On 24 February 2022, workers at the Chornobyl nuclear power station in Ukraine woke to the sound of explosions. A battle was going on, not far from the contaminated exclusion zone. By late afternoon, the Russians had arrived. A column of military vehicles pulled up at a checkpoint and an officer got out. Moscow, he said, was now in charge.

The plant’s 300 personnel – specialist operators and firefighters, plus troops from Ukraine’s national guard – became prisoners. Over the next few weeks, they kept the station’s systems going, working in cramped conditions and living side by side with their armed Russian masters. The enemy had invaded from Belarus. Its main force trundled onwards towards Kyiv.

Chernobyl Roulette by the Ukrainian historian Serhii Plokhy is a gripping account of the extraordinary events inside the plant (Plokhy spells the power station with an “e”). It is a tale of bravery and selflessness, reminiscent of the sacrifice demonstrated by the Chornobyl employees who went through the 1986 nuclear disaster, when reactor No 4 blew up. Some of those on duty in 2022 were involved in the original Soviet-era clean-up.

They included Valentyn Heiko, the 59-year-old shift foreman who was taken hostage with his colleagues. He proved to be a subtle and resilient leader. Heiko met the Russian commanders and told them they would have to follow Ukrainian safety rules and behave in a “civilised manner”. If they didn’t, he promised to unleash a radiation incident, killing them and everyone else. This was blackmail. And a bluff. It worked.

According to Heiko, some of the Russians were polite and rational. About a third of the soldiers, though, were brainwashed and often drunk. The occupiers moved into the fourth floor of the administration building. The station got crowded. There was a shortage of food, cigarettes and razors. The captive nuclear operators – unable to go home to the nearby town of Slavutych – grew beards and puffed on butts.

There were small acts of resistance. Liudmyla Kozak – one of 17 imprisoned women – refused a demand to wear a white armband. The Russians warned her she might be shot. Kozak found a white medical cap, embroidered it with a blue and yellow patch and wore that instead. An order was given to turn off the radio, which brought news of the Russian army’s setbacks around Kyiv. Staff switched it on anyway.

After three weeks, Heiko and his stressed and exhausted workmates could scarcely function. Astonishingly, 46 colleagues volunteered to replace them. The old shift exited the plant, travelled by bus through Belarus and crossed the Dnipro River in a fishing boat. Heiko carried the station’s Ukrainian flag with him. The new team went in the same way – uncertain if or when they would return.

The Kremlin’s occupation of the nuclear plant was an act of astounding recklessness. Soldiers dug trenches in the red forest, one of the world’s most toxic places. It is unclear if they suffered lasting health damage, their heads “full of sawdust”, as one gleeful Ukrainian official put it. Plokhy suggests this might be wishful thinking. Overall, though, radiation levels went up, as thousands of tracked Russian vehicles churned up deadly dust.

In the south of the country, meanwhile, another Russian unit captured the Zaporizhzhia nuclear power station, Europe’s biggest. The attackers fired rocket-propelled grenades at civilian infrastructure and damaged a reactor. Two and a half years on, the Russians are still there. Its turbine halls are stuffed with military kit and weapons. From the territory, they regularly bombard nearby Ukrainian towns with Grad missiles.

Last month, Russian soldiers started a fire in a cooling tower – an apparent warning, after Ukraine’s surprise counter-invasion of Russia’s Kursk region. Since the beginning of Moscow’s all-out attack, Vladimir Putin and his minions have issued a string of mass destruction threats directed at Kyiv and the west. State TV hosts talk about nuking London, Berlin and Paris.

The Chornobyl 2 story at least had a happy ending. On 30 March 2022, Russian servicemen fled north, as part of a pull-out from the Kyiv region. They departed with numerous items stolen from the plant: radiation dosimeters, computers and cars. In the town of Chornobyl, military looting parties carried off sacks of household goods. They even took ancient stuff: black-and-white TVs and video recorders.

The Ukrainian workers who put duty before personal survival narrowly averted another Chornobyl crisis. In Plokhy’s view, Moscow’s 2022 violent takeover of two atomic energy stations should serve as a “wake up call to the world”. It was, he argues, an act of nuclear terrorism carried out by a large nuclear power – a rogue one. The distinction between tactical nuclear weapons and civil nuclear facilities looks increasingly blurred, he says.

How the international community should respond to these alarming developments is less clear. Plokhy calls for a reform of the laws governing nuclear state behaviour and of the body that is supposed to administer them – the International Atomic Energy Agency (IAEA). When Russian tanks entered Chornobyl, the IAEA, led by Rafael Grossi, issued no condemnation of the Kremlin. Nor did it call on the occupiers to get out, appealing instead to “both sides”.

Plokhy is the author of several previous nonfiction books on Ukraine. These include Chernobyl: History of a Tragedy, which won the 2018 Baillie Gifford prize, and The Russo-Ukrainian War, an account of the conflict and its origins, published last year. Chernobyl Roulette is equally compelling. It salutes the singular men and women who stepped up – as their predecessors did before them – when protocols and governments failed.

• Luke Harding’s Invasion: Russia’s Bloody War and Ukraine’s Fight for Survival, shortlisted for the Orwell prize, is published by Guardian Faber (£10.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply

• Chernobyl Roulette: A War Story by Serhii Plokhy is published by Allen Lane (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply