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Comment Re:sunfire / in my stellerator / makes me... happy (Score 1) 97

Fast neutron cross scattering sections in the couple MeV range barely vary over more than the range of 1-10 barns

1-10 barns is, of course, by definition, an order of magnitude. There is a massive difference between 10 barns and 1 barn. Tenfold, to be precise. ;)

More to the point, you can't just combine all cross sections like that. The energy imparted from an elastic collision isn't the same as from an inelastic collsiion, which isn't the same as an (n, gamma), and so forth. Elastic collisions are particularly low energy, particularly the higher Z the target. Taking them out of the equation yields much greater differences between materials in the range of a couple MeV. The upper end of the neutron energies are "somewhat" similar (up to about one order of magnitude), but down below 6 or 7 MeV or so there's quite a few orders of magnitude difference.

Likewise, total cross sections have no bearing on the accumulation of impurities in the material. The particular cross sections are relevant not only in terms of reaction rate, but also what sort of impurities you tend to accumulate and what effect they have on the properties of the material. Which of course varies greatly depending on what exactly they are.

Integration of annealing cycles into blanket design is not brought up enough in some design studies, but is a consideration to help

It's not a side issue, it's a fundamental issue to the design of a material designed for high temperature operation under a high neutron flux.

Blanket design is extremely constrained by tritium breeder ratio to ensure more tritium is produced than used, which squeezes volume allowed to be used by coolant, ... but they have much lower neutron flux to worry about. Gen 4 reactor designs are in the 500-1000 C temperature range, exceeding in some cases what is thought reasonable for fusion blanket design. ... Blanket replacement is considerably more complex than fuel replacement in a fission reactor

Perhaps they've been heading in a different direction since I was last reading on the topic, but I was under the impression that a prime blanket material under consideration was FLiBe. Which operates in a temperature range of 459-1430C, and is its own coolant. That doesn't change what the first wall has to tolerate, but as for the blanket itself, you have no "structural properties" to maintain, and cooling is only limited by the speed that you can cycle it.

The last paper I read on the subject also suggested that for breeding purposes one needs not only beryllium (they were reporting really poor results with high-Z multipliers), but the optimum ratio (to my surprise) worked out to be significantly more beryllium than lithium. So building structural elements out of beryllium serves double purpose, you don't have the excuse of "I need to use steel because it's cheaper" - you need the beryllium either way. It's strong, low density, similar melting point to steel, but retains strength better with heat, and highly thermally conductive. Beryllium swelling from helium accumulation stops at 750C+ as helium release occurs. So pairing a beryllium first wall with a FLiBe-based blanket seems like a very appropriate option.

Please don't get me wrong, I'm not at all disputing the great amount of engineering work left to do. I'm just more optimistic that appropriate solutions will be found. Perhaps I'm just naive in that regard ;)

Comment Re:Stupid design (Score 3, Informative) 121

The second one is the device is dropping voltage and consuming power. In standard USB with 500mA at 5V, if the MOSFET takes 1V, that's half a watt of power you're losing in the transistor. (And really, you just use a diode). USB-C with up to 100W, you're looking at losing a lot of power in your reverse protection components.

100% wrong.

The MOSFET is not a diode. Diodes DO cause a 0.6-1V drop. That's why they use a MOSFET instead here in applications where a diode drop is too much. The MOSFET only drops as much as its internal Ron on-resistance allows. For a high-grade MOSFET, that can be in the single milliohms, so it's effectively a dead short. Cheapo MOSFETs are still in the low tens of milliohms. So with 3A of power, that's 1/4W with a crappy 30mohm MOSFET, or 72mW with one with a 8mohm on-resistance. The only reason you'd leave this out if reverse polarity is at all possible is cheapness.

Comment Re:Basic auth or TLS client certificate (Score 1) 387

Then use progressive enhancement. In the HTML page, send a "To log out, close your browser" message. Attach a script that replaces this message with a button to log out as described in the linked answer. To get past the extension that blocks non-free scripts, distribute this script under a free software license and add appropriate metadata.

Comment Re:freedom (but only for those we like) (Score 1) 85

This. Exactly this.

The correct answer to people spouting bullshit is to call out their bullshit. Don't silence them by squelching them, silence them by showing them that they are wrong, that they are not the "vocal minority that dares to say what others only think", but that they are a loudmouth few who babble what everyone else knows is BULLSHIT.

Comment Re: No transit costs. (Score 2) 100

The free market is a nice idea but fails at the entrance fee.

If I have an established system, I can operate at much lower cost than someone who would have to establish the system first. If I already have a factory pumping out a product (which has redeemed its cost already by me being able to set the price due to having a de facto monopoly due to a lack of competitors), I can easily squish any and all competition that may arise by lowering the price to the point where it is not feasible for someone who still has to redeem his investment. By fixing the price at a level where he cannot redeem his costs, I can ensure the continuation of my de facto monopoly. This is crucial in markets where the initial cost of doing business is magnitudes higher than the operational cost. Like, say, ISPs.

There are a few ways to crack open such a monopoly. But that first and foremost needs the will of the law makers to actually do something against it.

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