“The fallout would contaminate parts of Europe and the Russian south” The possible consequences of an accident at the Zaporizhzhia NPP

Vulnerability to shellfire

The Soviet Union built the Zaporizhzhia NPP in the 1980s, equipping it with VVER-1000 pressurized light water nuclear reactors. Damaging such a reactor would unseal its primary circuit, releasing the accumulated radioactivity with water into the environment. Further on, the interruption to the cooling system may result in a core meltdown.

Claims that no missile can breach the reactor lid are false, says nuclear physicist Andrey Ozharsky. The design of the NPP was aligned with Soviet standards, so its protective lid can withstand the crash of a 5.7-tonne plane at the most. It’s the weight of an An-2, the corn crop duster. Any hard-structure missile system is a lot more powerful than that because its munitions were designed to breach armored structures. A direct hit with a shell over 150 mm in diameter will damage the protective cover, which is not an armored lid made from reinforced concreted several meters thick, like those used in military construction, the expert reminds.

Another potential threat is the nuclear waste storage facility on the Zaporizhzhia NPP grounds. The waste is stored in hard concrete casks, but their surface is already chipped, Ozharsky warns. The spent nuclear fuel inside the casks is highly radioactive and therefore hazardous. The expert insists that damaging these casks is comparable to damaging the reactor.

Vulnerability to power outages

Not only the NPP, which currently has one unit in operation, but also the power line that supplies it with electricity is under the threat of shellfire. Every reactor is disconnected from the power grid and disabled annually. However, whereas the so-called “cold shutdown” is a routine procedure, it lasts at least a week under the constant monitoring of personnel, whereas a sudden power outage at the NPP may result in an accident similar to that at Fukushima, says Ozharsky. Moreover, the power plant needs electricity even in a cold shutdown.

“You can't shut down a nuclear reactor instantly: there is a cooldown period, and then there’s residual decay heat release, in which the energy is not produced through the fission of uranium or plutonium but through the α- and β-decay in the progeny of all the artificial radionuclides: cesium, strontium, and so on – a total of over 2,000. Even in the absence of a chain reaction, they continue to emit heat, maintaining a small fraction of the reactor’s nominal power output. If the nominal power output is 3,000 MWe, and the real output is 1,000 MWe, which is realistic considering the low efficiency of all NPPs, 1% of that capacity amounts to dozens of megawatts. Thirty megawatts is an immense output, so the reactor needs cooling if we want to prevent its meltdown, which implies pumping water through it, and pumps need an external power supply.”

If the reactor was in cold shutdown, a direct hit would result in the discharge of radionuclides, which would contaminate the plant and the adjacent territories (a similar scenario would be damaging a warehouse full of chemicals). This would also be a disaster but without the discharge of radioactive materials to the upper atmosphere or their spreading across hundreds of kilometers. However, the accident would still be serious in the temporal sense, contaminating the area for the nearest three or five centuries.

The accident scenario involving the loss of the final heat absorber is well known to nuclear experts, which is why NPPs are equipped with emergency power generators. Such generators normally run on diesel fuel and must be kept operational and with enough fuel to power the pumps and other systems crucial for nuclear safety. However, as Ozharsky points out, we cannot rely on them in Zaporizhzhia:

“In the current conditions, these safeguards are questionable: someone could have nicked the fuel or removed a certain part of the generator. The operational capacity of any element is currently an open question. We’ve seen reports of transmission towers destroyed, which means the power plant has only one power supply line, which is unacceptable considering the requirement of two or even three backups. The lines differ in voltage, and they might have been restored, but should something happen to the remaining line, we risk leaving the NPP without an external power source. Transmission towers are easily damaged. You can't hide them and everyone knows their location, so you can’t protect them from a sabotage attack. If the NPP is cut off from the electric grid, the reactors must be shut down and the emergency diesel generators must be launched. In this case, there will be no accident. If they fail to launch, we may see a disaster similar to that at Fukushima, where the generators were swept away by a tsunami. This resulted in a nuclear meltdown with the fuel penetrating the concrete containment vessel and reaching soil and water.”

Olga Kosharna, a nuclear energy expert and former member of the State Nuclear Regulatory Inspectorate of Ukraine, believes that emergency generators should save the day in this scenario:

“After Fukushima, NPPs have been equipped with massive numbers of such generators. The generators at Fukushima were flooded, and getting the military to deliver new ones was considered too costly. That accident could have been averted. It was a major design basis accident with a core meltdown in the event of the loss of external electricity supply. Our calculations allow for the engagement of over twenty diesel generators with ten days worth of fuel to prevent the reactor core meltdown.”

If the accident does happen, how will it unfold?

According to Olga Kosharna, Energoatom has assessed the consequences of a core meltdown accident in the event of the loss of external power supply and the discharge of primary circuit coolant.

“As of July 27, 2022, they estimated that, depending on the wind direction, humidity, precipitation, and air temperature, the radioactive cloud would reach Romania, Crimea, or Bulgaria in six or seven hours and Turkey in 23 hours. However, most of the fallout would contaminate the Krasnodar Krai [in the south of Russia]. We are operating on the premises that the cesium-137 contamination 350 kilometers away from Enerhodar would reach 100,000 Becquerel per square meter with the limit of 400 Bq per square meter. A hundred thousand Becquerel would require creating an exclusion zone. So Russia would take the heat even with the northern wind, whereas a western wind would blow the entire cloud into Russia up to the Ural mountains.”

Could the Zaporizhzhia NPP supply Crimea with electricity?

The Russian government has repeatedly announced its plans of disconnecting the seized power plant from the Ukrainian grid and redirecting the energy to the occupied Crimea. But, as Ozharsky says, it's easier said than done:

“The Ukrainian power grid is currently out of sync with the Russian one. We are using alternating current, which implies that all generators within a single grid must operate in sync. This doesn't mean the systems are completely cut off from each other, but a direct power exchange is impossible without so-called direct-current inserts. In a nutshell, the alternating current from one grid is converted first into direct current and then into alternating current synchronized with a different power grid. It’s not a small device but an installation comparable in size to a switchgear assembly, which, in turn, may sound like something akin to an electrical fuse but is in fact a major energy facility, a giant, costly object. As I understand, it's not currently available because the two countries’ power grids used to run in sync. Such facilities are yet to be built.”

The expert points out that, even if Russia rebuilds the transmission lines between the NPP and Crimea or mainland Russia, only one or two units can be synchronized with the Russian grid without direct-current inserts. “They could do it right this moment, but such transmission lines are vulnerable to acts of sabotage. One such attack in 2015 proved successful, as the Ukrainians blew up multiple transmission towers on the line supplying Crimea. After that, the peninsula was critically low on electricity, with rotating blackouts every two hours for a month. The situation was not remedied until Russia completed the construction of two large cogeneration plants and a power bridge from the mainland.”

What does Russia want with the Zaporizhzhia NPP?

Ozharsky believes that neither Russia nor Crimea needs this much energy. Russia's economy is stagnant, and so is its energy consumption; therefore, the available supply is more than enough, according to the expert. Further on, the Rostov NPP in the Russian south had its fourth unit launched not so long ago.

“I was at a hearing in Volgodonsk where they said they had so much energy they could supply it to Crimea. Can you imagine transmitting electricity over a distance of a thousand kilometers? Electricity flows either way, but what are we supposed to do with the Rostov NPP in this case? The situation is similar in the Luhansk and the Donetsk regions and Zaporizhzhia. There are no major industrial consumers. There was the Azovstal steel mill, which consumed an immense amount of power, but it is no more. The plant in Kramatorsk that built reactors for Russia has been bombed out too – another energy-intensive metallurgical facility. Therefore, an NPP has few uses. What we need is multiple small boiler stations running on coal and providing both central heating and electricity, like CHPs.

If Russia succeeds at connecting one of the VVER-1000 reactors of the Zaporizhzhia NPP to the Russian grid, restoring the transmission line, and supplying Crimea with energy, it will have to shut down one of the reactors in Rostov because all that energy has to go somewhere. Elon Musk knows how to store energy, but we don’t, so we have to balance out energy production and consumption. We have to either rebuild Azovstal, which would take years, or find another major consumer – but there are none. All that talk pursues a goal other than meeting Russia’s energy needs.”

As Olga Kosharna is convinced, Russia seized the Zaporizhzhia NPP for nuclear blackmail and to integrate its power output into a single Russian electrical grid.

“From my perspective, Russia has resorted to nuclear blackmail and is shelling the facility to get Ukraine to sit down at the negotiating table. Russia isn't looking to cause a nuclear accident; it needs a power plant that is operating safely. Once they entered the plant, they announced to the personnel: ‘We're going to have a referendum. You will get new passports and become Rosatom employees.’ Apart from the Zaporizhzhia NPP, they also want the Kakhovka Hydroelectric Station and the wind turbines in the south of the Kherson Region, which is exactly why they have restored the transmission line connecting the Crimean neck of land and Kakhovka. They plan to switch not only the Zaporizhzhia NPP but other power plants to the Russian electrical grid, and they’ve been working on it since May.”

The shelling that took place on July 11 before the Chinese representative’s address at the UN Security Council is a telling sign, according to Kosharna: “Russia is upping the stakes to get our international partners to urge Ukraine to negotiate and to cement the status quo on the occupied territories. They have no advances on any of the fronts and fear launching an offensive in the south.”

Nuclear power plants affected by war

Before 2011, such force majeure events as an armed conflict or a plane crash were barely taken into account in the nuclear power plant design. Rather, they were treated as one-off incidents. It was enough to make allowances for a complete failure of any element, regardless of the cause. The design guaranteed the safety of the power plant following any such incident. The Fukushima disaster was a game-changer: the accident had a very low degree of probability and yet occurred.

The probability of an armed conflict affecting the operation of an NPP has increased too. The probability index used to be lower because a nuclear generating country was presumed to be powerful enough to avoid being dragged into an armed conflict on its soil. Reality has proved this assumption wrong. Moreover, Ukraine is not the only country with a nuclear power plant to be torn by hostilities.

· The Krsko NPP, Slovenia (with a 700 MWe pressurized water reactor). A joint project of Slovenia and Croatia, which were both parts of Yugoslavia at the time, the NPP found itself in a war zone in 1991. In June 1991, Slovenia’s declaration of independence was followed by a ten-day war. Federal troops crossed the border and faced armed resistance from the local police. The battle took place on a road a few kilometers away from the NPP. The conflict had a death toll of around 70. The NPP continued its operation without interruptions.

· The Bushehr NPP in Iran (with a 1000 MWe pressurized water reactor). Its construction began in 1975 but was halted due to the Western sanctions since the German company Kraftwerk Union could no longer be the contractor. The first unit was about 75% ready. In 1980, the eight-year war with Iraq broke out, featuring multiple attacks on the NPP by the Iraqi Air Force. The absence of nuclear fuel limited the possible consequences of damage to the plant. However, even though its containment buildings include an extremely thick layer of reinforced concrete, the repeated bombing is reported to have resulted in two holes in the containment of the second unit, each around half a meter in diameter. In 2010, an Iranian missile defense system took down a friendly plane, which crashed some twenty kilometers away from the NPP. Despite all this, the Bushehr power plant successfully passed the commissioning trials and was connected to the national grid in 2011.

· The bombing of nuclear reactors in Iraq. The first two Iraqi nuclear reactors, Tammuz 1 and Tammuz 2, were destroyed by an Israeli attack in April 1978. The next reactor was built in France and delivered to Iraq in 1980, to be installed alongside an operating Soviet reactor (a 2 MW IRT-5000) in a recently built underground nuclear facility outside Baghdad. Israeli intelligence believed that the new reactor's purpose was to produce plutonium and that military intervention was necessary before the reactor was loaded with nuclear fuel. On June 7, 1981, a group of Israeli fighter jets launched an airstrike on the reactor. Operation Opera, also known as Operation Babylon, damaged the reactor complex beyond repair.

· The destruction of a reactor in Syria. The relations between Syria and Israel resulted in a similar failure of Syria's nuclear program. The Syrian nuclear reactor in Deir ez-Zor was eliminated by the Israeli Air Force. Ten fighters, each equipped with a 500-pound (230 kg) bomb, took out the missile defense system with a direct hit and bombed out the reactor. The destruction of a research reactor, even one in operation, comes without severe nuclear safety consequences due to the small amount of fission material. In the case of the Syrian reactor, which had no nuclear fuel, the consequences were limited to financial losses and the collapse of Bashar al-Assad’s nuclear hopes.

· The Indo-Pakistani conflicts. India has five NPPS, as compared to two in Pakistan. Armed conflicts between the two countries have mostly been limited to skirmishes along the border, while all the reactors are far removed from it. However, the situation is aggravated by the two countries threatening each other with nuclear weapons. In such a setting, the issue of power plant security becomes secondary to the mutual nuclear threat.

· The Armenian NPP (two VVER-440 reactors). The Armenian NPP has been less affected by hostilities than the aforementioned plants, as the First Nagorno-Karabakh War between Armenia and Azerbaijan (1988-1994) had no bearing on its operation. The power plant is situated close to Yerevan and far from the war zone. The NPP was shut down after a severe earthquake in 1988, but the second unit was put back into operation in 1995. However, the Nagorno-Karabakh issue is yet to be resolved.