An accident at Zaporizhzhia Nuclear Power Plant would be “almost impossible” and any damage would be a deliberate act by Russian forces, Ukrainian nuclear personnel have told openDemocracy.

Russia has occupied the plant, in the city of Enerhodar, since the beginning of the full-scale invasion. Its forces are currently preparing to damage the occupied plant, Ukrainian officials claim, in order to stop Ukraine’s counter-offensive in the country’s southeast.

President Volodymyr Zelenskyi said on Sunday that Russia has “approved the scenario of mining” the Zaporizhzhia plant (ZNPP). Ukrainian military intelligence chief Kyrylo Budanov, in turn, asserted that the Russian military has mined four out of six reactors, by allegedly placing vehicles rigged with explosives next to them.

“The situation has never been as severe as now,” Budanov emphasised.

But while Ukraine has sounded the alarm over ZNPP, the US – one of the country’s main allies – has been more cautious.

Speaking on Monday, US National Security spokesperson John Kirby said he hasn't “seen any indication that that threat [of blowing up the ZNPP] is imminent”, noting that the US is monitoring radio signals in the vicinity of the nuclear plant.

The Ukrainian authorities have not clarified how exactly Russia is preparing to cause damage to the plant and at what scale, with Zelenskyi only mentioning that Russian forces could cause a “radiation leak”.

Ukrainian nuclear energy specialists told openDemocracy that Russia turning the ZNPP into a military base is a gross violation and a danger in itself that may lead to irreversible radioactive damage. They say as work at the plant is stabilised, to damage it one needs to know what they’re doing.

“It is almost impossible [to cause damage] without the [Russian forces] following a plan,” says Pasha Oleshchuk, who worked as a staff engineer at Rivne Nuclear Power Plant in northwest Ukraine.

On 22 June, Dmitry Peskov, press secretary for Russian president Vladimir Putin, called Zelenskyi’s claims “another lie”.

Mines at ZNPP

Earlier last week, the Ukrainian authorities claimed Russia had mined the cooling pond at ZNPP. The pond has a critically low level of water after the destruction of the Kakhovka dam on 14 June.

The International Atomic Energy Agency (IAEA), said it had found no mines near the cooling pond, but confirmed Ukraine’s claim that the perimeter of ZNPP had been mined for some time and in some places inside it.

“No mines were observed at the site during the director general’s visit, including the cooling pond,” the IAEA said. “However, the IAEA is aware of previous placement of mines outside the plant perimeter [...] and also at particular places inside [it]”.

So far, the evidence strongly suggests Russian forces blew up the Kakhovka dam – and that means the Ukrainian government’s risk assessment for critical infrastructure currently occupied by Russia has changed. Rosatom claims that Ukrainian forces have increased their alleged targeting of ZNPP since the Kakhovka dam explosion.

Ukrainian intelligence believe that Russia might be inclined to damage ZNPP if Ukrainian army advances on the left bank of Dnipro river in the south, which is currently under Russian occupation. But Ukraine’s offensive in the south is moving slowly at the moment. Hanna Malar, deputy minister of defense of Ukraine, said since the beginning of the offensive, Ukraine has liberated 130 square kilometres of land.

Shutdown mode

Senior Ukrainian officials say that ZNPP is not currently operating. The last operating power unit was put into shutdown mode in September 2022, they say.

Ukraine’s State Scientific and Technical Center for Nuclear and Radiation Safety told openDemocracy that the fifth reactor is in “hot shutdown” mode at the moment. That means it provides thermal power on a very low level, but the reactor does not generate electricity.

“Because the reactors are in shutdown mode, because they’ve been cooled for quite a long time, the consequences will not be as catastrophic as they were at Chernobyl,” says Dmytro Humeniuk, head of the security analysis department of Ukrainian state nuclear research centre.

An accident at ZNPP is very unlikely in normal secure working conditions of the plant because of the way the plant was built, according to Oleshchuk.

All six nuclear reactors at the ZNPP are of VVER-1000 type – unlike the RBMK reactors that were at Chernobyl. The main difference is that the VVER reactors are placed in hermetic confinement, which is a metre-thick concrete shell that stops the release of radioactivity outside the nuclear power plant even if the hull is destroyed.

"At the Chernobyl plant, they were conducting an experiment at that time [of the accident], they turned off all the protection. A series of events that led to [what happened]. That was a completely different type of reactor," Oleschuk explains.

Power grid

Asked what would happen if Russia theoretically blew up the four cold reactors in Enerhodar, Humeniuk says the consequences are difficult to predict – and could range from relatively mild to significant, though he stressed the latter is unlikely.

“I don’t think that they will blow up four reactors, so that only funnels will remain and it will spread [radiation] all over Ukraine. This is my point of view, it depends significantly on the force of the explosion, what will be blown up. It can be like an accident, it can be limited to the industrial site of the Zaporizhzhia plant, it can be wider."

It is worth noting that the reactors do not detonate in chain reaction, according to Oleshchuk.

Olexiy Pasiuk, deputy director of Ekodiya, an environmental protection NGO, believes the Russian army turning ZNPP into a military base poses danger in itself. Even small damage to equipment at the plant is a serious problem for Ukraine, Pasiuk says, as the country will have to manage the consequences.

With the violation of standards of physical protection of nuclear materials at the plant, and the fact that the Russian military violated all nuclear safety measures, it is difficult to predict what might happen.

According to Oleshchuk’s contacts among ZNPP workers, Ukrainian personnel are banned from certain rooms at the plant, and when they move around on the premises under Russian military escort to their posts and back, they are forbidden to look around. Oleshchuk believes we might not know everything that is happening at the plant, or what has already happened.

ZNPP does not provide energy into the Ukrainian power grid, but receives it to enable the cooling of nuclear fuel in reactors that are in “shutdown” mode. So disconnection of the ZNPP from the Ukrainian network could have consequences.

“Among options of the development of the ‘accident’, there may be a loss of connection with the Ukrainian power grid or a loss of water in the cooling pond, in which cases the removal of energy from nuclear fuel will be impossible,” Humeniuk said.

“So in this case, the water that cools the reactor will heat up to the point where it will lead to the reheating of the fuel and its partial or not melting. Then, in principle, it is possible [for], well, a certain emission of radioactive fission products, i.e. radiation, into the environment.”

Regarding the possible detonation of stored spent nuclear fuel held at ZNPP, Humenyuk rejects the risk of significant consequences, though notes it could lead to radiation pollution. “The fuel [if exploded] could dissipate across the ground, it could get into the groundwater. This is what the pollution could look like,” he said.