(Un)safe shelter: the fallout of Russia’s 2025 attack on the Chornobyl Nuclear Power Plant

In February 2025, a Russian drone struck the protective shell of the fourth reactor unit of the Chornobyl Nuclear Power Plant. It caused a large-scale fire and, as it turned out later, numerous devastating consequences for the structure. Overcoming these dangers poses daunting tasks for the Ukrainian and global scientific communities.

Here is what we know about the situation today, the risks it creates for the future of the Chornobyl zone, and why Russia is still not being held accountable for the crimes committed.

New Safety Measures

In November 1986, following the tragedy at the Chornobyl NPP, a sarcophagus known as the Shelter Object was erected over the infamous fourth power unit. It combined the structures that survived the accident with superstructures that physically prevented the leakage of radioactive substances into the environment.

To protect the population from the threat of radiation, over 90,000 people were involved in the construction of the Shelter Object. The situation demanded swift and effective decisions, so it was constructed without regard to structural design rules and norms. Although a number of hazards were accounted for in the facility (systems for ventilation, power supply, fire extinguishing, and control were provided), over time it suffered from corrosion, and the load-bearing structures and their connection joints became overloaded under the weight of the debris.

So, in 1992, a competition was announced in Ukraine to transform the Shelter Object into an environmentally safe system. In 2019, following extensive research and thanks to the cooperation of leading global engineers and designers, the New Safe Confinement (NSC) emerged over it — a complex consisting of a protective arch over the Shelter Object. It was designed to be the size of a 35-story building (109 meters) and 160 meters long. It was intended not only to protect the population, Exclusion Zone workers, and the environment from hazardous substances, but also to create safe conditions for the removal of nuclear fuel and dismantling or stabilizing the Shelter Object.

The construction of the New Safe Confinement required unique engineering solutions and was unprecedented: no one in the world had experience creating such structures.

Funds for the construction were collected by 45 donor countries of the Chornobyl Shelter Fund, and the confinement was built by the French consortium Novarka, which was created specifically for this tender. The metal structures were manufactured in Italy using Ukrainian steel.

The arch was built in two sections, which were lifted and installed using special hydraulic jacks. Inside, a Main Crane System was installed for the dismantlement of the Shelter Object and the remains of the fourth power unit.

“At the beginning, no one knew how to do this because such challenges had never been faced before. The arch itself was built to the side and then slid on rails over the Shelter Object to avoid overexposing the personnel to radiation,” explains Olena Pareniuk, a senior researcher at the Institute for Safety Problems of Nuclear Power Plants.

To slide the new arch over the old sarcophagus, a special system of jacks was used: some pulled the structure forward, while others pushed from behind. The arch moved on special guides with a slippery coating (Teflon and grease) to reduce friction. Moving the structure took several days to ensure the safety of the personnel and the facility.

This very structure, which took decades of work and 1.5 billion euros to construct, was struck by a Russian Shahed drone, which was likely produced for under $50,000.

The Unburnt Bush

“At the moment of the strike, to be honest, we didn’t realize the scale of the consequences,” says Greenpeace Nuclear and radiation protection expert Jan Vande Putte. “And the consequences are enormous”.

The New Safe Confinement was built taking into account extreme weather and heavy loads (it was designed to withstand even a class 3 tornado and a magnitude 6 earthquake), but it was not intended to withstand military actions.

The strike caused a serious fire that was extinguished over the course of three weeks following the attack, the primary object that suffered burns was the EPDM sheeting.

“The structure of the confinement is a ‘sandwich,’” explains Vande Putte. “Metal decking, mineral wool, the EPDM sheeting, mineral wool, metal decking. This was done to prevent condensation, and the rubber sheeting is necessary to keep moisture from penetrating inside and to create a more or less airtight space between the two roofs that is conditioned. This conditioning is critically important for several reasons, the main one being to prevent corrosion and maintain humidity under 40%. This space is also slightly heated to avoid condensation.”

Extinguishing a fire in these conditions is an extremely difficult task, primarily because it is hard to notice the paths of the fire’s spread. Firefighters used a thermal imaging drone, but through the layers of metal cladding and mineral wool, the burning was not immediately visible. “So, in a sense, they were ‘chasing’ what had already spread further,” explains Vande Putte.

Moreover, air was able penetrate the damaged structure—in particular, through the seam where the two parts of the confinement were joined during installation, as it was sealed only after assembly. It was in this spot that oxygen entered more easily, facilitating the spread of the fire.

The northern side of the structure suffered the most, where 50% of the EPDM sheeting burned. The fire also spread to the southern side, damaging 10% of the rubber sheeting. To extinguish it, 332 holes had to be made in the confinement’s shell. This method posed no radiation risks to the public: radiation levels are within normal limits, and the Exclusion Zone protects people not involved with work in Chornobyl from the consequences of the nearby strike.

The strike also damaged the Main Crane System, which had been installed for dismantling the Shelter Object. “Inside the New Safe Confinement, there were rails for a robotic arm to move to dismantle the old Shelter object, in order to remove all fuel-containing materials and then dispose of them,” explains Pareniuk. “But these rails were warped by the drone strike.”

The Worst is Yet to Come

“It is not clear how to replace the rails over the Shelter Object,” says Pareniuk, primarily because of the high radiation levels. To carry out repairs, moving the New Safe Confinement was also considered, but due to the critical instability of the Shelter Object, this idea has currently been abandoned.

Potentially, dismantling the Shelter Object will be entirely impossible due to the disruption of the pressure levels inside the facility. “A pressure difference is needed so that radiation doesn’t escape outside; reduced pressure is created inside the confinement and relative excess pressure in the annular space, so that air moves in a way that minimizes the risk of particles escaping. The point is that it must be a hermetic environment — not necessarily one hundred percent, but enough so that radioactive particles don’t escape. But right now this is not working properly, and dismantling is impossible,” says Vande Putte.

Because of the burning of the rubber sheeting, the humidity inside the structure cannot be controlled, which increases the risk of metal corrosion. This significantly reduces the operational lifespan of the New Safe Confinement, which was designed to last 100 years.

“The confinement is sometimes compared to the Eiffel Tower in Paris, as it is also a steel structure and is constantly painted. That is precisely why it is still standing. The New Safe Confinement is also made of carbon steel. Why can’t it just be painted like the Eiffel Tower? Because of the radiation levels,” explains Vande Putte.

“On-site repairs will be very, very difficult, but this does not mean we should fall into despair. At the end of February, engineers were already saying: we need to move step by step, which requires a certain ‘segmentation’ — both in thinking and in practice. Start with the most important,” he adds.

That most important task was determined to be patching holes over an area of approximately 15 square meters. However, this is not a full repair — it is important to restore the complete roof so that moisture doesn’t penetrate inside and the annular space ventilation system can be restored.

“Research is ongoing on how to do this; it will be very difficult, but we must keep moving,” concludes Vande Putte.

Moreover, the work is unlikely to begin before the end of hostilities in Ukraine. This is related, among other things, to the policies of foreign companies that could perform such tasks: most of them do not allow their employees to work in the Exclusion Zone while there is a direct threat from Russia. Currently, they only send observation missions consisting of a few people.

“The situation may develop in such a way that Ukraine will begin to perform part of the work independently. This is similar to the cases involving the supply of weapons, which Ukraine waited years for from the West and at some point decided to produce itself,” believes Vande Putte. “I think that Ukraine’s role will become larger, and we at Greenpeace believe that this is a good thing — so that the money remains in Ukraine as much as possible. Right now, the European Bank for Reconstruction and Development is talking about approximately 500 million euros for repairs, and this amount may increase. I hope that the majority of these funds will go to Ukrainian companies, and not to Western ones.”

The Complicity of Rosatom

The Greenpeace expert emphasizes that the strike was targeted. The Russian military deliberately hit the Chornobyl confinement with a Shahed drone. Of course, Russia denies this. Still, there are several pieces of evidence that point to Russia’s intent. Among all the drones that attacked Ukraine that night, this one flew extremely low, avoiding detection from radars. And before the strike, it made a maneuver: it climbed higher and struck the structure at an angle of approximately 45 degrees.

Such attacks cannot happen without the direct involvement of Rosatom, Russia’s state holding that unites nuclear industry companies and institutions, says Vande Putte.

However, there are still no international sanctions on Rosatom or exclusions from global nuclear programs. Furthermore, French and German nuclear companies have even increased their cooperation with the Kremlin-controlled company after the start of the full-scale invasion. And the First Deputy Director General of Rosatom, Kirill Komarov, still remains a board member of the World Nuclear Association.

The holding is building two new power units at the Paks Nuclear Power Plant in Hungary. The agreement for this was signed back in 2014, shortly after the occupation of Crimea, and the main stage of construction recently began.

“Two months ago, in February, in Hungary, at the Paks NPP, the Minister of Foreign Affairs of Hungary, the Director of Rosatom, [Alexey] Likhachev and the Director General of the International Atomic Energy Agency met. Mr. Grossi (the head of the IAEA — ed.) congratulated his Hungarian colleagues and his friend Mr. Likhachev, and called it a ‘great day for Russia,’” recalls Greenpeace senior nuclear specialist Shaun Burnie. However, he hopes that, after the defeat of Viktor Orbán’s government in the recent Hungarian elections, this situation will change.

Moreover, there are areas of nuclear energy from which it is especially challenging to exclude Russia. In particular, this involves the supply of fuel materials, which are technologically difficult to abandon (Ukraine navigated this dynamic from 2014 to 2022), and uranium enrichment.

In European nuclear structures, there is still a sentiment towards Russia on a purely human level, adds Vande Putte: “In various European structures, I heard an argument at the beginning of 2023 along the lines of, ‘Oh, this is a temporary situation. Why should we give up this very important cooperation with our Russian nuclear friends over a problem in Ukraine?’ From our point of view, this is very cynical, but for them, in their little bubble, everything looks just like that. This is not the only factor, but on a psychological level, it is hard for Western countries to sever these ties.”

Burnie emphasizes that “the role of Rosatom in nuclear exports and trade is not so much financial as it is political. [They want] influence in these countries. It is a way to buy political influence, as they did in Hungary.”

For those reasons, sanctions against Russia or punishment for its crimes in Ukraine in the nuclear sector are currently not even on the agenda. Burnie concludes, “The lobbying of the nuclear industry, for example, in the European Union, has essentially blocked the punishment of Rosatom for its crimes, in particular for this crime in Chornobyl. Serious contradictions exist among some EU member states: they very clearly support Ukraine politically, militarily, economically, morally. At the same time, they directly finance the war against Ukraine by continuing nuclear business with Russia. This has to change. This must stop.”