The staff were not able to return home and became increasingly drained. That risked compromising their ability to fulfil their safety and security duties.
"It was mentally and emotionally difficult," Shelestiy explained.
Employees were also closely watched and forced to navigate a dizzying network of checkpoints set up by the Russians on the plant's grounds -- hindering basic movements and maintenance at the facility.
Ukrainian authorities have since accused the Russians of showing wanton disregard for basic safety during their occupation of Chernobyl, saying its soldiers dug trenches and set up camps in contaminated areas of the facility that had received heavy doses of radiation.
"They dug bare soil contaminated with radiation, collected radioactive sand in bags for fortification, breathed this dust," said Energy Minister German Galushchenko in April, claiming the Russian forces had been exposed to a "shocking" amount of radiation.
"Every Russian soldier will bring a piece of Chernobyl home. Dead or alive," the minister added.
The head of the International Atomic Energy Agency, Rafael Grossi, later said "an increase in the levels" of radiation had been recorded at Chernobyl but insisted the matter was under control.
"The situation is not one that could be judged as posing a great danger to the environment and to people at the moment we were taking these measures," he added.
Shelestiy was unable to confirm details about alleged Russian misconduct at Chernobyl, where he was mostly forced to remain at his workstation and had little interaction with their troops.
'WORRIED, NERVOUS'
Amid the uncertainty, Shelestiy said he tried to console his team, whose families in the nearby town of Slavutych had been largely surrounded by Russian forces.
Back in Slavutych, mayor Yuriy Fomichev walked a fine line, managing relations with Russian forces, helping smuggle supplies into the besieged community and comforting the families of the captive workers.
"I had to calm them down and explain that it was necessary to be patient," said Fomichev.
Built in the aftermath of the Chernobyl accident as a settlement for evacuated families who had been living near the plant in 1986, Slavutych was one of the last purpose-made towns constructed from scratch during the final days of the Soviet Union.
For many of its residents, seeing chaos engulf Chernobyl again was an unwelcome case of deja-vu.
"We were worried, nervous," said Tamara Shyrobokova, 75, a former Chernobyl employee who was resettled in Slavutych following the meltdown.
"I was literally shocked by the fact that Russia attacked Ukraine. No-one could ever imagine this," she added.
The whole episode also perplexes Shelestiy. He was released following a round of negotiations days before the Russians retreated, after their troops were routed in the battle for Kyiv.
"They said they were trying to free me from something but I don't understand from what," said Shelestiy. "I can't understand it."
