As energy-hungry computer data centers and artificial intelligence programs place ever greater demands on the U.S. power grid, tech companies are looking to a technology that just a few years ago appeared ready to be phased out: nuclear energy. After several decades in which investment in new nuclear facilities in the U.S. had slowed to a crawl, tech giants Microsoft and Google have recently announced investments in the technology, aimed at securing a reliable source of emissions-free power for years into the future. Earlier this year, online retailer Amazon, which has an expansive cloud computing business, announced it had reached an agreement to purchase a nuclear energy-fueled data center in Pennsylvania and that it had plans to buy more in the future. However, the three companies’ strategies rely on somewhat different approaches to the problem of harnessing nuclear energy, and it remains unclear which, if any, will be successful. Energy demand Data centers, which concentrate thousands of powerful computers in one location, consume prodigious amounts of power, both to run the computers themselves and to operate the elaborate systems put in place to dissipate the large amount of heat they generate. A recent study by Goldman Sachs estimated that data centers currently consume between 1% and 2% of all available power generation. That percentage is expected to at least double by the end of the decade, even accounting for new power sources coming online. The study projected a 160% increase in data center power consumption by 2030. The U.S. Department of Energy has estimated that the largest data centers can consume more than 100 megawatts of electricity, or enough to power about 80,000 homes. Small, modular reactors Google’s plan is, in some ways, the most radical departure — both from the current structure of the energy grid and from traditional means of generating nuclear power. The internet search giant announced on Monday that it has partnered with Kairos Power to fund the construction of up to seven small-scale nuclear reactors that, across several locations, would combine to generate 500 megawatts of power. The small modular reactors (SMRs) are a new, and largely untested, technology. Unlike sprawling nuclear plants, SMRs are compact, requiring much less infrastructure to keep them operational and safe. “The smaller size and modular design can reduce construction timelines, allow deployment in more places, and make the final project delivery more predictable,” Google and Kairos said in a press release. The companies said they intend to have the first of the SMRs online by 2030, with the rest to follow by 2035. Great promise Sola Talabi, president of Pittsburgh Technical, a nuclear consulting firm, told VOA that SMR technology holds great promise for the future. He said that the plants’ small size will eliminate many of the safety concerns that larger reactors present. For example, some smaller reactors generate so much less heat than larger reactors that they can utilize “passive” cooling systems that are not susceptible to the kind of mechanical failures that caused disaster at Japan’s Fukushima plant in 2011 and the Soviet Union’s Chernobyl plant in 1986. Talabi, who is also an adjunct faculty member in nuclear engineering at the University of Pittsburgh and University of Michigan, said that SMRs’ modular nature will allow for rapid deployment and substantial cost savings as time goes on. “Pretty much every reactor that has been built [so far] has been built like it’s the first one,” he said. “But with these reactors, because we will be able to use the same processes, the same facilities, to produce them, we actually expect that we will be able to … achieve deployment scale relatively quickly.” Raising doubts Not all experts are convinced that SMRs are going to live up to expectations. Edwin Lyman, director of nuclear power safety for the Union of Concerned Scientists, told VOA that the Kairos reactors Google is hoping to install use a new technology that has never been tested under real-world conditions. “At this point, it’s just hope without any real basis in experimental fact to believe that this is going to be a productive and reliable solution for the need to power data centers over the medium term,” he said. He pointed out that the large-scale deployment of new nuclear reactors will also result in the creation of a new source of nuclear waste, which the U.S. is still struggling to find a way to dispose of at scale. “I think what we’re seeing is really a bubble — a nuclear bubble — which I suspect is going to be deflated once these optimistic, hopeful agreements turn out to be much harder to execute,” Lyman said. Three Mile Island Microsoft and Amazon have plotted a more conventional path toward powering their data centers with nuclear energy. In its announcement last month, Microsoft revealed that it has reached an agreement with Constellation Energy to restart a mothballed nuclear reactor at Three Mile Island in Pennsylvania and to use the power it produces for its data operations. Three Mile Island is best known as the site of the worst nuclear disaster in U.S. history. In 1979, the site’s Unit 2 reactor suffered a malfunction that resulted in radioactive gases and iodine being released into the local environment. However, the facility’s Unit 1 reactor did not fail, and it operated safely for several decades. It was shut down in 2019, after cheap shale gas drove the price of energy down so far that it made further operations economically unfeasible. It is expected to cost $1.6 billion to bring the reactor back online, and Microsoft has agreed to fund that investment. It has also signed an agreement to purchase power from the facility for 20 years. The companies say they believe that they can bring the facility back online by 2028. Amazon’s plan, by contrast, does not require either new technology or the resurrection of an older nuclear facility. The data center that the company purchased from Talen Energy is located on the same site as the fully operational Susquehanna nuclear plant in Salem, Pennsylvania, and draws power directly from it. Amazon characterized the $650 million investment as part of a larger effort to reach net-zero carbon emissions by 2040.