Triso Fuel And The Rolls Royce Of Nuclear Reactors

Bangor University scientists think that the way to go big with nuclear power is to, in fact, go small. Their tiny nuclear fuel pellets called triso fuel are said to be the size of poppy seeds and are meant to power a reactor by Rolls Royce the size of a “small car.” We aren’t sure if that’s a small Rolls Royce or a small normal car.

The Welsh university thinks the reactor has applications for lunar bases, here on Earth, and even on rockets because the reactor is so small. We can’t tell if the fuel from Bangor is unique or if it is just the application and the matching reactor that is making the news. Triso fuel — short for tri-structural isotropic particle fuel — was developed in the 1960s, and there are multiple projects worldwide gearing up to use this sort of fuel.

The U.S. Department of Energy calls Triso “the most robust nuclear fuel on earth.” Each tiny pellet consists of a kernel made of uranium, carbon, and oxygen. The fuel has an outer jacket around the kernel made of three layers of carbon- and ceramic-based materials to isolate the radioactive material. Traditionally, the kernel contained uranium dioxide, but recently, the pellets contain uranium oxycarbide. Because of the self-containment system, the pellets won’t melt and release radioactive material even when heated for 300 hours at 1800C. If you want to know more about the history of this fuel and where it has been used so far, Power Magazine has a good overview. We’ve talked about it before, too. Turns out that making a nuclear reactor is hard, but making the fuel for one is one of the hardest parts.

59 thoughts on “Triso Fuel And The Rolls Royce Of Nuclear Reactors

  1. Interesting article. I studied electronic engineering at Bangor between 1983 and 1986. My first class B.Sc. degree has served me well over the years.

    In the mid-1980s, it was a small rural University college of some 3000 students, about 250 miles north west of London, surrounded by the beautiful mountains of Snowdonia.

    Now it appears to be forging ahead with 21st century nuclear technology, aimed at distributed power generation (Rolls Royce) and lunar/space applications.

    I am proud to be a Bangor Allumni of nearly 40 years ago.

        1. Rhyl is Brill? I always thought Bangor was an innuendo anyway…

          While in the area, on a stag weekend we happened across a doorbell with an “out of order” sign on it.

          My observation? “Don’t press dat in.”

          1. “The term aluminum was created by the man who first identified the existence of the element, British chemist Humphry Davy. Davy originally referred to the element as alumium but ultimately altered the name to aluminum.”

            School schedule = skool skedule (US) = Skool shhhhedule (UK)

    1. You don’t need a critical mass unless you want an explosion. Since we want a sustainable chain reaction in a fission reactor, you keep the uranium (which will split, or fission) enrichment low and moderate the neutron flux across the core (in 3 dimensions) to run the reactor at the capacity you desire.

  2. You do not have critical mass in nuclear reactors. Critical mass is the minimum amount of material needed for a nuclear chain reaction to become a runaway reaction in a nuclear weapon.
    The pelletization of nuclear fuel in addition to it’s reauirement of being much less radioactive, is meant to make it more difficult to refine and use in nuclear weapons.
    Large, older, industrial scale nuclear reactors need(/ed) large amounts of highly radioactive fuel to run efficiently. That is not ideal as that type of fuel is much more easily refined for use in nuclear weapons, bith with nuclear detonations and without (dirty bombs).

      1. That’s not exactly complete either IMO.

        Most of the neutrons in the nuclear reaction come out instantly, but a few come after a delay when the products of the reaction decay according to their half life. For a reactor, you’re probably in a “prompt subcritical, delayed critical condition: the prompt neutrons alone are not sufficient to sustain a chain reaction, but the delayed neutrons make up the small difference required to keep the reaction going.” (

        So it may not be entirely false to say that the reactor is subcritical, although in fact it is just prompt subcritical. You can also imagine that some hypothetical reactor could be made so that a full load of fuel is “a few” neutrons short of being inherently critical, both prompt and delayed. But then a neutron generator could be aimed at the reactor and sustain the reaction…. (As a simple example of one, you can get neutrons by hitting beryllium with gamma rays.)

          1. No. If you try to moderate the reaction at the limit of prompt criticality, it goes bang before you can say “oops”. Like the SL-1 reactor that reached 20 GW output power in 4 milliseconds. It was designed for 3 MW so that’s “only” 6,700 times the nominal power output, faster than you can even blink.

        1. The fuel is subcritical in air, but when surrounded with a neutron moderator (water, graphite, etc.), fewer neutrons are needed for criticality. Neutron absorbers (control rods) are then used to control the reaction.

          That’s also a safety feature in many reactor designs. When the moderator boils or drains away, the reactor stops.

        2. >then a neutron generator could be aimed at the reactor

          That’s a proposal for consuming nuclear waste – forced fission in a subcritical fuel using a particle accelerator. They haven’t come up with a cheap enough particle accelerator for the job yet.

    1. Peanut M&M’s contain peanuts. peanuts per 100g contain 332 mg of Potassium. Potassium is mostly stable, buy 0.0120% of all natural Potassium is K-40 which is radioactive (emits beta particles).

      Chocolate M&M’s contain Chocolate. Chocolate per 100 g contain 372 mg of Potassium. Potassium is mostly stable, buy 0.0120% of all natural Potassium is K-40 which is radioactive (emits beta particles).

      But it is nothing to worry about, your body keeps strict control on how much Potassium is within a human body at all times, it is typically about 0.4 percent of the total mass of a average human body (62 kg ; ~9 stone 11 pounds) which is about 24.8 grams (~0.87 ounces ). And because Potassium is distributed throughout the cells of the entire body it is relatively safe, there is no concentrated source of radiation.

      1. Sorry forgot to say the the total K40 mass within the entire human body is approximately 3 micrograms (0.0000001 ounches) or about 1800000000000000000 atomic mass units or about 45,200,000,000,000,000 potassium-40 atoms (~45.2 quadrillion atoms).

    1. A friend in the Midlands had a Rolls for his wedding chauffeur business. We rode in it once but I had to help push it out of a parking spot because it had no reverse gear, couldn’t afford the repair. Those things are HEAVIER than they look. It was quiet and smooth, though.

  3. Every time I hear about innovations like this I get excited. To be clear, I’m not fundamentally a fan of nuclear power; I believe we should have come up with sustainable technologies and practices – on both the demand and supply sides of the equation – to not need nukes.

    That said, I believe that we’re at a stage where we can either ‘go nuclear’ or lose a good part of what we call civilization. We might even lose our own species. So at this point I think it’s nuclear power FTW. And I think SMR’s are the way to go. We can bring them online faster than full-sized plants, and they support the roll-out of city-sized or even neighbourhood-sized grids that provide redundancy and resilience. Reliance on a trans-national power grid vulnerable to single points of failure gives me the willies…

    1. The transnational grids do not have this “single point of failure”. They contain safety devices on various levels. And they allow a stable supply. Especially for the increased use of renewables very good interconnects are important to equal out the fluctuations of demand and supply.

      1. The transnational grids also become more fragile against disruptions when they rely on “very good interconnects” to balance supply and demand. There are many cases where breakdowns on distribution lead to cascading failures across the grid that spread for thousands of miles around.

    2. A great deal of energy demand is in heating. That’s a good thing because nuclear reactors designed for heating do not have to operate very hot to generate superheated steam – only hot water. That means the reactors can be designed with physical safeties where the boiling of water triggers extra cooling and/or shuts the reactor down automatically without active safety mechanisms.


      The reactor design is such that the core sits in an insulating “thermos bottle” with water at the bottom. If it ever gets too hot, the water will boil and the steam fills the middle cavity and starts to conduct heat across the gap to the surface of the bottle. The entire thing sits at the bottom of a pool of water, which is the emergency cooling pond. If it gets flooded by a storm, good – more coolant.

    1. Pebble bed reactors have other problems than traditional reactors where the pellets are fixed into fuel rods. The main issue is that the fuel balls or pebbles physically chafe against each other as they move inside the reactor.

  4. BWXT (nuke subs and bombs) is behind the triso fuel SMR plans. The American Military laughed them out of the yard when they floated the idea for foreign deployment. Then Micheal Flynn (Trump) and Eric Prince (Blackwater mercenaries) were in a deal with UAE (see Mueller Report). Then BWXT and the USA DoD thru project Pele poured in $$$ and are now aiming to make Northern Canada their guinea pig for first deployment. Great excuse to have foreign mercenaries on 🇨🇦 soil. Closed loop economy = uranium mine in northern Saskatchewan powered by BWXT all paid for with taxpayers donations and lives lost due to cancers …. forever (still no functioning long term waste facility on this planet). Buy stocks in uranium. I’d suggest Cameco cuz they’ve stockpiled tons and now profit through Westinghouse (à la Mark Carney). Or Rosatom if you’re into weaponizing nuke power station. But hey, good thing the science is so cool, eh guys? ☠️💰☢️🤑

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