Tungsten Samples Pass Another Test

[DerekShannon]

From LPP’s December 30th, 2013 report, original news item here:

Tungsten Samples Pass Another Test

LPP’s plans for greatly increasing density and cutting impurities in the plasma depend on substituting tungsten electrodes for the present silver-plated copper ones. Since the tungsten electrodes are expensive and have a lead time of three months, LPP’s team wanted to ensure that the prospective supplier, Tungsten Heavy Powder ,could provide material that would easily withstand the condition in the FF-1 device. In the latest tests, an impendent testing company measured the impact strength of tungsten samples from the supplier. Since tungsten is a brittle material, LPP need to make sure that the tungsten could withstand the sudden mechanical stress that occurs when the magnetic fields in the device, generated by million-amp currents, push on the electrodes.

The two samples passed the test with flying colors, exhibiting an impact tight of 25 kJ/m2, far above the impact energy expected in FF-1, even at its peak planed current of 2.8 MA. After one further test for tensile strength, LPP expects to order the tungsten electrodes in early January, and begin experiments with them in April, 2014.

UPDATE JANUARY 28, 2014: The final tungsten tensile test was fine, and the raw material (blank to be machined) has been ordered.

[JimmyT]

Might I ask how much this electrode will weigh? When we get to the point where these are being produced by the hundreds of thousands; is the world tungsten supply going to provide any bottleneck?

[Tulse]

I believe the tungsten is just for the current round of tests. The intent is to make the production electrodes out of beryllium, as it is relatively transparent to x-rays and thus won’t heat up as much and absorb energy that would be captured by the “onion” and produce power.

[zapkitty]

Tulse wrote: I believe the tungsten is just for the current round of tests. The intent is to make the production electrodes out of beryllium, as it is relatively transparent to x-rays and thus won’t heat up as much and absorb energy that would be captured by the “onion” and produce power.

Yep, but the more immediate concern would be the x-rays adding even more heat to an already serious, but solvable, electrode cooling problem.

So using tungsten or any other high-z material for the electrodes in a [em]production[/em] machine would be a recipe for deep-fried fofu.

Tungsten is needed for the intermediate stages of testing, though, as it can take quite a bit more abuse from the researchers as they figure out how to build one of these things 🙂

[Tulse]

And, to address the spirit of the original question, the annual production of beryllium in 2011 was 400 metric tons. (Interestingly, that source also indicates that production may increase to meets the needs of ITER, so yet another fusion connection.)

[JimmyT]

Are you sure about this? I believe that only the central electrode is to be made of Be. The plasmoid is actually inside a dimple in the central electrode for most (All?) of it’s life. Therefore high x-ray or gama ray absorption is of paramount importance there. Also the thin cross section of the outer electrodes will not avail them to cooling as readily as the central electrode.

While I think the outer electrodes will be made of tungsten in the production models as well as this test model, they will be shorter. So will weigh a bit less. And that was my question. How much does this and production model’s tungsten electrode weigh?

Maybe Eric needs to weigh in on this to get a definitive answer.

[DerekShannon]

The volume of the finished piece will be ~2026cm^3, which at our measured density (of a sample actually sent from our supplier) was 19.23g/cm^3. So the mass will be ~38.96kg.

Tulse and ZapKitty are correct, however, that production electrodes would be made from beryllium, which seems to be in even shorter supply than W–It should be the actual bottleneck in future FoFu energy generation, but no real reason production can’t be increased. For the experiment, we do anticipate needing a beryllium anode, and are still crunching the numbers to determine whether a beryllium cathode is necessary.

[zapkitty]

… and a stronger cathode redesign, such as this one mentioned in the July 15 2013 LPP report, might also be more amenable to cooling solutions than the current array of cylinders.

Attached files

[Joeviocoe]

If Beryllium electrodes need to be replaced at regular maintenance intervals in a production machine…. would their costs (energy and money) be high enough to consider the material as “fuel”?

What interval would a replacement electrode be needed?
Monthly?
For cleaning or refurbishment or complete replacement?
Would the electrodes be recycleable?
If recycleable, what percentage is recycled? (I assume 99% would be recycleable since Beryllium is not part of the reaction)

Worst case (assuming monthly replacement without recycling electrodes):
A 5MW reactor will produce 700 MWh of electricity each month, but consume 40 kg of Beryllium…
for 17.5 MWh
Fission gets 44 MWh electrical per kg of natural Uranium

Is this a problem we will have to face?

[Henning]

The Beryllium itself will not vanish. At most it will be distributed around the vacuum chamber, vacuum pump, exhaust (where it should be filtered out). The electrodes need to be replaced because they don’t have the perfect shape anymore, so reactions don’t deliver enough energy anymore. Melting them and recasting (or re-3D-ing) is all you need.

[zapkitty]

The beryllium is to be recycled into new electrodes.

In fact I can’t think of anything in an FF unit that can’t be reused or recycled.

Component recycling and reusability shows an additional way that the FF unit’s lack of radioactive waste gives it a major advantage over all fission and D-T fusion plants.

[Tulse]

Joeviocoe wrote: Worst case (assuming monthly replacement without recycling electrodes):
A 5MW reactor will produce 700 MWh of electricity each month, but consume 40 kg of Beryllium..

I very much doubt the electrodes will evaporate over a kilo of beryllium a day into the chamber.

[Joeviocoe]

zapkitty wrote: The beryllium is to be recycled into new electrodes.

In fact I can’t think of anything in an FF unit that can’t be reused or recycled.

Component recycling and reusability shows an additional way that the FF unit’s lack of radioactive waste gives it a major advantage over all fission and D-T fusion plants.

Awesome! 🙂 thank you.

I just needed good answers to the inevitable accusations if/when this goes really public.
Like when Electric Vehicles sparked accusations that they were just trading Petroleum supply issues with Lithium Supply issues.

[Rownolds]

Zapkitty’s picture of the cathode has a smaller capture profile for the x-rays than the anode, so it will heat less, as well as being farther from where the x-rays are produced. (Most of the x-rays will go through the open spaces).

[DerekShannon]

From the February 28th, 2014 news item located here (click for pic!).

Tungsten electrodes are on their way with improved anode design

The tungsten electrodes needed for LPP’s next set of experiments are rolling forward. The electrodes are needed to eliminate impurities, and cleaner plasma is expected to raise density and yield in the tiny plasmoids where fusion reactions take place. They are on track to be installed by mid-May. The tungsten blank for the cathode (the larger outer electrode) has been completed by Tungsten Heavy Powder and is being shipped to New Jersey. There another company, New Jersey Precision Technology, will machine the block into the exact shape required, a complex process expected to take about 10 weeks.

In the meantime, LPP’s research team decided that the tungsten anode needed an improved design. Calculations by Chief Scientist Eric Lerner indicated that the highest current anticipated with FF-1 will be 2.8 Mega-Amperes, about twice the highest yet achieved. Lerner’s calculations showed this high current could cause arcing at the joint between the anode and its steel base. So the anode was redesigned into a plate-and-cylinder combination shape so that the anode, like the cathode, will connect to the rest of the circuit outside the vacuum chamber. Not only will this design eliminate any possibility of plasma impurities from arcing, but by spreading the current at the join out into a larger diameter, it will eliminate any arcing at all, even at the highest currents. LPP Consultant John Thompson and LPP Board of Advisors member Rudy Frisch helped with the anode design and the corresponding design of a “ring of steel” that will apply even pressure to the anode connection, ensuring no arcing. With the re-design, the anode, too, is now being manufactured in time for May installation.

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