Nuclear startup X-energy raised $1 billion in its initial public offering yesterday, selling 44.3 million shares for $23 each, a hefty premium above the $16 to $19 per share it was seeking. Initially, the company had hoped to raise around $800 million.

The stock is expected to begin trading on Friday on the Nasdaq Exchange under the ticker XE. X-energy is building small modular reactors capable of generating electricity or delivering heat to industrial processes. The company has a deal with Dow to provide heat and power to a chemical plant in Texas, and another with Amazon to sell as much as 5 gigawatts of nuclear power by 2039.

Ax energy says its reactors will generate 80 megawatts of electricity. Each Xe-100 reactor is cooled by helium gas, which flows over billiard ball-sized ‘pebbles’ that are packed with BB-sized TRISO fuel pellets. TRISO fuel, which contains a kernel of uranium wrapped in carbon and silicon, was developed years ago to be safer than existing fuel designs, though it hasn’t been widely used.

X-energy says its fuel can withstand higher temperatures, helping to keep the fuel contained and reduce the potential of a meltdown. Nuclear startups like X-energy have been buoyed by surging demand for electricity from data centers and other parts of the economy that have been electrifying.