What could threaten Finland?

Impacts of a radiation accident can only affect a large area if large amounts of radioactive gases and particles are released into the air. Depending on the weather conditions, a serious nuclear power plant accident in Finland or in a nearby country could require measures to protect the population, which are intended to prevent health hazards over a long period of time. However, even a serious accident at a nuclear power plant would not cause immediate health detriments to Finns.

In addition to nuclear power plant accidents, nuclear and radiation safety must also take into account various radiating sources, possibly a dirty bomb built with the radiation sources, as well as nuclear-powered and nuclear-weapon-carrying vessels in the Baltic Sea region.

A serious nuclear power plant accident in Finland or nearby

Only severe accidents involving reactor damage in a nuclear power plant could release a large amount of radioactive substances into the environment. However, such accidents are improbable, as the reactors are protected by multiple shielding and security systems.
In Finland, protection of the population may be required in the event of a serious accident at one of the following nuclear power plants:

• The Olkiluoto or Loviisa plants in Finland
• The Leningrad (Sosnovyi Bor) or Kola facilities in Russia
• The Forsmark plant in Sweden.

Depending on the weather conditions, a serious accident could have radiation effects requiring extensive protective measures also in Finland. For example, along the radioactive plume path, it might be necessary for people to protect themselves by staying indoors at a distance of a maximum of one hundred kilometres. The purpose of protective measures is to protect the population from exposure to radiation, the consequences of which could be felt by the population in years or decades to come.

Nuclear power plants in Russia, Sweden and Europe are located so far away from Finland that a serious accident in them would not require protective measures in Finland. However, measures to protect food safety could be required in adverse weather conditions.

Nuclear facilities near the Finnish borders (situation in March 2024).

Serious reactor damage can occur if the cooling of the nuclear fuel is prevented. The fuel overheats and releases radioactive substances into the reactor pressure vessel. In most nuclear power plants, a gas-tight containment building surrounds the reactor. If there is no containment building or it is not leak-tight, radioactive substances released from the plant will be carried by air currents. The wind speed dictates the velocity of the radioactive plume, and the direction of the wind determines which areas will be contaminated. A radioactive plume in the air cannot be seen or smelled. It can only be detected by a radiation meter. Radiation measurements aim to obtain as good a picture as possible of the radiation situation and its development. Based on the weather conditions, it is known when and where it is necessary to take protective measures.

Protect yourself indoors during the passage of the plume to avoid inhalation of radioactive air and direct radiation from the plume. In the event of an accident, there is time to protect yourself if you act efficiently. For example, with a wind speed of nine metres per second, the plume travels 100 kilometers in three hours.

The radioactive plume will not continue to travel indefinitely. The plume will expand and lose its radioactivity as it progresses.

When the radioactive plume has passed over an area, the air in that area will no longer contain radioactive substances. Instead, there will be radioactive substances on the ground and on the surfaces of buildings. There can be major local differences in the deposition. For example, rain will increase the number of particles falling to the ground. In the most polluted urban areas, the environment is cleaned, for example, by washing the roofs and walls of buildings. For the duration of the clean-up operations, the population may be relocated to other areas.

It may take a long time before the environment is completely free of radioactive substances. However, the concentrations will drop significantly during the first year. To keep the radiation dose as low as possible, farmers are advised to make sure that all foodstuffs on sale are clean. If necessary, restrictions on the use of, for example, mushrooms and berries are given.

Nuclear fuel

The fresh, unused uranium fuel of a nuclear power plant emits very little radiation. An accident during fuel transport will not cause a radiation hazard situation to humans or the environment. Finnish nuclear power plants receive fresh fuel shipments a few times a year. In addition, nuclear fuel is transported to other countries via Finland. The Radiation and Nuclear Safety Authority inspects the security plans concerning transport in good time, and transport is supervised.

The fuel becomes highly radioactive in the nuclear power plant’s reactor. The activity of spent fuel removed from the reactor falls to one hundredth of its original level in a year and to one thousandth in 40 years. Spent fuel is placed in intermediate storage in deep water storage basins located in the nuclear power plant. A serious accident in the intermediate storage may at most contaminate the immediate vicinity of the plant, and could require protective measures within a couple of kilometres’ distance from the storage.

Spent nuclear fuel from the Olkiluoto and Loviisa nuclear power plants is finally disposed of in the Eurajoki bedrock. Containers for spent nuclear fuel transportation are subject to strict safety requirements. The containers must stay intact, for example, in the event of a strong collision, fire and sea dumping. Even if the containers were to brake, the impacts would only extend to a maximum of a couple of hundred metres from the accident site.

Spent nuclear fuel contains uranium and plutonium that is still usable. They can be recovered and re-used in fuel manufacturing. A serious accident in a spent nuclear fuel reprocessing facility would cause a hazard situation in the facility’s vicinity and could possibly require cleaning and other actions up to tens of kilometres away.
Finland’s nearest treatment facilities are Sellafield in the UK, La Hague in France, and Mayak in Russia.

Nuclear weapons

The destructive military power of a nuclear weapon is mainly based on the pressure surge created by the explosion and the thermal radiation released at the time of explosion. They cause buildings to collapse and fires. Outside the immediate impact zone, there would be a risk of radiation from the radioactive substances released 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 along the routes of the radioactive substances. The impacts of the explosion of a smaller, kiloton tactical nuclear weapon might extend to tens of kilometres. The use of a nuclear weapon would cause a more serious radiation hazard situation than a nuclear power plant accident.

A nuclear weapon does not go off accidentally, even if it is dropped or the vehicle carrying the weapon crashes. However, it could be damaged in a fire or chemical explosion, exposing and releasing the uranium or plutonium to the environment. As a result, the radiation situation near the accident site could be harmful to health up to tens of kilometres away.

Underground nuclear tests are carried out deep under the ground. Underground nuclear tests may release small amounts of radioactive substances, which modern measuring instruments can detect far from the test area. Only a massive explosion-induced leak into the atmosphere could release enough radioactive substances to cause significant radiation doses for humans near the test area.

Nuclear weapons have been tested in air, water and underground nuclear tests since 1945. In 1963, nuclear tests were banned, with the exception of those carried out 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. 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 sensors.

Nuclear-powered submarines and other vessels

Nuclear reactors are mainly used to power missile submarines and some other warships, as well as icebreakers operating in the Arctic. In nuclear-powered vessels, the reactor of the vessel contains only a few per cent of the amount of radioactive substances in a nuclear power plant reactor. Serious reactor damage in a nuclear-powered vessel could cause a radiation situation requiring protective measures at a maximum distance of tens of kilometres.

The utilization of nuclear power in military vessels is based on the fact that they can operate at sea for up to years without refuelling.

The nuclear-powered vessels closest to Finland are in the Murmansk region, which is located more than a hundred kilometres from the Finnish border. Even the most serious reactor accident would not require protective measures in Finland. Occasionally, nuclear-powered vessels may also cruise in the Baltic Sea.

Nuclear-powered submarines have sunk as a result of different accidents, such as fires. Nuclear submarines that have remained at the bottom of the sea can, over time, release radioactive substances into the environment. However, according to international estimates, the impacts of releases will remain very small and local.

Nuclear-powered satellites

Electricity required by satellite equipment is usually produced with solar panels, but some satellites also have plutonium batteries or nuclear reactors. The safety systems and satellite structure design of nuclear-powered satellites aim to ensure that no radioactive particles fall to Earth after the expiry of the satellite’s service life.

When the satellite reaches the end of its useful life, the security systems will launch the nuclear reactor into upper orbit, to wait for the activity to decrease. If the launch is not successful, the reactor will be disconnected before the satellite crashes to the ground. Failure to remove the reactor may result in the spread of radioactive particles over a wide area. The objects can be large and strongly radiating or microscopically small. The time of the satellite's fall can be predicted with relative accuracy. However, it is difficult to predict the exact location of the crash, so there might be a need to make preparations in a large area.
 
The contaminated area is isolated and cleaned. Radiation doses to the population as a whole are likely to remain low, but in populated areas, the remains of the reactor core can cause large individual doses. Severe radiation burns can occur quickly if the remains are touched with bare hands.

The structure of plutonium batteries that are used as an energy source is designed so that they remain intact in all situations. Intact batteries are harmless. Plutonium can only be released into the environment if the battery is damaged and the plutonium crumbles or catches fire. Plutonium is dangerous if it is transported as particles into the lungs through inhaled air. Plutonium particles in the lungs can cause cancer.

Accidents involving nuclear satellites are very rare. In 1978, a satellite with a reactor crashed into an almost uninhabited area of Canada. The incident led to a major search for radioactive debris.

Radiation sources

Radioactive substances are transported for use in hospitals, industry and research institutions. Most transport concerns short-lived radioactive substances used in hospitals. The impacts of transport accidents would remain local even in the worst case, as they would extend to a maximum distance of hundreds of metres from the accident site. In the event of an accident, the area is isolated and cleaned.

In research and industry, radioactive substances are used, for example, in the inspection of metal structures and in process control and monitoring devices. In hospitals, radioactive substances are used to examine patients and treat cancer. A hazard situation related to the use of radioactive substances may occur in connection with a fire or if the radiation source or its shield is otherwise damaged. The effects of the accident would be limited to the immediate vicinity and, in most cases, indoors.

A hazardous situation may also arise if a radiation source is discarded as iron scrap and melted in metal smelting. The metal smelting plant, the material produced and the slag created in the process may be contaminated. Consignments from Finnish smelting plants are measured to detect radiation sources in them. A hazard may also be caused by a strong radiation source left in the environment without a shield or if a person breaks a radiation source they have found.
 
Illegal trade and smuggling of radioactive substances may pose a health risk to the smugglers, travelling companions and recipients. There are several radiation measurement stations monitoring passenger and goods traffic on the Finnish borders.
 
A radioactive substance released by an ordinary explosive device, a so-called dirty bomb, can contaminate an area of a maximum of a couple of square kilometres. In such a situation, the area is isolated and people are evacuated and tested to confirm possible contamination. Furthermore, the environment is decontaminated.