Fears of a nuclear incident in Ukraine rose to the surface on Friday when a drone armed with a warhead blasted through the protective outer shell of the melted-down reactor at Chernobyl, the site of the world's worst nuclear accident.
The strike, which Kyiv blamed on Russia, did not breach the concrete "sarcophagus" containing the reactor itself and radiation levels did not increase, according to the International Atomic Energy Agency.
However, the prospect of an attack on the highly radioactive site cast a cloud over newly proposed peace talks between Russia and Ukraine's Western backers aimed at ending the three-year conflict.
Who was responsible for the attack?
While Ukraine's government immediately pointed the finger at Russia, the Kremlin denied any involvement in the drone attack and it accused Ukraine of pulling off a false-flag operation.
Neither of the two competing claims could be independently verified.
"There is no talk about strikes on nuclear infrastructure, nuclear energy facilities. Any such claim isn't true. Our military doesn't do that," Kremlin spokesman Dmitry Peskov said in a conference call with reporters.
"It's obvious that there are those [in the Ukrainian government] who will continue to oppose any attempts to launch a negotiation process and it's obvious that those people will do everything to try to derail this process."
Foreign Ministry spokesperson Maria Zakharova described the drone attack as a "reckless" act by Kyiv, and noted that Russia had been part of the international effort to build the structure that was hit.
Ukraine, meanwhile, said it planned to provide detailed information to US officials about the Chernobyl strike during the Munich Security Conference, which began on Friday.
Appearing at the conference, Ukrainian President Volodymyr Zelenskyy said he thought the attack on Chernobyl was a "very clear greeting from Putin and the Russian Federation" to the assembled leaders.
Authorities at the power plant displayed metal fragments of the drone recovered from inside the containment shell after the blast, including what appeared to be an MD-550 engine, which the Russians have been using to power Iranian-built Shahed drones since late last year.
What's at stake right now?
The timing of the attack is sensitive as it has taken place against the backdrop of the Munich Security Conference, a gathering of world leaders that some had hoped would be an opportunity for Ukraine's allies to present a united front against Russia's invasion.
It also occurred just a day after US President Donald Trump and Russian President Vladimir Putin spoke on the phone and agreed to negotiations to end the war, alarming leaders in Ukraine and across Europe who fear Mr Trump might attempt to end the conflict unilaterally by conceding too much ground to Moscow on issues such as NATO membership and territorial boundaries.
That development followed US Defense Secretary Pete Hegseth declaring it was not "realistic" for Ukraine to believe its borders could return to how they were before 2014, when Russia did not control Crimea.
EU foreign policy chief Kaja Kallas said the attack on Chernobyl "clearly shows" the Russians "don't want peace".
"What is up to us right now is to decide and discuss how we support Ukraine … because our values haven't changed, the goals of Russia haven't changed either," she said.
Polish Foreign Minister Radoslaw Sikorski said the drone attack "strengthens the argument for improving Ukraine's air defences in our own self-interest".
"In 1986 the radioactive cloud endangered all Europe and beyond," he added.
Just how dangerous could an attack be?
The drone and its warhead pierced the outer shell covering the remains of Chernobyl's Number 4 reactor — the same one that exploded on April 26, 1986, killing at least 30 people and spewing radioactive fallout over much of Europe.
The 2.1 billion euro ($3.7 billion) outer shell structure, completed in 2019 and known as the New Safe Confinement, encloses the original concrete shelter, known as the "sarcophagus", that was hastily built over what was left of the exploded reactor shortly after the explosion.
Made of steel and designed to prevent any radioactive release from the exploded reactor, the New Safe Confinement is also meant to protect the reactor from any external hazards.
Experts have said the drone attack did not threaten the integrity of the concrete sarcophagus, which can withstand a much heavier impact.
However, Rafael Mariano Grossi, the head of the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), said Friday's incident was deeply concerning and underlined the persistent risks to nuclear safety during the ongoing war.
"There is no room for complacency, and the IAEA remains on high alert," he said in a statement.
"I once again call for maximum military restraint around Ukraine's nuclear sites."
All three other nuclear reactors at Chernobyl have been shut down since 2000, but the plant still houses spent fuel and contaminated equipment that is slowly being dismantled over the course of a decommissioning process that is expected to continue until 2065.
Russian troops occupied the Chernobyl plant in the opening weeks of the war after heavy fighting in the exclusion zone that surrounds the facility.
They left after controlling the plant for just over a month, effectively handing the plant back to Ukraine amid fears they could trigger a radioactive accident.
Since the Russians' withdrawal, Ukraine has mounted a drive to install further protections at the defunct site, including anti-drone systems and anti-tank barriers.
[Map: Chernobyl nuclear power plant site]Some parts of the Russian-occupied Zaporizhzhia nuclear power plant, which is Europe's biggest, have been repeatedly struck by drones during the war — attacks Russia and Ukraine have also blamed on each other — but none have led to radioactive accidents.
Still, the plant had to be shut down early in the conflict, and a slew of attacks earlier this week prompted the cancellation of a planned rotation of IAEA monitors.
What about other risks to the reactor?
Nearly three years of fighting have seen repeated power cuts to the critical cooling system at Chernobyl, as well as at Ukraine's four active nuclear plants, causing fears that spent nuclear fuel could overheat.
The cuts often follow shelling or drone strikes on nearby power lines, disrupting supply to cities across Ukraine.
Internal radioactive decay continues for thousands of years inside nuclear fuel rods after they have been used to generate power, giving off a large amount of heat.
Because of this, the rods are put in cooling pools, where they are cooled by both water and an electric-powered heat exchange pump.
The Swedish Radiation Safety Authority estimates that a power outage at Chernobyl would not lead to a dangerous radiation incident for at least a couple of weeks.
This is because the plant's fuel storage ponds are very deep, and it would take a long time for the water inside them to boil down, even if the cooling pumps were to stop.
However, a lack of electricity would blind the IAEA's radiation monitoring systems, which have been installed at the facility to boost security.
And even if experts say a drone or missile strike is unlikely to trigger a major radioactive release — at least not without giving authorities time to take action — a power cut or the deliberate targeting of nuclear plants is still liable to cause significant panic and undercut efforts to bring an end to the war.
ABC/AP
