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THE NUCLEAR RENAISSANCE AND THE SPREAD OF NUCLEAR WEAPONS
Introduction
The world is on the brink of a nuclear renaissance in which many countries will construct and operate new nuclear-power reactors. New nuclear-power reactors will be of a new generation probably fuelled by a mixed-oxide (MOX) nuclear fuel, a mixture of uranium and plutonium dioxides, instead of uranium dioxide, the fuel used today in most nuclear-power reactors. MOX fuel has serious implications for nuclear-weapon proliferation and nuclear terrorism because the plutonium dioxide in it can easily be separated by straightforward chemistry from the uranium dioxide and used to fabricate nuclear weapons.
If the nuclear industry gets its way, this new generation of reactors will lead, after about 2030, to the construction of another new generation of reactors, reactors that will, the nuclear industry hopes, be the eventual core of any nuclear renaissance. These reactors will, for example, be fast breeder reactors. A number of countries are experimenting with breeder reactors. Designed to produce more nuclear fuel than they use, they will be fuelled with plutonium, with only a small input of uranium. The plutonium will be of a type suitable for use in the most efficient nuclear weapons.
These two new generations of reactors will, to say the least, very seriously increase the risk of the proliferation of nuclear weapons to countries that do not now have them and, perhaps more seriously in today’s world, the risk of nuclear terrorism. Nuclear terrorist groups will probably eventually acquire plutonium, fabricate primitive nuclear weapons and use them in terrorist attacks.
Any country operating new nuclear-power reactors, particularly breeder reactors, will have relatively easy access to plutonium usable in effective nuclear weapons and will have competent nuclear physicists and engineers who could design and fabricate them. Because they could produce a nuclear force in a short time – months rather than years – these countries will be latent nuclear-weapon powers. It must be expected that some of them will take the political decision to become actual nuclear-weapon powers. Nuclear-weapon proliferation is the most serious global problem we face.
Within 30–40 years, about 30 countries are likely to have access to fissile materials from their civil nuclear power programmes that can be used for nuclear weapons and competent nuclear physicists and engineers who could design and fabricate them. It has to be expected that some of these countries will take the political decision to become nuclear-weapon powers.
Moreover, the world of the nuclear renaissance will be one containing a huge amount of separated plutonium, some of which is bound to fall into the wrong hands including those of nuclear terrorists. The potential spread of nuclear weapons to terrorists clearly has very major implications for global security. Surprisingly, it is receiving very little attention.
Nuclear terrorism
There are number of nuclear terrorist activities that a terrorist group may become involved in:
- stealing or otherwise acquiring fissile material and fabricating and detonating a primitive nuclear explosive;
- attacking a nuclear-power reactor to spread radioactivity far and wide;
- attacking the high-level radioactive waste tanks at a reprocessing plant, like Sellafield, to spread the radioactivity in them;
- attacking a plutonium store at a reprocessing plant, like Sellafield, to spread the plutonium in it;
- stealing or otherwise acquiring a nuclear weapon from the arsenal of a nuclear-weapon power and detonating it; and
- attacking, sabotaging or hijacking a transporter of nuclear weapons or nuclear materials; and
- making and detonating a radiological weapon, commonly called a dirty bomb, to spread radioactive material.
Apart from a dirty bomb, all of these types of nuclear terrorism have the potential to cause large, or quite large, numbers of deaths. Of them, nuclear terrorists would probably prefer to set off a nuclear explosive, because of the great damage it would do, perhaps using a stolen nuclear weapon or more likely using a nuclear explosive fabricated by them from acquired fissile material. Terrorists would be satisfied with a nuclear explosive device that is far less sophisticated than the types of nuclear weapons demanded by the military. Whereas the military demand nuclear weapons with predictable explosive yields and very high reliability, most terrorists would be satisfied with a relatively primitive nuclear explosive.
A primitive nuclear explosive
Terrorist could make a nuclear explosive from highly enriched uranium or plutonium. The simplest nuclear explosive uses the 'gun technique' in which a mass of enriched uranium less than the critical mass is fired, down a gun barrel, for example, into another less-than-critical mass of uranium. The sum of the two masses is greater than critical. When they join together a nuclear explosion occurs.
Highly enriched uranium is harder to obtain than plutonium. Therefore, terrorists may go for plutonium. The gun technique cannot be used to assemble a super-critical mass of plutonium in a nuclear explosive device; implosion must be used. The implosion technique can, however, be used to assemble a super-critical mass of highly enriched uranium. In a nuclear explosive using the implosion design, a sphere of plutonium or highly enriched uranium is surrounded by conventional high explosives.
When exploded, the high explosive uniformly compresses the sphere of fissile material. The compression reduces the volume of the sphere of fissile material in the core and increases its density. The critical mass is inversely proportional to the square of the density. The original less-than-critical mass of fissile material will, after compression, become super-critical, and a fission chain reaction and nuclear explosion will take place.
If it could acquire the fissile material, a small group of people with appropriate skills could design and fabricate a crude nuclear explosive. The size of the nuclear explosion from such a crude nuclear device is impossible to predict. But even if it were only equivalent to the explosion of a few tens of tonnes of TNT it would completely devastate the centre of a large city. Such a device would, however, have a strong chance of exploding with an explosive power of at least a hundred tonnes of TNT. Even one thousand tonnes or more equivalent is possible, but unlikely.
It is a sobering fact that the fabrication of a primitive nuclear explosive using plutonium or highly-enriched uranium would require no greater skill than that required for the production and use of the nerve agent produced by the AUM group and set off in the Tokyo underground.
Terrorist attack on a nuclear-power station
Instead of exploding a nuclear weapon, a terrorist group may decide to attack a nuclear facility. It is generally recognised that a terrorist group with significant resources could attack and damage a nuclear-power plant. There is argument, however, about how much damage and how many people would be harmed by such an attack. It is probably true that attacks on nuclear-power plants that could do a great deal of damage and cause many fatalities do not have a large chance of success. But many believe that the damage caused by and the number of people killed by a successful terrorist attack on a nuclear-power plant could be so catastrophic that even a small risk of such an attack is not acceptable.
There are two potential targets in a nuclear-power station for a terrorist attack: the reactor itself and the ponds storing the spent fuel removed from the reactor. An attack on the reactor could cause the core to go super-critical (as happened during the 1986 accident at the Chernobyl reactor) or cause a loss of the coolant that removes heat from the core of the reactor (as happened during the reactor accident at Three Mile Island).
Spent fuel elements are normally kept in storage ponds for five or ten years under three or so metres of water before they are either finally disposed of in a geological repository or sent to a reprocessing plant where the plutonium inevitably produced in the fuel elements is chemically separated from unused uranium and fission products in the fuel elements. The ponds are normally built close to the reactor building. The buildings containing the spent fuel ponds are less well protected than the reactor and are, therefore, more attractive targets than the reactor building.
Terrorists could target a reactor or spent fuel pond by: using a truck carrying high explosives and exploding it near a critical part of the target; exploding high explosives carried in a light aircraft near a critical part of the target; crashing a high-jacked commercial airliner into the reactor building or spent-fuel pond; attacking the power station with small arms, artillery or missiles and occupying it; or by attacking the power lines carrying electricity into the plant.
Alternatively, a terrorist group may infiltrate some of its members, or sympathisers, into the plant to sabotage it from inside. A saboteur may attack, for example, the systems cooling the reactor core or drain water from the cooling pond. This could cause the temperature of the reactor core to rise, resulting in a release of radioactivity from the core, or cause the temperature of the spent fuel rods to rise, again resulting in a release of radioactivity.
Terrorist attacks on high-level radioactive liquid waste tanks or plutonium stores at Sellafield
It is hard to think of a nuclear terrorist attack which could, at least in theory, be more catastrophic than a successful attack on the tanks at Sellafield that contain the liquid fission products separated from spent reactor fuel elements by the two reprocessing plants.
A major concern after the September 11, 2001 terrorist attacks in New York and Washington is an attack on Sellafield in which a large commercial aircraft, such as a Boeing 747 carrying a full load of fuel, is dived from a high altitude into the liquid high-level radioactive waste (HLW) tanks. A fully laden jumbo-jet travelling at between 200 and 300 metres a second would have a very large momentum and the crash would have a huge impact. In addition, the aircraft may be carrying about 150 tonnes of aviation fuel and the crash would create a very fierce fire.
Highly radioactive liquid waste, fission products arising from the operations of the two reprocessing plants at Sellafield, is stored in 21 water-cooled tanks. Normally, at any one time, fourteen of these tanks are full of liquid fission products; the other seven are kept empty in case it is necessary to empty some of the other tanks.
So far as the contamination of the human
environment and damage to human health are concerned, the most important radioisotope in the HLW tanks at Sellafield is caesium-137 (Cs-137). Based on figures published by NIREX in 1998 inventory, the total amount of Cs-137 in the HLW tanks is weighs about 1,800 kilograms. For comparison, the Chernobyl accident released about 25 kilograms of Cs-137. Each HLW tank, therefore, hold about 5 times the amount of Cs-137 as that released by the Chernobyl accident. The number of fatal cancers produced worldwide by the Chernobyl accident is estimated to be about 30,000.
Scaling up the calculated Sellafield release to the Chernobyl accident suggests that a terrorist attack on the HLW tanks could result worldwide in about 150,000 fatal cancers per tank. Depending on the strength and direction of the winds at the time of the release of the radioactivity, these deaths will occur in the United Kingdom, Ireland and parts of Europe and perhaps even further a field. If a terrorist attack uses a commercial jet airliner more than one tank may be involved.
Terrorist use of a radiological weapon
The simplest and most primitive terrorist nuclear device is a radiological weapon or radiological dispersal device, commonly called a dirty bomb. A dirty bomb would consist of a conventional high explosive (for example, semtex, dynamite or TNT), some incendiary material (like thermite) surrounding the conventional explosive, and a quantity of a radioisotope, probably placed at the centre of the explosive.
When the conventional high explosive is detonated the radioactive material would be vaporised. The fire ignited by the incendiary material would carry the radioactivity up into the atmosphere. It would then be blown downwind, spreading radioactivity. A dirty bomb is not the same as a nuclear weapon in the normal sense of the phrase– it does not involve a nuclear explosion.
Many types of radioisotopes (radioactive isotopes) could be used in a dirty bomb. But the most likely one to be used is one that is that is relatively easily available, has a relatively long half-life, and emits energetic radiation. Suitable ones include caesium-137, cobalt-60, and iridium-192; these emit mainly gamma rays (electromagnetic radiation). Strontium-90, which emits beta particles (electrons) and is concentrated in bone, is also a possible candidate. The use of plutonium in a dirty bomb would cause the greatest threat to human health, because of its very high inhalation toxicity, and the most extensive contamination. However, terrorists would find it very difficult to acquire significant amounts of plutonium.
The detonation of a dirty bomb is likely to result in some deaths but would not result in the hundreds of thousands of fatalities that could be caused by the explosion in a city of a crude nuclear weapon. Generally, the explosion of the conventional explosive would be the most likely cause of any immediate deaths or serious injuries. The radioactive material in the bomb would be dispersed into the air but would be soon diluted to relatively low concentrations. If the bomb is exploded in a city, as it almost certainly would be, some people are likely to be exposed to a dose of radiation. But the dose is in most cases likely to be relatively small. A low-level exposure to radiation would slightly increase the long-term risk of cancer.
The main potential impact of a dirty bomb is psychological – it would cause considerable fear, panic and social disruption, exactly the effects terrorists wish to achieve. The public fear of radiation is very great indeed, some say irrationally so.
The explosion of a dirty bomb could result in the contamination of an area of a city and the surrounding areas with radioactivity. Areas as large as tens of square kilometres could be contaminated with radioactivity to levels above those recommended by the National Radiological Protection Board for the exposure of civilians to radioactivity. The area would have to be evacuated and decontaminated.
The degree of contamination would depend on the amount of high explosive used, the amount and type of radioisotope released during the explosion of the bomb, the nature of the device used to spread the radioactivity, whether it was exploded inside a building or outside, and speed and direction of the wind, the general weather conditions, and the size and position of buildings near the detonation site. The size of the radioactive particles released by the device will determine how far they are carried by the wind and how easily people inhale them. Radioactivity will be carried away on people’s clothes and spread by vehicles passing through the contaminated areas. People may also ingest radioactivity by eating contaminated food and drinking contaminated water.
In the longer term, any exposure to ionising radiation can cause fatal cancers. The number of fatalities in a group of people will be proportional to the total radiation dose received by the group.
The effects on the health of people exposed to the radioactivity released by a dirty bomb will depend on how long they remain in the contaminated area, the size of the particles released by the explosion and the type of radioactivity emitted by the radioisotopes in the bomb. Decontamination is likely to be very costly (costing millions of pounds) and take weeks or, most likely, many months to complete. There are no ways to decontaminate effectively buildings contaminated with significant amounts of radioactivity; the buildings may, in practice, have to be demolished. If a dirty bomb were detonated in, for example, London’s Oxford Street or in the City of London, the cost would be huge, potentially many hundreds of millions of pounds.
Such is the public fear of ionising radiation that even relatively small levels of radioactive contamination on or in buildings, on roads or footpaths, or on public areas would be publicly unacceptable. Decontamination would have to be virtually complete. Roads and walkways in contaminated areas, for example, would have to be re-surfaced. Radioactive contamination is by far the most threatening aspect of a dirty bomb.
Measures to counter nuclear terrorism
To effectively counter nuclear terrorism it is important to prevent terrorists from acquiring fissile materials, plutonium and highly enriched uranium, needed to fabricate a primitive nuclear explosive and from acquiring significant quantities of radioisotopes, particularly caesium-137, strontium-90, cobalt-60, and plutonium to build a dirty bomb. The protection of these radioactive materials is clearly of the utmost importance. There are literally millions of radioactive sources used worldwide in medicine, industry and agriculture; many of them could be used to fabricate a dirty bomb. They are often not kept securely.
Making existing nuclear-power reactors less vulnerable to terrorist attack is not very feasible although storage ponds for spent fuel elements could be more hardened. And greater care could be taken to vet staff to make it more difficult for a terrorist group to infiltrate people into a nuclear-power station.
The protection of a nuclear facility with, for example, fighter aircraft or surface-to-air missiles is, to say the least, not an easy task. If a terrorist group hijacks a commercial aircraft on a regular flight path that takes it close to, for example, the Sellafield establishment and dives it on to a target in the nuclear facility, the time available to make sure that the aircraft really is attacking the facility and then to scramble fighter aircraft or fire surface-to-air missiles is probably too short to make a successful interception.
The importance of good intelligence
The importance of effective intelligence in countering nuclear terrorism cannot be over estimated. Monitoring the communications of terrorist groups – the activity known as signal intelligence (SIGINT) – has been crucial to this end. Modern terrorists can, however, take steps to protect their communication systems, including, for example, the use of encryption, frustrating the efforts of SIGINT.
The penetration of terrorist groups, particularly fundamentalist ones, by undercover intelligence agents or double agents (human intelligence or HUMINT) is, therefore, of critical importance. In fact, counter-terrorism is likely to succeed only if HUMINT can be made effective. This is why it is, to say the least, not going to be easy to defeat the new terrorists.
Experience shows that setting up effective intelligence activities against terrorist groups is extremely challenging. Rivalries between intelligence agencies within countries and lack of cooperation in intelligence matters between countries seriously reduce the effectiveness of intelligence. Effective and single leadership of national agencies and international cooperation between national agencies are the keys to good counter-terrorism intelligence.
The intelligence and security agencies, in their fight against the future terrorism, face an awesome task that will require the acquisition of any new technological developments relevant to counter-terrorist activities, a close study of new terrorist threats, and, perhaps most importantly, an imaginative approach to the issues.
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