The bureau, a state agency that operates independently of the government, made the announcement as Ukraine braces for winter with its power sector under frequent fire by Russia and regularly facing power outages.
The agency alleged on social media that behind the scheme was a "high-level criminal organisation" led by a businessman and including a former adviser to the energy minister, nuclear power operator Energoatom's head of security and four "back office" workers.
"In total, approximately 100 million USD ($A153 million) passed through this so-called laundromat," the agency said.
None of the individuals was named in the statement.
Energoatom said in a statement on social media that anti-corruption officials were conducting searches in its offices on Monday, and it was cooperating with the investigation.
Ukraine's President Volodymyr Zelenskiy said in his evening address that officials needed to work with the anti-corruption bureau to root out graft.
Four months ago, Zelenskiy sought unsuccessfully to restrict the bureau's independence, before being forced into to u-turn by protests.
"Everyone who has been involved in corruption schemes must receive a clear legal response. There must be criminal verdicts," Zelenskiy said on Monday.
Ukraine's power system has been significantly damaged by a campaign of Russian bombardment in recent months, causing power cuts across the country as Moscow presses on with its war against its smaller neighbour.
Russia has not hit nuclear plants, but has hit substations connected to them, according to Ukrainian authorities.
The bureau published photographs of thick bundles of Ukraine's hryvnia currency, US dollars and euros stuffed into bags and stacked on a table.Â
It did not specify who they belonged to.
"The minister's adviser and the director of security at Energoatom took control of all the company's purchases and created conditions under which all Energoatom's contractors had to pay illegal benefits," NABU's chief detective, Oleksandr Abakumov, said.
He alleged that those involved in the scheme had discussed raising the kickback rate to 15 per cent in October during the construction of protective structures at the Khmelnytskyi nuclear power plant.
According to investigators, Energoatom's counterparties were forced to pay kickbacks of 10-15 per cent to avoid having payments for services or goods blocked, or losing their supplier status.
"A strategic enterprise with an annual income of over 200 billion hryvnias ($A7.33 billion) was managed not by the proper officials, but by third parties who had no formal authority," the statement said.
The anti-corruption bureau said it had conducted 70 searches and all its detectives had been involved in an investigation that had lasted 15 months and gathered 1000 hours of audio recordings.
Opposition lawmaker Yaroslav Zheleznyak, a prominent champion of the anti-corruption agency, said he had tabled a motion in parliament to seek the dismissal of energy minister Hrynchuk, as well as her predecessor, German Galushchenko, who is now justice minister.
Hrynchuk declined to comment on the motion, while Galushchenko did not reply to a request for comment.
In July 2025, large protests and international criticism forced President Volodymyr Zelenskiy to reverse course and restore the independence of Ukraine's two main anti-corruption agencies following a government move to rein in their powers.
Eradicating graft and shoring up the rule of law are key requirements for Kyiv to join the European Union, which Ukrainians see as critical to their future as they fend off a Russian invasion.
