Lawrence Livermore claims that the combustion of nuclear fusion is sort of balanced – cotton wool with that?

Guest contribution by Eric Worrall

Inertial confinement fusion researchers have claimed that experimental nuclear fusion combustion was close to break-even, where the energy generated by the fusion reaction was comparable to the energy injected to initiate the combustion.

National Ignition Facility experiment puts researchers on the threshold of fusion ignition

On August 8, 2021, an experiment at the National Ignition Facility (NIF) of the Lawrence Livermore National Laboratory (LLNL) made a significant step towards ignition. Achieve a yield greater than 1.3 megajoules (MJ). This advancement brings researchers to the threshold of fusion ignition, a key goal of the NIF, and opens up access to a new experimental regime.

The experiment was made possible by focusing laser light from NIF – the size of three soccer fields – onto a target the size of a BB that creates a hotspot the diameter of a human hair and generates more than 10 quadrillion watts of fusion power for 100 trillionths of a second .

“These exceptional results from NIF advance the science that NNSA relies on to modernize our nuclear weapons and manufacturing and to open new avenues of research,” said Jill Hruby, DOE Undersecretary for Nuclear Safety and NNSA Administrator.

The central task of NIF is to provide experimental knowledge and data for the science-based Stockpile Stewardship program of the NNSA. Fusion ignition experiments are an important part of this effort. They provide data on an important experimental regime that is extremely difficult to access, expand our understanding of the basic processes of fusion ignition and combustion, and improve our simulation tools to aid inventory management. Fusion ignition is also an important gateway to achieving high fusion yields in the future.

“This result marks a historic advance in inertial confinement fusion research and opens up a fundamentally new regime for the exploration and advancement of our critical national security missions. It is also a testament to the innovation, ingenuity, dedication and courage of this team and the many researchers in the field over the decades who have steadfastly pursued this goal, ”said Kim Budil, Director of the LLNL. “To me, it shows one of the most important roles the National Labs play – our relentless commitment to address the greatest and most important scientific challenges and to find solutions where the obstacles might keep others away.”

While a full scientific interpretation of these results will be provided through the peer-reviewed journal / conference process, the initial analysis shows an 8-fold improvement over the experiments conducted in Spring 2021 and a 25-fold increase over the record yield from NIF in 2018.

“Experimental access to thermonuclear combustion in the laboratory is the culmination of decades of scientific and technological work spanning nearly 50 years,” said Thomas Mason, Los Alamos National Laboratory Director. “This enables experiments that test theory and simulation in the area of ​​high energy density more rigorously than ever before and enable fundamental achievements in applied science and technology.”

The experiment built on several advances gained from knowledge the NIF team had developed over the past few years, including new diagnostics; Improvements to target manufacturing in the cavity, capsule shell, and fill tube; improved laser precision; and design changes to increase the energy coupled to the implosion and the compression of the implosion.

“This significant advance has only been made possible through the continued support, dedication and hard work of a very large team over many decades, including those who contribute to the efforts of the LLNL, industrial and academic partners, and our staff at Los Alamos National Laboratory and Sandia have supported National Laboratories, the Laboratory for Laser Energetics and General Atomics at the University of Rochester, ”said Mark Herrmann, LLNL associate program director for Fundamental Weapons Physics. “This result builds on the work and achievements of the entire team, including the people who have followed inertial fusion since the early days of our lab. They too should share in the enthusiasm for this success. “

Looking ahead, access to this new experimental system will inspire new avenues for research and the opportunity to compare modeling used to understand proximity to ignition. Retry plans are well underway, although it will take several months to complete.

Source: https://www.llnl.gov/news/national-ignition-facility-experiment-puts-researchers-threshold-fusion-ignition

I find inertial confinement fusion exciting because it is in principle possible to reduce inertial confinement to an affordable size, unlike magnetic confinement fusion.

The gigantic international magnetic confinement ITER tokamak currently being built in France represents a kind of brute force approach to viable nuclear fusion. The heat generated by a nuclear fusion reaction depends on the volume of the plasma, while the heat loss depends on the surface. The simple geometry dictates that if you make the volume of plasma really large, the heat generated by such a large volume of the melting plasma is more likely to overcome the surface losses, resulting in a self-sustaining fusion reaction.

My concern with this magnetic containment approach is that even if ITER is successful, the sheer size and cost of the precision engineered reactor vessel will be a significant barrier to adoption. Fusion reactors, each costing $ 50 billion and taking decades to build, are unlikely to make a significant contribution to the global energy mix as long as cheaper options are available.

There is also a real danger that after all of these billions of dollars in spending and thousands of years of effort, the most expensive components of ITER will simply crumble under the radiation explosion of an ongoing fusion fire. Deuterium-tritium fusion creates a blizzard of hot neutrons that are more than capable of causing physical structural damage to anything near the plasma. The search for building materials that can survive such a hostile environment without crumbling to dust is ongoing.

The break-even burn facility at Lawrence Livermore is large, but much cheaper than the ITER facility.

Lawrence Livermore still has a long way to go to prove that inertial confinement is a viable way of connecting an operational nuclear fusion reactor to the national grid. Although the energy produced was comparable to the energy used to initiate the combustion, the lasers that used that energy are not 100% efficient. The total energy expended to conduct the experiment probably far exceeded the fusion yield.

An inertial confinement fusion generator would economically have to perform thousands of burns per day rather than a single exciting experimental burn. And, of course, we still don’t know how much a net energy producing inertial confinement fusion reactor would cost even if such a thing were possible.

Correction (EW): h / t Eric Lerner, corrected the link and the story – I accidentally copied into an old story.

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