Nuclear weapons

A nuclear weapon is a bomb whose destructive power is mainly based on the pressure wave and thermal radiation created by the explosion. Another threat is radiation from both radioactive substances released by the explosion and neutron radiation released immediately in the explosion. 

The effects of a nuclear explosion depend significantly on whether the bomb explodes on the surface, underground or in the air. The extent of the radiation hazard area depends on the size and especially the explosion height of the nuclear weapon. If the explosion occurs so low that it creates a risk of significant deposition, protection against the radiation caused by the nuclear weapon explosion is provided by civil defence shelters. 

A nuclear weapon does not go off accidentally, even if it is dropped or the vehicle carrying the weapon crashes. However, a fire or chemical explosion can damage a nuclear weapon so that the uranium or plutonium it contains is exposed and released into the environment. As a result, the radiation situation near the accident site could be harmful to health up to tens of kilometres away.

Nuclear weapon construction is a demanding process that requires weapons-grade material, such as highly enriched uranium or plutonium. 

Air detonation of a nuclear weapon

In an air detonation, the nuclear weapon explodes so high that the fireball of the explosion does not touch the ground. As a result, the areas of the destructive pressure effect and thermal radiation are biggest and the impact zone of the nuclear weapon is thus as wide as possible. Detonating a 100 kiloton nuclear weapon at an optimum height in the air, for example, would kill a large proportion of completely unprotected population within a radius of about four kilometres from the point of explosion. The radioactive substances created in an air explosion rise high up in the atmosphere, and a local fallout, which is particularly dangerous in terms of radiation, does not usually occur. 

Surface detonation of a nuclear weapon

In surface detonation, a nuclear weapon explodes on or near ground surface. Shortly after the explosion, a large proportion of the resulting highly radioactive substances fall on ground as a local fallout. Outside the immediate impact zone, there is then a threat of radiation from the radioactive substances generated by the explosion. 

The extent of the radiation hazard area depends on the size and explosion height of the nuclear weapon, as well as on the weather conditions. When a large, megaton nuclear weapon explodes, people even hundreds of kilometres away from the explosion site have to go to civil defence shelters in the direction of the spread of fallout. The corresponding impacts of the explosion of a smaller, kiloton tactical nuclear weapon might extend to tens of kilometres.

Consequences of a radiation hazard situation caused by the use of a nuclear weapon

As a result of the use of a nuclear weapon, some areas would be completely destroyed and normal life and economic activities would be impossible. The conditions would be similar to those after a devastating earthquake. However, the thermal radiation generated by a nuclear explosion would cause many serious burns to those surviving the explosion, whose treatment would require a lot of attention. In the immediate vicinity of the explosion, people would also be exposed to intense direct radiation, which can cause conditions such as radiation sickness. In addition, possible radioactive fallout would cause a risk that does not occur in natural disasters. 

The radioactive fallout resulting from a surface detonation  differs in its composition from possible fallout resulting from a nuclear power plant accident. It causes an immediate radiation risk, especially through external radiation. The fallout also threatens the safety of rescue personnel and slows down rescue work and helping survivors.
As after a nuclear power plant accident, the  fallout can contaminate food. Radioactive substances may find their way into cereals and other food or feed plants directly from the air, with rain or dry deposition or from the ground extracted by plant roots. Animals can breathe contaminated air, and some of the fallout that enters surface water is transferred to fish via water food chains.

A serious fallout situation would not only cause a radiation hazard. Long-term psychological consequences could be significant, especially for the survivors in the area who are concerned about long-term health effects. This would probably make it much more difficult to return to normal life than in a natural disaster of a corresponding scale. In addition, it is known from nuclear power plant accidents that the radiation effects of fallout may cause concern even far away from the actual accident area.

Food production would have to be restricted over a much wider area than where people are protected. The economic consequences would also be significant. The economic impacts would be considerable around the world, especially if the nuclear weapon were used in an area that is strongly linked to world trade. In addition to direct damage, the fallout and its threat would hinder economic activity and transport in extensive areas. The accident at the Fukushima nuclear power plant in 2011, for example, had such consequences much further away than would have been justified on the basis of mere radiation.

The need to perform radiation measurements on goods and people arriving from the presumed fallout area would probably also have a significant impact on international trade and the movement of people. Such an area can extend to thousands of kilometres. Following the Fukushima accident, pressure arose to ensure the cleanliness of all goods, vehicles and people arriving from or passing through the presumed fallout area.

The type of explosive, the yield of the explosion, explosion height and weather conditions all affect the radiation hazard situation and exposure caused by the use of nuclear weapons. 

Nuclear test ban

Nuclear weapons have been tested in nuclear tests conducted in air, water and underground since 1945. In 1963, nuclear tests were banned, with the exception of those conducted underground. There have been no nuclear tests in the atmosphere since 1980, although not all countries have committed to complying with the agreement. Tests in the atmosphere released radioactive substances into the environment, and small amounts of these substances can still be detected around the world. In 1996, a treaty banning all nuclear tests was signed, but it has not yet entered into force. However, compliance with the ban on nuclear testing is monitored with a global network of measurement stations.

Nuclear Material Regulation and the Non-Proliferation Treaty

The aim of safeguarding nuclear materials is to assure that nuclear materials and other nuclear products remain in peaceful use in accordance with permits and declarations and that nuclear facilities and nuclear technology are used only for peaceful purposes. Regulation aims to prevent the proliferation of nuclear weapons and to ensure that nuclear materials are not produced, used or transferred for the manufacture of nuclear weapons. 

The international basis for regulation is the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which was ratified in 1969 and entered into force in 1970 and is monitored by the IAEA. Finland has been involved in the treaty from the very beginning.

In the EU, the use and procurement of nuclear materials is also supervised by the Commission’s Safeguards Department. The basis for supervision is the Euratom Treaty of 1957, the Treaty establishing the European Atomic Energy Community. 

Nuclear material safeguards are a prerequisite for the peaceful use of nuclear energy. States have an undivided responsibility to ensure that no activities contrary to the Non-Proliferation Treaty are conducted in their territory. 

International agreements

Disarmament is the most effective way to prevent the proliferation, testing and use of nuclear weapons. In addition to the Non-Proliferation Treaty, there are many other international agreements that support this goal: the Treaty Banning Nuclear Weapon Tests in the Atmosphere, In Outer Space and Under Water; also known as the Partial Test Ban Treaty (PTBT), and the Comprehensive Nuclear-Test-Ban Treaty, CTBT). The CTBT was signed in 1996, but it will not enter into force until all 44 countries using nuclear technology are involved in it. 

Activities under the CTBT Treaty are monitored by CTBTO, which has a worldwide monitoring network for the detection of nuclear tests. The system measures radionuclides and also detects seismic, hydroacoustic and infrasound-based signals. Among other things, the system has detected all nuclear tests reported by North Korea. 

Monitoring in Finland and the role of STUK

The Radiation and Nuclear Safety Authority (STUK) is an authority that sets requirements concerning nuclear and radiation safety and monitors their fulfilment. STUK also maintains and develops the national control system for nuclear materials, whose goal is to take care of fulfilling the obligations of the Treaty on the Non-Proliferation of Nuclear Weapons in Finland. The IAEA, on the other hand, monitors the functioning and results of the national control system also in Finland.

The monitoring targets are nuclear power plants and other nuclear facilities, nuclear materials and the final disposal of nuclear waste, based on the accounting and reporting of nuclear materials. Operators and STUK must always be aware of the number, location and use of all nuclear materials. 

STUK also acts as the national data centre (FiNDC) required by CTBT. The FiNDC collects and analyses data produced by the CTBT monitoring network, for example, and reports suspected nuclear tests to the government.  

When a radiation hazard is imminent, STUK carries out a situation assessment and evaluates the severity of the situation from the safety standpoint. STUK gives recommendations to other authorities regarding protective measures. STUK has 24-hour emergency preparedness for nuclear accidents and other radiation hazard situations.

Nuclear-weapon states

Of nuclear-weapon states, the Nuclear Non-Proliferation Treaty (NPT) has been signed by

• United States
• Russia
• The United Kingdom 
• France
• China 

Countries outside of the Nuclear Non-Proliferation Treaty that have declared that they own nuclear weapons:

• India
• Pakistan
• North Korea

In addition, Israel is estimated to have a significant number of nuclear weapons. North Korea has carried out several nuclear tests since 2009.
In addition to the current nuclear-weapon states, there are countries that have had a nuclear weapons programme or nuclear weapons:

• South Africa abandoned its programme and nuclear weapons and now has a nuclear power plant and other nuclear activity.
• Iraq had a nuclear weapons programme that was revealed during the Gulf War but did not make significant progress before the war broke out. The country has no nuclear weapons or nuclear activity. 
• Syria secretly built a reactor suitable for the production of plutonium, which was bombed by Israel in 2007. The reactor was similar to the one in North Korea. Since then, it has been unclear where the other necessary facilities, nuclear material, etc., are. The programme ended soon after it had started, but the investigation has not progressed due to the state of war. Syria has minor nuclear activity.
• During the Gulf Wars, Iran had a preliminary nuclear weapons programme similar to a feasibility study, which it itself abandoned. The country secretly built two uranium enrichment plants using technology from secret networks, which later came under the control of the IAEA. Iran has a rather large nuclear power programme, which has also been suspected to prepare the ability to build a nuclear weapon, if necessary.