What is the risk of a nuclear accident in Ukraine? A radiation expert speaks from Kyiv.

In this war, many unthinkable things have become real.

There are two different sources of radiation. X-ray machines are used to treat cancer. If they are switched on, they emit some radiation. It's just a piece of metal when you switch it off.

The second source uses radioactive substances like cobalt or cesium, which are used in nuclear medicine and radiation therapy. They are protected from theft in the hospital. They aren't protected against being hit by a bomb.

There is a chance that we will see something like the Goiânia accident in Brazil in 1989. Some people stole and dismantled a radiotherapy device from an abandoned hospital site in order to sell the parts as scrap metal. At night, this small amplifier glowed blue. It is a long story, but the single destroyed source of radiation contaminated much of Goi. There were four deaths and 20 needed hospital treatment. 200 of the people living in the homes that were contaminated were evacuated. This scenario needs to be considered. Without thinking about the use of the sources, that is.

What kinds of malevolent uses? 

The spent fuel assembly is a good material for making a dirty bomb, which is a scenario for a terrorist attack. A radiological dispersion device is a more technical term. If you attach a device to a radioactive source and explode it, it will cause a large area to be contaminated with radioactive material. There are many scenarios of this kind on the table.

How are the nuclear power plants in Ukraine being monitored now? 

Real-time data from the radiation monitoring networks at the nuclear power plants have been disconnected. The Ukrainian government and authorities no longer have access to this network, which was quite sophisticated and operational before this invasion.

The country has a remote monitoring network to detect radiation. The points closest to the plants are disabled or cut from the general network. It would be noticed by more distant monitors if something really bad happened. Hours would pass before it would be noticed. Unless it was reported by people under Russian control.

Have there been any problems so far? 

According to official reports, there was a fivefold increase in radiation dose rates at the Chernobyl site after the invasion. The most plausible explanation is that tanks disturbed radioactive material.

The Chernobyl exclusion zone is not open to the public. It can be dangerous if you follow the rules, but if you follow the rules it is pretty safe. Tanks were moved back and forth off the road. Some of the most contaminated areas were covered with soil and vegetation to keep radioactivity out of the air.

These layers of soil are heavily contaminated and could be disturbed immediately by the tanks. Russian soldiers neglect law and radiation safety rules. They have radiation in their bodies after inhaling this dust. It is stupid from the ecological point of view and the global point of view. It is very dangerous and stupid at the local level. A local problem would be presented by the fivefold increase in dose.

How would you measure contamination in people if an incident were to occur now? 

Two or three types of devices are important at the time of an accident. Many of the devices we have in Ukraine are obsolete.

Between 1987 and 1991 we had a period of accumulating radiation monitoring capacity. The interest in Chernobyl has fallen since then. Many of our dosimetry devices are from 1991 or 1992. The lifetime for those kinds of instruments is usually 10 years. They are more than 30 years old now. The equipment is not in good shape. We really need that new equipment. We have made official demands for such equipment, but I have also made requests to colleagues in the US.

What are the devices that you need? 

A survey meter is one type. They are similar to a Geiger-Müller tube. You can see which areas are dangerous and which are not on a display. The special dose-rate meters are useful for measuring the level of contamination of clothes, hair, and surfaces after an emergency.

Whole-body monitors can be used to measure internal contamination in people who drink milk or breathe polluted air. Dosimeters look like badges. They are small and attached to people's clothes. They are sent to the lab to find out the dose a person has been exposed to.

Can we draw lessons from Chernobyl? 

Not really. Everything was under control after the Chernobyl disaster. It was possible to get a thousand buses to evacuate the population. It was not the same story.

Some territories are out of control and others are under fire. I don't think it would be possible to evacuate such a process. We don't have the means to evacuate and we don't know where to go. What is happening in Mariupol could happen to the routes of evacuate.

If such an emergency were to happen, I would recommend that you shelter for as long as possible. Don't move. Don't try to run away. Simply shelter. Even apartment blocks provide enough shielding against radiation if you stay away from the windows.

You have moved out of Kyiv. Where are you staying now? 

I live in a country house 25 kilometers away from Kyiv. This area is safe and I am able to communicate with Kyiv. I'm staying within a one-hour drive of Kyiv so I can go if necessary. If my work is needed, I will go back to work. We decided not to flee because of that.

The Ukrainian military is doing well against the Russians. Ukraine won't be subdued. It's not an option to give up or forgive.

Our children have two 4-year-old daughters, so we moved them to a safer place. But the elderly stay here. I’m old enough to sacrifice my life if needed.