Atomic Show #297 – Krusty – The Kilopower reactor that worked
Patrick McClure and David Poston successfully developed, obtained funding, constructed and operated a new atomic fission power source that produced useful quantities of electricity during the period from 2014-2018. That puts them into a rarified, perhaps unique position. Few US-based technologists have been through that process in the past 40 years.
Aside: Without some way to frame the statement so it excludes the US Navy it isn’t accurate to say no one else has accomplished this feat. End Aside
Patrick and David – and their supporting team – developed and operated the Kilopower reactor, also known as KRUSTY. That name comes from a creatively framed acronym – Kilopower Reactor Using Stirling TechnologY.
The proposed application for the system is to produce power for space missions that cannot be accomplished using either solar collectors or radioisotope thermal generators. The former imposes operational constraints with both intermittency factors and increasing distance from the sun. The later uses rare isotopes with limited heat production that constrain individual power devices to a thermal output of approximately 300 W when the device is new.
In brief, Krusty was a tiny reactor that was operated at a power level of 5 kWth to produce the equivalent of 1 kWe using Stirling Engines qualified for space travel. Heat pipes arranged around a solid UMO alloy annular core transferred heat from the reactor to the hot end of the Stirling engines. The cold side of the engines were designed to radiate heat into the vacuum of space. Reactor reactivity was adjusted using a movable beryllium reflector on the outside of the core. A boron carbide rod in the center of the annular core provided a second means of controlling the reactor. The core was 10 inches tall and had an outside diameter of 4 inches. The center annulus for 2 inches in diameter.
Aside: Past tense is the accurate way to describe Krusty. The system, including the core used, no longer exists. End Aside.
The program cost $18 M and took 3.5 years from initiation to final testing. It was funded partly by NASA and partly by NNSA.
We will be publishing a more detailed description of the technology and the development process in the near future, but for now, please listen to the show. If the audio program stimulates questions or comments, please join in a conversation here.
If you are intensely curious and cannot wait for our coming post, you can learn more about Krusty by visiting Space Nukes Technical Papers.
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This is an exciting development. I am encouraged. I am constantly amazed at the amount of power we can get from a super small core. I was looking at their website and feel the are bragging about success when they are actually in a totally different environment than most of the paper reactors. The reason “Paper Reactors” are constantly developed is the NRC. Space Nuclear’s ability to use a different license system is a testament to the painful process the NRC uses to block and hinder any commercial reactor. They were successful precisely because they were not aiming at a this world reactor but a space reactor. Let’s see them sell that for applications here and now and get through the NRC like the NuScale and Oklo. I really don’t mean to be disrespectful, but I a deeply frustrated at the rube goldberg regulations inside a package of rube goldberg regulations, on top of a rube goldberg regulations (repeat about 1000 times).
Wow! This thing reminded me of the comic books used to read as a kid back in the 1960s. I see it as an example of what used to be called “progress.”
Rod noted a real change since that time. He made the analog to sports. However, I think an analog to old craftsmen is more realistic. Reactors are harder and more expensive to build. It’s been fashionable for a long time to blame the government for this and darn near everything else. However, there are external factors. The loss of manufacturing in the West and the loss of skilled craftsmen of all sorts has a real “negative trickle down” effect that affects many endeavors. I think the high price of new reactors is an example of this “negative trickle down.”
I’d like to also think the two guys that Rod interviewed are an exception to the general trend that has been a part of society for the past 40 or so odd years. This trend has been that everything is for money. Everything is shunted aside for money. I’d like to think these guys did this because they were interested in finding out whether there idea could work. It was not for money but like the guys who climb Mt. Everest, i.e. “because it’s there.” Everything costs money, but I think this idea of “all for money,” has stymied new developments like this one rather than encouraged them.
Hopefully, there will be a follow up on Atomic Insights that shows a diagram of this reactor.
Thanks for allowing my BS comment.
The NRC’s core mission on behalf of the fossil fuel industry lobbies was to end domestic nuclear power. They have been and still, today are wildly successful in this mission. They will make sure NuScale and Oklo are so overburdened with safety systems and construction specifications that they are uneconomical. Again, mission accomplished.
The long term effect of a policy is the direction that was intended or the policy would have been changed to accomplish the actual intentions.
This small team demonstrated that a simple safe nuclear reactor can be built by a small team in a reasonable length of time. The very accomplishment puts a lie to the “need” for safety regulations. I was thinking about the cost per kwh of a core that would last several hundred years. A 10 KW system working for 400 years would be 14 cents / kwh. Almost reasonable.
@David
The Krusty team did not accomplish their task without safety regulation and a keen internal eye towards engineering decisions that would ensure safety.
But they were not overly burdened by the safety regulator. They were able to work with the regulator to devise effective testing programs to give both the regulator and the design team the answers to the questions that needed to be addressed to provide confidence.
@ Rod,
Yes exactly and a similar design could be done faster and just as safely if others were allowed to work in this pattern. I was impressed reading through some of the history of Nuclear in the 1960’s that many companies who had a core business in some other area would get a few engineers together and build a new nuclear power design. We CAN Still do that. We have more than enough people who are perfectly capable of doing it. I am exhausted with the “safety” issue in design. I wish the focus on the NRC was shifted to limiting actual deaths from any accident within the first 2 years. That would put Nuclear on par with other energy generation.
We need Nuclear Power plants this size or into the MW range to function as power plants for hospitals. Every hospital should have one on site. They could sell excess power to the grid.
I wonder how these little units would work to make process steam. It seems that the production of ethanol burns quite a bit of the corn to make the ethanol. These guys furnish the numbers.
https://ilsr.org/wp-content/uploads/files/ethanolnetenergy.pdf
This seems like there would be many niche markets for this technology.
I must admit that cost for an HEU core surprised me. I think the chance of such a thing flying on any civilian missions is nearly zero, but $5M for an HEU core custom made at Y-12 is pretty darn cheap… Hopefully this project continues to push forward and we get fission reactors back in space again!
Why would NASA test with 2 NASA-grade Sterling Engines and 6 simulators instead of 2 NASA-grade Sterling Engines and 6 commercial ones?
Perhaps because Space Nukes seem to have claimed that they have improved Stirling efficiency from a terrible 20% to just an awful 25%. Quite the trick. So now they “only” have to reject 75% of the heat as waste, versus 80%. In space. Via thermal radiation I guess. Tiny turbines must be really really terrible if this is the best NASA could come up with. So far.
Paul
Perhaps you missed the part of the show where Dave explained the goals of their project. Maximizing efficiency was not one of them.
Bear in mind the T^4 dependence of heat radiated per unit area, as well as the (1-Tc/Th) dependence of efficiency of the heat engine.
You want Tc as low as possible for efficiency, but in space you want Tc as high as possible to minimize the area & thus mass of the radiator. I expect the sweet spot will have Tc fairly high & so the efficiency will not be as high as you could get with a similar system on earth dumping heat into water or air.
This was a good show. Some very good points about pragmatism and the need to just get some non-LWR’s built vs continuing to pump out highly optimized paper designs.
Maybe a slightly larger version could have powered the Ford Nucleon?
Small nuclear engines are appropriate for robotic vehicles such as spacecraft. Nuclear powered aircraft are conceivable, but they too would have to be robotic. Neutron leakage would threaten humans nearby to unshielded nuclear powered vehicles such as cars. Even the B 36 nuclear reactor-carrying bomber had 11 tonnes of shielding but still irradiated its crew.