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Nuclear Notes — Tuesday, Nov. 22, 2022

Matthew Wald

Getting Ready to Put a Reactor on the Moon

The successful launch of NASA’s new Artemis 1 rocket, which is in lunar orbit as of this writing, is a reminder that humankind is going back to the moon in the next few years, and it will be bringing nuclear energy along.

Spacecraft in the vicinity of Earth generally rely on solar power, which is available all the time, except when the craft are in Earth’s shadow. Rovers on Mars, meanwhile, have used a mix of solar panels and nuclear batteries called radiothermal generators, known as RTGs, which convert heat from a radioactive source into electric current. Beyond Mars, spacecraft mostly rely on RTGs exclusively.

But the plan is for a future Artemis launches to carry an honest-to-goodness fission reactor to the Moon. It will go to a base camp near the Moon’s south pole, which has a night that is two weeks long and very cold.

The Energy Department has awarded contracts to three design teams. The plan is to build a reactor that will run for ten years and generate 40 kilowatts. On Earth, that would be enough to power eight or ten suburban houses. A lunar or Mars base could deploy several of these reactors to power facilities there.

The reactor might be monitored by the astronauts, but it would certainly not have an operator in a control room, and thus it would have to modulate its output automatically, to meet demand. That is something that few reactors on earth do; they generally run flat out for months at a time, and leave it to other plants—gas or coal plants, or sometimes hydro plants—to ramp up or slow down in response to changes in demand.

The Energy Department has previously demonstrated sophisticated designs to allow the reactor to match itself to the amount of work required, or, in the terrestrial utility lingo, “follow load.” One promising technique is to withdraw heat from the nuclear core at a variable rate, depending on how much electricity is needed. If heat withdrawal goes up, the core cools and thus shrinks a bit, and the fuel, now squeezed closer together, is in a geometric configuration favorable for fission, so it increases its heat output. If demand declines, heat withdrawal slows down, and the core gets hotter, which makes it expand. As the core gets bigger, conditions inside become less favorable for fission, and it slows down.

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Faith in a U.S. Nuclear Renaissance—from Canada

Mention hunting for uranium deposits, and what comes to mind may be a bearded prospector with a Geiger counter trekking through the hills out West, with a pack mule behind. But the largest known undeveloped uranium deposit in the United States, Coles Hill, is in southern Virginia.

There are no technical barriers to mining the uranium, which has a value estimated at $6 billion, but a 40-year-old Virginia law prevents it.

Now a mining company based in Toronto, Consolidated Uranium, has struck an agreement to buy the 3,000-acre property. The company, known as CUR, cited a changed political climate. Glenn Youngkin, who became governor of Virginia in January, released an energy plan in October that says, “the only way to confidently move towards a reliable, affordable and clean energy future in Virginia is to go all-in on innovation in nuclear, carbon capture, and new technology like hydrogen generation, along with building on our leadership in offshore wind and solar.”

It calls for “launching a commercial small modular nuclear reactor in the next 10 years.”

According to CUR, “this level of support for nuclear energy at the state level, combined with the local support for Coles Hill, gives CUR confidence that the moratorium on developing uranium projects in the state may ultimately be overcome and the risk/return profile for the transaction is extremely compelling.” It paid $32.2 million.

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Stanford Study is Wrong: Waste from advanced reactors IS “roughly comparable” to what current reactors produce

A Stanford-led study made some waves in May with an assertion in a study published in the Proceedings of the National Academy of Sciences that small modular reactors would produce vastly more waste per unit of electricity generated. At the time, the study was criticized for a variety of reasons, including that it did not reference any findings from the NRC’s licensing reviews or pre-licensing topical reports, or studies undertaken by the Canadian Nuclear Safety Commission. Nor did it note that some advanced reactor designs have higher thermal efficiencies (meaning less fuel used per megawatt-hour produced) and more thorough burnup of the fuel (meaning less volume of fuel left behind.) And in the case of the NuScale reactor, it based the analysis on outdated design information.

Now a report from Argonne National Laboratory concludes that although the waste streams from the new reactors will differ—some will have less density, and thus produce more volume, while others will be more concentrated—they will all be roughly comparable to existing reactors. One is NuScale’s small modular pressurized water reactor, one is Natrium’s sodium-cooled reactor with built-in thermal storage, and one is X-energy’s pebble-bed reactor, with a graphite moderator and helium gas coolant.

Smaller reactors have smaller cores, and thus the neutrons, the sub-atomic particles that are liberated when an atom is split, and go on to split other atoms, may leak more readily from a small core. When they leak, they can be captured by a piece of steel or concrete, which can t radioactive. However, ​“it’s not correct to say that because these reactors are smaller they will have more problems proportionally with nuclear waste, just because they have more surface area of waste compared to the core volume,” said Taek Kyum Kim, a senior nuclear engineer at the lab. ​“Each reactor has pluses and minuses that depend upon the discharge burnup, the uranium enrichment, the thermal efficiency and other reactor-specific design features.”

They are, he said, “roughly comparable.”

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