“There are many, many steps from a nuclear reactor to a nuclear weapon”


Hi there… Sophie Grape, senior lecturer in applied nuclear physics, group leader in Technical Nuclear Non-Proliferation and Safeguards, and work package leader in the Alva Myrdal Centre for Nuclear Disarmament at Uppsala University.

Nuclear power reactor buildings by water
The Ukrainian Zaporizhia nuclear power plant is Europe’s largest and consists of two cooling towers on the left and six VVER reactor buildings. The other buildings belong to a thermal power plant.
Foto/bild: Ralf1969, CC BY-SA 3.0 via Wikimedia Commons

In connection with Russia’s invasion of Ukraine, Russian forces have taken control of several nuclear power plants, including Europe’s largest at Zaporizhia, and Chernobyl. How serious is the situation?

“One of the major concerns is that it has not been possible to relieve the workforce in the way that would normally have occurred. Instead, they are stuck inside the nuclear power plant. There are questions as to whether they are being given adequate rest, whether they have food, whether they are injured after the attacks, quite simply whether they are in good health and are well able to do their jobs. This has been brought to the attention of the International Atomic Energy Agency (IAEA), which is also in dialogue with the nuclear power plants. To sum up, there is very little transparency about what the situation is and what the conditions are for doing a proper job at the power plants. Remote data transfers from IAEA monitoring systems installed at Zaporizhia and Chernobyl nuclear power plants has also been lost, making it difficult to monitor what is happening in these facilities.”

“In addition, fighting at or near nuclear power plants is a cause for concern, since this can result in both direct and indirect damage. We have seen this in the last few days at Chernobyl, where the power supply to the plant was recently disrupted, which ultimately risks causing local damage to the plant. The fighting and the circumstances of the invasion are making it difficult and potentially dangerous to carry out repairs. Fortunately, Chernobyl has succeeded in carrying out repairs and the nuclear power plant is again receiving power from external electricity networks.”

How great is the risk that damage to a nuclear power plant could lead to the spread of radioactive material, and what might the impacts be?

Sophie Grape
Sophie Grape, senior lecturer in applied nuclear phy-
sics at the Department of Physics and Astronomy.
Photo credit: Private

“First of all, many nuclear power plants are built with strong barriers against external forces. But in a bad scenario, parts of the reactor building might be damaged and possibly in a worst case scenario, such as an explosion, nuclear fuel could also be damaged. With other radioactive material, it could then perhaps cause radioactive contamination either inside the plant or possibly outside the reactor building. But the impacts of such a scenario would probably be quite localised, radioactive material would not spread to Sweden. However, the damage in the area could be great and radiation exposure to staff on site may increase.”

What processing is required to transform the material contained in a nuclear reactor into a nuclear weapon?

“There are quite a few steps involved. The material in these facilities cannot explode like the material in a nuclear weapon, nor can it be used ‘as is’ to produce nuclear weapons. Nuclear weapons are extremely powerful weapons, and the enormous blast and damage from a nuclear weapon comes from having a mass of a certain material that is able to sustain a powerful chain reaction during a very short time span. This releases a huge amount of energy in a very short time. The material in a nuclear reactor has a completely different composition which makes it impossible to use for nuclear weapons purposes without first being subjected to extensive reprocessing activities where elements are chemically separated from each other. This requires a completely different infrastructure than the one currently in place, and of course, it would require experts with knowledge and experience in this area.”

“But we should also remember that a mass of nuclear-weapons-grade material that can maintain a chain reaction is still quite far from being a nuclear weapon. We can see that countries that have manufactured nuclear weapons have had extensive nuclear weapon programs with large organisations dedicated to developing and ensuring that the weapons function as intended. This includes the need to develop and assemble a number of different components and get them to interact in a very intricate way, the development of weapon carrier systems and a program for testing nuclear weapons. So, there are many, many steps between a nuclear reactor and a nuclear weapon.”

You lead a technical working group at the Alva Myrdal Centre for Nuclear Disarmament at Uppsala University – how is your research linked to the Centre?

“I’m doing research at the Division of Applied Nuclear Physics on technical nuclear safeguards. These are measures and tools aimed at deterring countries from acquiring nuclear weapons, and to enable early detection if this were to happen despite the deterrents. We develop measurement techniques and analysis methods that can be used by organisations such as the IAEA or the Swedish Radiation Safety Authority when inspecting nuclear facilities such as nuclear power plants or spent fuel storage facilities. These measurements provide information on whether nuclear fuel is being diverted for purposes other than those stated by a facility operator, such as for manufacturing nuclear weapons. Therefore, nuclear safeguards assessments may provide an early warning if states do not live up to their non-proliferation and safeguards obligations.”

The Alva Myrdal Centre
The Alva Myrdal Centre, Uppsala.
Photo credit: David Naylor

“Our research is thus part of the non-proliferation mechanisms that are intended to deter and hinder the diversion and misuse of peaceful nuclear energy systems and the proliferation of nuclear weapons, nuclear weapons technologies, and nuclear weapons materials by state actors. My work on nuclear safeguards and non-proliferation is linked to nuclear disarmament, which is the focus of the Alva Myrdal Centre. There, I lead the only technical working group looking into how to research and develop technical tools to assist the global community with nuclear disarmament.”

Are there any possible alternatives to prevent radioactive substances from falling into the wrong hands and posing risks to the world at large?

“Preventing radioactive substances from falling into the wrong hands is exactly what non-proliferation is all about. Nuclear safeguards are an important part of this, but not the only aspect. Other aspects include export controls of sensitive materials and components, physical protection of various types of installations, and forensics methods for detecting the smuggling of nuclear and radioactive materials. Unfortunately, we can see from the situation in Ukraine that a number of facilities that handle radioactive materials, such as hospitals and research facilities, are coming under fire. This can in turn lead to the proliferation of radioactive substances. But in a situation like a war, it’s difficult to ensure that this does not happen.”

Anneli Björkman


Division of Applied Nuclear Physics at Uppsala University

Last modified: 2023-08-04