KYIV, Ukraine — Moscow’s renewed attacks on Ukraine’s electricity infrastructure this winter have heightened scrutiny over the Ukrainian Energy Ministry’s failure to protect the country’s most critical energy facilities near nuclear power sites.

Despite more than a year of warnings that the sites were vulnerable to potential Russian attacks, the Energy Ministry failed to act swiftly, current and former Ukrainian officials in Kyiv told the Associated Press.

Two years of punishing Russian strikes on its power grid have left Ukraine reliant on nuclear power for more than half of its electricity generation. Especially vulnerable are the unprotected nuclear switchyards located outside the perimeters of its three functioning nuclear plants, which are crucial to transmitting power from the reactors to the rest of the country.

“The switchyards that handle electrical routing from nuclear power plants are a vital component of Ukraine’s nuclear energy infrastructure — powering homes, schools, hospitals and other critical civilian infrastructure,” said Marcy R. Fowler, head of the office for research and analysis at Open Nuclear Network, a program of the U.S.-based NGO PAX sapiens that focuses on reducing nuclear risk.

“Given Ukraine’s heavy reliance on nuclear energy, military attacks on these switchyards would be devastating, severely impacting civilian life and undermining the resilience of the energy grid,” she said.

Only in the fall, after Ukrainian intelligence agencies warned of potential Russian strikes targeting the nuclear switchyards, was action taken to begin building protection — far too late in the event of an attack, analysts said.

“If two (nuclear switchyards) are hit, we are out of supply for a minimum of 30 to 36 hours, and there will be a huge limitation on energy supply for at least three weeks, best-case scenario,” said Oleksandr Kharchenko, a Ukrainian energy industry expert.

He said it would take three to five weeks to transport and install new equipment, a miserable scenario for Ukraine's people during the bitterly cold winter months.

Even more worrying, nuclear switchyards also have a second critical function: delivering electricity to nuclear plants from the offsite grid that is essential to cooling their reactors and spent fuel. A disruption could potentially spell disaster, the U.N. nuclear agency has repeatedly warned since the Russian attacks began in August.

And while Ukraine's nuclear plants have backup emergency power systems, these “are designed to provide temporary support,” Fowler said. “Without functioning switchyards, the backup systems alone would not be sufficient to sustain operations or prevent safety risks during an extended outage.”

Lawmakers cited failure to protect these sites in a resolution last month calling for the removal of Energy Minister Herman Haluschenko. The list of grievances, which also censured Haluschenko for alleged systematic corruption and inadequate oversight of the energy sector, must still be voted on by parliament.

Haluschenko maintained at a news conference Tuesday the allegations were “a manipulation” and that fortifications for the electrical grid were “done.” But he would not answer direct questions about whether Ukraine's nuclear switchyards in particular were protected.

“Today we have light, we have no restrictions” on electricity, he said, suggesting that was proof that despite “massive attacks” on Ukraine's energy infrastructure, fortifications were in place.

Russian attacks in November and December came dangerously close to the country’s nuclear power plants, causing five out of its nine operating reactors to reduce power generation. The attacks did not strike the nuclear switchyards about a kilometer (half-mile) away from reactor sites but came alarmingly close.

The task of building protections for energy transmission substations, both nuclear and non-nuclear, fell to state and private companies, with the Energy Ministry supervising.

Three layers of fortifications were ordered: sandbags followed by cement barricades capable of withstanding drone attacks and — the most costly and least complete — iron-and-steel-fortified structures.

Following a government decree in July 2023, many state energy companies began immediately contracting to build first- and second-layer fortifications for their most critical power facilities. In the spring of 2024, the government repeated the urgent call to get the work done.

But nuclear switchyards, under the responsibility of Ukraine's state nuclear company Energoatom, did not issue contracts to build second-layer concrete fortifications until this fall. By then, state energy company Ukrenergo, which manages the high-voltage substations that transmit power from the nuclear reactors to the grid, had already completed 90% of its 43 sites.

The bidding process for two nuclear plants — in Khmelnytskyi and Mykolaiv — only started in early October, according to documents seen by the AP. The tender for the Rivne Nuclear Power Plant was even later, at the end of November.

Construction is not expected to be completed until 2026, the contract documents said.

Concerns over the delays were raised repeatedly in closed-door meetings and letters sent to energy officials over the last year, three current and former government officials told the AP, speaking on condition of anonymity to discuss the foot-dragging by the Energy Ministry.

“We wrote officially to the Energy Ministry several times stating this problem over the last 12 to 14 months,” said Volodymyr Kudrytskyi, the former head of Ukrenergo, who was fired in September and blamed for the failures to protect the energy infrastructure — a move widely criticized as politically motivated.

Energy Minister Haluschenko gave reassurances the situation was under control and prioritized other projects, including lobbying for parliamentary approval for the construction of costly nuclear reactors that take up to a decade to build.

Ukraine's Western partners were also repeatedly told “all” critical infrastructure was protected, according to two Western diplomats with knowledge of Western financial assistance to the country’s energy sector, who spoke on condition of anonymity to discuss the issue.

Energoatom did not respond to requests for comment from the AP about the delays, citing the sensitivity of the issue.

Over the summer and again in December, Ukraine raised the alarm internationally about potential Russian attacks targeting nuclear infrastructure and compromising nuclear safety. In mid-December it convened an extraordinary session of the International Atomic Energy Agency after attacks a month earlier damaged electrical substations deemed crucial to Ukraine’s nuclear safety, heightening the possibility of a nuclear emergency.

The U.N. nuclear agency sent teams in December to electrical substations at Ukraine’s Khmelnytskyi, Rivne, and South Ukraine nuclear power plants to document damage and gathered evidence “highlighting the electricity grid’s vulnerabilities as a result of attacks,” the agency's Director General Rafael Grossi said in a statement in January.

“These attacks impact grid stability and jeopardize the reliability of the off-site power supply, creating risks to nuclear safety,” Grossi said, warning of similar concerns at the Russian-held Zaporizhzhia plant, Europe's largest.

The presence of the IAEA inspection teams led some in the Ukrainian government to believe the country's nuclear sites were off-limits for Russian attacks, said a senior Ukrainian official who requested anonymity to speak candidly about the delays.

But that has proven to be a major miscalculation.

“Why didn’t they react?” Kudrytskyi, the former Ukrenergo director, said of the Energy Ministry's failure to quickly respond to the series of warnings. “I don’t have an answer to that.”