4 ms·

Is this the same thing as “pebble bed” reactors I read about many years ago?

DiabloD3 6y ago
I literally came here to say the same thing. It reads like someone is just trying to remarket the concept to people in their 50s and up to accept nuclear power as their one true God.
verandaguy 6y ago
Yes, this is about pebble bed reactors. From the article: The Xe-100 is a small pebble-bed reactor that is designed to produce just 75 megawatts of power. I should add that I'm thrilled steps are being made to make these a reality.
- api 6y ago
  Seems like the pebbles are much smaller in these. I recall one very mundane but difficult issue with previous pebble bed reactors was pebbles jamming and other mechanical problems with the fuel. These seem like they'd flow like that weird pseudo-sand stuff in kids toys.
  - pjscott 6y ago
    These very small fuel particles are embedded in larger graphite structures with whatever geometry is convenient for handling. (Pebble bed pebbles are one such possibility, and PBRs have been made which use TRISO-based fuel pebbles.)
tersers 6y ago
I also believe it's true of liquid fluoride thorium reactors: https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor#Safety https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto... I remember watching a documentary on nuclear power in the US and how the thorium reactor was the focus of a lot of research in the 70s, but I can't remember for sure.
- pjscott 6y ago
  To clarify: molten fueled reactors (like LFTRs) trivially can't have their fuel accidentally melt, because their fuel is already molten. (And there are some nice options for dumping their fuel into a subcritical passively-cooled configuration in case of an emergency.) This is different from TRISO fuel, which isn't supposed to be molten in normal operation but which structurally limits the spread of fuel and fission products at high temperatures.
  - acidburnNSA 6y ago
    They can melt. They all do during fuel synthesis. They're pre-melted.
- acidburnNSA 6y ago
  No. LFTRs have fluid fuel. There are some solid-fueled clean molten salt cooled reactors that are called Fluoride salt cooled high-temperature reactors (FHRs).
Gibbon1 6y ago
I read a detailed report of the one in Germany. Thing totally sucked. Two big problems the indestructible alumina pebbles cracked and contaminated the reactor. Second was inhomogeneous burn rates. I think I remember some pellets got stuck when they decommissioned the reactor.
- corty 6y ago
  THTR-300 https://de.wikipedia.org/wiki/Kernkraftwerk_THTR-300 https://de.wikipedia.org/wiki/Kernkraftwerk_THTR-300 . Not alumina pebbles, graphite pebbles with enclosed BISO particles (predecessor to TRISO from the original article). Whole containment is contaminated with graphite dust, very high beta radiation levels. They had problems with broken graphite pebbles all over the reactor because the pebbles were brittle, often got jammed and had to be unjammed by force. They even produced a radiation release to possibly "blow out" graphite dust from the gas pipes that had collected there.
jabl 6y ago
Yes, and no. Most(?) pebble bed reactors have used triso style fuel (there was a similar earlier fuel type called biso, don't know if any reactors using it were ever built), but triso fuel can be used in other reactor types as well. And yes, triso is pretty cool tech. Like the article says, it can withstand exceptional temperatures without any fission products escaping.

I literally came here to say the same thing. It reads like someone is just trying to remarket the concept to people in their 50s and up to accept nuclear power as their one true God.

verandaguy 6y ago

Yes, this is about pebble bed reactors. From the article: The Xe-100 is a small pebble-bed reactor that is designed to produce just 75 megawatts of power. I should add that I'm thrilled steps are being made to make these a reality.

api 6y ago
Seems like the pebbles are much smaller in these. I recall one very mundane but difficult issue with previous pebble bed reactors was pebbles jamming and other mechanical problems with the fuel. These seem like they'd flow like that weird pseudo-sand stuff in kids toys.
- pjscott 6y ago
  These very small fuel particles are embedded in larger graphite structures with whatever geometry is convenient for handling. (Pebble bed pebbles are one such possibility, and PBRs have been made which use TRISO-based fuel pebbles.)

tersers 6y ago

I also believe it's true of liquid fluoride thorium reactors: https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor#Safety https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto... I remember watching a documentary on nuclear power in the US and how the thorium reactor was the focus of a lot of research in the 70s, but I can't remember for sure.

pjscott 6y ago
To clarify: molten fueled reactors (like LFTRs) trivially can't have their fuel accidentally melt, because their fuel is already molten. (And there are some nice options for dumping their fuel into a subcritical passively-cooled configuration in case of an emergency.) This is different from TRISO fuel, which isn't supposed to be molten in normal operation but which structurally limits the spread of fuel and fission products at high temperatures.
- acidburnNSA 6y ago
  They can melt. They all do during fuel synthesis. They're pre-melted.
acidburnNSA 6y ago
No. LFTRs have fluid fuel. There are some solid-fueled clean molten salt cooled reactors that are called Fluoride salt cooled high-temperature reactors (FHRs).

Gibbon1 6y ago

I read a detailed report of the one in Germany. Thing totally sucked. Two big problems the indestructible alumina pebbles cracked and contaminated the reactor. Second was inhomogeneous burn rates. I think I remember some pellets got stuck when they decommissioned the reactor.

corty 6y ago
THTR-300 https://de.wikipedia.org/wiki/Kernkraftwerk_THTR-300 https://de.wikipedia.org/wiki/Kernkraftwerk_THTR-300 . Not alumina pebbles, graphite pebbles with enclosed BISO particles (predecessor to TRISO from the original article). Whole containment is contaminated with graphite dust, very high beta radiation levels. They had problems with broken graphite pebbles all over the reactor because the pebbles were brittle, often got jammed and had to be unjammed by force. They even produced a radiation release to possibly "blow out" graphite dust from the gas pipes that had collected there.

jabl 6y ago

Yes, and no. Most(?) pebble bed reactors have used triso style fuel (there was a similar earlier fuel type called biso, don't know if any reactors using it were ever built), but triso fuel can be used in other reactor types as well. And yes, triso is pretty cool tech. Like the article says, it can withstand exceptional temperatures without any fission products escaping.