dongobongo

This actually happened in August and September of 2023 and it’s great validation for High Temperature Gas-cooled Reactor (HTGR) at larger scales. I hope they have the guts to also do a full loss of coolant test. I’ve also heard the these two reactors have been turned off for quite a while due to issues with the primary heat exchangers, temperature fluctuations, and uneven cooling - characteristically disadvantages of pebble beds.

There’s of course 2 flavors of HTGR (prismatic and pebble bed), and people choose the pebble version for continuous refueling despite all the drawbacks [1]. But there’s a lot of reasons to do prismatic. Can’t wait to see China’s prismatic HTGR.

[1] https://lvenneri.com/blog/pebble-bed-nukegumball

people in the center, cargo in the peripherals

From Luke Smith's post on GDP: https://lukesmith.xyz/articles/why-its-bad-to-have-high-gdp/

"GDP is only a measurement of how reliant a place or country is on the global economy. Self-sufficiency has a GDP of 0. Wasteful consooomerism has an extremely large GDP."

I have a feeling that in hindsight, 30-40 years from now, this will seem like no brainer and that the period prior was heavily anti-meritocratic and counterproductive.

More evidence: https://michaelshellenberger.substack.com/p/us-blew-up-russi...

Little bit of circumstantial evidence: https://seapowermagazine.org/baltops-22-a-perfect-opportunit...

oops thought it was July...

If the pipeline started operating, which it probably would in a few months with energy catastrophe in Europe - it would be total victory for Russia: natural gas revenues through the roof, end of war, etc etc. USA for some reason believes that Russian victory is against its interests.

See Biden recently: https://twitter.com/ah114088/status/1574435558675316737

Act of war by USA? (equivalent if done through ally)

Better metrics -- $/operation which includes the capital and operating cost and expected lifetime of the chip OR $/transistor or something like this.

In some respects, vulnerability to attack is a feature, not a flaw for promoting peace and collaboration instead of violence. A country with nuclear reactors is less likely to piss neighbors off enough to lead to an invasion. If invasion occurs, everyone will be extra careful. A country with nuclear reactors is less likely to be bombed to shit by other countries due to the reactor's radioactivity inventory potentially containing other countries as well as the country in question - ie. don't spoil the prize.

Meltdown accident: basically, reactor is turned off, however heat continues to be generated because of a thing called decay heat which is when isotopes generated by the fission reactions decay to more stable isotopes and release energy. It's about 7% of a fission reactor's power and continues for a few hours until it's negligible. 7% of a gigawatt reactor is like having a couple of jet engines going full blast inside the core. This heat has to be removed, and meltdowns happen when people fail to do so - basically pumps break, coolant leaks, or coolant is blocked from cooling down the core. Recent micro reactors get around this because they don't need active coolant or people to cool down the reactor - they just cool off by conduction or simple heat rejection systems. I read recently that fusion reactor will also generate decay heat from all the activated components and this is comparable to a fission reactor. The difference is there's a lot less radioactive crap in a fusion reactor - but the fusion reactor will still meltdown and they are expensive...

The typical radioisotope generator is a Plutonium-238 source like the MMRTG on the Mars rovers. The Plutonium decays by alpha emission with a half life of 80+ years. The problem is there is a very limited supply of Plutonium-238 - we use the entire supply for Mars Rover - and it's very controlled material.

The CAB starts with a non-radioactive material like Cobalt-59 spheres placed in a ceramic matrix. It is then put into a nuclear reactor where it turns into Cobalt-60, which releases energy by beta and gamma emission with a half life of 5 years. This charging can be done every couple years to generate more Cobalt-60 inside the device. Such a power source is something like 40x as power dense as the Pu-238 source and since it's made of high temperature ceramics, it can go to very high temperatures which is very useful for space generators where you have to reject heat using blackbody radiators.

Regarding Omouamoua, we just observed for the first time in human history, a cylinder or plate shaped object from another star flying through our solar system with questionable orbital velocities (we are not quite sure how to explain a small acceleration it had). A cylinder/plate is not a low energy geometry (things like to turn into spherical type objects over time), it's from another solar system, we don't know very much about it. How could you not want to visit it?

It's an opportunity to pull off a speed and distance record, visit something from another solar system, resolve big research questions about its shape, composition, origin and rule out any theories of its possible intelligent origin. They are also pursuing it to showcase the benefits of nuclear heat for space.

A company I work with recently started design and development for space craft to catch Borisov or Omouamoua, the other extra solar object that recently passed by, using a nuclear decay heat source and Hall effect thrusters. It's pretty realistic and doable - no bleeding edge technologies. Very high power density, very high isp, very fast space craft. Apparently, they can achieve 100km/s + velocity delta for a very small payload: https://www.nasa.gov/directorates/spacetech/niac/2021_Phase_...

The same system could do a Mars visit and return to Earth for small payloads in 50 days.

This stuff needs to get funded! They are funded for initial studies and design with NASA, but I know they are looking for extra funding to pull off the mission faster without being tied to NASA's timelines and mercurial objectives.

I was going to mention CANDU, basically the only exception to the above comment about running at too high power density.

This is just the dumb/old kind of nuclear in which the reactors are operated at really high power which means they have to be actively cooled so that the fuel doesn't melt itself and cause release of radiation. The reason they run at really high power, is because they think it's cheaper to get more power out of the same reactor. But of course they have to build a bunch of emergency systems, themselves expensive, to make sure the reactor is actively cooled - and these inevitably fail at some point.

The alternative, pursued most prominently by new companies like (usnc.com) is to operate at much lower power density which means the reactor does not have to be cooled to prevent it from melting. It can just dissipate the small amount of heat without any active measures or expensive equipment. Making the economics work is the trick.

These guys explicitly want to couple their nuclear plant with wind/solar: https://usnc.com/mmr-energy-system/. And from top level, it looks a lot like a natural gas plant.

I think that's their plan: https://usnc.com/space/

Nuclear detonations are very effective earth movers, perhaps capable tools in an Megascale structure project. See project plowshare. I'm not sure if the energy to make a weapon (enrichment primarily) is less than using conventional diggers and haulers. That is, are nuclear detonations efficient relative to other earth moving methods? Almost certainly.

https://en.wikipedia.org/wiki/Project_Plowshare

Then you should also refuse to comment.

fyi, this disappeared from the Top 120 of HN. Not a good look dang

sign of the times.

Mr. Musk is a closet Trump supporter.

Very fair. We should just bite the bullet of Covid. The goal at the beginning was just to prevent overwhelming medical capacity. No one ever signed up to save everyone at the expense of everyone else!

1% of commercial reactors Have failed catastrophically. Seems like terrible track record.

But they don’t lose the liquid coolant - which seems like a pretty reasonable scenario.