A question about fusion

a reply to: TEOTWAWKIAIFF

Thank you.

-MM

Here is an update on how they plan on containment in a tokamak (this is being proven in China at their EAST reactor)

"We demonstrated a continuous, recirculating lithium flow for several hours in a tokamak," said Rajesh Maingi, head of boundary physics research and plasma-facing components at PPPL. "We also demonstrated that the flowing liquid lithium surface was compatible with high plasma confinement and with reduced recycling of the hydrogen isotope deuterium to an extent previously achieved only with evaporated lithium coatings. The recirculating lithium provides a fresh, clean surface that can be used for long-lasting plasma discharges."

Posted at EurekAlert.org - PPPL scientists help test innovative device to improve efficiency of tokamaks

Sounds like they are using part of the reactors own magnetic containment system to keep the liquid lithium smooshed against the side of the reactor. They let it drip down the inside of the containment walls where it is recirculated to the top for another run through!

That is even neater than I imagined!

a reply to: TEOTWAWKIAIFF

Plus, some of the lithium is fissioned into tritium by neutron flux, so it makes part of the fuel.

originally posted by: Bedlam
a reply to: TEOTWAWKIAIFF

Plus, some of the lithium is fissioned into tritium by neutron flux, so it makes part of the fuel.

I have nothing to add other than I've always considered the term "neutron flux" super cool. Pepper that unto your conversation and people will LISTEN (or back away gently)

Neutron flux

There has been a newsletter release from W7-X.

They created a plasma of 100 million degrees Celsius lasting up to six seconds. The total number of plasma shots was 906 with hydrogen plasma.

Link: Max Plank Institute for Plasmaphysics, April 2016 - Wendelstein 7-X Newsletter

There was a talk given by former American River Current professor about ITER.

Much of the talk centered on the fourth state of matter, plasma, and its role in nuclear fusion.

“Understanding (plasma behavior) has turned out to be a really ugly problem, because in math terms, it turns out to be a set of highly non linear equations. How do we solve those? We can’t,” [Professor Chuck] Hunt said.

Source: The American River Current ARC professor presents on international fusion reactor

Non-linear equations are math expression with extremely difficult forms and the variables end up in power functions (like the x in x^2) but think of strings of multiple equations each relying on some power or returning some power! So the quip is well founded--you cannot solve the equations to a mathematical satisfactory state to explain nuclear fusion plasma. In some ways it is a best guess and an engineering feat--you build it so it works even if you cannot model it in math! Amazing if you stop and think about it.

[ETA: Neutron flux! : p]

Uh-oh. This does not give me warm fuzzy feelings.

Focus fusion is funding raising for each test firing of its pulse fusion system. It will take about $150,000 to fire 200 shots. This is $750 per shot.

Shots at present are cleaning remaining impurities from the machine and it may take quite a few more, 100-200, to get to the purity level they need.

If successful with their research and then commercialization they will achieve commercial nuclear fusion at the cost of $400,000-1 million for a 5 megawatt generator that would produce power for about 0.3 cents per kwh instead of 6 cents per kwh for coal and natural gas.
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If LPP Fusion can’t get more money in soon, they will have to cut back or even stop their experiment and concentrate everything on fundraising.
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LPP's mission is the development of a new environmentally safe, clean, cheap and unlimited energy source based on hydrogen-boron fusion and the dense plasma focus device, a combination we call Focus Fusion

Source: NextBigFuture.com LPP Fusion needs some crowdfunding help to keep tests going and reach a better funding milestone

Aneutronic fusion would be welcomed! They have to spend more time up front doing all the engineering so it is a long road (and higher temperatures) but the pay-off is a non-radioactive shell. I wish I had a couple hundred thousand lying around! This is the only example I know of trying the hard route right off the bat. They, like any other fusion device, fire test shots to clean the insides of the device. All those shots cost money. And they still need to upgrade their electrodes.

The article (nbf) has link to donate.

An article on controlling a fusion device is up on phys.org

Phys.org - Controlling ITER with fuelers, ticklers, and terminators

Oddly enough, they shoot frozen deuterium-tritium pellets into ITER! You would think that is counter productive since you are trying to heat the hydrogen plasma up over 100 million degrees C.

The pellets are much more efficient at fueling the fusion plasma because they can penetrate fairly deep into the hot plasma before being ablated and ionized into additional plasma," explained Larry Baylor of ORNL's Plasma Technology and Applications Group.

"The alternative method of injecting gas that is primarily used in today's smaller devices will not add fuel efficiently in ITER because of its large size and high magnetic field."

It is because the tokomak is so huge they need to use frozen fuel pellets! About the pellets, a little later in the article they say,

[T]he fuel pellets are a little larger than .177-caliber air rifle pellets. To keep ITER going, the system will need to inject about four each second, or 15,000 an hour.

The same system produces the tickler pellets, which are about four times smaller than the fuel pellets. The tickler pellets are designed to prevent a fusion reactor's version of damaging solar flares—bits of plasma that peal off and hit the plasma-facing surfaces on the inner wall of the vessel. They do this by creating a series of smaller flares to diffuse the built-up energy.

Even with magnetic confinement they are worried about the hot plasma touching the surface. When the whole thing starts to get unruly they have "kill shots" of frozen neon to halt the reaction. Explaining how that is accomplished,

The tubes that carry the terminator pellets into the plasma will have a sharp bend, causing the pellets to shatter just before they reach the plasma and ensuring that the frozen neon is injected as a spray. The spray will stop the fusion reactions and cool the plasma, turning it back into a gas.

The article states the people that make the pellets have been researching this method for 35 years! The whole effort of nuclear fusion has been going on for some time. It is nice to know this information. Seems each fusion device approaches things a bit differently which I think only increases the chances of success!

[ETA: article, Sept. 2015, so I am behind on my reading!]

Two fusion device news stories! Bad news first.

ITER chief Bernard Bigot said [the reactor] under construction in Cadarache, France, would not see the first test of its super-heated plasma before 2025 and its first full-power fusion not before 2035.

"The previous planning, which foresaw first plasma by 2020 and full fusion by 2023, was totally unrealistic," said Bigot.

Source: Business Insider, May 2, 2016 - 'Totally Unrealistic': The international nuclear fusion prototype is a decade late and 4 billion over budget (Euros)

Good news!

[W]e are, again, making the appropriate amount of investment today,” [Rob] Weiss said. “It’s basically at this stage we are increasing the temperature at which the fusion could occur, and our process for containing the reaction, and we will continue to elevate the level of the temperature and testing the containment theory.”

Weiss also confirmed the team has achieved “initial plasma,” an important early step for the reactor.

Source: DefenseNews.com - Lockheed Still Supporting Portable Nuclear Generator

This is almost the first news from Lockheed Martin concerning their compact fusion reactor (CFR)! The last news (I know of) was from a speech given at MIT where the types of confinement were revealed. That was back in October 2015. They are being funded that is good news! They created a plasma in the device! That is better news!

Like all fusion devices, test plasmas are run through for testing and calibration of monitoring instruments. The non-reactive plasma also cleans the interior of the device.

Last August the company said it had succeeded in keeping a high-energy plasma stable in the vessel for five milliseconds—an infinitesimal instant of time, but enough to show that it could be done indefinitely. Since then that time has been upped to 11.5 milliseconds.

The next challenge is to make the plasma hot enough for the fusion reaction to generate more energy than is needed to run it. How hot? Something like 3 billion °C, or 200 times the temperature of the sun’s core. No metal on Earth could withstand such a temperature. But because the roiling ball of gas is confined by a powerful electromagnetic field, it doesn’t touch the interior of the machine.

Source: NextBigFuture, May 20, 2016 - Nuclear Fusion company(sic) Tri-alpha Energy has raised $500 million to make a prototype reactor in the 2020s

MM, how's that for hot! There is a good review of Tri-alpha energy’s machine at the link. They are doing a complete conversion of hydrogen and boron-11 so they have to heat up their plasma to 3 billion °C. They too keep the plasma from touching the walls using magnetic confinement. Since there is no neutron created by the fusion reaction they do not need to have a thermal blanket/heat converters. 11.5 ms is also nice to know since TAE does not run around shouting about their work that often.

a reply to: Bedlam

Princeton Plasma Physics Laboratory has a news story of their upgrade liquid lithium wall protectors.

[A]n innovative device used to test the liquid metal as a first wall that enhances plasma performance. The first wall material faces the plasma.
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The value of lithium as a first-wall material comes from its ability to sponge up particles that stray from the core of the plasma and keep them from recycling back and cooling down the edge and then the core. Lithium is a highly reactive material that combines with other elements and doesn’t let go.

In LTX experiments, researchers use an electron beam to evaporate a pool of liquid lithium at the base of the tokamak. The evaporated metal then coats the shells. Keeping the temperature of the shells above the melting point of lithium sustains its liquid state.

Source: PPL.gov, May 10, 2016 - A major upgrade of the Lithium Tokamak Experiment at PPPL will explore liquid lithium as a first wall for hot plasmas

(MM how's that for an answer to your OP?) Seems like a great approach to keep the reactor's walls from melting! Evaporate lithium to coat the walls. Heck, if some gets in the plasma it does not hurt the plasma either! Generate a tritium particle?, come on in and enjoy the plasma party! Excess heat can be exchanged before starting at the pool to be evaporated again.

And they are installing a neutral beam injector while they are performing the lithium recirculation upgrade. It is on loan from Tri-alpha Energy!


[ETA: The technical name is "liquid lithium limiter" which does not appear in news article]

Called a "liquid lithium limiter," the device has circulated the protective liquid metal within the walls of China's Experimental Advanced Superconducting Tokamak (EAST) and kept the plasma from cooling down and halting fusion reactions. The journal Nuclear Fusion published results of the experiment in March 2016.
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"We demonstrated a continuous, recirculating lithium flow for several hours in a tokamak," said Rajesh Maingi, head of boundary physics research and plasma-facing components at PPPL. "We also demonstrated that the flowing liquid lithium surface was compatible with high plasma confinement and with reduced recycling of the hydrogen isotope deuterium to an extent previously achieved only with evaporated lithium coatings. The recirculating lithium provides a fresh, clean surface that can be used for long-lasting plasma discharges."

Source: Phys.org, April 6, 2016 - PPPL scientists help test innovative device to improve efficiency of tokamaks

So missed it in previous post. The correct answer is: deuterium. So the high energy neutron created from the D-T fusion reaction goes flying off into the liquid lithium limiter and creates another deuterium particle that then is trapped back in the plasma by the magnetic confinement. The excess heat is in the lithium, the walls of the reactor are kept safe, the liquid lithium pools back on the bottom ready to be vaporized again (and/or heat exchanged). They only need to add a little more tritium to the plasma (and some heat) to keep a continuous, steady state, plasma.

I am on phys.org all the time! Not sure how I missed this article (shakes head). Oh well... it is nice to hear from the main scientist on their developments. This is pretty cool science!

Six weeks after resuming firing, FF-1’s fusion yield reached 0.25 Joules on May 23, 2016 a nearly 50% increase over the highest-yield shot previously achieved with this device. This increase, confirmed by a second shot on May 24, provides the most concrete evidence yet that our continuing effort to reduce impurities in FF-1 increases fusion yield.
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These shots are a record not just for LPP Fusion. For all researchers working with this type of device, a dense plasma focus or DPF, their May 23 shot is 50% more than any previous shot at this peak current of 1.1 MA (million amps) and double the previous record for their total input energy of 60 kJ. This is important, as this shows they are moving back towards the steep scaling law that predicts energy increasing as the fourth power of the peak current. In previous work, this scaling curve has leveled off for current over 1 MA.

Source: NextBigFuture.com - June 05, 2016, Despite rocky start and funding for only about 25 shots - LPP Fusion yield is up 50% to a record for any dense plasma focus device

There is a great graph in the article showing where this device places among other fusion devices. It is now behind China's EAST and tied with W7-X and JET devices for plasma heat and density. They will be doing the more difficult boron-11 reaction so their temperature has to be higher. Their shots were of deuterium.

Props to Lawrenceville Plasma Physics team! This is a cool achievement. They need to upgrade their heating tip which is going to cost about quarter million US. This device could jump the others and show net energy!