A new strategy aimed at improving the efficiency of fusion fuel involves aligning the quantum spins of deuterium and tritium and modifying the fuel mixture. This could enhance the efficiency of tritium burning by as much as 10 times, which would decrease the need for tritium and reduce the costs associated with fusion systems. This innovative method could lead to safer and more compact fusion setups, ultimately making fusion energy more feasible and economical.
According to a recent study, using a different combination of fuels with improved characteristics could help resolve significant challenges in making fusion a viable energy solution.
The new method would still utilize deuterium and tritium, which are widely recognized as the most suitable fuel pair for fusion energy generation. However, it involves adjusting the quantum characteristics of the fuel to achieve optimal efficiency through a technique called spin polarization. In this method, half of the fuels would be spin-polarized, and the proportion of deuterium would be increased beyond the typical amount of around 60%.
Models developed by researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) indicated that this approach could significantly enhance tritium burning efficiency without compromising fusion output. This improvement could lead to a dramatic reduction in the amount of tritium required to initiate and sustain fusion reactions, resulting in smaller and more cost-effective fusion facilities.
“Fusion is tremendously challenging, and nature doesn’t make it easy for us,” stated Jason Parisi, a staff research physicist at the Lab and lead author of the study. “Thus, the extent of the improvement was quite unexpected.”
The findings, published in the journal Nuclear Fusion, suggest that the new method could enhance tritium burning efficiency by as much as tenfold. This research emphasizes PPPL’s pioneering role in fusion technology advancements, particularly concerning systems like the one examined in Parisi’s study, which involves superheating gases to create a plasma held in magnetic fields, shaped like a core apple. The Lab’s main fusion device, the National Spherical Torus Experiment — Upgrade (NSTX-U), shares a similar design to what the researchers analyzed during their experiments.
“This is the first instance where researchers have explored how spin-polarized fuel could enhance tritium burning efficiency,” remarked co-author and staff research physicist Jacob Schwartz.
Reducing tritium needs by maximizing burn efficiency
Ahmed Diallo, principal research physicist at PPPL and co-author of the study, compared tritium burning efficiency to that of a gas stove. “When gas exits a stove, the goal is to burn all of it,” Diallo explained. “In a fusion reactor, tritium isn’t completely burned, and obtaining it is challenging. Hence, our objective was to enhance tritium burning efficiency.”
The PPPL team engaged with professionals from the fusion community and the broader spin polarization field to enhance tritium burning efficiency. “Fusion spans multiple scientific and engineering disciplines. Progress requires advancements across numerous areas, but often surprising outcomes arise when disparate research fields converge,” Parisi noted.
A new kind of spin
Quantum spin differs significantly from the physical spin one might observe on a baseball. For instance, a skilled pitcher can execute several types of spin. However, there are only limited options for the quantum spin of a particle, such as “up” or “down.”
When two fusion fuel atoms have the same quantum spin, their fusion likelihood increases. “By enhancing the fusion cross-section, it’s possible to generate more energy from the same quantity of fuel,” Parisi explained.
Although current spin polarization techniques do not align every single atom, the gains observed in the PPPL model do not necessitate complete spin alignment. In fact, the study showcases how even moderate levels of spin polarization can substantially enhance tritium burning efficiency, improving overall fuel utilization and decreasing tritium consumption.
Boosting efficiency to lower tritium needs
With a reduced requirement for tritium, the overall size of the fusion power plant can be minimized, simplifying licensing, installation, and construction processes. This collective advancement should reduce the operating expenses of fusion systems.
Tritium is radioactive; although its radiation lasts a shorter time compared to the spent fuel from nuclear fission reactors, decreasing the amount used enhances safety by lowering the risk of leakage or contamination.
“The less tritium you have flowing through your system, the less that will infiltrate the components,” Parisi elaborated. Additionally, the storage and processing facilities for tritium can be significantly smaller and more efficient. This factor simplifies nuclear licensing processes. “A common belief is that site boundary size correlates with the quantity of tritium present. Thus, having less tritium allows for smaller plants, which can accelerate approval processes and reduce costs,” he added.
New opportunities to investigate
The DOE’s Office of Science has funded additional research into the technologies necessary for injecting spin-polarized fuel into the fusion vessel. Further investigation is required to identify the elements necessary for implementing the proposed system, which is still uncharted territory. “We still need to determine whether it’s feasible to sustain high-quality fusion plasma with specific flows of surplus fuel and ash from the plasma,” Schwartz stated.
Diallo acknowledged potential challenges related to polarization techniques but emphasized that these also represent opportunities. “One challenge will be to develop methods for generating spin-polarized fuel in bulk and subsequently storing it. This would open up an entirely new technological realm.”
