Calm Kakhovka Reservoir waters at the edge of the at-risk Russian-occupied nuclear reactor complex in Zaporizhia.
The area near the Zaporizhzhia Nuclear Power Plant Credit: Ralf1969 - Own work CC BY-SA 3.0 Wikimedia Commons

A Catastrophic Nuclear Meltdown at the Zaporizhzhia Nuclear Power Plant in Ukraine is Suddenly in the Realm of Possibility

The Zaporizhzhia Nuclear Power Plant in Ukraine is Europe’s largest. In March, Russian forces captured the plant and a crew of Ukrainians are maintaining operations at the plant — effectively at gun point.

In recent weeks, fighting around the Zaporizhzhia Nuclear Power plant has intensified, causing some damage to the plant and raising the prospect that in the context of armed conflict, a catastrophic nuclear accident becomes a very real possibility.

In this episode, we are joined by Jon Wolfsthal, senior advisor at Global Zero and a member of board of Science and Security at Bulletin of the Atomic Scientists. We kick off by discussing how Zaporizhzhia operates in normal circumstances and how the fighting may have impacted current plant operations. We then discuss what a catastrophic event at the power plant may look like. This includes the global impact of  a nuclear meltdown at Zaporizhzhia.

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Transcript lightly edited for clarity

What is Zaporizhzhia Nuclear Power Plant (ZNPP)?

Jon Wolfsthal [00:00:00] The problem is those generators are not like your car engines that are designed to start and stop repeatedly over time. And in the middle of a war zone, Ukraine does not have easy access to diesel fuel.

Edited News Clips [00:01:03] “Shelling around a key nuclear plant in Ukraine is drawing international concern.” “And now Ukraine’s top nuclear official is raising fears that Russian trucks which have been parked inside the plant’s turbine hall, could be laden with explosives or cause an accidental fire.” “Fears are growing over a potential nuclear disaster. After weeks of shelling, Europe’s largest nuclear power plant temporarily lost power today for the first time ever.”

Mark L. Goldberg [00:02:02] At time of recording, the International Atomic Energy Agency was seeking access to the plant, though it is unclear if they will be granted that access and able to assess the safety of the plant any time soon. The situation around Z is rapidly developing, but this conversation will give you the context you need to understand events as they unfold.

Jon Wolfsthal [00:02:42] So the ZNPP is one of the largest nuclear power complexes in the world. It has six separate nuclear reactors that provide a majority of the electricity for Ukraine. It was built during the Soviet era to actually provide electricity to the then Soviet Republic of Ukraine and is situated on the upper massive river complex in Ukraine at a town that’s basically called Energy Town, where they have both hydroelectric dams, nuclear reactors, and it’s basically the energy hub for Ukraine.

How has Russia handled the Zaporizhzhia power plant since their invasion of Ukraine?

Mark L. Goldberg [00:03:17] So the Zaporizhzhia nuclear power plant (ZNPP) was captured in March by Russia. What do we know about these circumstances inside the plant since the Russian occupation of it?

Jon Wolfsthal [00:03:30] Not a huge amount. It’s disputed territory. There have been some photographs released online, but I’m always cautious about relying on photographs, given particularly Russia’s use of disinformation. But it does appear that the Ukrainian workers are still staffing the plant but that there are Russian military equipment that’s being stored not only around the facility, but actually inside the facility to try to shield it from potential counterattacks. We do know that there’s been no elevation of radiation coming from the plant. It doesn’t appear that there’s been any sort of leak or accident at the plant itself, but it has been subject to shelling by Russian forces. Russia has claimed that the Ukrainians are the ones doing the shelling and we have more recently seen the power lines to the plant, which are critical to its safe operation, being attacked in a number of cases, including recently, the power lines have been cut. So, it’s pretty much the definition of a dangerous situation around a nuclear power plant.

Who is operating the Zaporizhzhia power plant under Russia’s occupation?

Mark L. Goldberg [00:04:31] And it’s my understanding that the Ukrainians who were working in the plant prior to the invasion are now down to something like a skeleton crew and are essentially like working at gunpoint, right? The Russian soldiers are occupying the plant, but they are relying on Ukrainian civilians to keep the plant operational.

Jon Wolfsthal [00:04:51] Yeah, my understanding from Ukrainian reporting is that it’s still Ukrainians running the plant. Again, because I’m not there and I’m very mindful not to buy into unverified narratives from either side at this point, even though clearly the Russians are the illegal aggressors, but really don’t have a good sense of what’s going on in the plant. There have been reports that several of the plant workers have been wounded and two have been killed so I can’t imagine that it’s a pleasant or stress-free situation for anybody in the plant, especially given the fact that these are still operating nuclear reactors in the crosshairs of military gunfire.

Why do nuclear power plants require electricity?

Mark L. Goldberg [00:05:28] So in recent weeks and days, even, there has been an uptick in fighting near the plant, which has been intermittently shelled. We’re speaking Thursday, August 25th, and today the plant was briefly cut off from the main power grid where fires from shelling disrupted a line, apparently. And this incident seemingly reinforced and underscored just how dangerous the situation is right now. For a non-technical audience, can I have you just briefly explain why a nuclear power plant like the ZNPP requires outside electricity?

Jon Wolfsthal [00:06:10] Sure. So, without getting into nuclear physics or engineering, any power plant produces heat to produce steam to turn a turbine. Nuclear power plants do that by irradiating uranium and the reactor core, which has the uranium fuel in it, gets quite hot and it needs constant flow of cool water to dissipate the heat. Nuclear power plants rely on external sources of electricity for that cooling because if the reactor shuts down, you still need to run the cooling system for the heat to be taken out of the reactor. And so, this power plant, like all other well designed nuclear power plants, has multiple backup systems for electricity, including from the main transmission line on the grid, and then, should that fail, access to onsite generators. But in the case that the power supply fails and the generators, which run on diesel fuel, run out of fuel or are damaged, then there’s no way for the reactor to cool itself. And eventually the water boils off, the fuel can then melt. And people have probably heard the term a nuclear meltdown. It literally is that. If the fuel is not cooled, it will melt through the floor of the reactor and actually get down into the earth and hit the groundwater, which creates a giant explosion of nuclear tainted steam, which is the definition of a really, really bad day for any nuclear power plant and people within hundreds and hundreds of miles in it. So, you generally don’t want to mess around with the power supplies for nuclear reactors. They run all of the safety systems, the control systems, as well as the cooling. And the fact that we’ve now seen the power supply breached is another sign of just how dangerous this situation is.

What safety measures are used in nuclear power plants to prevent a meltdown if power is cut?

Mark L. Goldberg [00:07:57] Can you just briefly explain what sort of safety and backup mechanisms exist? So, it’s my understanding that there are various connections to the main power grid, which in the course of the fighting in this conflict have mainly been severed and today, briefly, one of them was severed, apparently. What safety measures would kick in at that point to prevent a meltdown?

Jon Wolfsthal [00:08:21] A number of things should happen in normal time, so any plant is going to have multiple sources of electricity. It can potentially draw on its own electricity generated from the plant. Again, that’s not deemed to be a safe and reliable system because if the reactor has to shut down for safety or other reasons, then your supply is gone. There’s the main transmission grid from Ukraine, which again is under great stress because it’s been targeted by the Russian military. And then there are also backup systems. There are reports that this plant is fed by either a geothermal or a coal fired plant nearby, which can provide backup power. But should all of those connections fail, there are then on-site diesel generators which can kick in. And my understanding is, in fact, they have turned on and operated for certain periods of time over the past several months and then turned back off when the electricity is restored. The problem is those generators are not like your car engines that are designed to start and stop repeatedly over time and in the middle of a war zone, Ukraine does not have easy access to diesel fuel. So, these diesel generators can help in a pinch, but are not designed to have the reactors main energy source provided by them for any significant length of time. So there are these backup systems in place, but because it’s a very confused, chaotic situation, I don’t think we have a very clear picture on exactly what’s been working and what hasn’t, which is why a number of governments, including the United States, have called for the International Atomic Energy Agency, which has a UN mandate to help provide for the safety of nuclear power plants around the world, to go and visit the site and assess the situation.

What is a nuclear core meltdown?

Mark L. Goldberg [00:09:58] I do want to get into those ongoing efforts by the IAEA and its director general, Rafael Grossi, to access the plant. But before we do, I’m interested in having you explain what would be a bad case scenario should all of those safety mechanisms fail. You know, we are in a war zone, unfortunately, a bad case scenario is not implausible. What would happen if indeed a meltdown occurs?

Jon Wolfsthal [00:10:33] I think everybody who hears the words Ukraine and nuclear accident, or nuclear reactor immediately think about the Chernobyl disaster in the 1980s for understandable reasons, but I think it’s important to point out that this reactor is a totally different design and has a number of different features which make the consequences and the risk of an accident different. In Chernobyl, the reactor itself was designed in a way that, when it shut down, it would not do so safely and did not have any sort of cement containment system around the reactor. So, when it caught fire, the core itself then spewed radioactive gas and material pretty much everywhere. These reactors are a little different. They are a little bit bigger, but because they are pressurized light water reactors, meaning that they have to build up pressure through steam in the reactor, that means the reactors themselves are built inside cement and steel containment building, so that can help contain any spread of radiation should there be a smaller accident. But the worst-case scenario is actually quite severe. If the reactor loses the ability to cool itself, and if the uranium fuel and the metal fuel in the reactor core melts, it can burn through the cement and steel containment building down into the earth and into the groundwater. And that means you basically have uncontained uranium fire burning into the atmosphere and into the groundwater, which can create a large-scale explosion that can lead to a fire at the plant, and it can spew extremely radioactive byproducts up into the atmosphere and into the wind stream. So there have been some models done by U.N. and other treaty organizations to look at the potential spread of radioactivity. And in the case of a meltdown, the worst case you could see radioactivity spread all over Europe and beyond very quickly, something that would have dramatic effects both on the health and the economies of the populations in Europe, and I think would actually drive to a much greater escalation of the fighting in Ukraine because of the fact that the damage being done would no longer be contained to Ukraine itself, but would be basically a European conflict.

In the case of a severe nuclear meltdown in Zaporizhzhia, how far could the radiation spread?

Mark L. Goldberg [00:12:47] So in this worst-case scenario, depending on which way the wind is blowing, like people in Paris could be impacted, people in Berlin, like how wide a geographic area might you expect people to experience some sort of like sickness or illness from the radiation?

Jon Wolfsthal [00:13:06] So again, it really does depend on a lot of factors, including how much radioactivity is released, what the wind patterns are, is it raining, at what point the meltdown takes place in terms of the reactor cycle? But just for example, there are contaminants from Chernobyl all over the planet in Antarctica, in the Arctic, in the United States, in South America. There is no part of the world that has been immune from the spread of radioactivity from that plant. Just as every man, woman and child in the world today has radioactive elements in their bodies that come from the atmospheric nuclear testing that the United States, Soviet Union, and other countries engaged in up until the 1960s. So, the consequences could be global. It’s impossible to predict without knowing the details, whether you’re talking about significant doses of radiation to millions of people throughout Europe or whether you’re dealing with smaller exposures. But any additional intense exposure to radiation is a risk to people’s health, is a risk to people’s livelihood, to farming, to commerce and trade. And as we saw in the case of the Fukushima partial meltdown in Japan, even if the radioactivity is contained in the case of a partial meltdown, it becomes extremely difficult for anybody to conduct any kind of normal business in and around the vicinity of the plant. So there really is no upside to a potential accident caused by this conflict, and it could have extremely severe circumstances all over Europe.

What is the International Atomic Energy Agency and why does it want access to Zaporizhzhia?

Mark L. Goldberg [00:14:38] So to potentially prevent that outcome, the international community right now, or I should say many elements of the international community are seeking access to that plant, namely the IAEA and its director general. What information would you expect the IAEA to seek to ascertain about that plant, if and when it arrives, or what is the IAEA seeking to do here?

Jon Wolfsthal [00:15:07] First and foremost, I would say, even before we talk about the calls by countries and individuals for the IAEA to get involved, there have been very valuable and important calls for Russia to simply stop attacking the nuclear power plant. This situation is one of Russia’s own making. It’s irresponsible and dangerous. It is illegal and under international law and just the normal common sense of humanity, it should end. And so, I think predominantly we should focus on the need for Russia to cease these attacks. That being said, because there is not a clear understanding of the safety systems at the plant, nor is there a clear sense of what the United States, Europe or other countries can do to help ensure that the plant remains stable and does not have a meltdown or another accident, the IAEA can conduct a full safety assessment at the site to identify certain things. Are the containment buildings of the reactor vessels intact and are the safety systems and the plant in the control rooms up and running? That’s a basic question. What power supplies are currently available to the plant and what backup systems are in place? And are they fully functioning? That’s another element. And the third is to assess the state of the backup generators, to determine whether they are operable, how much fuel they have, and whether or not they can run for an adequate length of time, should the outside power sources be cut in the future? So those are three basic things that the IAEA can do in addition to providing some independent sense beyond the monitors that are currently on site, what the radiation signals are outside the plant? Has there been any elevation of radioactivity? And also, what is the condition of the crews that are staffing the control rooms and the safety operations of the plant? All of those, I think, would be valuable information for the outside world, particularly European countries, to know. And also, that the IAEA has the authority, in fact, the responsibility to report findings to the U.N. Security Council, which can then either ask or require countries to take action to prevent some sort of nuclear accident or event at the plant.

Is it likely that the International Atomic Energy Agency will get access to Zaporizhzhia?

Mark L. Goldberg [00:17:14] But at this point and again, we’re speaking on Thursday, August 25th, it is unclear whether or not Russia will indeed grant access to the plant. Ukraine has consented and its Ukrainian territory, but Russia obviously has de facto control, and the IAEA can’t just invade the plant. They need the consent of the Russian occupying forces to access it and as of now, it’s not clear that that consent is forthcoming.

Jon Wolfsthal [00:17:38] That’s right. And also, there are a couple of things to keep in mind here. One, even if Russia consents, there are certain protections that must be required or should be applied to IAEA inspectors, including to Director General Rafael Grossi, to make sure that they’re safe. So, are they going to be escorted by Russian troops or Ukrainian troops? What equipment can they bring in? This is disputed territory. Will they operate under safeguards agreements that are in place under Ukrainian law, or will they operate under voluntary agreements that are implemented under Russian law? So those things are unclear, the methodologies here. But also, it’s not clear, while the Ukrainians have said that they welcome a visit, they also have concerns because, in fact, the assistant director general or deputy director general for nuclear energy at the International Atomic Energy Agency is a Russian official. And so, they have some concerns about the extent to which the facility visits will be used by the Russians for disinformation or whether, in fact, they will be open and honest and fair inspection. So, there’s still a lot to be worked out here. I think the bottom line is that both countries need to agree to this rapidly. And most importantly, Russia needs to cease military operations in and around the plant.

Why is Russia occupying Zaporizhzhia?

Mark L. Goldberg [00:18:48] So you have posited, and I’ve seen a Guardian report backing up this posit that Russia’s ultimate objective by occupying ZNPP is to disconnect it from the Ukrainian power grid and connect it to the Russian power grid. And this would fit into a broader pattern by Russia since the invasion of Ukraine to use access to energy as part of its overall diplomatic and war effort. What would be the significance if indeed Russia were to do that, were to disconnect the power plant from Ukrainian power grids and connect it to Russian power grids?

Jon Wolfsthal [00:19:31] You know, I don’t think it’s a surprise to anybody that Vladimir Putin views Ukraine as part of Russia. He’s said as much and that he’s prepared to use energy as a weapon, he’s done as much. And so, we’ve seen the Russian battle plan target Ukrainian critical infrastructure, including energy, transportation, telecommunications, in order to link as much of Ukraine to Russia as possible. Right now, Ukraine draws a significant percentage of its electricity production from ZNPP, and so disconnecting it from the Ukrainian grid does two things for Vladimir Putin. One, it compromises Ukrainian energy security, something that is very much in Putin’s interest. And two, it enables him to provide that electricity reliably to the parts of Ukraine that he has occupied, including the Crimea and the Donbas and elsewhere, but also then to supplement Russian energy production. While Putin is selling as much oil and gas as he can, he has an incentive to get electricity production from elsewhere. So, for both these reasons, I think there’s good suspicion that this is what Russia is trying to do. The problem, of course, is that not only is this illegal, but it’s highly dangerous. And he’s doing it at the end of a gun where we’ve seen Russian military officials and soldiers not only engage in atrocities, but make mistakes, colossally stupid and dangerous mistakes, whether it’s in terms of their logistics or operations. And so, in the effort to try to seize control or disconnect this plant. I don’t think anybody should have confidence that the Russians will do so safely if, in fact, it looks like Russia will seize control of this plant. There’s the risk that not necessarily the Ukrainian government, but Ukrainian resistance fighters might try to take action and that will cause additional bloodshed and dangerous military operations at the site. Not to be flip about it, but there’s a reason that people don’t attack in and around nuclear power plants. It’s because it’s colossally dangerous. And so Russian activity here really needs to cease rapidly. But it does appear that part of their war plan is to seize control of this plant and seize it for their own.

Mark L. Goldberg [00:21:34] I mean, it just seems like there are so many opportunities right now for things to go colossally wrong. In the coming days or weeks or months even, are there any key inflection points or indicators that you will be watching or looking towards that will suggest to you whether or not things are indeed moving in a more or less dangerous direction?

Jon Wolfsthal [00:21:58] I mean, I’ll obviously be interested to see whether or not the IAEA inspectors and leadership are able to get access to the site but what we have seen so far in the war leads me to believe that there’s really very little to watch here because Putin has been very open about what is planned. He plans to capture and if he cannot capture, destroy as much of Ukraine as possible, including things that could lead to negative implications or negative impacts on Russia itself. And we should keep in mind that a disaster at the plant would not only affect Europe, it would likely affect Russian territory as well. It’s one of the reasons that I think Russian disinformation campaigns have said, oh, Ukrainians are trying to sabotage the plant because if Russia does destroy it and there is an accident, Putin wants to be able to blame Ukraine and not have to accept responsibility himself. So, I expect this activity to continue. I’ve seen nothing to suggest the Russians will come to their senses or gain some new appreciation for the dangerous activities they’re engaged in. So sadly, I will be watching, but I don’t have any expectations for things to change outside of a wholesale change in behavior by Russia, or potentially a dramatic escalation by Ukraine in order to have Russia pay a higher set of consequences for their actions. And I think that’s something the United States, President Biden and others have been very mindful of. And I think Ukraine itself has been mindful of knowing that if it were to turn around and start to escalate the war in Russia itself, it would lose public support and probably much military support. So, there’ll be things to watch for, but I don’t expect major changes in the Ukraine.

Mark L. Goldberg [00:23:35] This was very helpful. Thank you so much for your time.

Jon Wolfsthal [00:23:37] Happy to do it. Thank you so much.

Mark L. Goldberg [00:23:46] Thank you for listening to Global Dispatches. Our show is produced by me, Mark Leon Goldberg, and edited and mixed by Levi Sharp.