WASHINGTON — The Energy Department will give a small company in Corvallis, Ore., up to $226 million to advance the design of tiny nuclear reactors that would be installed under water, making meltdown far less likely and opening the door to markets around the world where the reactors now on the market are too big for local power grids.

The company, NuScale Power, has made substantial progress in developing “an invented-in-America, made-in-America product that will export U.S. safety standards around the world,” Peter B. Lyons, the assistant secretary for nuclear energy, said in an interview. For supplying electricity without global warming gases and for providing the United States with a new export product, the reactor had “immense global and national importance,” he said.

The award is the second of two under a $452 million, multiyear program to assist in the development of “small modular reactors,” which would be built in American factories, potentially improving quality and cutting costs, and delivered by truck. The first award, in November 2012, went to Babcock & Wilcox, which formerly sold full-scale reactors. Its small model, called mPower, is a step ahead of NuScale’s because it has a preliminary agreement with a customer, the Tennessee Valley Authority.

In seeking a high-tech, high-value export product, the Energy Department is hardly alone. On Tuesday, Sergey V. Kirienko, the director general of Rosatom, the Russian state atomic energy company, told a small group of reporters in Washington that a floating nuclear power plant, which could be moored near a load center, was “entering its finalization stage.” The units will be built in pairs near St. Petersburg, Russia he said, and the first pair are to be installed in Russia in 2016. His company is in preliminary discussions with potential customers around the world, he said.