ORNL reactor technology might provide power in U.S. within 15 to 20 years – News – Oakridger – Oak Ridge, TN

By the middle of the century, many existing nuclear power plants in the United States, mostly aging water-cooled reactors, will be decommissioned. Lou Qualls would like to see them replaced with passively safe, salt-cooled, salt-powered reactors based on Melted Salt Reactor (MSR) technology developed at Oak Ridge National Laboratory in the 1950s and 1960s.

By the middle of the century, many existing nuclear power plants in the United States, mostly aging water-cooled reactors, will be decommissioned. Lou Qualls would like to see them replaced with passively safe, salt-cooled, salt-powered reactors based on Melted Salt Reactor (MSR) technology developed at Oak Ridge National Laboratory in the 1950s and 1960s.

He is the national molten salt reactor technical director for the Department of Energy’s Nuclear Power Bureau and director of reactor technology integration for ORNL.

“The US goal is to revitalize molten salt reactor technology so that it will remain a long-term low-carbon source of energy,” said Qualls, who holds a PhD. in nuclear engineering from the University of Tennessee at Knoxville.

“At Oak Ridge, we argued that MSR technology deserves a revision because it offers advantages that other technologies cannot. My job is to facilitate the development and use of molten salt reactors by telling a credible and workable story “so that private companies, investors and regulators feel confident that MSRs can be a reliable, safe and affordable future energy source .

He told attendees at a Friday morning lecture at the Oak Ridge Institute for Continued Learning (ORICL) that several companies, backed by DOE and venture capital firms, are hoping to build their first salt-cooled or salt-powered reactors in 10 years. And he added that they hope to be able to build these types of reactors in 15 to 20 years and sell them to utilities for power generation.

“I am an optimist and an enthusiast,” said Qualls. “But developer, customer and regulator have to be on one side.”

He noted that US developers of salt-cooled and salt-powered reactor power plants of the future will need to cut costs in order to compete with electricity-generating natural gas turbines. The developers plan to create smaller, factory-built reactors that fit into the rooms that previously housed fossil fuel plants. New MSRs will only sell if “there is market access for them,” said Qualls.

Also, the US industrial base needs to be developed to support salt reactors. Salt valves and pumps for MSRs cannot be bought in the US today. He later added that 3D printing or additive manufacturing could solve this problem.

“We have a great opportunity,” said Qualls. “Molten salt reactors are a versatile class of advanced reactors. They promise a revitalization of the nuclear industry. They are proven achievements. New concepts are being developed and may be operational in a decade. But we still have a lot to do. “

American companies that operate salt reactor technology include FliBe Energy (developer of a liquid fluoride-thorium reactor based on ORNL-MSR technology); Kairos Power (developer of a fluoride salt cooled high temperature reactor that uses solid enriched uranium fuel, which could grow plutonium, another nuclear fuel), TerraPower (developer of the “traveling wave reactor” chaired by Microsoft co-founder Bill Gates) and Terrestrial Energy (developer of a integrated molten salt reactor).

Other countries interested in the technology include European nations, Canada and China, which claim to be building a proof-of-principle reactor with a salt or pebble bed that will be completed in a couple of years, Qualls said.

In the 1950s and 1960s, the Atomic Energy Commission, the predecessor of DOE, investigated three ways to generate core power: water-cooled reactors, sodium-cooled growers, and molten salt reactors and growers. Since the US Navy successfully used a pressurized water reactor to propel a submarine, the AEC initially focused on water-cooled reactors. Then when it came to breeder technology, it focused on the sodium-cooled rather than the salt-cooled option.

These commonly used light water reactors are safe but have two problems. First, they require strong, thick, and expensive structural materials to contain high pressure or high temperature water, and second, their solid uranium fuel could melt in a severe coolant loss accident.

In comparison, according to Qualls, the molten salt reactor offers passive safety, lower costs, fewer consequences of accidents, greater options for dimensioning and location, better use of resources and fewer end-waste products.

The salt coolant is maintained at normal atmospheric pressure; As a result, thinner structural materials can be used which are less expensive and less likely to fail.

To explain what makes the salt reactor passively safe, Qualls described it as a pot, pump and heat exchanger (to generate steam for power generation) with an externally cooled “freezer plug”. If the salt fuel or coolant in the pot get too hot, the core salt will melt the frozen plug and “drain into a passively cooled configuration where nuclear criticality is impossible”.

With a budget of $ 5 million, DOE can help MSR developers with guidelines, analysis, and licensing, according to Qualls. In the meantime, more data needs to be collected and more modeling needs to be done to better understand the fate of radionuclides in an MSR system. Do they stay in the salt or do they migrate to the graphite moderator, to the surfaces of the reactor components (where they can cause corrosion) and to the exhaust gases?

Qualls found that the advantages of salt reactors over coal-fired power plants include virtually no emissions of climate-changing carbon dioxide and very high energy density.

Four nuclear fuel pebbles, which are smaller than golf balls, can be “burned” in a fluoride salt-cooled high-temperature reactor with a bed of pebbles to supply an average US household with electricity for a whole year. In contrast, 8.1 tons of anthracite coal or 17 tons of brown coal have to be burned in a coal-fired power plant to produce the same amount of electricity.

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