is speculative.
Explosives And Binder Ingredients Used In U.S. Nuclear Weapons
Barium nitrate: Heavy metal oxidizer used in baratol slow explosive mixture.
BDNPA-F: Liquid polymer/plasticizer mixture used in PBX compositions. 50% bis(2,2-dinitropropyl), 50% acetal/bis(2,2-dinitropropyl) formal (plasticizer)
Boric Acid: Low density, low atomic number inert material used inboracitol slow explosive mixture.
CEF: Plasticizer used in PBX mixtures. tris-beta-chloroethylphosphate.
DATB: Main high explosive, insensitive. 2,4,6-trinitro-1,3-benzenediamine; also called DATNB, diamino trinitrobenzene.
DNPA (pDNPA): Solid explosive used in a binder mixture. 2,2-dinitropropyl acrylate.
FEFO: Liquid explosive used in a binder mixture. 1,1-[methylenebis(oxy)]-bis-[2- fluoro-2,2-dinitroethane].
HMX: Main high explosive, very powerful. Octahydro-1,3,5,7-tetranitro-1,3,5,7- tetrazocine; also called beta-HMX, octogen, cyclotetramethylene tetranitramine, (HMX is WWII code name, from His Majesty’s eXplosive). Dual use material, export restricted.
HNS: Relatively insensitive, a very heat stable high explosive, used in slapper detonators. 1,1′-(1,2-ethylenediyl) bis-(2,4,6-trinitrobenzene); also called hexanitrostilbene. Dual use material, export restricted.
Kel-F: Inert plastic binder. Copolymer consisting of chlorotrifluoroethylene / vinylidine fluoride (3:1 ratio).
Lead nitrate Heavy metal oxidizer used in plumbatol slow explosive mixture.
NC: Solid explosive used as a plastic binder. Nitrocellulose.
PETN: Sensitive powerful high explosive, used in detonators. 2,2- bis[(nitroxy)methyl]-1,3-propanediol dinitrate; also called pentaerythritol tetranitrate.
RDX: Main high explosive, powerful. hexahydro-1,3,5-trinitro-1,3,5-triazine; also called cyclonite, hexogen. Dual use material, export restricted.
TATB: Main high explosive, very insensitive and heat stable. Special fine-grained TATB used in boosters. 2,4,6-trinitro-1,3,5-benzenediamine; also called TATNB,
triaminotrinitrobenzene. Dual use material, export restricted. Produced on an industrial scale in the U.S. at a cost of $90 to $250/kg. Currently available to customers outside DOE for about $200/kg.
TNT: Main high explosive, used as a meltable binder. 2-methyl-1,3,5- trinitrobenzene; also called trinitrotoluene.
Viton A: Rubbery solid used as a plastic binder. Copolymer consisting of 60% Vinylidine fluoride/40% hexafluoropropylene.
Solid Pit Designs
Since shock waves inherently compress the material through which they pass, an obvious way of using the implosion wave is simply to let it pass through the fissile core, compressing it as it converges on the center. This technique can (and has) been used successfully, but it has some inherent problems not all of which can be remedied.
First, the detonation pressure of available explosives (limit 400 kilobars) is not high enough for much compression. A 25% density increase is all that can be obtained in uranium at this pressure, delta-phase plutonium can reach 50% due to the low pressure delta->alpha phase transformation. This pressure can be augmented in two ways: by reflecting the shock at high impedance interfaces, and by convergence.
Since the fissile material is about an order of magnitude denser than the explosive itself, the first phenomenon is certain to occur to some extent. It can be augmented by inserting one or more layers of materials of increasing density between the explosive and the dense tamper and fissile material in the center. As a limit, shock pressure can double when reflected at an interface. To approach this limit the density increase must be large, which means that no more than 2 or 3 intermediate layers can be used.
The second phenomenon, shock convergence, is limited by the ratio of the fissile core radius to the outer radius of the implosion hardware. The intensification is approximately proportional to this ratio. A large intensification thus implies a large diameter system – which is bulky and heavy.
Another problem with the solid pit design is t he existence of the Taylor wave, the sharp drop in pressure with increasing distance behind the detonation front. This creates a ramp-shaped shock profile: a sudden jump to the peak shock pressure, followed by a slope down to zero pressure a short distance behind the shock front. Shock convergence actually steepens the Taylor wave since the front is augmented by convergence to a greater degree than the material behind the front (which is at a larger radius). If the Taylor wave is not suppressed, by the time the shock reaches the center of the fissile mass, the outer portions may have already expanded back to their original density.
The use of intermediate density “pusher” layers between the explosive and the tamper helps suppress or flatten the Taylor wave. The reflected high pressure shock reinforces the pressure behind the shock front so that instead of declining to zero pressure, it declines to a pressure equal to the pressure jump at the reflection interface. That i s, if P is the initial shock pressure, and P -> 0 indicates a drop from P to zero through the Taylor wave, then the reflection augments both by p:(P + p) -> (0 + p).
The Gadget/Fat Man design had an intermediate aluminum pusher between the explosive and the uranium tamper, and had a convergence factor of about 5. As a rough estimate, one can conclude that the 300 kilobar pressure of Composition B could be augmented by a factor of 4 by shock reflection (doubling at the HE/Al interface, and the Al/U interface), and a factor of 5 by convergence, leading to a shock pressure of 6 megabars at the plutonium core. Assuming an alpha phase plutonium equation of state similar to that of uranium this leads to a compression of a bit less than 2, which when combined with the phase transformation from delta to alpha gives a maximum density increase of about 2.5. The effective compression may have been significantly less than this, but it is generally consistent with the observed yield of the devices.
Levitated Core Designs
In the solid pit design, the Taylor wave is reduced but not eliminated. Also, the kinetic energy imparted by the convergent shock is not efficiently utilized. It would be preferable to achieve uniform compression throughout the fissile core and tamper, and to be able to make use of the full kinetic energy in compressing the material (bringing the inward motion of material in the core to a halt at the moment of maximum compression).
This can be accomplished by using a shell, or hollow core, instead of a solid one (see Section 3.7.4 Collapsing Shells). The shell usually consists of an outer layer of tamper material, and an inner layer of fissile material. When the implosion wave arrives at the inner surface of the shell, the pressure drops to zero and an unloading wave is created. The shock compressed material (which has also been accelerated inward) expands inward to zero pressure, converting the compression energy into even greater inward directed motion (approximately doubling it). In this way energy loss by the outward expansion of material in the Taylor wave region is minimized.
Simply allowing this fast imploding hollow shell to collapse completely would achieve substantial compression. In practice this is never done. It is more efficient to allow the collapsing shell to collide with a motionless body in the center (the “levitated core”), the collision creating two shock waves – one moving inward to the center of the stationary levitated core (accelerating it inward), and one moving outward through the imploding shell (decelerating it). The pressure between these two shocks is initially constant so that when the converging shock reaches the center of the core, the region extending from the center out to the location of expanding shock has achieved reasonably even and efficient compression.
I use word “reasonably” because the picture is a bit more complicated tha n just described. First, by the time the shell impacts the levitated core it has acquired the character of a thick collapsing shell. The inner surface will be moving faster than the outer surface, and a region close to the inner surface will be somewhat compressed. Second, the inward and outward moving shocks do not move at constant speed. The inward moving shock is a classical converging shock with a shock velocity that accelerates and strengthens all the way to the center. The outward moving shock is a diverging or expanding shock that slows down and weakens.
In the classical converging shock region (the levitated core, and the innermost layer of the colliding shell) high compression is achieved and the material is brought to a halt when the shock reaches the center. In the outer diverging region, only about half of the implosion velocity is lost when the diverging shock compresses and decelerates it, and there is insufficient time for inward flow to bring it to a hal t before the converging shock reaches the center. Thus the outer region is still collapsing (slowly) when the inner shock reaches complete convergence (assuming that the outer shock has not yet reached the surface of the pit (tamper shell plus core) and initiated an inward moving release wave).
Immediately after the converging shock reaches the center, the shock rebound begins. This is an outward moving shock that accelerates material away from the center, creating an expanding low density region surrounded by a layer compressed to an even greater degree than in the initial implosion. Once the rebound shock expands to a given radius the average density of the volume within that radius falls rapidly.
For a radius well outside the classical converging shock region, the true average density may continue to increase due to the continuing collapse of the outer regions until the rebound shock arrives. The structure of the shell/core system at the time of rebound shock a rrival is actually hollow – a low density region in the center with a highly compressed shell, but the average density is at a maximum. Whether this configuration is acceptable or not depends on the weapon design, it may be acceptable in a homogenous un-boosted core but will not be acceptable in a boosted or a composite core design where high density at the center is desired.
Since the divergence of the outward shock is not great, and it is offset somewhat by the slower collapse velocity of the outer surface of the thick shell, we can treat it approximately as a constant speed shock traversing the impacting shell. The converging shock can be treated by the classical model (see Section 3.7.3 Convergent Shocks). This allows us to estimate the minimum shell/levitated core mass ratio for efficient compression, the case in which the shock reaches the surface of the shell, and the center simultaneously.
If the shell and levitated core have identical densities and compre ssibilities, then the two shocks will have the same initial velocity (the velocity change behind the shock front in both cases will be exactly half the impact velocity). If the shell has thickness r_shell, then the shock will traverse the shell in time:
If the levitated core has radius r_lcore, the shock will reach the center in time:
Alpha is this case is the convergent shock scaling parameter (see Section 3.7.3). For a spherical implosion, and a gamma of 3 (approximately correct for most condensed matter, and for uranium and plutonium in particular), alpha is equal to 0.638 (the exact value will be somewhat higher than this).
Since we want t_shell = t_lcore:
That is, the thickness of the shell is smaller than the radius of the core by a factor of 0.638. But since volume is proportional to the cube of the radius:
This gives us the mass ratio:
Thus we want the impacting shell to have at least 3.4 times as much mass as the levitated core. The ratio used may be considerably larger.
Now it is important to realize that in principle the shell/levitated core mass ratio is unrelated to the tamper/fissile material mass ratio. The boundary between tamper and fissile material can be located in the shell (i.e. the shell is partly tamper and partly fissile, the levitated core entirely fissile), it can be located between the shell and core (i.e. the shell is tamper and the core is fissile), or it can be located in the core (i.e. the shell is tamper, and the core is partly tamper and partly fissile). The tamper/fissile material ratio is determined by neutron conservation, hydrodynamic confinement, and critical mass considerations.
It appears however that the initial practice of the US (starting with the Mk4 design and the Sandstone test series) was to design levitated core weapons so that the shell was the uranium tamper, and the levitated portion was a solid fissile core. The mass of the tamper would have been similar to that used in the Gadget (115 kg), a large enough mass to allow the use of different pit sizes and compositions while ensuring sufficient driver mass. These early pure fission bombs were designed to use a variety of pits to produce different yields, and to allow the composition (U-235/Pu-239 ratio) to be varied to match the actual production schedules of these materials.
Levitation is achieved by having some sort of support structure that will not disrupt the implosion symmetry. The most widely used approach seems to be the use of truncated hollow cones (or conically tapered thin walled tubes if you prefer), usually made out of aluminum. Six of these are used, pairs on opposite sides of the levitated core for each axis of motion. Supporting wires (presumably under tension) have also been used.
The levitated core of the Hurricane device (the first British test) used “caltrops” (probably six of them) for support. A caltrops is a four pronged device originally used in the Middle Ages as an obstacle against soldiers and horses, and more recently against vehicle tires. Each of the prongs can be thought of as the vertex of a tetrahedron, with the point where they all join as the tetrahedral center. A caltrops has the property that no matter how you drop it, three of the prongs forms a tripod with the fourth prong pointed straight up. Dimples on the core might be used to seat the support prongs securely.
Another possibility is to use a strong light weight foam to fill the gap between shell and core (such foams have been produced at the Allied-Signal Kansas City Plant). A significant problem with using a foam support is that plastic foams are usually excellent thermal insulators, which could cause severe problems from self-heating in a plutonium levitated core.
A serious problem with hollow shell designs is the tensile stress generated by the Taylor wave (see Section 3.6.1.1.2 Free Surface Release Waves in Solids). As the release wave moves out from the inner shell surface, it encounters declining pressure due to the Taylor wave. The “velocity doubling” effect generates a pressure drop equal in magnitude to the shock peak pressure. If the pressure that the release wave encounters is below this pressure, a negative pressure (tension) is created (you can think of this as the faster moving part of the plate pulling the slower part along). This tensile stress builds up the farther back the release wave travels. If it exceeds the strength of the material it will fracture or “spall”. This can cause the entire inner layer of material to peel off, or it may simply create a void. A new release wave will begin at the spall surface.
Spalling disrupts implosion symmetry and can also ruin the desired collision timing. It was primarily fears concerning spalling effects that prevented the use of levitated core designs in the first implosion bombs.
One approach to dealing with spalling is simply to make sure that excessive tensile stresses do not appear in the design. This requires strong materials, and at least one of the following:
relatively weak implosion pressures;
a highly suppressed Taylor wave; or
thin shells.
The first option is extremely undesirable, but the latter two can be used in viable designs.
Another approach is to adopt the “if you can’t beat’em, join’em” strategy. Instead of trying to prevent separation in the shell, accommodation for the phenomenon is included in the design. This can be done by constructing the shell from separate layers. When the release wave reaches the boundary between shell layers (and tensile stress exists at that point), the inner layer will fly off the outer layer, and a new release wave will begin. This will create a series of imploding shells, separated by gaps.
As each shell layer converges toward the center, the inner surface will accelerate while the outer surface will decelerate. This will tend to bring the layers back together. If they do not rejoin before impact occurs with the core, a complicated arrangement of shocks may develop. The design possibilities for using these multiple shocks will not be considered here.
The concept of the levitated core and colliding shells can be extended to multiple levitation – having one collapsing shell collide with a second, which then collides with the levitated core. The outer shell, due to the concentration of momentum in its inner surface and the effects of elastic collision, could enhance the velocity of the inner shell. This idea requires a large diameter system to be practical. It is possible that the “Type D” pit (that is, the hardware located between the explosive and fissile core) developed in the early fifties for the 60 inch diameter HE assemblies then in the US arsenal was such a system. It considerably increased explosive yields with identical cores.
It seems almost certain that the most efficient kiloton range pure fission bomb ever tested – the Hamlet device detonated in Upshot-Knothole Harry (19 May 1953) – used multiple levitation. It was described as being the first “hollow core” device, presumably the use of a fissile core that itself was an outer shell and an inner levitated core. A TX-13D bomb assembly (a 60 inch implosion system using a Type D pit) was used with the core. The yield was 37 kt.
Thin Shell (Flying Plate) Designs
Thin shell, or flying plate designs, take the hollow core idea to an extreme. In these designs a very thin, but relatively large diameter shell is driven inward by the implosion system. As with the regular hollow core design, a levitated core in the center is used.
The advantages of a flying plate design are: a greatly increased efficiency in the utilization of high explosive energy; and a higher collision speed – leading to faster insertion and greater compression for a given amount of explosive. Thin shell flying plate designs are standard now in the arsenals of the nuclear weapon states.
A thin plate, a few millimeters thick, is thinner than the Taylor wave of an explosive shock. The shock acceleration, followed by full release, is completed before the Taylor wave causes a significant pressure drop. The maximum initial shock acceleration is thus achieved.
Even greater energy transfer than this occurs however. When the release wave reaches the plate/explosive interface (completing the expansion and velocity doubling of the plate), a rarefaction wave propagates into the explosive gases. The gases expand, converting their internal energy into kinetic energy, and launching a new (but weaker) shock into the plate. A cyclic process thus develops in which a series of shocks of diminishing magnitude accelerate the plate to higher and higher velocities. If viewed from the inner surface, the observer would see a succession of velocity jumps of diminishing size and at lengthening intervals. The plate continues to accelerate over a distance of a few centimeters.
The maximum velocity achievable by this means can approach the escape velocity of the explosive gases, which is 8.5 km/sec for Comp B. Velocities up to 8 km/sec have been reported using HMX-based explosives. This can be compared to the implosion velocity of the plutonium pit in the Gadget/Fat Man design, which was some 2 km/sec.
Optimum performance is found when a small gap (a few mm) separates the high explosive from the plate. Among other things, this gap reduces the strength of the Taylor wave. The gap may be an air space, but it is usually filled with a low impedance material (like a plastic).
The mass ratio between the explosive and the plate largely determines the system performance. For reasonable efficiency it is important to have a ratio r of at least 1 (HE mass/plate mass). At r=1 about 30% of the chemical energy in the explosive is transferred to the plate. Below r=1, the efficiency drops off rapidly. Efficiency reaches a maximum at r=2, when 35% of the energy is transferred.
Since a higher mass ratio means more energy available, the actual final velocity and energy in the plate increases monotonically with r, as shown in the table below. Higher values of r also cause the plate to approach its limiting value with somewhat shorter travel distances.
Flying Plate Drive Efficiency
Plate/HE Mass Ratio (R)
Energy Fraction Transferred
Relative Velocity
Plate/Detonation Velocity Ratio
0.25
0.16
1.00
0.07
0.50
0.22
1.65
0.12
1.00
0.30
2.74
0.20
2.00
0.35
4.18
0.30
5.00
0.30
6.12
0.40
7.00
-
7.65
0.50
10.00
0.25
7.91
0.56
40.00
0.11
10.60
0.75
By the time the flying plate converges from a radius of 10-20 cm to collide with the levitated core, it is no longer a thin shell. The velocity difference that is inherent in thick shell collapse leads to a collision velocity of the inner surface that is higher than the average plate velocity. Collision velocities of experimental uranium systems of 8.5 km/sec have been reported.
The flying plate can be used in a variety of ways. It can be the collapsing shell of a levitated core design. Or it can be used as a driver which collides with, and transfers energy to a shell, which then implodes on to a levitated core. Combined Tamper/Reflector Systems By the time the flying plate converges from a radius of 10-20 cm to collide with the levitated core, it is no longer a thin shell. The velocity difference that is inherent in thick shell collapse leads to a collision velocity of the inner surface that is higher than the average plate velocity. Collision velocities of experimental uranium systems of 8.5 km/sec have been reported.
Cylindrical Implosion Comparison of Reflector Materials Below is a list of candidate materials, and their atomic densities. The list includes the six highest atomic density pure elements (C – in two allotropic forms, Be, Ni, Co, Fe, and Cu), and a number of compounds that are notable for having high atomic densities. Atomic densities for the major tampers materials are also shown. Highly Enriched Uranium (HEU)Highly enriched uranium (HEU) is produced by processing natural uranium with isotopic separation techniques. Natural uranium consists of 99.2836% U-238, 0.7110% U-235, and 0.0054% U-234 (by mass). Enrichment processes increase the proportion of light isotopes (U-235 and U-234) to heavy ones (U-238). Enriched uranium thus contains a higher percentage of U-235 (and U-234) than natural uranium, but all three isotopes are always present in significant concentrations. The term “HEU” usually refers to uranium with a U-235 of 20% or more. Uranium known to have been used in fission weapon designs ranges in enrichment from 80-93.5%. In the US uranium with enrichment around 93.5% is sometimes called Oralloy (abbreviated Oy) for historical reasons (Oralloy, or Oak Ridge ALLOY, was a WWII codename for weapons grade HEU). As much as half of the US weapon stockpile HEU has an enrichment in the range of 20-80%. This material is probably used in thermonuclear weapon designs.
The flying plate can be used in a variety of ways. It can be the collapsing shell of a levitated core design. Or it can be used as a driver which collides with, and transfers energy to a shell, which then implodes on to a levitated core.
The discussion of implosion has implicitly assumed a spherically symmetric implosion since this geometry is the simplest, and also the most efficient and widely used. Few changes are neede