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Comment Re:I bet many have nicer cars too (Score 1) 214

Actually: yes.

I use Uber a few times a week... and I am starting to see more and more senior drivers. When talking to them about why they do Uber they always remark that it's a great way to meet people and have interesting conversations. One guy the other day actually said "I can either sit at McDonalds and listen to women chatter about nothing or I can drive people around and have good conversations" (his words, not mine!)

I typically find the senior citizen drivers to be quite nice to ride with... although they are definitely slower ;-)

Comment Re:Rate of fusion research (Score 1) 645

You are correct that "used" fuel is mostly made up of Uranium that is an energy resource.

The issue is that it's co-mingled with a bunch of nasty stuff. Stuff that generates heat and radioactivity while it decays (which makes handling the used fuel difficult and expensive for reprocessing) and stuff that is a neutron "poison" (meaning it soaks up neutrons, lowering the neutron economy of the fuel).

We have the technology to separate out the good stuff from the bad (France does it in fact) but it is very expensive. At current Uranium prices it's uneconomical - France does it because it believes "it's the right thing to do" (TM). However, in the future we could come up with new reprocessing technology that makes it cheaper (many scientists are working on that) _or_ the price of Uranium could go up to where reprocessing would be economical (although, it may just price nuclear out of the market completely).

One interesting thing: The (failed) Yucca Mountain fuel repository was explicitly designed to allow for retrieval of used fuel. Fuel was to sit on moveable platforms on "train tracks" that would allow both simple placement _and_ retrieval at a later date. This was a "just in case" type deal... at the advent of simplified reprocessing Yucca Mountain would have just been "hanging out" with tons of good stuff that's easily retrievable. All of the other long-term geological repository solutions (like salt-mines and bore-holes) don't have this nice property ;-)

Comment Re:Lack of fuel (Score 2) 645

"Uranium reactors, regardless of 'Gen' use fuel that is enriched to about 6%. That means 6% fissionable Uranium, 94% non fissionable."

Two words to learn:

Fissile: Can be easily fissioned with "thermal" neutrons (typically, neutrons around 0.025 eV... also known as "slow" or "low energy" neutrons).

Fissionable: Can fission. Period.

U-235 is "fissile" while U-238 is "fissionable".

The "94%" you talk about (BTW: in the U.S. the limit for enrichment is 5%, most fuel is enriched to 4.8% or so to leave a little bit of headroom) is U-238 and is definitely "fissionable". Several types of reactors have been built over the years that can burn U-238 directly including fast reactors and others that are "high neutron economy" reactors like CANDU, Magnox and AGR which can burn Uranium with very little or no added enrichment.

Fast reactors can work with U-238 because above 1 MeV the fission cross-section for U-238 is large enough (and the capture cross-section simultaneously low enough) that U-238 can sustain the nuclear reaction. This works because neutrons are born with energies ranging from keV up to 20 MeV (although, the average is around 2 MeV).

CANDU can burn natural uranium (Which is only about 0.7% U-235) because of good neutron economy. It utilizes "heavy water" (deuterium/H-2) to slow down the neutrons. H-2 has an almost negligible capture cross-section meaning that nearly all of the neutrons that are born make it down to "thermal" energies where it will fission with U-235. However, since it is still relying on the small amount of U-235 the fuel is depleted fairly quickly, requiring constant refueling (not joking, it is literally refueled continuously). It would certainly be able to burn "spent" light-water reactor fuel though... that "measly" less than 1% (not 3% like you state) enriched stuff would actually be more than the amount of U-235 that typically goes into a CANDU reactor! Of course, some of the built up fission products are neutron poisons, so that would reduce the neutron economy a bit... but it would still be able to maintain a critical reaction.

However, this is not done because it's just not economically feasible. Getting the old fuel from LWRs and shipping it somewhere to be disassembled (which has to be done carefully because when it comes out of the reactor it stays hot (both thermally and radioactivity wise) for quite a while) and put into fuel forms that would work in a CANDU reactor would cost way more than the effort is worth.

It is interesting that you simultaneously insult someone else, screw up a bunch of facts AND manage to make a (terrible) misogynistic joke all in the same post. That certainly undermines your credibility in my eyes...

Comment Re:Lack of fuel (Score 1) 645

"But there is no way that you take spend fuel from one reactor and put it into another one and continue burning it there."

That's not exactly true. Just the U-238 that's left in "used" fuel is good enough to sustain a critical reaction in a fast reactor or possibly even a thermal reactor that can utilize natural uranium like CANDU. However, there are many issues that keep this from being a reality (mostly economics).

Comment Re:Hmm... (Score 4, Insightful) 555

(Note: I'm not a gun owner, so I'm just speculating)

I think one issue is a general "loss of control".

Guns are about controlling your immediate environment. Being able to respond (with the most basic of responses: physical harm) to threats to yourself and your family.

Anything that threatens to weaken that sense of control is going to have an uphill battle.

What is the end game on "smart guns"? Right now, it's just being used to make sure that the owner is the one firing the gun. In the future? Could it be used to remotely disable the gun?

For instance, many people are pushing for cars to feature a remote "kill switch"... where the police can remotely disable any car just by sending a wireless message to it. Could the same thing be coming to guns?

If smart guns take hold... could you imagine legislation coming down that requires smart guns to be disabled on demand by the police/military? This sounds "great": police roll in to a hostage situation and disable the guns of the assailants and then storm in. However, this may also be a Constitutional violation: is it a restriction on our right to bear arms? Does it give the government the exact authority (to oppress the populace without their ability to stand up to the government with force) the Constitution was trying to protect against?

Like I say: I'm not a gun owner... but that doesn't mean that I can't understand why gun owners would be against this. It's simply about control. Guns don't need to be "smart" to work... adding anything like this is opening the way toward more governmental control that possibly infringes our rights.

Comment Re: Publish a description (Score 1) 62

You don't have to mess with your license at all. Scientists are good at citing things if you give them something to cite.

We try to publish a few papers yearly about new aspects of our software... and the scientists that use those pieces of the software naturally cite this papers without issue. We post our citations on our website and many people also email the mailing list to ask for the appropriate thing to cite when they're publishing findings based on our software.

Comment Re:Comparison (Score 1) 255

Exactly this. We do the very same.

However, Clang is significantly faster for our application. I would do some timings for you right now... but it takes too damn long to compile the entire stack with GCC ;-) Last time I checked it was on the order of 25% faster. Over a whole day of compiling that can make a big difference.

Comment This Discussion Proves It (Score 2) 311

The fact that, years later, _WE_ are still arguing about this proves that the case has merit.

If WE can't come to a consensus about this... then how is Joe Scmoe supposed to figure it out?

The fact is: this was _misleading_ advertising. They could have easily come up with another name for it (like Intel did with Hyperthreads)... instead they consciously chose to call the extra ALUs _cores_... which does have a meaning to the typical consumer. They did this, on purpose, to muddy the waters... and they REALLY did.

Does that mean that people shouldn't be more careful about what they buy? Sure. But that doesn't absolve AMD from putting out misleading advertising.

Comment Re:Massive Scientific Visualization (Score 1) 111

Like I mentioned... the actual drawing is NOT the bottleneck (but every little bit helps).

Those images you see on the screens are backed by TB of data that has to be read in and distilled down before being renderable. That's what the thousands of cores are doing.

Also: those rotateable ones you see in the beginning are small. If you skip forward to the 2:30 mark you can see some of the larger stuff (note that we're not interactively rotating it). That movie at 2:30 took 24 hours to render on about 1,000 cores.

Again: The bottleneck was NOT rendering time. It was the time to read TB from disk and crunch the data down to the point where you had a renderable image.

Comment Re:Massive Scientific Visualization (Score 1) 111

Like I said: raw rasterizing isn't the main bottleneck... reading the data and transforming the data is.... both things better done on the CPU. Drawing frames takes up a very small amount of the overall runtime... but it's always nice to speed it up!

GPUs wouldn't help much in this scenario... and our CPU clusters are used for many things other than visualization.

Yes, we do have some dedicated "viz" clusters as well... but we typically don't use them because they are too small for loading many TB of data.

Comment Massive Scientific Visualization (Score 3, Informative) 111

This is seriously useful for massive scientific visualization... where raw rendering speed isn't always the bottleneck (but of course, faster is better).

We do simulations on supercomputers that generate terabytes of output. You then have to use a smaller cluster (typically 1000-2000 processors) to read that data and generate visualizations of it (using software like Paraview ( ) ). Those smaller clusters often don't have any graphics cards on the compute nodes at all... and we currently fall back to Mesa for rendering frames.

If you're interested in what some of these visualizations look like... here's a video of some of our stuff:

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