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Category: nuclear energy

Better helium reporting to improve fission and fusion materials modeling

Standardizing calculations of the helium byproducts generated in advanced fission and fusion energy system materials can increase reactor safety and longevity, according to a study led by University of Michigan Engineering with collaborators at Oak Ridge National Laboratory and its management contractor UT-Battelle.

Through a series of simulations, the researchers found that modeling assumptions and key alloy elements—like carbon, nitrogen and nickel—significantly influence helium generation predictions. If left unaddressed, excess helium in real-world reactors could lead to faster component failure as materials swell and become brittle.

“If used, our reporting methods will improve the experimental and modeling fidelity of the nuclear materials databases being generated both domestically and internationally, driving the rapid deployment of advanced nuclear,” said Kevin Field, a professor of nuclear engineering and radiological sciences at U-M and corresponding author of the study published in the Journal of Physics: Energy.

US federal funds awarded to spur SMR deployment

In October 2024, the US Department of Energy (DOE) — under the Joe Biden administration — opened applications for funding to support the initial domestic deployment of Generation III+ small modular reactor (SMR) technologies, with up to USD800 million to go to two “first-mover” teams, with an additional USD100 million to address so-called gaps that have hindered plant deployments. According to the solicitation documentation, a Gen III+ SMR is defined as a nuclear fission reactor that uses light water as a coolant and low-enriched uranium fuel, with a single-unit net electrical power output of 50–350 MWe, that maximises factory fabrication approaches, and the same or improved safety, security, and environmental benefits compared with current large nuclear power plant designs.

The solicitation was re-issued by the DOE in March 2025 to better align with President Donald Trump’s agenda on unleashing American energy and AI dominance.

In December last year, the DOE selected Tennessee Valley Authority (TVA) and Holtec Government Services to each receive USD400 million in federal cost-shared funding to support early deployments of advanced light-water small modular reactors in the USA. TVA’s application was selected for funding to accelerate the deployment of a GE Vernova Hitachi BWRX-300 at its Clinch River site in East Tennessee. Holtec plans to deploy two SMR-300 reactors — named Pioneer 1 and 2 — at the Palisades Nuclear Generating Station site in Michigan.

Mostly empty foam overturns assumptions of electron beam stopping

When physicists fire beams of fast electrons at materials, they often need to know exactly how much energy those electrons will lose as they travel through. Through new research published in Physical Review Letters, a team led by Ke Jiang at Shenzhen Technology University in China has found that porous, mostly empty foam materials can stop high-current electron beams far more effectively than denser materials—overturning many previous assumptions about how these beams interact with solid materials.

When a beam of electrons travels through a solid, its energy is lost through collisions with the atoms and electrons already present in the material. But when electron beams carry extremely intense currents, driving electrons to travel close to the speed of light, individual collisions are no longer the dominant factor.

Instead, the beam generates powerful electromagnetic fields as it moves, which shape how the beam propagates and loses energy. In fields ranging from nuclear fusion to studies of planetary interiors, it is often crucial for physicists to manage this energy loss as tightly as possible.

How Neutrino Oscillations Affect Supernovae

Numerical models of core-collapse supernovae have matured greatly over the past few decades. With impressive accuracy, they now couple relativistic gravity, magnetohydrodynamics, nuclear physics, and neutrino transport. Neutrinos, copiously produced in the collapsed core, are the main driver of most of these supernovae. Neutrino oscillations are probably the most crucial ingredient that is still missing from the majority of models, even though their presence and possible importance have long been suggested. The reason for this gap in modeling is twofold: Many relevant physical parameters are poorly known, and the most important oscillation processes are very difficult to simulate. Now Ryuichiro Akaho at Waseda University in Japan and colleagues have made a key step toward a self-consistent model and revealed some complexities that arise when incorporating neutrino oscillations [1].

Stars are supported against their own gravity primarily by gas pressure, which is maintained by exothermic nuclear reactions. In high-mass stars, nuclear burning starts with the fusion of hydrogen into helium and continues through progressively heavier elements until the core is dominated by iron-group nuclei, at which point fusion no longer releases energy. Pressure support then no longer suffices to stabilize the core, and it collapses to a protoneutron star, a hot compact object with about 1.5 solar masses concentrated in a radius of a few tens of kilometers. During the collapse, a shock wave forms at this object’s surface and stalls after propagating outward for only about 100 km (Fig. 1). Neutrinos generated in and around the protoneutron star can heat the surrounding gas, increasing its energy.

“Can We Survive Technology?” by John von Neumann

This is an essay written by John von Neumann in 1955, which I think is fairly described as being about global catastrophic risks from emerging technologies. It discusses a bunch of specific technologies that seemed like a big deal in 1955 — which is interesting in itself as a list of predictions; nuclear power! increased automation! weather control? — but explicitly tries to draw a general lesson.

Von Neumann is regarded as one of the greatest scientists of the 20th century, and was involved in the Manhattan project in addition to inventing zillions of other things.

I’m posting here because a) I think the essay is worth reading in its own right, and b) I find it interesting to see what the past’s intellectuals thought of issues related transformative technology, and how their perspective differs/is similar to ours. Notably, I disagree with several of the conclusions (e.g. von Neumann seems to think differential technological development is doomed).

Void-Filled Material Stops Intense Electron Beam

An intense electron beam is stopped more efficiently by a highly porous material than by a less porous material, suggesting new strategies for controlling beams.

New experiments show that porous materials consisting mostly of empty space can absorb the energy carried by an ultraintense electron beam more effectively than porous media with higher mass densities. The finding contradicts the prevailing notion that denser and thicker obstacles always provide more stopping power and suggests that the microstructure of a material fundamentally changes its electron-stopping ability. Simulations by the experimental team revealed the physical mechanisms behind this “anomalous-stopping” effect, which the researchers believe provides a new way to control the propagation of electron beams in extreme environments [1].

The study focuses on relativistic electron beams (REBs), which travel at close to the speed of light. REBs that carry currents in the mega-ampere regime can deliver petawatts (1015 watts) of power to a small target in a pulse lasting for a few picoseconds. This high intensity makes them ideal for creating and probing extreme states of matter that exist in stars, planetary cores, or nuclear events. The short bursts of intense energy provided by REBs are also used in inertial-confinement fusion—a scheme in which high-power lasers heat a fuel pellet and trigger nuclear fusion.

NASA Powers Down Voyager 1 Instrument As It Fights To Survive Deep Space

Voyager 1 is losing power, and NASA just shut down a decades-old instrument to keep it going. The sacrifice could help the spacecraft continue exploring interstellar space a little longer.

On April 17, engineers at NASA’s Jet Propulsion Laboratory (JPL) in Southern California transmitted commands to switch off an instrument on Voyager 1 known as the Low-energy Charged Particles experiment, or LECP. The spacecraft, which runs on nuclear power, is steadily losing energy, and shutting down this instrument is the most effective way to extend the mission of the first human-made object to reach interstellar space.

A 49-Year-Old Instrument Falls Silent

Understanding how lasers can rapidly magnetize fusion plasmas

The mechanism that can cause a rapidly expanding plasma—the superhot state of matter harnessed in fusion energy systems—to spontaneously generate its own magnetic fields was identified through a new set of simulations. This improves our understanding of naturally occurring plasmas in our universe and advances the development of fusion systems based on an approach called direct-drive inertial fusion.

In a direct-drive inertial fusion system, powerful lasers compress a small, fuel-filled capsule, heating it until fusion reactions occur. Unexpected magnetic fields can change how heat moves through the plasma in ways that existing simulation tools can miss. Accurate simulations are critical to designing fusion systems that will behave as expected and deliver net energy on a long-term basis.

In laboratory experiments, researchers found that high-powered lasers can vaporize a solid target in an instant, turning it into plasma that rapidly expands. Experiments have repeatedly detected very strong magnetic structures emerging from this expanding plasma, but the precise origin of these fields has long been a matter of debate.

DAMPE satellite reveals cosmic rays share spectral break near 15 teravolts

A century after their discovery, cosmic rays—particles of extreme energy originating from the far reaches of the universe—remain a mystery to scientists. The DAMPE (Dark Matter Particle Explorer) space telescope is tackling this phenomenon, particularly investigating the role that dark matter may play in their formation. This international mission, which includes the University of Geneva (UNIGE), has made a major breakthrough by highlighting a universal feature of these particles. The results are published in the journal Nature.

Cosmic rays are the most energetic particles observed in the universe, far surpassing the energies of particles produced by man-made accelerators on Earth. Their exact origin is still under study, and it is believed that they originate from extreme astrophysical phenomena, such as supernovae, black hole jets, or pulsars.

The DAMPE space telescope, launched in December 2015, aims to provide answers regarding the origin and nature of these cosmic rays. This space mission, with the astrophysics group from the Department of Nuclear and Particle Physics (DPNC) at the University of Geneva (UNIGE) being one of its main contributors, has made a crucial breakthrough. Through the analysis of high-precision measurements collected by the telescope, scientists have identified a universal feature in the energy spectra of primary cosmic ray nuclei, ranging from protons to iron.

Laser-plasma accelerators can preserve polarization of Helium-3 ions

Particle accelerators such as those at the European Organization for Nuclear Research (CERN) in Geneva are typically highly complex large-scale devices. In these ring-shaped facilities, which are often several kilometers in length, magnets and radio-frequency cavities are used to accelerate elementary particles. An alternative approach is now emerging: compact laser–plasma accelerators that can be built and operated at a fraction of the cost. These accelerators can achieve acceleration gradients up to around 1,000 times higher than those of conventional accelerators. Researchers at HHU contributed significantly to this development.

A research team led by Prof. Dr. Markus Büscher, a professor of physics at HHU and group leader at the Peter Grünberg Institute in Jülich, presented the current state of research in a review article in Reports on Progress in Physics. In a separate study published in High Power Laser Science and Engineering, they report on one specific aspect of laser–plasma acceleration, namely whether the polarization—that is to say, the collective spin alignment—of accelerated particles is preserved in laser–plasma accelerators.

Why is this relevant? “Spin alignment is crucial to a range of fundamental scientific questions as it influences the interaction between particles,” explains Professor Büscher. “In controlled nuclear fusion, the reaction probability—and thus ultimately the energy produced in the reactor—increases significantly when the spins of the fusing nuclei, the ‘fusion fuel’ so to speak, are aligned in parallel.”

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