Avdekke sikker og praktisk fusjon – Nye innsikter i fanget drivstoff

Fusjon & drivstoffeffektivitet

Nuclear Fusion is potentially the ultimate green energy source, producing no dangerous byproducts, radioactivity (the only “waste” is helium), or greenhouse gases. And it could be powered by a fuel so abundant that it is a significant percentage of the entire Universe: deuterium, an isotope of hydrogen.

But this is also a very difficult to achieve form of energy generation. It requires replicating on Earth the conditions in the core of the Sun, with tremendous pressures and tens or hundreds of millions of degrees.

Nuclear fusion has been achieved in physics laboratories for decades, but a net energy-positive fusion reaction is still to be reached. This is what many are racing to accomplish, from det internasjonale megaprojektet ITER to commercial fusion projects like Commonwealth Fusion Systems and Proxima Fusion.

Commercial viability will depend not only on achieving stable and energy-positive plasma generation, but also on the general efficiency of the process.

One open question is the fuel efficiency. Deuterium is known to be partially absorbed by the walls of the tokamak fusion reactors. Researchers at Princeton University, University of California, University of Tennessee, Sandia National Laboratory, and General Atomics are figuring it out.

Kilde: Princeton University

De publiserte resultatene sine i Nuclear Materials and Energy¹, under tittelen “Deuterium retention behaviors of boronization films at DIII-D divertor surface”.

Deuterium, tritium & fusjon

The lighter an atom is, the more potential energy is released when it undergoes nuclear fusion. So it makes sense that most nuclear fusion projects focus on merging together variants of hydrogen, with the most popular option being deuterium-tritium fusion.

Kilde: Nature

Deuterium-deuterium-fusjon er også mulig, men av tekniske årsaker antas det å være enda vanskeligere å oppnå kommersielt. Dette er grunnen til at nesten alle kommersielle prosjekter eller prototyper av kommersielle prosjekter som ITER planlegger å bruke deuterium-tritium som drivstoff.

Et problem med tritium er at det er radioaktivt, i motsetning til deuterium. Så du vil ikke akkumulere for mye tritium i reaktoren, og du vil heller ikke miste oversikten over det. Dette er ikke bare et sikkerhetsproblem, men også et regulatorisk.

“Det er svært strenge begrensninger på hvor mye tritium som kan være i en enhet til enhver tid. Hvis du overskrider dette, stopper alt, og lisensen blir trukket.

Så, hvis du vil ha en fungerende reaktor, må du sørge for at din regnskap av tritium er nøyaktig. Hvis du overskrider grensen, er det en showstopper.”

Alessandro Bortolon – Ansvarlig hovedforsker ved PPPL (Princeton Plasma Physics Laboratory)

Ettersom deuterium-tritium-drivstoff sannsynligvis vil bli brukt i kommersielle kjernefusionsreaktorer, er det svært viktig å vite hva som skjer med drivstoffet. Og vi vet allerede at en del av det blir absorbert av reaktorens vegger.

Deuteriumabsorpsjon

Nuclear fusion reactors’ walls are made of graphite and coated with boron. The boron helps reduce the plasma impurities such as oxygen, carbon, and tungsten.

Kilde: Nuclear Materials and Energy

Det har vært kjent en stund at disse borbelagte veggene absorberer noe deuterium fra plasmaet. Imidlertid var mekanismen og mengden involvert ikke klare.

For å forstå det, utførte de tester på DIII-D, en tokamak-fusjonsreaktor hos General Atomics.

De oppdaget at synderen for deuteriumabsorpsjon faktisk ikke var bor, men karbon.

Kilde: Nuclear Materials and Energy

Karbon og bor sammen kan binde så tett til deuterium at det vil kreve temperaturer på rundt 1 000 grader Fahrenheit for å bryte bindingen, noe som gjør det svært utfordrende å fjerne drivstoffet uten å skade fusjonssystemet.

“Karbon må minimeres. Selv om vi ikke kan få den til null, bruker vi alle midler vi har for å redusere mengden karbon så mye som mulig.

Vi ønsker å bli kvitt all karbon og ha rene wolframvegger for å sikre at beregningene er enda nærmere det som vil bli opplevd i ITER.”

Florian Effenberg – PPPL forskningsfysiker

Finne løsninger

Ved å grave dypere fant forskerne at eksponering for plasma med små mengder karbonforurensning økte mengden fanget deuterium betydelig.

For hver fem enheter bor fanget i en prøve, ble to enheter deuterium fanget.

Fenomenet er også temperaturavhengig. Over 600 000°K (1 million °F) er deuteriumretensjonen begrenset, og veggen frigjør deuterium igjen ved 900 000°K.

Imidlertid bør slike temperaturer som berører veggbelaget unngås for materialets langsiktige stabilitet, så det er ikke en praktisk løsning å unngå drivstoffakkumulering i reaktorveggene.

En mer sannsynlig løsning er å prøve å begrense til det absolutte maksimum hvor karbonforurensninger kan komme inn i reaktorveggene, noe som hittil ikke var kjent å ha så stor betydning.

Dette vil ha en direkte praktisk innvirkning på den endelige designen og produksjonen av ITERs reaktorvegger.

“ITER og fremtidige enheter bør være nøye med å minimere C-forurensningskontaminasjon for å redusere deuteriumretensjon.”

Det er også sannsynlig at det vil begrense praktisk anvendelse eller kommersiell levedyktighet for enhver kjernefusionsmotor som bruker grafittfliser på veggene (grafitt er laget av karbonatomer), som DIII-D-fusjonen brukt i dette eksperimentet, da dette designet sannsynligvis vil akkumulere for mye tritium over tid til å bli autorisert for drift som kraftverk.

Konklusjon

Nuclear Fusion is progressively becoming a well-understood technology, with the record for stable plasma duration beaten regularly, the latest being 22 minutes in a French-Chinese collaboration.

With the help of AI, it is likely that fusion will keep getting more efficient over time, up to the point where net energy is achieved.

As the technology inches closer to commercialization, new challenges are emerging, like following regulations regarding fuel accumulation and radioactivity, something experimental reactors had less to be concerned about.

Luckily, these issues are also being ironed out, and optimizing the quality of materials used for the reactors will help.

Combined with constant improvements in our understanding of superconductivity, this could help make our trouble generating green energy a thing of the past in the next 1-2 decades.

Fusjonsselskaper

Currently, none of the companies dedicated solely to making nuclear fusion commercially viable are publicly listed. These include Helion, General Fusion (GFUZ ), Commonwealth Fusion, TEA Technologies, ZAP Energy, and NEO Fusion.

You can find an extensive list of startups in the nuclear fusion space on the dedicated page of Dealroom.

Still, one publicly-listed company has been active in the field of fusion, with a redirection of its concept from energy production to space propulsion: Lockheed Martin (LMT ).

One notable exception to privately-listed startups dominating the field is the publicly traded company Lockheed Martin Corporation, a giant of the defense industry.

Lockheed has been working since the early 2010s on Compact Fusion, a nuclear fusion reactor that is expected to be ready by the 2020s. However, it has since been announced that the work on the project was stopped in 2021.

The company has been very discreet about this project since the 2021 public announcement. To this day, it is unclear what could have prompted the company to abandon the idea.

At the same time, it seems that it did not fully abandon the concept, notably with investments in 2024 in Helicity, a startup developing a fusion engine.

The idea is to propel spacecraft with short bursts of fusion. Helicity plans to use a plasma gun, the same approach as General Fusion. Potentially, Lockheed’s internal results have shown that its design could not sustain fusion in a way that is compatible with energy production.

But maybe, at the same time, are short bursts enough for the need for propulsion in space and much closer to becoming an actual product? It would also be a better fit with the company’s overall aerospace and defense-focused profile.

Besides fusion projects, Lockheed Martin is one of the world’s largest aerospace & defense companies, which we covered in detail in november 2025 in “Lockheed Martin (LMT) Spotlight: A Leader In Defense and Aerospace”.

In short, this is the company behind aircrafts like the Black Hawk helicopters or the F-16, as well as advanced equipment like the F-35, flying radar planes, or logistical aircrafts like the C-5 Galaxy & C-130J Super Hercules.

Kilde: Lockheed Martin

It is also the producer of some of the US military’s most important missile systems like the JAASM, Javelin, ATACMS, and HIMARS, in extremely high demand following the depletion of stockpiles by the conflict in Ukraine.

Lockheed is the lead contractor for the design, development, testing, and production of the Orion spacecraft, which may be the least controversial part of the entire Artemis program.

The company is active in other space programs, like the GOES-R weather satellites, the collection of asteroid samples by OSIRIS-REx, Jupiter probe JUNO, a wearable radiation-shielding vest AstroRad,

Overall, from key military systems to equally important space and nuclear fusion programs, Lockheed Martin is at the forefront of American innovation and seems to have kept its edge a lot sharper than many of its large defense contractor competitors.

Siste om Lockheed Martin Corporation

Studierreferanse:

^{1. Shota Abe et al. (2025) “Deuterium retention behaviors of boronization films at DIII-D divertor surface”. Nuclear Materials and Energy Volum 42, mars 2025, 101855.}