A top global nuclear body has launched a new program to assemble, validate, and distribute data on tungsten impurity processes in fusion plasmas. The International Atomic Energy Agency’s (IAEA) new five-year Coordinated Research Project (CRP F43028) could assist in the advancement of nuclear fusion energy development.

There are plans to use tungsten as a wall material in next-generation fusion devices (even in ITER) because it offers favorable thermal and mechanical properties for future fusion reactors.

However, there are speculations among researchers that interactions between plasma particles and tungsten walls can lead to erosion. Such erosion can release tungsten impurities into the plasma.

The IAEA emphasized that these impurities in the plasma core can severely impact stability and performance by increasing radiative energy losses and triggering disruptive instabilities. The new project would work on understanding the behavior of tungsten ions in fusion plasmas to reduce risks.

IAEA has also revealed that critical uncertainties remain in the interaction processes of tungsten with plasma fuel particles in the one to ten kilovolts energy range because discrepancies persist between theory and experiments. In addition, processes involving neutral atoms or protons interacting with low-charge tungsten ions require further study to improve predictive models.

This project is expected to provide evaluated experimental and computational data on tungsten ion properties under fusion-relevant plasma situations. The results of this research will directly support the operation of future fusion reactors using tungsten-based plasma-facing components.

The project will assess and verify the ionization cross-sections and rate coefficients from metastable values of tungsten’s first ionization stages. It will also investigate the collisional interactions of neutral atoms and protons with tungsten ions.

The research will also experimentally assess the low and medium ionization stages of tungsten in the unresolved transition array (UTA) and quasi-continuum (QC) regions. UTAs are a method of approximating complex atomic physics in plasma opacity calculations, and as such are very important in modern plasma dynamic simulations. With the goal of modeling an atomistic system without explicitly treating every atom in the problem, QCs provides a framework whereby degrees of freedom are judiciously eliminated, and force/energy calculations are expedited.

Multiple studies have also found that tungsten-based materials are considered to be one of the most promising plasma-facing materials, but there are still many problems in practical applications.

In previous work, researchers have stressed that plasma-facing materials are subjected to the multi-field coupling effect of thermal shock and multiple radiations, which requires tungsten-based materials to have not just good mechanical properties but also a certain resistance to irradiation.

There have also been claims that the utilization of tungsten fiber reinforced tungsten (Wf /W) could broaden the operation temperature window of tungsten significantly. It could also mitigate problems of deep cracking occurring typically in cyclic high heat flux loading. This is especially crucial when considering material degradation from neutron-induced transmutation and embrittlement.

Designed to mitigate tungsten’s brittleness, tungsten fiber-reinforced tungsten (Wf/W) composites incorporate tungsten fibers into a tungsten matrix. The approach aims to achieve pseudo-ductile behavior which means that the material can withstand deformation and cracking without losing its load-bearing capacity, even at room temperature.

IAEA

For decades, fusion energy has held the promise of a revolutionary power source that is clean, safe, and virtually limitless.

Unlike fossil fuels or even traditional nuclear power, nuclear fusion mimics the energy production of the Sun. Atomic nuclei fuse together to release massive amounts of energy without greenhouse gas emissions or long-lived radioactive waste.

However, one serious problem has kept this dream out of reach. That is the inability to reliably contain high-energy particles inside fusion reactors.

These particles are essential to keeping the plasma hot enough for sustained fusion. However, they tend to escape through holes in the reactor’s magnetic field, draining energy and halting the reaction.

Now, a team of researchers from The University of Texas at Austin, Los Alamos National Laboratory, and Type One Energy Group have developed a faster, more accurate way to fix those magnetic flaws. This could accelerate the development of stellarators, one of the most promising fusion reactor designs, by a factor of ten.

Fusion reactors require a superheated plasma confined within strong magnetic fields. An important issue has been the escape of high-energy alpha particles, which are supposed to help maintain the plasma’s heat and pressure. When these particles leak, they weaken the reaction which prevents the conditions necessary for sustained fusion.

However, these magnetic fields often contain ‘holes’ through which alpha particles escape. Finding and correcting these flaws using traditional methods based on Newton’s laws is computationally intensive and slow. The design process becomes cumbersome as engineers need to simulate and test hundreds of variations in the configuration of the coils.

To make the process more manageable, scientists have used a faster but far less accurate technique called perturbation theory, which often leads to serious errors.

The new method, developed by the research team and detailed in their recent paper, uses symmetry theory to locate and eliminate magnetic holes while requiring just a tenth of the computational power.

Josh Burby is an assistant professor of physics at UT and first author of the paper. He said, “What’s most exciting is that we’re solving something that’s been an open problem for almost 70 years. It’s a paradigm shift in how we design these reactors.”

Although the method was designed for stellarators, its applications also extend to tokamaks which are the more widely studied cousin of stellarators.

In tokamaks, the danger lies in runaway electrons, which can puncture the walls of the reactor if not properly contained. The new technique can help find the weak spots in magnetic fields, potentially improving reactor safety and durability.

Burby said, “There is currently no practical way to find a theoretical answer to the alpha-particle confinement question without our results. Direct application of Newton’s laws is too expensive. Perturbation methods commit gross errors. Ours is the first theory that circumvents these pitfalls.”.

This breakthrough not only solves a specific technical bottleneck but also provides an important tool for companies racing to commercialize fusion power.

Type One Energy Group contributed to the research. It is working to construct next-generation stellarators for energy production.

Type One Energy Group