Nearly 30 years after Chernobyl spewed nuclear dust across Europe and sparked fears of fallout around the globe, a strapped, war-torn Ukraine is opting for "upgrades" rather than shutdowns of its fleet of Soviet-era nuclear power reactors.
Kyiv is planning to spend an estimated $1.7 billion to bring the facilities, many of which are nearing the end of their planned life spans, up to current Western standards.
Ukrainian officials hope to further their energy independence from Moscow and potentially export some of the resulting electricity to Western Europe as part of an "EU-Ukraine Energy Bridge" that can further cement Kyiv's ties with Brussels.
But can they allay fears, in Ukraine and beyond, that the plans will put Europe at risk of another Chernobyl?
The project has the backing of the West, including a $600 million contribution split evenly between the European Bank for Reconstruction and Development (EBRD) and Euratom, the EU's nuclear agency.
"The project we support -- ourselves, the EBRD, and Euratom -- is actually about the country's energy independence, and essentially, survival. Because for the country, where nuclear power plants produce over 50 percent of electricity, this sector remains vital -- very, very important. This is a necessity," says Anton Usov, senior adviser for Eastern Europe and the Caucasus at the EBRD, an international institution funding projects in Central and Eastern Europe and Central Asia.
For Kyiv, keeping its nuclear power stations humming makes sense given the government's strategy to wean the country off Russian energy, namely gas. Ukraine is also making moves to end its dependence on Russia for the fuel powering the nuclear plants.
Nuclear power accounts for around half of Ukrainian electricity. Enerhoatom, the state-run nuclear energy operator, runs 15 reactors at four nuclear power plants, including Europe's largest power plant at Zaporizhzhya, which houses five reactors. They are all equipped with pressurized reactors known by their Russian abbreviation, VVER, which are Russian-designed but an upgrade to the graphite-moderated RBMK reactors found at the decommissioned Chernobyl nuclear power plant.
Most of the reactors came online in the 1980s, with the oldest -- Unit 1 at the Rivne nuclear plant -- generating power since December 1980, three years before the ill-fated reactor No. 4 at Chernobyl started churning out power.
That Ukraine is opting to upgrade its nuclear power plants is not surprising, according to Steve Thomas, a recently retired professor of energy policy at the University of Greenwich in the United Kingdom.
"There is a lot of pressure around the world to life-extend existing plants as it becomes more difficult to build new ones. As a result, the utilities are wanting to hang onto the ones they've got," Thomas tells RFE/RL. He says Europe's biggest producer of nuclear power, France, plans to spend an estimated 80 billion euros ($89 billion) to upgrade its 58 nuclear power reactors.
The EBRD says the program of 87 safety-measure upgrades is vital for Ukraine, especially since the Russian-backed conflict in the east of the country has affected coal supplies from the Donbas region.
Supplies of the kind of high-quality black coal that the Ukrainian power sector has relied on so heavily in the past "could no longer be a sustainable solution for its power plants," Usov says, "because the pace of their supply from Donbas has been erratic."
Enerhoatom says the upgrades are being done to the highest standard, but critics have their doubts.
They say Ukraine's nuclear reactors should be shut down as soon as possible, noting that one of the reactors still churning out power is older than the unit that exploded at Chernobyl on April 26, 1986. They also raise doubts over whether the program will be carried out to the highest standards.
"One of the reasons why the EBRD was ready to finance this program is that they said they will have a say in what is going on in Ukraine with the reactors, and that they will have leverage to ensure that everything is done properly,” says Iryna Holovko, a Ukranian nuclear activist with the NGO Bankwatch. "Now we see that it is not happening because the [Ukrainian] regulator still makes decisions without the safety procedures done."
Usov says the concerns raised by outside groups -- including Bankwatch -- are being addressed.
"We've touched on these issues numerous times with the environmental groups. They attend our annual meetings and regular meetings of the banks. And we had a proper panel, with the likes of Bankwatch, where we touched upon these issues," Usov says.
Enerhoatom vowed through a spokesman that "Ukraine has some of the most demanding conditions for extending" the life of its nuclear reactors.
"For example, in Ukraine, a nuclear power unit with a 30-year lifeline can be granted a 10-year extension after a safety assessment," spokeswoman Ilona Zaets said in an e-mailed response to RFE/RL. "In the United States, reactors are given a 30-year extension right away -- and this number could rise. The [Ukrainian] Nuclear Regulatory Commission is discussing the possibility of raising the extension period to 80 years."
The upgrade work is just part of a bold plan to make Ukraine a major energy player in Europe beyond its decades-long role as a major transit country. In a state energy strategy document released in 2006 and covering the sector until 2030, Kyiv foresaw the construction of 11 new nuclear units.
Ukraine's current financial straits could put such bold plans on hold. However, Kyiv appears to be moving ahead with intentions to make Ukraine part of the European power grid by 2017, a target set out by President Petro Poroshenko after he took office in mid-2014.
In March, Ukrainian energy distributor Ukrenergo signed a deal to export electricity to its Polish counterpart as part of the Ukraine-EU energy bridge. The proposal envisages a 750-kilowatt transmission cable from Khmelnitskyy, in Ukraine, to Rzeszow, in Poland, that will also carry electricity from a coal-fired energy plant at Burshtyn, in Ukraine's far west. Under the project, the Khmelnitskyy Unit 2 reactor will then be disconnected from the Ukraine grid and plugged into the European one.
But the project hinges on completion of two reactors at the Khmelnitskyy plant -- Units 3 and 4 -- whose construction was halted in 1990. Critics have questioned whether finishing reactors that have been mothballed for 15 years makes economic sense.
"They clearly do have to modernize their generation, but completing half-built nuclear power plants could still be a much more expensive option than building renewables, gas-fired plants, or whatever," Thomas says. "I don't think nuclear is necessarily the cheapest option."
In a sign that Kyiv is working to cut its nuclear ties with Moscow, Poroshenko in October ripped up an agreement with the Russian atomic energy giant Rosatom to complete construction at Khmelnitskyy.
Aleksandr Nikitin, chairman of the Environmental Rights Center Bellona, said at the time that the decision made it clear that Ukraine and Russian "are breaking all ties."
"The two countries essentially are in a state of war, and therefore there can't be any discussion of joint construction of such a huge project as a nuclear power plant," Nikitin said of the formerly close partners whose relations soured dramatically when unrest unseated pro-Moscow Ukrainian President Viktor Yanukovych in February 2014.
Enerhoatom has insisted money for the reactor work will be no problem. Spokeswoman Zaets said Enerhoatom had an offer from a Polish company to finance the construction, and "therefore the current financial problems do not affect the project."
Ukraine is also opening other doors with Western nuclear partners.
In November, Enerhoatom signed an agreement with the French engineering firm Areva "for safety upgrades of existing and future nuclear power plants in Ukraine, lifetime extension, and performance optimization."
U.S.-based Westinghouse, which has been operating in Ukraine since 2003, signed a deal with Kyiv in December 2014 "to significantly increase" nuclear fuel deliveries to Ukraine until 2020.
Russia's Foreign Ministry reacted to the deal between Westinghouse and Kyiv by calling it "a dangerous experiment."
Ukraine still depends on TVEL, a nuclear-fuel subsidiary of Russia's Rosatom, for fuel at 13 of its 15 reactors, highlighting Russia's continuing sway over Ukraine's nuclear program.
Westinghouse has been challenging TVEL for a bigger cut of the nuclear-fuel market in Eastern and Central Europe, where Russian-designed reactors are the norm.
The U.S. Export-Import Bank has offered significant loans for several Westinghouse projects in the region, and U.S. officials have lobbied governments to diversify away from dependence on TVEL, according to Statfor, a U.S.-based analytical center.
It is unclear whether Ukraine's nuclear gamble will pay off. But the stakes are high, and Holovko suggests that Kyiv has left itself few other options.
"For now, we have a situation where we have no Plan B," Holovko says.