It's a liquid-sodium-cooled, graphite-core system with no need for pumps, aka 'passively cooled' via heat [edit] pipes. Output is:
> "The microreactor can generate 5 MW of electricity or 13 MW of heat from a 15 MW thermal core. Exhaust heat from the power conversion system can be used for district heating applications or low-temperature steam."
Control systems are kind of interesting:
> "The only moving or mechanical parts in the reactor system are reactivity control drums, which manage the power level and allow absorber material to passively turn inward toward the core if power demand is reduced or lost, and turn a reflector material toward the core if demand increases automatically. Hence the term “nuclear battery.”"
I'm generally not a nuclear advocate but if they've really managed to eliminate the need for active cooling, and have a robust system that can safely shut down with concerns about meltdown even without external power, that's a pretty big advance. Looks remarkably promising... keep your fingers crossed. (New nuclear tech hasn't had the greatest track record over the past several decades, i.e. pebble beds didn't work out etc.)
It’s good to see the designers absorbed a dose of inspiration from the pioneering excursions in US sodium reactors.
Mechanical coolant pumps were the Achilles heel of the infamous Sodium Reactor Experiment (SRE) from 1957-64 at Santa Susana field laboratory. It had 50,000 lbs of liquid sodium in two coolant loops.
When 4 pints of tetralin leaked from a pump seal into molten sodium surrounding the SRE reactor core (500-950F), it fouled the fuel cladding with “brown stuff” and various fission products from the melted rods were found on both sides of the fence. [1]
A “small amount of sodium” in sealed heat pipes sounds pretty safe. But since Westinghouse filed all the eVinci’s NRC pre-application materials as “proprietary”, the actual design details aren’t available to the public for review.
“Disruption” I assume refers to hundreds of rule exemptions (licensing innovations) they filed as a non-LWR. Not judging, just stating the record. [2]
It uses TRISO fuel, which are fissionable materials enclosed in a carbon and ceramic shell that's extremely tough and can handle far higher temperatures than are present in a reactor without melting.
The shell prevents the release of radioactive materials, so TRISO fuel encapsulation would turn a melt down into a reactor damaging event rather than an emergency/crisis. A runaway reactor would get hot, melt its structure, and maybe drop parts inside its containment, but the fuel wouldn't melt and wouldn't travel far. Most likely the reaction would stop as soon as the structure of the core fell apart.
> It uses TRISO fuel, which are fissionable materials enclosed in a carbon and ceramic shell that's extremely tough and can handle far higher temperatures than are present in a reactor without melting.
I was going to make a top level comment along the lines of:
"How thick/expensive a bunker would one need to build around one of these to prevent it from spreading radioactive materials about when hit by say, an airplane?
As I understand it, large legacy reactors are hardened for this. Would the same level of safety still allow these smaller reactors to be economically viable?"
But now that I have read your comment, would a kinetic event happening to a TRISO fueled reactor be more of a non-event? Follow up, would non-fuel components of the reactor become radioactive over time as well?
Sorry if dumb questions, not very educated in this space.
For small reactors, with minimal requirements for support equipment and ~no need for active cooling during emergency shutdown, the design trend I've seen is "put it underground". Which makes sense - bomb shelters, military bunkers, etc. have been put underground for centuries because that's a relatively quick & cheap way to make something that's very hard to destroy.
I could be wrong, I'm not an expert on the matter by any means, but I think the reason traditional nuclear reactors are so heavily fortified against attack is specifically because of the threat of a catastrophic meltdown if their cooling and control systems are destroyed. If these nuclear batteries can't melt down and rely on passive safety measures then the need for fortification is drastically reduced. Placing them in a fairly standard concrete building either underground or bermed with earth on all sides would likely be sufficient. You'd probably still want security around to make sure no one tried to manually tamper with the equipment.
I wonder if that fuel is usable in a breeder after it's "spent". Usually "spent fuel" has spent a few percent of the usable fissionable material, but the products of decay (and partly synthesis) prevent it from working efficiently.
Being sodium cooled, both a steam explosion and hydrogen gas generation via water is ac minimized. Lots of safety advantages to a coolant that is still liquid at operating core temperature with no added pressure. But of course liquid sodium does come with some other caveats that are of concern. Making it a sealed unit with minimum moving parts helps with some of those potential problems for sure. As does keeping the total thermal capacity relatively low, below the threshold where secondary fission products need active cooling to prevent meltdown even after the reactor is shutdown.
I think it's 'with', as in 'regarding'. "With the rising concerns around orange peel ethics, we put focus on creating a humane peeling device for fruits."
What about security? In the UK nuclear installations are under 24/7 armed guard from a special police force. That would be expensive to maintain in a remote region, although I guess they already have security at diamond mines, or instance
Reasonable Assumption: The "remote communities", "mining sites", etc. which both qualify for a nuclear power plant, and can afford it, will be fairly select & high-budget places.
Vs. Wikipedia says the entire U.S. Army (active duty) has ~485,000 personnel.
Divide...and that's ~0.17 Army people per acre, even if the US Army had NO job except holding down the NTTR. (Which is actually US Air Force, BTW.)
[Edit: But +1 - because in the bigger picture you make a valid point. However vast the open spaces, at the spots where the cool & expensive stuff sits, there does have to be some sort of "real" security. If only so dodgy locals don't swing by with a pair of bolt cutters, and start helping themselves.]
I would be more concerned about security than trained personnel to run it. Obviously, there will be trained people on site. You don't put a small reactor onsite and tell Cletus and Bubba to press this button to start it and that button to stop it.
> "The microreactor can generate 5 MW of electricity or 13 MW of heat from a 15 MW thermal core. Exhaust heat from the power conversion system can be used for district heating applications or low-temperature steam."
Control systems are kind of interesting:
> "The only moving or mechanical parts in the reactor system are reactivity control drums, which manage the power level and allow absorber material to passively turn inward toward the core if power demand is reduced or lost, and turn a reflector material toward the core if demand increases automatically. Hence the term “nuclear battery.”"
I'm generally not a nuclear advocate but if they've really managed to eliminate the need for active cooling, and have a robust system that can safely shut down with concerns about meltdown even without external power, that's a pretty big advance. Looks remarkably promising... keep your fingers crossed. (New nuclear tech hasn't had the greatest track record over the past several decades, i.e. pebble beds didn't work out etc.)