Technicians have achieved a chain reaction in the No 1 reactor of the controversial Belarusian nuclear power plant in Ostrovets, the last step before connecting it to the electrical grid, Russian media have reported.

It remained unclear, however, when that step might be taken after a report from Radio Free Europe that said the reactor’s commercial launch had been delayed until 2022.

Built by Russia’s state nuclear corporation Rosatom and financed by Moscow with a $10 billion loan, the long-running project is opposed by neighboring EU member Lithuania, whose capital, Vilnius, is just 50 kilometers away.

Having reached minimum controlled power, the reactor will now undergo a battery of experiments on the neutronic characteristics of the first fuel charge, as well as confirm the operational reliability of the reactor’s entire monitoring and safety systems, World Nuclear News reported.

The results of these experiments will be passed on to Belarusian nuclear watchdog Gosatomnadzor, whose permission is required for power start-up. If the results are found satisfactory and permission is granted, the unit will then be prepared for start-up when the reactor power is gradually increased.

The Belarusian plant features two 1.2 gigawatt Rostaom-designed VVER-1200 reactors, the first of which was fueled in August. Construction of the second reactor is still ongoing but Rosatom expects it to be completed by 2022.

The Baltic states that neighbor Belarus have long been uneasy about the prospect of a nuclear plant so close to its borders. Vilnius has led the charge against buying electricity from the plant and has outlawed such purchases via a parliamentary vote.

Last month Estonia and Latvia followed suit and joined a Lithuania’s boycott of the Belarusian plant’s electricity. The three countries will now require proof that power they import in the future isn’t coming from the Russian-built facility.

Lithuania has also voiced fears that a nuclear plant located in one of the eastern bloc’s most repressive dictatorships is not being built to safety standards and lacks transparency – claims Rosatom has repeatedly denied.

But numerous incidents at the construction site have given Vilnius pause. In 2015, builders at the Ostrovets site made headlines when a crane operator dropped a 330-ton reactor pressure vessel, a sensitive structure that houses the reactor core, from a height of four meters. Minsk sought to cover the incident up, but it was eventually brought to light by a whistleblower.

Another reactor pressure vessel bound for the plant was accidentally run into a cement column when it was being unloaded from a railcar.

The Belarusian plant, when both reactors reach full power, is expected to meet about a third of the country’s electricity demand.