Despite the problems, small nuclear reactor salesmen aggressively marketing: it’s make or break time for the nuclear industry.

Entrepreneurs Look to Small-Scale Nuclear Reactors, The American Society of Mechanical Engineers, Mar 2, 2021, by Michael Abrams ‘‘……… even concepts that are predicated on being small, modular, and fast to build seem locked into decades-long development cycles.

The key to reviving the nuclear power industry is building these small reactors not as projects, but as factory-made products. That’s easier said than done. “Usually, a bunch of nuclear engineers go in a room and then they come out after a year or two, and they have a design that doesn’t have a lot of foundation in realty, and nobody can make it, and the projects dies,” said Kurt Terrani, a senior staff scientist at Oak Ridge National Laboratory………..

In terms of reactor physics, the NuScale concept is fairly bog standard: low-enriched uranium, light-water cooling. In essence, their reactor is just a smaller version of the nuclear plants already in operation. That NuScale didn’t go with a more revolutionary design to mitigate waste or utilize an alternative fuel cycle is no accident. To do so would require the Nuclear Regulatory Commission to come up with an entirely new licensing framework, said José Reyes, cofounder and chief technology officer at NuScale.

“Pressurized water-cooled reactors have benefited from billions of dollars of research and development and millions of hours of operating experience over the past 50 year,” Reyes said. “NuScale went with a more traditional approach to assure a design that is cost-competitive and capable of near-term deployment.”

…………. The containment vessel will also sit underground in a giant pool capable of absorbing radiation from a leak. Multiple reactors would share the same pool. Being underground, they are also earthquake- and airplane-resistant. [ Ed. no mention of what would happen in the case of flooding, or of an emergency requirinfpeople to quickly respond underground] The company believes that its design is robust enough that utilities could site the reactors much closer to population centers, rather than in remote locations surrounded by an emergency planning zone.

So far, the concept and design have been convincing enough to win funding from the DoE and to move NuScale farther along in the regulatory process than any of its would-be competitors.

“NuScale’s small modular reactor technology is the world’s first and only to undergo design certification review by the U.S. Nuclear Regulatory Commission,”

NuScale set out to design a reactor that was small enough to transport to site, essentially complete. Not everyone agrees, however, that building out a power plant in 60-MW modules is optimal.

“The whole idea of SMRs is that smaller is better,” said Jacopo Buongiorno, a professor of nuclear science and engineering at MIT and the director of the Center for Advanced Nuclear Energy Systems. “But within the class of small reactors, larger is still better. If you can design a reactor that is still simple, that is still passively safe, that can still be built in a factory, but that generates 300 megawatts, that for sure is going to be more economically attractive than the same thing that generates 60 megawatts.”

Buongiorno points to GE’s BWRX-300 concept as a potentially better option. It, too, is a light-water reactor with fuel rods and passive cooling. But its larger size makes it a more of a plug-and-play replacement for coal plants……

Holtec’s SMR-160 is intended to be installed deep underground; the steel containment vessel is strong enough to keep the core covered during any conceivable disaster. “

…… Other SMR designs are dispensing with solid fuel altogether. These reactors would instead dissolve uranium in a molten salt. Some of these designs are miniaturized versions of the Molten Salt Reactor Experiment built by the Oak Ridge National Laboratory in the late 1960s………

The one downside to molten salt reactors is that the salts usually contain fluoride, which is extremely corrosive. Simplifying the mechanical design of the cooling system cuts down on the parts in danger of corroding, but the pins that will contain the fuel are still at risk…..

Make or Break for Nuclear

Moltex is aiming for build costs at around $2,000 per kW—more than wind or solar, but less than newly built coal or gas plants, let alone competing nuclear concepts. “We’ve believe we’ve come up with a concept that can radically reduce the cost of nuclear power,” ……

Other SMR companies are less aggressive with their cost estimates—NuScale has its scopes on a cost of around $3,600 per kW, while GE is aiming for less than $2,500—but still come in under conventional nuclear power. …….

Proof of whether those costs can be achieved will be actual construction and commissioning. “This decade will be very telling,” said Chicago’s Rosner. “It’s the make or break decade for nuclear.”

Furthest along is NuScale, which in September 2020 announced its SMR design had been issued a standard design approval from the U.S. Nuclear Regulatory Commission. That means the design can be referenced in an application for a construction permit—a big step, and one that had not been before achieved by a small modular reactor design. In August 2020, the NRC had completed its Phase 6 review and issued a Final Safety Evaluation Report (FSER).

The company also announced in November that it had uprated its Power Module to 77 MW, which should improve its economics by around 25 percent….

The key is getting the cost and scale right. https://www.asme.org/topics-resources/content/entrepreneurs-look-to-small-scale-nuclear-reactors