[jamesr]

Alchemist32 wrote: I just wanted to clarify a few points. Boric acid is not used in reactor water, this would create a major radiation problem from the production of approx 10^18 to 10^20 prompt gamma photons per second. It would also cause major problems regarding the conductivity of the water (causing corrosion). Instead, in some reactors, boric acid is added to the concrete surrounding the core. This boric acid is normal abundance boron since the 20% B-10 is more than sufficient for this purpose.

Unfortunately, the separation of B-10 and B-11 is not done on an industrial scale. It hypothetically could be, it just isn’t. The major use of isotopically enriched boron is in semiconductor doping, where B-11 is used to produce neutron-hardened ICs for the military. A secondary and much smaller use is for B-10 enriched boron compounds utilized in boron neutron capture therapy (BNCT) (I am a professor in this area). B-11 enriched decaborane would be exorbitantly expensive, ~ $10,000 per gram, although, this cost could be brought down to about $5k per gram.

From my masters last year we had several lectures on PWR water chemistry and they went through a number of operating scenarios used in the past and how they have improved the corrosion rates by carefully adjusting the pH, and adding small amounts of things like zinc. But they all use boric acid. Initially all at natural isotopic ratios, but as it stays in there longer the proportion of B10 drops slightly as it is used up.

The pH condition is normally kept at ~7.4 (neutral pH at 300C is 5.71) but varies over the fuel cycle as the concentration of boron is reduced from ~1200ppm to 0 by diluting it as the fuel is used up over an 18month or so period, before refueling again. So it is overall basic, due in part to the lithium, which is carefully controlled and kept at around 2ppm concentration. The large change in boron concentration over a fuel cycle to maintain criticality means it cannot be built into the structure and has to able to be gradually reduced to compensate.

Advanced operating cycles are now using enriched boron of around 30% B10 in order to work with higher enrichment MOX fuels, and longer cycles to achieve higher burn-up rates. This has been done at Gosgen and other Seimens plants since 1999. The B-10 concentration again drops normally during a fuel cycle but is topped up with 98% B-10 solution.

At 1200ppm considering the many tonnes of water in the system this corresponds to several kg of boron in the primary circuit and CVCS (chemical & volume control system) at any one time. So I assumed if they are using kg quantities of B-10 enriched boron for some PWRs, then there must be the equivalent amount of B-11 by-product lying around somewhere.

I don’t doubt the price though – I’m sure they spend millions on the boron systems for PWRs

For BWRs the water chemistry is complicated further due to the concentrating effect of the boiling action. But the principle of the neutron absorption rate having to change over a fuel cycle is still the same.

[jamesr]

Breakable wrote: IMHO “Skepticism and the Scientific Method” is a very important topic.
I dont have much problem with others, but just to put some arguments forward:
ZPE – you need a place to put all the quacks or they will start making up conspiracies.
Also as far as I know a lot of topics we nowadays consider science were pseudo-science once. Some people consider FF to be it.
I for myself am interested in seeing evidence, whenever it comes from.

I completely agree skepticism and scientific method is very important. Indeed it take a critical thinker to consider the pros & cons of Focus Fusion vs conventional magnetic or inertial confinement methods, together with the probability of success.

It is just that I doubt you would threads on forums discussing ITER or NIF that have titles like
– Musings on mysticism
– Scientific proof of the existence of God.
– Mind, Spirit, Science connection?

[jamesr]

Extracting data from neutron detectors is far from trivial, or any electronic device for that matter given the harsh EM pulse given off.

With ordinary hydrogen you wouldn’t get any fusion at all. Even with deuterium the device couldn’t release anything like 30kJ. The size (diameter) of the device was designed for a heavier fill gas (ie boron) – at the moment it has a slightly longer anode to give better results for deuterium, but this will get replaced with a shorter anode for boron operation. Only then will the current be able to get upto the >3MA with a high enough capacitor voltage in order to get any appreciable yield.

Also given the radiation hazard, I doubt they want to be producing high D-D (with a some D-T secondary) fusion neutron counts. Otherwise they’ll end up activating the whole device and be unable to work on it by hand without extra precautions.

[jamesr]

I second that.

Also I would like to see the “Skepticism and the Scientific Method” and in particular the ZPE category removed completely. Although there are a number of interesting discussions under those sections, I think even the mention on the site (and so search engine indexable) of topics like consciousness, mysticism, zero point energy etc. lowers the tone, and reduces the credibility of the science and technology we are trying to promote.

The sticky note could direct people to other sites not affiliated with us to carry on those kind of discussions.

[jamesr]

Welcome to the forum!

I don’t have any inside knowledge to answer your question directly, but I suspect efforts are currently focused on setting up, calibrating and reducing the noise on all the diagnostics. Its pointless trying to tweak anything else to improve the performance until you have good measurments of, for example, ion temperature.

Also I gather there is also a lot of work going into getting ready to reconfigure the device to work with decaborane, and all the headaches that go with that.

[jamesr]

Brian H wrote:
I may be wrong, but it is my impression that solenoids are used almost ubiquitously, without noticeable heat issues. I’d have assumed that the resistance of the coil wiring is low enough to minimize that.

If you think that we want to be getting roughly the same power induced in the rogowski coil as is put through the anode at the start (with the excess energy output coming from the x-rays), then the resistive heating issues could be the same order of magnitude as for the anode.

I suspect though since the pulse from the ion beam will be much shorter in duration than the current flow in the anode, the skin effect would be even more pronounced. If the induced voltage is much higher then the current, an therefore heating losses, will be correspondingly lower. There will be a trade off between having a large minor radius to increase the voltage, and a small enough minor radius in comparison to the major radius of the coil to reduce its inductance and so response to the high frequency pulse.

See wikipedia for the relavent formulae.

[jamesr]

I would expect the ion beam to have an angular spread of at least a few degrees. However since the Rogowski coil (NB which is a coiled-coil so not technically a solenoid) will just be slowing down the ions in the direction along the beam, as it slows the beam will spread out further. Until all the parallel motion is extracted from the ions, or they collides with the edge.

The perpendicular ion velocity also increases due to the like charges repelling. So you want the coil long enough & with enough turns to extract enough energy, before the beam blows up significantly. However I suspect you want it short enough that you can let it expand and dissipate the perpendicular component of its energy once safely out the other side.

[jamesr]

Rezwan wrote:

Separating Boron into B-10 & B-11 is done on an industrial scale already for conventional nuclear plants. I’m not sure what the cost is but it shouldn’t be significant in the whole scheme of things.

Do you have any links on this? The process, cost and safety concerns?

I think normally it is done by ion exchange chromatography. Here are a few links
Musashi et al, Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution (2008)
Song et al, Advances in boron-10 isotope separation by chemical exchange distillation (2009)

If you can’t access the paper directly here’s an extract where he discusses the history of boron separation (I’m useless at chemistry so don’t ask me what it all means!):

The separation of B-10 was started during World War II. Aether was originally selected as the donor ([Palko and Drury, 1961a], [Palko and Drury, 1961b], [Palko and Drury, 1964] and [Saxena et al., 1961]) and the process condition was: a glass distillation column with a height of 4 m and a diameter of 19 mm, and packing Dixon ring of 1.6 mm × 1.6 mm were adopted. The operation temperature was 70 °C and the pressure was 2.7 kPa at the top and 4.0 kPa at the bottom. The operation cycle lasted 88 days and the yield of B-10 was 2 kg/year with a mass purity of 83%. However, due to the irreversible decomposition of (C2H5)2O·BF3, the decomposition rate of the feed was 12% per day. Higher temperature (70 °C) and high vacuum were required in this process, which consequently limited the production capacity.

Later, aether was replaced with ether and the industrial equipment which can yield 300 kg B-10 (95%) per year was built (Conn and Wolf, 1958). The process condition was as follows: 9 cascaded columns made of Monel steel were adopted. The diameters of the first 3, the second 3 and the final 3 columns were 457.2 mm, 304.8 mm and 152.4 mm respectively. The columns had an average height of 8.33 m and were packed with Stedman Packing. The operation pressures and temperatures were 20 kPa/90 °C at the top and 38.7 kPa/104 °C at the bottom. Compared with the former donor aether, although the irreversible decomposition still existed, the decomposition rate of the feed was only 1.2% per day and the vacuum was allowed to be ten times lower. Production yield increased obviously, yet a certain degree of vacuum was still necessary.

At present, anisole, instead of ether, is widely used in the production of B-10. Compared with ether, anisole has a higher single stage separation coefficient. The process condition is as follows: the whole apparatus consists of four parts: the exchange column, the decomposer column, the recombination device and the solvent purification tank. The copper exchange column is 81.3 m high and operates at 25 °C and normal pressure. The decomposition rate decreases remarkably to only 0.01% in every operation circle.

Katalnikov (Frank, 1995) explored the kinetics and thermodynamics in the separation of B isotopes by chemical exchange distillation using complex anisole, and demonstrated two ways to improve the process: (1) operate at a high pressure so that the capacity of the column would be increased and the kinetics would be improved and (2) apply ideal temperature gradient technology to optimize the separation process. In the past few years, Weijiang Zhang, et al. ([Jiang et al., 2007], [Han et al., 2007], [Han et al., 2006], [Wang et al., 2006] and Yu et al., 2005 J.Y. Yu et al., A Mathematical model in separation of boron isotopes by chemical exchange reaction method, J. Isotopes 18 (4) (2005), pp. 216–219 196.[Yu et al., 2005]) experimentally studied problems such as decomposition reaction and evaluation of donors in chemical exchange distillation. Modeling and simulation were also carried out by them to illustrate and optimize the separation process, which provide an effective way for further studies.

Here is a company that does it currently: Ceradyne Inc

[jamesr]

Aeronaut wrote:
That was my understanding- a metal or plastic water tank containing a 1m (distilled?)water shield, covered by 10cm of boron (type unspecified), covered by 2cm of lead or boronated polyethylene. We discussed this with Eric and Rematog around March of ’09 iirc. Searching the site for boronated polyethylene may bring up the thread.

Sounds familiar… I found this reference from Eric from way back in 2006 https://focusfusion.org/index.php/forums/viewthread/91/#346

[jamesr]

Brian H wrote:
What is the penetration of the gamma? Assuming the B10 to be an external shell around the water, would it be a danger in the surrounding service space? Since the =>12s decay time you give for the B10 is so brief, I would assume that the gamma would be produced only while the core was active, and a short period afterwards (a few minutes to subside to insignificant levels).

The B10 would normally dissolved in the water as boric acid not as a shell An alternative to water could be borated polyethene sheets, as they wouldn’t need to be as thick to slow down the neutrons. The decay time is 1ps not 12s ie. pretty instantaneous.
The low energy gammas do need some additional shielding, but a steel water tank plus a few inches of lead, or a foot of high density concrete should be sufficient.

[jamesr]

I would expect the B10 to be dissolved in the water sheilding as boric acid. So any neutrons produced are slowed down (or moderated in nuclear terminology) to thermal speeds. They then, while bouncing around in the water get captured by a B10. The resulting lithium will not travel very far in water, as it is charged and slow down within a 10-100 nm. Heating up the water a little in the process (similarly for the helium). The lithium will react with the water producing lithium hydroxide. The boric acid and lithium hydroxide can then react, as any acid and base do leaving a salt, lithium borate in this case. If the concentration of the salt gets too high it can precipitate out – taking some of the boron out of the bulk of the water and reducing the chance of neutron capture slightly.

However, given the low levels of neutrons produced, I wouldn’t expect the shielding water to have to be filtered & topped up with fresh boron for at least 5 years if not the life of a reactor.

Separating Boron into B-10 & B-11 is done on an industrial scale already for conventional nuclear plants. I’m not sure what the cost is but it shouldn’t be significant in the whole scheme of things.

[jamesr]

When B10 absorbs a thermal neutron it doesn’t stay as B11. It is formed in an excited unstable state which decays in ~10^-12s to He-4 (1.47MeV) & Li-7 (0.84MeV) and a gamma ray photon (0.48MeV)

[jamesr]

Henning wrote: I just read on Wikipedia:

The physical characteristics of decaborane(14) resemble those of the organic compounds, such as naphthalene and anthracene, in that it can be sublimed under vacuum at moderate temperatures. Sublimation is the common method of purification.

So as we are working in a vacuum, possibly heating isn’t required at all.

I think at the 10-40torr or so pressure FoFu will be operating you’ll need to warm it slightly to sublimate it. You also want the rest of the chamber warmed, as it would condense on room temperature surfaces & leave residues everywhere.

[jamesr]

Tulse wrote:

would the oxygen or the sodium in borax create problems in the plasmoid?

I would presume that reactions with those elements would not be aneutronic.

Their cross-sections for fusion are pretty negligible, even if you could get it hot enough so no need to worry about producing neutrons. But given their high Z of 8 & 11 respectively, even a few percent of them in the plasma would pollute it to the extent that it would radiate too much to achieve a sufficient temperature for the boron to fuse.

[jamesr]

mchargue wrote:

My understanding is that we’re validating McNally’s 1975 observation that bremstrahlung can be reduced by raising field strength, which has a lot to do with why high input currents are critical to reaching unity. This was mentioned in the GoogleTalks and in the patent, if I remember correctly. At this point it’s a theory which seems to be proving out experimentally, but I may be wrong on that- the relative motion of ions and electrons are beyond my direct understanding of the process.

That’s kinda’ what I was thinking, which was why I mentioned it. It seemed to be ‘supporting evidence’ for the contentions made in the patent, and in the talk. I didn’t describe as well, though.

And my point, not explained clearly either, was that although they phenomena may sound similar, in that they involve consideration of electrons & ions separately. The effect of supersonic plasma on a dipole field (whether on laboratory or astrophysical scale), and McNally’s observed effect of bremsstrahlung are entirely different processes, and so is in no way ‘supporting evidence’.

The formation of a bow shock & magnetopause of a low density plasma around a dipole field, and the subsequent affect of the motion of ions & electrons around it are primarily collisionless processes. The particle motions are governed by the fields and in turn effect the field as per Maxwell’s equations, but they very rarely come close enough to each other to have binary collisions. NB. this kind of collisionless shock is also entirely different from supersonic shocks in air which is a purely collisional effect.

Bremsstrahlung is a collisional process where electrons must pass close enough to an ion to undergo a large angle scatter. The proposed effect in a large field is that the electron larmor radius is of the order of it’s de Broglie wavelength and so the electron’s energy is quantized, restricting the scattering energy change and so radiative process.

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