The recipe (you’ll need a centrifuge plant, very good explosives, a good cannon or missile and a nuclear reactor) :
- Some very depleted uranium (the more depleted, the better, for instance you’ll find that French depleted uranium is officially acknowledged as going down to 0.14% of U235)
- A few grams of highly enriched uranium (HEU)
- A neutron source, a strong alpha emitter for instance, or tritium
- Hydrogen-rich plastic !
We make a depleted uranium arrow so that the body is made of highly depleted uranium (in an alliage so very solid) and the tip of highly enriched uranium (without an alliage so highly ductile). The whole ammunition has a percentage of U235 of 0.2%, but you can climb to 0.72% so that the resulting ash can be discarded as coming from the ground (as in the case of the Khiam crater where, in spite of an uranium concentration 10 times higher in a short perimeter around it, UNEP used the fact it was natural uranium to discard the military origin). This allows to use more HEU on the tip.
The tip, the grey triangle on the right, is made of beryllium. Beryllium is always used in the forehead of uranium shells and in missiles.
In a hole made inside the beryllium tip, when the day of war has come, one has to insert the neutron source, for instance a strong alpha emitter like bismuth 212 (thanks to its short half life it will not leave traces on the ground, even though we have found high quantities of its stable decay product, lead 208, in the teeth of malformed babies in Bassorah (Savabieasfahani et al 2016) as well as in the hair of prematured and malformed babies in Gaza, even though teeth is much better than hair for researching lead (Manduca et al 2014) – on the use of tritium see here). This works as well with a shaped charge missile, you just need to put a small dice of highly enriched uranium inside the cone (keep it shaped), to cover it with beryllium and then to insert on top of the beryllium cover the neutron source.
At the impact the first thing that happen is that beryllium and the alpha source are merged. Thanks to the (a,n) reaction fast neutrons will be produced. Those who go in the direction of the tip of the shell are then moderated by the crossing of the beryllium. They are slowed down. Then they meet the small tamper of highly enriched uranium. Its mass is very strongly increased by the strength of the impact (it is ductile and the solid U238 arrow compresses it – all fission bombs work like that, even “gun-type”, to go vastly above critical mass). Of course it goes critical, this is calculated to happen. For instance, for an APFSDS tank shell fired at 1750 meters / second and an impact time of 0.005 seconds (very short because of ductility !), a 2.7 grams tamper of pure U235 (as an approximation for 95%) will have an effective mass of ((1750 / 0.005) *0.0027)/9.81 = 96.3 kilograms. Much above the mass required for criticity at this level of enrichment (according to Carey Sublette from Nuclear Weapon Archive the 64 kgs of 83% HEU of Little Boy amounted to almost 3 critical masses, they must have been separated into three pieces). If the HEU is mixed with hydrogen-rich plastic the criticity threshold is even significantly lower (hydrogen being an excellent neutron moderator), as confirmed by James Mahaffey, who worked for the Defense Nuclear Agency, in his book Atomic Awakening (an experiment by Otto Frisch in the framework of the Manhattan Project, in 1944, which certainly explains why Little Boy amounted to almost 3 critical masses). This is so certainly also used for HEU tips in “depleted” uranium shells and shaped charges. It is also public, for instance, that dissolving U235 into water will strongly reduce the critical mass (to 1,4 kgs without neutron reflectors according to the European Nuclear Society).
The resulting chain reaction should have a yield inferior to Little Boy (because the neutron source is outside the block), so that if we take a yield of 1%, 0.027 grams of U235 actually fission, liberating 2.24 billions of Joules, the equivalent of the combustion of 53 kilograms of oil, or the explosion of 535 kilograms of TNT, but the energy is mostly produced as heat and neutrons (Jane’s, the specialized defense periodical, once acknowledged the temperature reached at the explosion of depleted uranium shells is around 10 000°C).
In our example, we also have the production of 0.007 grams of uranium 236, which has been found everywhere in Iraq and Afghanistan (by Durakovic and Gerdes from the UMRC ; this has been even noted in the abovementioned parliamentary report).
The molten shell goes instantaneously through the armour and is spread in the tank, which is still closed except for the fission hole of the impact. U235 is in gaseous state in the “cave”. The bodies of the crew have been burned down very deeply (see pic below) so there is vapor (human body = water). Then come the delayed neutrons from the first chain reaction ; vapor is a very good neutron moderator (it is known that the critical mass is very low for U235 dissolved in water, here it’s a gas !) so the delayed neutrons produce another chain reaction. An ignited mass of 4.5 kilograms of depleted uranium (or, more probably, natural uranium) is on a first glance unlikely to see a chain reaction happen, but these delayed neutrons are very very numerous (1% of the neutrons of an uncontrolled chain reaction, that’s a lot). Delayed neutrons spraying out onto the top of the “cave” and reflected into the core are slowed down by the vapor, U235 has lots of chances to cross neutrons because atoms of a gas move very fast, so the tank behaves exactly as a nuclear reactor with a positive void coefficient. We thus see quite frequently an explosion with a flash typical of supercritical nuclear fission in destroyed tanks, a few seconds after the first impact. They are clearly a proof of the arrival of the delayed neutrons.
Another three confirmations of what is here claimed :
- the absence of a secondary flash in weapon demonstrations on tanks (we find many videos of this kind on the Web, esp. for missiles) can easily be explained by the absence of crewmen inside the tanks targeted for the weapon demonstration (for arms dealings etc.)
- the absence of plutonium 239 in samples from Iraq and Afghanistan, whereas lots of uranium 236 have been found, confirm that fission happens essentially in highly enriched uranium (on the nose of the shell, and then in the water vapor + U235 gas mix, mix in which there is not a lot of U238).
- also, the very limited findings of Pu239 vs. the numerous findings of U236 confirm that the presence of U236 is not the simple consequence of the use of recycled depleted uranium (from used fuel, heavily contaminated with Pu239 and other actinids) but proof of transmutation. Also, why use recycled depleted uranium (difficult to manipulate because highly radioactive) when there are tons of depleted uranium from centrifuges available ? (as well as tons of highly enriched uranium from the Cold War)
See also our article in French on military camps for a list of the proof of nuclear fission, and our article on depleted uranium weapons and jihadist radicalisation.