Ingredients

• 3-metre length of metal drain piping
• Several sacks of concrete
• Standard household power tools
• Several metres of copper plumbing piping
• Photoelectric cell and lightsource
• Various electrical components
• A household video recorder
• A mobile phone
• A house
• A medium-sized van
• An old metal safe
• A collection of used furniture
• Protective clothing
• A quantity of commercial-grade high explosive
• Commercial explosive detonators
• A neutron emitter
• Two sub-critical masses of uranium 235

Shopping

As can be clearly seen, the majority of the articles on the shopping list can be easily obtained in any large city. So we will concentrate on the last five items on the list.

Protective Clothing

This is freely available from any number of laboratory equipment suppliers and, providing a good reason can be thought of, the purchase of such safety equipment would not be a problem.

A Quantity of Commercial-grade High Explosive and Detonators

Considering the type of people likely to be manufacturing this sort of device, a relatively small quantity of commercial high explosive and the associated detonators should not be hard to come by.

Two Sub-critical Masses of Uranium 235

Frighteningly enough, weapons-grade uranium is not likely to be the hardest of the items on the list to pick up. The most likely source would be the ex-Soviet Union.

Since the break-up of the Soviet Union, the nuclear industry has been completely neglected and seriously underfunded, with the result that some technicians and scientists are not being paid for months at a time. To add to this problem, security at nuclear facilities is extremely lax. Since the breakdown of centralised control, accounting for fissile material has been virtually impossible, and it would be relatively simple for a dedicated group to obtain a sufficient quantity of uranium.

Getting the material out of the country would also be quite easy. The southern frontiers of the old Soviet Republic would be the most likely border crossings to use; Afghanistan, Iran and Turkey being just some of the possible exit points.

A Neutron Emitter

While this is an optional device, it would greatly increase the efficiency of the bomb. This article would be one of the hardest to obtain. Theft would be one alternative, whilst posing as a research or university establishment would be an alternative method for openly obtaining the equipment needed.

Importing the Materials

Assuming the target to be London, all of the materials required could be acquired within the United Kingdom, with the exception of (as mentioned in the previous paragraph) the fissile material.

Because of the relatively small volume of uranium required, smuggling it into Europe, perhaps via Turkey, should not be a problem. At this point, the old furniture and the van come into their own. With the uranium stored in the old safe, in the back of a van, piled high with furniture, the group would just sail/drive across the channel. The fact that the radioactive material was within an iron safe should mean that the sensors on the Channel Tunnel  would not pick it up.

The Principles of the Device

The device itself is similar in design to that used for the Hiroshima bomb - a 'gun-barrel' design. This involves having the two subcritical masses at either end of the gun barrel and, using the conventional explosive as a propellant charge, shooting them at one another at a high velocity. On meeting in the middle, the combined mass would instantly reach super-critical point, and an uncontrolled nuclear reaction would be initiated. The addition of the neutron emitter would greatly increase the yield of the device itself.

It could be noted at this point that the Hiroshima bomb was only about 2% efficient, 98% of the fissile material was blasted away from the critical mass by the initial nuclear explosion, thus stopping the chain reaction long before it attained its maximum capacity.

Assembling the Device

Firstly, embed the drain pipe horizontally into a bed of concrete, ensuring that both ends of the pipe are clear, and that the top half of the pipe itself is free of concrete.

Then, drill several holes into the centre one-third of the pipe and weld on short lengths of copper piping over these holes. These holes will help the gases caused by the initial, conventional explosions, to dissipate without splitting the drainpipe.

Drill two more holes a third of the way down the pipe. These holes are used to fit the photoelectric cell and light source, which will be used to trigger the neutron emitter¹, which itself should be fitted adjacent to the centre of the pipe.

Insert the two sub-critical masses of uranium 235 into opposite ends of the pipe, followed by a conventional explosive charge. (If a plastic explosive is used, an improvement would be made if the conventional charges were to be 'shaped'. This involves forming the explosive into a 'bowl' shape, with the hollow face pointing inwards. This will have the effect of directing the explosion inwards and decreasing the likelihood of the pipe rupturing prematurely.)

After the detonators have been inserted into the explosive charges and wires run to the location of the trigger mechanism, the ends of the plates should be sealed, preferably by welding (if an inert conventional explosive has been used), or by bolting an end plate onto a previously welded flange if this is not possible.

At this stage, both the ends of the pipe and the upper surfaces should be covered with concrete, ensuring that the ends of the copper pipes used to let the expanding gases of the conventional explosion escape are not blocked. The idea of covering the pipe in concrete is simply to reduce the chance of the conventional explosive splitting the pipe.

Setting off the Device

There are three methods of exploding the device. The first and simplest method would be to manually attach the leads coming from the explosives to a battery. This, obviously would set off the device instantly, which could prove briefly uncomfortable for the person setting it off.

The two less suicidal methods would be either using a mobile phone, simply hooking the wires from the vibrator of a mobile phone into a simple amplifier circuit, and then to the detonators. The disadvantage of this system would be that if a complete stranger dialled the wrong number at the wrong moment, the effects could be catastrophic. The advantage is that the device can be detonated at any time, from anywhere in the world.

The third, and most foolproof, method is that used by the Provisional Irish Republican Army for the bomb detonated in the Grand Hotel, Brighton in 1984. The timer from a household video recorder was used to control detonation. The single disadvantage of this method is that once set, the deadline is fixed, and short of returning to the bomb itself, there is no way of altering detonation time.

The Resulting Damage

Even if the bomb itself was extremely inefficient, one should expect total destruction within a radius of between 500 and 1000 metres, with heavy damage to buildings extending far beyond this perimeter. If the bomb is detonated on the ground floor - or even better in the cellar - of the house, a crater, some 100 metres in diameter, and 5 to 6 metres deep would be formed, throwing thousands of tonnes of highly radioactive debris into the air. The majority of the damage would be due to this radioactive fall-out. The main difference between the Hiroshima bomb and this home-made device is that the device dropped over Japan was detonated at an altitude of 580 metres above ground level, which meant that though the area affected by the blast was much greater, the radioactive fallout caused by our home-made device would be many times greater. Depending on the prevailing weather conditions, one could expect radioactive fallout to effect an area extending some 50 to 100km downwind. The immediate effect of the blast would be the death of thousands of people, with many times that number injured. However, the extreme levels of radiation could affect literally tens of thousands of people, and the centre of London would be instantly uninhabitable for years, or even decades to come.

Conclusion