Brexit could be a big setback for nuclear energy in the United Kingdom. When the UK officially leaves the European Union, it might also be leaving the agency that oversees nuclear safety in EU member states, called Euratom, the Financial Times reports.

Quitting Euratom could interrupt the flow of nuclear fuel and ores from Europe and leave the UK’s nuclear power and radioactive waste management facilities largely unregulated. The UK has 15 nuclear reactors that produce about 21 percent of its electricity. It’s also home to a radioactive waste facility called Sellafield, which houses one of the world’s largest stockpiles of untreated nuclear waste.

Right now, Europe’s nuclear regulatory agency, the European Atomic Energy Community, or Euratom for short, inspects those facilities to ensure they meet nuclear safety standards. Euratom also checks that nuclear infrastructure is secure against possible attacks, and that materials aren’t secretly being used for weapons. Leaving Euratom would mean that the UK will have to beef up its Office of Nuclear Regulation to take on those roles, according to Politico.

It’s been a little more than seven months since British citizens voted to leave the European Union, a move more commonly known as Brexit. On Thursday, a bill was introduced in the British House of Commons that seeks to authorize Prime Minister Theresa May to take the first step towards actually leaving the EU. Once she starts the process, which could begin as soon as March, it will still take years for the UK to negotiate its exit terms with the remaining EU member states.

The UK’s plans to leave Euratom were tucked away in the explanatory notes of that larger bill, and they might jeopardize the UK’s broader energy strategy. That includes phasing out coal and building more nuclear power plants — like the contentious Hinkley Point C plant that was approved in September. Now, those plans could be in limbo until new treaties are ratified.

Update August 28 2:02 PM ET: This article was originally published on January 27, 2017 and has been updated to include video.