Energy News  
ENERGY TECH
Tungsten isotope helps study how to armor future fusion reactors
by Staff Writers
Oak Ridge TN (SPX) Sep 02, 2020

ORNL researchers used natural tungsten (yellow) and enriched tungsten (orange) to trace the erosion, transport and redeposition of tungsten. Tungsten is the leading option to armor the inside of a fusion device.

The inside of future nuclear fusion energy reactors will be among the harshest environments ever produced on Earth. What's strong enough to protect the inside of a fusion reactor from plasma-produced heat fluxes akin to space shuttles reentering Earth's atmosphere?

Zeke Unterberg and his team at the Department of Energy's Oak Ridge National Laboratory are currently working with the leading candidate: tungsten, which has the highest melting point and lowest vapor pressure of all metals on the periodic table, as well as very high tensile strength - properties that make it well-suited to take abuse for long periods of time.

They're focused on understanding how tungsten would work inside a fusion reactor, a device that heats light atoms to temperatures hotter than the sun's core so that they fuse and release energy. Hydrogen gas in a fusion reactor is converted into hydrogen plasma - a state of matter that consists of partially ionized gas - that is then confined in a small region by strong magnetic fields or lasers.

"You don't want to put something in your reactor that only lasts a couple of days," said Unterberg, a senior research scientist in ORNL's Fusion Energy Division. "You want to have sufficient lifetime. We put tungsten in areas where we anticipate there will be very high plasma bombardment."

In 2016, Unterberg and the team began conducting experiments in the tokamak, a fusion reactor that uses magnetic-fields to contain a ring of plasma, at the DIII-D National Fusion Facility, a DOE Office of Science user facility in San Diego.

They wanted to know whether tungsten could be used to armor the tokamak's vacuum chamber - protecting it from rapid destruction caused by the effects of plasma - without heavily contaminating the plasma itself. This contamination, if not sufficiently managed, could ultimately extinguish the fusion reaction.

"We were trying to determine what areas in the chamber would be particularly bad: where the tungsten was most likely to generate impurities that can contaminate the plasma," Unterberg said.

To find that, the researchers used an enriched isotope of tungsten, W-182, along with the unmodified isotope, to trace the erosion, transport and redeposition of tungsten from within the divertor. Looking at the movement of tungsten within the divertor - an area within the vacuum chamber designed to divert plasma and impurities - gave them a clearer picture of how it erodes from surfaces within the tokamak and interacts with the plasma.

The enriched tungsten isotope has the same physical and chemical properties as regular tungsten. The experiments at DIII-D used small metal inserts coated with the enriched isotope placed close to, but not at, the highest heat flux zone, an area in the vessel typically called the divertor far-target region. Separately, at a divertor region with the highest fluxes, the strike-point, researchers used inserts with the unmodified isotope. The remainder of the DIII-D chamber is armored with graphite.

This setup allowed the researchers to collect samples on special probes temporarily inserted in the chamber for measuring impurity flow to and from the vessel armor, which could give them a more precise idea of where the tungsten that had leaked away from the divertor into the chamber had originated.

"Using the enriched isotope gave us a unique fingerprint," Unterberg said.

It was the first such experiment conducted in a fusion device. One goal was to determine the best materials and location for these materials for chamber armoring, while keeping impurities caused by plasma-material interactions largely contained to the divertor and not contaminating the magnet-confined core plasma used to produce fusion.

One complication with the design and operation of divertors is impurity contamination in the plasma caused by edge-localized modes, or ELMs. Some of these fast, high-energy events, akin to solar flares, can damage or destroy vessel components such as divertor plates. The frequency of the ELMs, the times per second these events occur, is an indicator of the amount of energy released from the plasma to the wall.

High-frequency ELMs can release low amounts of plasma per eruption, but if the ELMs are less frequent, the plasma and energy released per eruption is high, with a greater probability for damage. Recent research has looked at ways to control and increase the frequency of ELMs, such as with pellet injection or additional magnetic fields at very small magnitudes.

Unterberg's team found, as they expected, that having the tungsten far from the high-flux strike-point greatly increased the probability of contamination when exposed to low-frequency ELMs that have higher energy content and surface contact per event. Additionally, the team found that this divertor far-target region was more prone to contamination of the scrape-off layer even though it generally has lower fluxes than the strike-point. These seemingly counterintuitive results are being confirmed by ongoing divertor modeling efforts in relation to this project and future experiments on DIII-D.

This project involved a team of experts from across North America, including collaborators from Princeton Plasma Physics Laboratory, Lawrence Livermore National Laboratory, Sandia National Laboratories, ORNL, General Atomics, Auburn University, the University of California at San Diego, the University of Toronto, the University of Tennessee - Knoxville, and the University of Wisconsin-Madison, as it provided a significant tool for plasma-material interaction research. DOE's Office of Science (Fusion Energy Sciences) provided support for the study.

The research could immediately benefit the Joint European Torus, or JET, and ITER, now under construction in Cadarache, France, both of which use tungsten armor for the divertor.

"But we're looking at things beyond ITER and JET - we're looking at the fusion reactors of the future," Unterberg said. "Where is it best to put tungsten, and where should you not put tungsten? Our ultimate goal is to armor our fusion reactors, when they come, in a smart way."

Unterberg said ORNL's unique Stable Isotopes Group, which developed and tested the enriched isotope coating before putting it in a form useful for the experiment, made the research possible. That isotope would not have been available anywhere but from the National Isotope Development Center at ORNL, which maintains a stockpile of almost every element isotopically separated, he said.

"ORNL has unique expertise and particular desires for this type of research," Unterberg said. "We have a long legacy of developing isotopes and using those in all kinds of research in different applications around the world."

In addition, ORNL manages US ITER.

Next, the team will look at how putting tungsten into differently shaped divertors might affect contamination of the core. Different divertor geometries could minimize the effects of plasma-material interactions on the core plasma, they have theorized. Knowing the best shape for a divertor - a necessary component for a magnetic-confined plasma device - would put scientists one step closer to a viable plasma reactor.

"If we, as a society, say we want nuclear energy to happen, and we want to move to the next stage," Unterberg said, "fusion would be the holy grail."

Research paper


Related Links
Oak Ridge National Laboratory
Powering The World in the 21st Century at Energy-Daily.com


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


ENERGY TECH
First results of an upgraded device highlight lithium's value for producing fusion
Plainsboro NJ (SPX) Aug 03, 2020
Lithium, the silvery metal that powers smart phones and helps treat bipolar disorders, could also play a significant role in the worldwide effort to harvest on Earth the safe, clean and virtually limitless fusion energy (link is external) that powers the sun and stars. First results of the extensively upgraded Lithium Tokamak Experiment-Beta (LTX-b) at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL), demonstrate that the major enhancements operate as designed and improve ... read more

Comment using your Disqus, Facebook, Google or Twitter login.



Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

ENERGY TECH
Finnish town offers prizes to turn residents green

Finnish town offers prizes to turn residents green

Russia bristles at proposed EU carbon tax

Sri Lanka rations power after Chinese generator crashes during blackout

ENERGY TECH
The factory of the future, batteries not included

CU scientists create batteries that could make it easier to explore Mars

Russian chemists proposed a new design of flow batteries

Red bricks can be charged, store energy

ENERGY TECH
Offshore wind power now so cheap it could pay money back to consumers

Trust me if you can

Ingeteam's advanced simulation models to ease wind power grid integration

Magnora ASA and Kustvind AB accelerate development of 500 MW offshore wind project in southern Sweden

ENERGY TECH
Raptor Maps Raises $5M for its Solar Lifecycle Management Software

Tandem solar cell world record: New branch in the NREL chart

NREL six-junction solar cell sets two world records for efficiency

3D-printed system speeds up solar cell testing from hours to minutes

ENERGY TECH
Framatome signs contract to provide field instrumentation to Hinkley Point C

US versatile test reactor program chooses Bechtel-led team

After Huawei, spotlight on China's role in UK nuclear power

UAE connects first Arab nuclear plant to power grid

ENERGY TECH
Researchers find that bacteria can produce common component in plastic

New device turns sunlight, CO2, water into carbon-neutral fuel

AFRL awards $1M to first Grand Challenge For Biotechnology

Beyond batteries: Scientists build methanol-powered beetle bot

ENERGY TECH
Libya unity government names new defence officials after protests

Sudan government and rebel groups agree peace deal

Greece, Cyprus, Italy, France to hold military exercises from Wednesday

Turkey's maritime doctrine author has dire warning for France

ENERGY TECH
Fossil leaves prove elevated CO2 triggered greening 23M years ago

China teenage climate warrior fights a lonely battle

Lockdown emissions fall will have 'no effect' on climate

Scientists say COVID-19 recovery plans should include climate change









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.